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ADVISORY GROUP FOR AEROSPACE RESEARCH th DEVELOPMENT 

? RUE ANCELLE 92200 NEJILLY SUR SEiNE Ci74NCE 

ACARID CONFERENCE PROCEEDINGS 622 

-@- NORTH ATLANTIC TREATY ORGANIZATION 

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Publlshed February 1993 

Dsfrrbulion and Avallabrliry on Back Cover

ADVOWRY GROW %OW AER0WME WESAWCW & CEVELOPMENT 

7 RUE ANCELLE 92200 NEUILLY SUR SEINE FRANCE 

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- North Atlantic Treaty Organization 

Organisation du Fait4 de I'AtIantique Nord

Acccorclinp tto 11s C”liirlcr. the mission of fit: \HI) is to hrinp together the lading personalities of the NATO nation?. in thc fields 

$of sclcncc ;ind tcchnolopy relating to +ice for thc following purposes: 

-- Hcccomnicncting cffcctivc w;iys for the nicmkr nations to usc their research and dcvelopmcnt c;ipahilitics for the 

coniniwl Iwtnefit of tht NATO commuiiity: 

- ProviJinp \,.icntific and tcchnica: advicc iind ;is istancc to thc Military C‘ommittcc in thc ficld nf acrospacc rcscarch and 

dcvcliiprncnt (with particular rcgiird t o it\ milit ’ry applicatiiln): 

- ( ‘oritiiiuiiusly stimulating ;idv;inccs in thc :icrio? i>;lcc scicnccs relevant to strcngthcning thc common dcfcncc posture: 

- imr,,ivinp thc co-opcr;ition iimconp ricnilwr n;i: ions in acrospacc research and dcvclopmcnt; 

-- Hcntlcrinp scientific ;incl tcctii!is:il ~i~wt;~iicc. :is rcqucstcd. to other NATO htdics and to nicmkr nations in aonncction 

uith rcwirch mil tlrvcllopnicy prohlcnis in the xrospacc field. 

lhc highest atit hiirity within ,IGt’\KI) is thc N;ition;il 1)cIcp;itcs Board consistiiig of officially ;ippointcd senior representatives 

from each mcmlw ii;iiiiiri. The miwit in of ACiARI) I\ c;irriid out through the Pancl\ which arc cnmpned of cxpcrts ;ippiiniccl 

ly thc Naticin:il I)clcptcs. thc C‘w\ult:int arid 1rrch;inpe Priogriimmc and the Aerospace Applications 9udic.s f’rogwnmc. The 

results of ACiAHl) work .Ire rcptrtcd 111 the rnemhr n;itions and the NATO Authorities through thc AGAR11 series of 

puhlicaticin5 of uhich this is one. 

f’3nicip;i;;on in AGARD activities iqi lly iiivit:hii\ only and is normally limited to citizens of the NATO nations. 

! 

Ihc ccontcnt of thi5 puhlication ha5 ken rcprtduced 

directly from m;itcri;il supplicd hy AGARD or the authors. 

Puhlished February I993 

Copyright 0 AGARD 1993 

All Rights Rcservec! 

ISBN 92-835-0700-2

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Theme 

rcrynt l)c\t-:t Storm operatiom undcrccimvl the rswntial nrd for space system% to hght and win a thcatrc war. An 

cnil*rpiiip ccmcclrt lor spacc systems currently rcce*:-kF *.idcsprcrad attrntioii for Ihc Wh I\ characterizcd hy thc term 7:icSats" 

(;11s,i c;illctl

0 

Im oyi.rationr rcccntc\ *Tcm+tc du I~kcrt. on1 swlignC le : Wn vital de sc doler de splcmcs spatiaux susccptihlcs dc mcner 

ct de papncr tine purrrc de thciitrc:. tin nwVeaii ccmccpt de systirncs spatiaua pour lcs dnnies IVY(). qui suscilc hcaucoup 

d'inti.ri.1 i I'hcurc actucllc. CSI ciirhctcrii par IC tcrme rTacSatsm (apple aursi CheopSals. 1-ightsats, SmallSats ctc.). Ccs 

cysti.rnc\ son1 cari1ctt%\h par dc\ couts mlntiwmcnt rnrdiqua et des satellites Icgcn avec des performances Ctudiccs pour 

rcpondrc mix hcuiinr du ccinmandcmcnt du th6iitrc. par opposition DUX satellites Icwnls CI complexes dcstinCs i satisfaire aux 

hcstnns natiiinaux. 

I.C coriccpt a'IilcSatc. parait p;irticuIii.rcrncnt dnptc au c~~textc sctucI dc cornpwssic?n dcs hudpcts c k dcfensc nniirsnaic et de 

reduction de\ fiircc\ iirm&x I.cc caliaciti's offcrtr\ F.ir cc\ syrtcmcs puvcnt ttrc acquiscs dc faqon prriprc\sivc. ccintraircmcnt 

aux \y$ti*nic\ 4lwi;iux clawiqucs. qui son1 tcmpljcwru ;iccompagncs dc cohs additionncls. En outre. ils pcuvcnt Ctre mi5 sur orhite 

pJr de5 vi'hicuIc4 de lnnccmcnt plus pctils CI miiins cciuleux. commantl6s cventucllcmcnt par IC commandant du thcitrc Incal. 

Lcs TncS;Ii\ wrnhlcnt offrir unc solution i'concmiquc et scx~plc au prohkmc dcs hcsoins de I'OTAN cn mati.ricl Jc survciliance, 

de ti.li.rcrmrnunir;iticon~ ct dc comniandcrncnl CI tcvntrc'ilc pour Ics ann& YO. Ihns unc situiiiion dc forces r6duitcs. iI importc de 

wwir c i G IC% Iawr* cnncmic3 pcoicnricllc\ pnirr:tiuni Ctrc situccs. qucl CSI lcur nomhrc. qucllc cst lcur route etc. Ccs inforrn:itions 

\mi incli*;prn\nhlcc i~ tout iiiplnicincnt cflicncs tl'un nonihre rcduit dc troupcs. Lcs systkmcs cpatiaux offrcirt peu!-Ctrc la sculc 

pb\\ihilitC tl'r-ubtcr ccs fonctionc J'unc m;iriiCrc clticace. I>nns cc cas. des TacSats di.ve1nppi.s pour WTAN. ii un prix 

ahmhhlc. prrncitraicnt de contrcr unc mcnacc qui i.voluc. dans un mondc ou Ics budgets ct Ics stnrct3rcs des forccs wnt cn 

diminution. 

Systcmcr -7;icSat\* 

- Architccturc et inpi.niCrie de\ sy\tCnic\ OTAN 

- Concepts CI i'tudcs dc la ch;irpc uiik 

- C(onccpis ct itudcs dcs huvpwr vkhiciicc

Mail from Europe: 

ACiARll-CJrA N 

Aiin: AVI’ Exccutivc 

7. me Anccllc. 

92200 Ncuilly-sur-Scinc 

France 

PANEL EXEC‘tlTlVE 

I.TC H. Caripl;-, IAF 

‘LA: 33( l)47 3H 57 OH 

Tclex: 610176 (France) 

Tclcfiix: 33 ( I ) 47 38 57 99 

V 

Ijclpi u m 

Mail fmm US and Cnnsds: 

AGA RI)-NATO 

Aim: AVP Exccuiive 

Unit 21.551 

APO AI: 09777 

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Theme 

'fieme 

0 - 

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Avionics Pencl and 'Technical F rqramm ('omnbiltcc 

Tactical SafclDitrc 

hy F.1 I. Ncurn:cn 

SESSI(9N I - TAIT'SAT CONCEPT ANI) REED 

Evolution OP Revolution - The Catch 22 of TrcSirts? 

hy ('J l:Ilii~t~ 

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SESSUON II - 'TACSATS - ASPECTS 

Papcr S cancelled 

TacSat Ground Control and Dsta C'ollweiam 

hy (.' Ci ('ixtiranc 

Paper 7 cancclled I 

TacSal-Spacecraft Bus Conccpt and Deslgd: Aiyplir*rtion of a Multimission Bus for 

TatSat in LEO (English and Frcnch) 

hy G. Hichard 

A Model to Chnparafively Assess AltcmaPive Satellite Communications Systems Options 

hy J.F.. t3rou.n 

SESSION III - TAkSA'T APPLICATIONS - SYSTEMS 

Sgstcmc de Navigation par Satellites i Couvcrlure Europknne 

par t I.l!arangcr. 1. tkwchard CI T. hlichal 

TakticaI Satellites for Air Command and Control 

hy M.Crixhci. J.Cyrnhiilisia and I..l.cvcquc 

Concept of Small SunciIIance SeteIlitcs Boa the Context of an Overall Spice System 

\ 

hy U.hI.Erict1, W.A. KriegJ and K.4.. Bitzcr 

Conccpts of Scnsors and Data Transmission for Small lactical 

Surveillance mnd Vcrification Satcllitea 

hy K.-I.. Iiiizcr. I4.(hil. K.tI.Zellcr nnd S.

SB:SSUON VI - I..\UNCI1 SYSTEMS 

Spacccrnlt and I.nunch Systems hr Tarsat Appl .rations 

I)! (' Ch;itlc. (;.I>. Hyc and RII. hlcuro 

SESSION VI1 - SPACECRAFT BUS 

QuickStar - S!citcm DesiKn, ('apehilitks and Tactical Applications 

of a Small. Smart Spacc System 

by T.l'.(;:irIiuin mid N.?'.i\ric!cruiii 

Alc'itudc- and Orhit Control Suhs! stem C'anccpts for TacSats 

by I I. 1i:ltnc.r. I!. tirudcrlc. hl. Si1r;iur.r ;inti Icl.Schwcndc 

Elcctric Propulsion lor I-ightsats: A Wcviarw of Applications and Advanlqcs 

hy Ci. I'crrtiii:~ and G.Cirri and ti. Matticari 

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SjES5JON l'lll- ADVANCEDTECIi;\;OI,

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Printed in Clawificcl puhlication CI'SZZ (Supplcmcnc). 

SESS96hi XI - PANEL DlSCllSSION 

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Rrlcrrncc 

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30' 

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32' 

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SU M MI A RY I 

Thc syniposium was high:. siicccssful in It:>! 11 

brought togcthcr a trmad spcclrum oI thr. NATO psc 

tcchnical community with quality papm or thc 

mistions. applicat'ws. and tcchnical ospcts cd 

TACSATs. Thc main iopics ccnerctl cm surncillaibcc 

and comniunica!ion sysicms. and thc issuc of 

clctcrmining rcquircmcnlq. At thc cmplction of thc 

symposium. it was clcar that statc-of-thc-arl tomi 

systcrns could hc built lhma would tw mpmasivc to hc 

thcatci' cominacdcr 31 a rcasonahlc cos[. Whilc hc 

lcvcl cf tcchnical dcLd varicd; thni is. morv cmphasis 

on ttic utzllitc options illan t h grtrunrl syatcmc. t.trrc 

was sufficirnt tlcuil to makc thc CJX f(n Lhc vnlioily of 

thc TPCSAT conccp as discus.wd in tPsc :;ympvium 

thcmc. 

Thc output from ihis syrnpo.:ium will ttc thc ccnlnl 

pint of ~k~rrtun: ftn thc Working Group I6 cffms o 

?hCSATc for NATO. In this rrpnl. Ihc symposium 

was an ouisunding succcss. I 

Thc synipxiiim was cqxncd with an ah!rcw by k hxt 

Dickman. 1lrigdi:r Gcncrd, USAF, who is thc Dcputy 

Chicf of Skiff fOr Phs at Air Forcc spxc Ctmnlmmd 

in Colorado Springs, Colorado. USA. His pnpxiivc 

was from the warfiightcr's pint-of-vicw within which 

hc challcngcd thc audicncc of mostly scicntists and 

cnginccrs to focus on thc nccds of thc uscr; 

cmphuixing. that if TACSATs an: U) ttc a paf of spacc 

in thc futurc. hcy mug bc mawrrd in lcrms of thcir 

uniquc concrihuiions IO mission succcss. 

To makc his pint, Gcn. Dickman cnprcswtl hc bclicf 

that spacc will hc a dominatc faclor in any futurc 

conflict; and. as a rcsult. will havc io improvc, not 

rlccm~, in thc futurc. tic cmphasimi tha: whilc this 

hclicl is wikly acccprd. in an agc of hmung 

rcsourccs. rcquircmcnis and affordability must comc 

iogcthcr. Thcrcforc, thc dcvclopcr must scck out hc 

yicw of thc warfightcr in an cffort to identify critical 

spcc dcficicncics. In this rcgrtrd. hc dcvclqwr will hc 

dcaling with a customcr who is smartcr. who will 

dcmwd nnlorc from spcc, and who will insist that ihc 

S ~ C C 

capahilitics hc lhcrc during hostilitics. 

To cmphasizc thcsc pinu. Gcn. Dickmm gavc a spacc 

"rcpon card' on Dcscn S m . 

Communication - ncvcr cnough, not mohilc 

cnough. and bc Wnninals wrrc in&qmtr. 

Wcathcr - dood information. hut ihc data 

disscmimtim was pr. 

Navigation - 3mr. hut MM cmgh rccrivcn. 

Itnagcry - a ccmlrovcrsial suhjcci. Whilc Ihcm was 

not crulugh swcillancc. it was xtu311y vicwcd as 

a failurc kcausc of rlisscmination pmhkms. 

AS a rcsu~t. hr OVC~II sprrcc rating can bc vicwcd as 

follows: 

Cspahilitv - grmt 

Payltmd hsbing - modcrac 

Disscrriination - tcnihlc 

T- I 

Hc wcnt on to cmphasix that thc rcawn for his "carz' 

rating gocs back to what thc warfighvr wants. tk 

wants: continuous availahility. flcxihility mi 

availahility to thc cnd uwr. hi anothcr way. from a 

combat pcrspcctivc thc wwfightcr will ask: 

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Can I gct what I want whcn I want it? 

Can I distrihutc it U, my forccs? 

In closing. Gen. Dickman chdlcngcd thc symposium 

U, locus on Ihc dcficicncicc. 

I. lmprovc distribution 

2. lmprovc dm swms. 

j. Dcvclap ncw spacc systcms; but. avoid 

uniqucncss. conccnmtc on intcropcnhility. and 

cnsurc bat wc can cxcrcisc as wc fight. 

Thc challcngc for TACSAT will bc: 

- whaimIhcnocds? 

- What arc hc options? 

- What is possiblc now? 

- What arc h c "mcasurcs of cffcctivcncss?" 

Session I - TACSAT Concept and Need 

Thc inlcnt hcrc. was to "SCI thc stagc" - WHAT AHE 

WE TALKlNG AROUT? 

In h is sccsion, as with almost lhc cntirc symposium. 

two mission arcas rcccivcd thc most aiicntion - 

survcillancc (imagcry) and communications. Of tho= 

two mission arcas. survcillancc took thc "lion's .shim" 

thc group's aitcntim. with most of thc discussions 

ccnlcrcd on nsolulion.

1'. 2 

c 

From tplc four pafcn. thcrc wrm wvcral zmas d 

conwnwc. two arcac of dhcrgcn: ~pniclnc. :nd nnc 

miistanding i-uc. 

'Ihar T,I(.'SATs ran tw M W ~ in untlcm with cnrc 

cycicnir by: micing mission awn rcqwnl;ivcncss, 

wlccwp orhits to match thc thrtzt. ccmcntnting 

011 ;I

0 

Whilc the discussicns in thi? arcs prcscntcd ncw 

thinking in how COMSATs coirld contrihutc lo thc air 

campaign and. to somc dcgrcc, tollistic miwlc dcfcnsc: 

morc analysis is nccdcd 10 (1i:tcrminc Ihc v:iliic of 

TACSAS's as a spccific class o; wtcllilc. This IS 

consisknt with thc issuc rciiscd in Session I cconccniing 

thc tix of lnrgc .SI~CIL~CS 3s TACSATS. 

Surveillance 

This .ma rcccivcd thc most attcnihn in this scssion. 

appearing in thrcc out of thc four palms. I 

As with conimunic;itions. survcillancc salcllitcs wcrc 

prcscntcll i1S kcy clcnicnts in tlcvclorinp the Air 

Tasking Order and in supp)rtinp bal:islic miscil,: 

dcfcnsc. lhc function of swvcill;rncc sntclliics W;LF 

consitlcwtl prirnc in dcticting airhisc activation, cud 

dctcction. hunch-r dctcction. (',ctcction of miusilc 

launch pri*par;itic.n. and mic.-tlc 1;iuni.h dctccticm. 

tiowcvcr. cpciiic rcquircmcnls that ;illow for thc uw of 

TAC'SAT class swllitcs h;ivc yct to bc drfincrl. 

Sonic lime w w sprit on h c pitriiti;il roll*#: TACSATs 

niight play from :I systcnis pinl-of-v:cw. It' wac 

cniphasircd h:ii surwillmc I'ACShTc coultl: 

- Hctlucc systcin ccmplcniiy 

iicrc again arc thc piinis th;it IAUATs pla) k c t in 

xlivilicc that arc pcopraphically krcaliictl and hat 

rquirc qurh rcxtitm to a cltwiton. 

Hccolutionc sccmcd io fall in the 3-S mctcr 

rcgionc. with w uc cxi-urcionc to 1.4 nictrrs. 

- fht spwccrdt wighis ucrc in thr fa) IO 750 

kp mngc. 

- Surveil lawc tn'hn iqucs inc Iwkd chin ~)pcical 

ad synthetic apmurc r;bku (SAR)] 

I 

At iswc in this arc3 was thc xccphhlc mwltiLi(m. As 

always, thc uscr asks for thc kst; howcvcr. it was 

gcncmlly apwd that &SI in survci!'.mcc mciins largc. 

rxpcnsivc, and limikd in quantity. This ilcm rcmaincd 

as a contentious iscuc chroughoui thc symposium. 

i 

Thr oh;cclivz of this scssion was lo cngagc the 

audic~~c in xfilrcssing my isutcs and conccms [hat may 

R.wc comc up in thc pyior scsekns. Four major issucs 

wcrc dimwcd. allhough no rcsolutions wcrc agad 

upon. Thc issucs wcrc: 

- ttow m quircmcnLs to bc cstahlishcd? 

- Should TACSAT he slriclly thcatcr oricntcd? 

- Will TACSAT hc complimcnlary to thc major 

spec syslcms? 

- Whai bunch suatcgy is appmprialc? 

Thcsc issucs will tw a prirnc conccrn of Working 

Group 16. 

Thc vsluc of this scssion was not in thc dikcussions. 

hui in thc hrinpinp fonh of thc.sc four kcy iss)cs. 

Sessioit V - Communications Conccflts 

In this scscion thc rmphasis was on technology and 

how it might lcad to TACSAT lypc comrniinication 

.utcllitcs. Ihc niain cmphasis was on EttF; althwgb 

hcrc was w nc discuvsion of SHF. 

Thc Ilow of thc scssion was paniculvly wcll dwc wih 

Pr. lncc leading off wilh a discussim of' Working 

Group 13's efforts on NATO Sarcllitc 

Communications. which was swmd in 1986. In thc 

discussion. hc rcmindcd thc audicncc that our pst 

emphasis was oricncrd to thc suatcgic mission whcrc 

ihc systcms had to hc highly survivahlc, cnsurc 

continuity of scrvicc. pvidc ECCM. and pvidc low 

capacity communication for cmcrgcncics. 

DUI timcs haw changcd. Dr. lncc cmphacii.cd hat 

wcllilcs should hc smalicr and chcapcr. wlth latrncli 

flcxihility hy cmploying systcms siich as clusurcd 

utcllitcs. Itc also cmphasiicd wmc movcmcnt froni 

S t IF to Et IF. Most immruntly, Dr. lncc pmvidcd a 

listing of NATO actions - 

- Dcfinc NATO and National rcquircmcnlr 

- Dcvclop and agrcc rm an archimturc 

- Dcfinc hc tcchmlogics 

- 

Encouragc companics to join togclhcr 

Thc rcmaining p;&rs discusscd thc lcchnoloyics hat 

will makc smallcr EHF satcllitcs possihlc and .wmc d 

thc protlcms that might tic cxpcctcd at Chcsc 

Irqucncics. In gcncral. thc cmphasis was to pmvidc 

tcchnologics that would allow morc uscrs to lakc 

itdvanlagc of &IC AJ charactcristics 01' EHF while 

gcniing at mcdium dala rarcs ralhcr than low ctla

Talcs. Thc lcchnology emphasis wnr on variable 

bcamviidth antcnnmc. frcqucncy syntils!$izcri. and 

proct.xxws. In Ihc ca9c of lplc antenna mchmlogy. he 

objjcctivcs wcrc ior micr opcration in cllrptical o&iu 

and for casc of switching gcogmphic IIxEmtio;ls for 

satcllitcs in gcosutionary orbits. Fw frcghcncy 

synthcsi7t:rs and for processors. thc cmpiiasis was on 

significant wcight and power rcducliont that would 

allow for payloads in Lhc 100 hg and 290 w rcdimc's 

with tcrminal capcilics of 27 LDR channels PI 45 

kbit.9 and 17 MDR channcls at 3 mbiu. 

Othcr discussions includcd MDK EHF synchronitalion 

tcchniqucs for minimizing acquisition timcs und an 

examination of intcrfcrcncc from mountains and 

foliagc. , 

Esscn:ially. this scssion vcrificd that thc tcchnology is 

availablc for TACSAT typc communication satcilitcs, 

par~L~larly at EHF. Thc qucslion rcmaincd conccrning 

thc aacquacy of such systcrns for military nccds. 

Ccminly, ihc capacity of such syslcnis can now bc 

dct-~ncxl with p u t confidcncc and no doubt Ihc . wc caul 

bc said for cost. Thc qucstion is. is thc tcrminal 

capacity dcscrihxi abow cost cffcctivc mln ;I mgc d 

SCCnariOS? 

Session VI- Launch Systems 

This scssion ccnfirmcd that ;I broad rangc of launch 

options will bc availablc aftcr 1995 to wpport 

TACSAT typc pa;loads as idcntificd in Scssion I. 

Thcse boostcrs, it: hcrcasing wcight carrying 

capability, arc: Pcgasus, Taurus, Dclla 11. MLV-3. 

Allas 11 and Arianc. 

Thc qucsiion that rcmains to bc addrcsscd is what 

dcploymcnt sualcgy will bc uwd for TACSAT. If thc 

boostcr is thc limiting factor, thcn stratcgics arc limitcd 

to thc following: 

t)oostcr Storc-on-Orbit Rapid Launch 

Pcgaws (1) X X 

Taurus (2) X X 

. Atlas II X 

- 

Arain: X 

.. .

- Low powcr arcjets ate thc bcst wdid2tc.s fm ohit 

aansfcr and raising. 

In gcncral, morc work is d d 

for clccvic propulsion; 

howcvcr, it should bc supportcd and cxamincd fw 

inlrnduction into any TACSAT program. 

Session VI11 - Advanced l’achondtagy 

This scssion was dividcd into two discussions -- thc 

DARPA (USA’ SPCC technology crrot-ts ~ IMJ CAMEO. 

Thc DARPA tcchnology discusion told oi significant 

suidcs king ma& to rcducc thc cost of doing husincK5 

in spacc. It is morc appropriate for thc rcadcr to 

cxnminc thc papcr than to prcsknt a dctiilcd summary 

hcrc. Howcvcr. a hricf summary is appprialc. 

This pmgnin includcs: 

Pcgaws 

TiurUS 

DAFY’ASA?‘ I 

Optical :cchnology for light ‘wcight sy.c.tcms 

Submarine law communic&ns Irchttology 

EHF tcchnology 

Salcllitc subsystems 

Common buscs 

An cxmplc of thc progrcss bcing ma& can bc sccn in 

Lhc EHF tcchnology work. This icchnology is on its 

way to lowcring spacccraft wcight and pwcr by >SO%. 

Thc ovcrall program will usc sniallcr salcllitcs to 

quickly validatc tcchnologics so largc saicllitcs can hc 

procurcd using mom advanced urhnology. 

A dcscription of CAMEO was pcscntcd. lu objcctivcs 

arc: 

- Multi-spcctral small sakllitc 

- DOD/civil cnvironmcnlal and wcalhcr 

- Dircct downlinking of dab 

- Usc of a cmmon bus 

During thc qucstion and answcr pcrid, thc swus of 

CAMEO was rcqucslcd. Thc msivcr was that funding 

was dcfcrrcd by Congrcss cvcn though it had thc full 

support of DOD. 

‘session IX - Radar Concepts 

As with thc following scssion. this scssion arldnr;scda 

spccific tcchniquc for battlcficld survtjllancc - using 

ydar in thc syntlictic opcnturc mock. TRc ppcrs WCIC 

in-liccping with thc gcncral approach of TACSAT, that 

bf supporting hcatcr opcraiions. This point w&s 

khown as pivotal in allowing a rcasonablc wcight 

spacccraft so that it fit thc smallcr class sakllitc 

calcgory. In gcncral. thc spacecraft wcights fcll in Ihc, 

500 to 800 kg rcgimcs. In thc past, most radar 

spacccraft wcighis wcrc in thc SO00 kg c1a.s; so why 

@c diffcmmcc? Basically, thc diffcrcncc was in thc sizc 

/ 

of Ihc rcgion of cowem (2000 x 200 km), .#hich in 

tun1 reduced pfre duty cyclc (530%) which duced thc 

weight and. rn some cxteni, reduced the sizc of the 

antenna. ihhcr spacecraft paramctcrs icll into the 

following areas: 

x-band (M c-band 

300 to 5 0 km aldiudc 

200 Io 4c#) mbit &la rate 

6 to 8 .carcllik conslcllation 

FWud may anlcnna 

4 x 2 mcicr antenna 

2-5 mclcr rcsolution 

30 imagcs pcr pass 

Ttacrc was a unanimous call for a dcmonstraiion flight. 

Thc ovcrall fccling was that a SAR spacccraft, built to 

thc abovc .specifications. is slatc-of-lhc-an. 

Additional papcrs wcrc prcscntcd that discusscd 

lightwcight, stofc and forward microwavc applications, 

a maritimc application of a SLAR and an altimctcr to 

dctcrminc wavc hcighls. 

Session X - Electro-Optic Concepts 

T-5 

This discussicn followcd thc paltcm sccn ir, ihc SAR 

scssion. In gcncd it was bclicvcd that slau-d-thc-m 

E-0 TACSATs could bc built according to thc 

following: 

1 -5M resolutions 

250-450 km altitudc 

350 to 650 kg spacccrdt wcight 

200 to 300 mbs data ralz 

Thrcc additional points wcrc madc: (I) thc ground 

station could bc air transportablc; (2) a convincing 

dcmonsmtion could bc conducted for $50- 100M; and 

(3) a $5OM pricc pcr satcllik is achicvablc. 

As with thc r;pdarSAR. thc group fclt a dcmonsuation 

was absolutcly necessary to gci somcihing into thc 

hands of thc uscr. 

Session XI - Panel Discussion 

This scssion rcvicwcd thc outputs from cach scssion 

followcd by qucstions and answcrs with thc audim. 

Thc discussions ccntcrcd on t hm thcmcs - can wc 

achicvc thc TACSAT objcctivcs. how much resolution 

c;cl wc expcct from survcillancc systcms, and how do 

w idcntify rcquiremcnu. 

RECOMMENDATION: 

, .. ,c, 

From thc con!cW,of thc papcrs, it appcars that 

TACSAT i$b ‘.:Spacccrafi for survci~~!incc 

ad 

communications could bc of grcat valuc to NATO. 

‘t.*hilc such systcms will bc morc arrordablc than largcr 

more capable systems. they will not bc procurcd by any 

onc mcmbcr nation and lherefwe should bc appro3chcd 

as a pint international effort.

These arc three spccific fecornmen&tiom: (1) These 

papers should be uscd as thc foundation for Ihc 

Working Group 16 cffw. (2) Thc rcsulrr. of Working 

Group 16 should lhcn be bricfcd lo mcrnbcr nations 

and NATO hcadquarlcrs. (3) A NA'J0,min s~uld bc 

cslablishcd IO drvclop tcchnical and opcrationai 

options, with costs. to be rcportCa out lo NATO by 

early 1994.

ABSTRACT 

The concept of a Tactical Space System. "TAC{,jAT' 

is a means to provide a rapid, on deqand, 

abgmentation of thn backbone U.S. militav space 

sbslems. Such augmentation would be valuat$e to 

temporarily replace lost capability or in times of Crisis, 

to accommodate surge demands. Because 

augmntation needs are not always known a-prtori, it 

WeuM ba desirable Po be able to rapidly consiitute 

the appropriate paybad-satellite bus combination to 

accommodate the need for a specific space 

cbpability. To do this. one can envision a staridard 

bus capable of accepting a variety of payloads, or 

better yet, a single spacecraft designed lo perform 

sbveral different missions. Both options are 

ansidered. A number of potential missions exist in 

the areas of surveillance, navigation, environmental 

sensing and communications. Of these, two are 

presented as strawman concepts; surveillance and 

communication. For surveillance, an electro-optical 

payload is described that could be used for missile 

surveillance, theater targeting or wealher data using 

the same optics, focal plane and processor. The 

satellite orbit selected dictates which mission is 

performed. For communication. both SHF and EHF 

payloads are defined to provide theater coverage 

for the tactical user. The advantages and pen2lties 

that accrue to the use of a common bus are also 

explored. In addition, launch options are identified 

and a compdrison made between "launch-on- 

demand" and "launch-on-schedule" strategies. 

Potential timelines for rapid launch are shown based 

on parallel processing and checkout of spacecraft 

and launcher. This technique is compared with 

launching satellites on a routins basis and storing 

them in orkit. Energy requirements for 

repositioning these stored satellites after they are 

aLlivi;ted in time 01 need are delined. 

TACTICAL SATELLITES 

F.H. Newman 

The Aerospace Corporation 

P.O. Box 92957 

Los Angeles, CA 90009 

DISCUSSION 

3-1 

The purpose OS this paper is to put into context the 

role of the tactical salellits and present some sample 

applications in order to provide an introduction to 

the more detailed design and operations papers to 

follow. The Tactical Space Systern. commonly 

referred to as TACSAT, was envisioned as 

providing a space capability directly under the 

control of the military field commander. When 

needed, the spacecratl can be quickly assembled to 

provide the required mission capability and quickly 

launched or repositioned in orbit to provide the 

required coverage. The system would be 

compatible with, and operate within the larger in 

place space architecture, or as a stand alone 

capability. In either case, however, its operation 

would be transparent td the user; that is, the user 

would be able to use the same ground terminals 

already in use for interaction with the larger 

backbone satellite systems. The need for a 

TACSAT can arise from several circumstances. First 

wol!W be to augment the existing space 

infrastructure in order to accommodate changes in 

requirements that could be caused by changes in 

the military alert posture, e.g., as we go from peace 

to crisis to war. TACSAT could also be deployed if 

areas of military instability shift from one 

geographical location to another. ,It may, in fact, 

become necessary to cover ssveral geographical 

locations simultaneously. During Desert Storm, for 

exampie, space assets were refwsitioned to support 

operations in the Persian Gulf. Had a crisid or conflict 

occurred in a different part of the world at that same 

time, we would have been hard pressed to support 

operations in both theaters. As I will show later in 

this paper, space launch systems are not very 

responsive, nor are satellites stored in orbit 

generally designed to be maneuvered rapidly. If a 

failure occurs in one of the backbone space 

systems, then TACSAT could be used to provide an 

interllli capability until that backbons corrstellation 

can be restored. This situation occurred several 

times in the L1.S. military space program, particularly

when WO Rave gone from one'modsl satellitd to a 

redesigned or upgraded ono. If one looks at an 

actual supply/demand curve it can bo se0n that for 

the sako of efsnomy, most space systems are 

designod to provide a nominal capability. In geheral, 

this capability is less than the peak demand 

requirements. Also, as mentioned earlier, the 

capability may be reduced due to system failures. 

When a crisis occurs, the shflfall &tween dernand 

and supply could be quite significant. 

For TACSAT to fill this gap, it must possess lhrse 

main characteristics; flexibility, respnsivenesb and 

affordability. The first criteria for TACSAT, flei'ibility 

means PRat i9 must be capable of suppoding multiple 

missbn areas. These mission areas are generally 

defined as surveillance, commuPications, navigation 

and environmental monitoring. As 1 will discuss later 

in the paper, there are several ways to design a 

system that is capable of performing more than one 

of these missions. If we can achieve this Ilexibility, 

the number of TACSATs to be built will be 

maximized, and accordingly, the unit price will be 

minimized. Another element of flexibility, alludecl to 

earlier, is compatibility with the existing 

infrastructure. From the logistics and well as an 

economic standpoint. no TACSAT specific data 

receiving or processing equipment should be 

required. This is true not only lor the user 

ehuipment, but for the facilities required to control 

and monitor the space systeiiis as well. The final 

flexibility criteria is launch resiliency. Currently, the 

military spaco launch strategy does not include 

'launch lhrough failure". When a launch failure 

occurs, a significant downtime is generally 

experienced in order to troubleshoot and conduct 

the analysis necessary to determine the cause of 

the launch failure. Failure is rarely accepted in terms 

of its statistical probability but rather. because 

spacecraft and launch systems are expensive, the 

financial risk attendant to the next launch warrahts a 

thorough lailure investigation. The TACSAT 

concept, on Ihc other hand, is premised on quick 

response and low cost. 

Responsiveness is the second characteristic that a 

TACSAT system must possess. Responsiveness 

can be achieved in two ways. Thd first is to store 

sbacecralt and launch vehicles on the ground and 

then launch rapidly when the need arises. 

Depending on ihe location of the launch site, it may 

ba possiS!o to launch Into the inclination of interest 

ancl thereby obtain gerlinent data on the first orbital 

pass. Another means of obtaining responsiveness 

requires the capability Po reposition satellites already 

in orbit. This is a particularly attractive option for 

satellites in the geostationary belt. 

Of all the TACSAT characteristics, the one that is 

absolutely essential is affordability. If a low unit cost 

can be achieved the TACSAT concept can be an 

attractive option especially in this era of limited 

defense spending. TACSATs can be incrementally 

acquired allowing the user to purchase the capability 

needed at present and then add to that capability as 

the need arises. 

One method of achieving affordability is to maximize 

design commonality across the spectrum of 

missions to be performed. In the iJltimate, one 

would desire to have a single satellite design 

capable of performing any mission. This, of course, 

is not possible. This paper will discuss, however, 

combining similar missions. A second level of 

commonality would be to have a common bus and 

bus subsystems such as power, attitude control, 

and thermal protection. In this concept, the 

payloads would be different for each mission. The 

least degree of commonality would be achieved by 

having a common bus with subsystems and 

payloads tailored to the individual mission. Af!y 

amount of commonality will result in a larger unit Suy, 

theroby amortizing the RDTBE costs over a larger 

base and taking advantage 0: the production 

learning curve to reduce the mil cost. Second, 

affordability can be achieved by using the existing 

infrastructure. Operating with TACSATs should be 

transparent to the user: it must use the same ground 

terminals as the backbone space architecture. Also, 

because TACSATs will tend to be smaller and more 

proliferated than the backbone system, it will be 

necessary to make these systems more 

autonomous thereby reducing the need for satellite 

control and the costs attendant to that function. For 

those systems employing the rapid launch option, 

satellite to launch vehicle integration and test will 

have to be simplified to allow operation by military 

personnel without contractor support. Finally, the 

largest cost driver to space systems are the 

requirements themselves. As mentioned earlier, 

the TACSAT concept will allow the user the option 

to buy only that capability that is needed; the more

capability bought, the higher the cost. OEIior factors 

that will tend to reduce cost are limited coverage 

(theater rathQr than workhide) reduced lifotima, and 

a minimum of extras, such as heroic survivability. 

A number 01 potential TACSAT missions were 

studied. These in c I u d e d sur ve i I I a 'ice, 

communicalions, environmental sensing, nuclear 

detomtbn detection, space surveillame and space 

experiments. The first two missions were chosen lo 

be discussed in furlher detail in this paper because 

they illustrate two levels of commonality than can bg 

achieved. Tho use of a single satellite desip to 

perform two diflerent surveillance missions, thtiater 

surveillance and tactical missile tracking, was 

explored. Although these missions have different 

requirements, it will be shown that by selecting the 

@ proper orbits, both missions can be met with a 

conimon payload dasign. Theater surveillance 

involves looking at relatively small target areas in 

order to do target location and then bomb damage 

assessment. These rarameters are also required to 

allow the user to monitor the battlefield in order to 

determine deployment and strategies. To do this 

with reasonable size optics requires that tho satellite 

be flown at relatively low altitude. A 500 hm circular 

orbii was chosen lor this applicalion. Tactical missile 

tracking, on the other hand, requires cove# age over 

a larger area and the ability to ,detect and track 

missile launches from the infrared signature given 

off by the rocket plumes. For this application, 

satellites in geostationary orbits were postulated. 

The theater surveillance system uses an electro 

optical payload in the visible region lor imaging of 

the selected target areas. At 500km altitude, the 

payload would be able to acquire targets within an 

area of 2900 km in track and 1000 km cross track. 

Within this acquisition basket, the payload would be 

directly commanded by the user to image target 

areas up to 9 X 9 km. The data taken by the satellite 

would be trarlsmitted directly back to the user who 

would have the capability to do data exploitation in 

near real time. It is envisioned that the entire 

process from tasking of the satellite, acquisition of 

the data and downlinking to the user would take a 

minimum of 15 minutes. The maximum timeline is 

governed by the revisit time and is a function of the 

number of satellites in the constellation and tho orbit 

inclination. The theater missile tracking, system, 

deployed in a geostationary orbit, uses a scanning 

infrared sensor 00 dePm tadical missiles and after- 

burning aircraW in a 2000 x 2000 km area. Within that 

target area, iRe system is capable of processing up 

to TOO0 potential targets and, after processing, 

tracking up to 100 real targets simultaneously. For 

ballistic missiles, b lh launch and impact points can 

be predicted. These predictions could then be 

used to initiate a counterlorce strike or cue 

defensive systems. 

A single sensor that could do both the theater 

surveillance and tactical missile tracking missions 

was conceived and is shown in Figure 1. The 

sensor has common opiics far both missions and a 

*ai focal plane array to accommodate both the wide 

field of view and the high resoiution requirements. 

The payload was compact in design and weighed 

approximately 100 kg. It was now possible to satisfy 

one of our aftordability criteria; a single satellite that 

could do more than one mission depending upon 

the orbit into which the satellite was deployed. 

Once the spacecraft and its payload had been sized, 

a study was conducted lo determine whether the 

spacecraft could do missions other than those for 

which it was designed. Figure 2 shows that the 

missions of multi-spectral imaging and space object 

surveillance could also be done from a satellite in a 

500 km orbit and that the mission of cloud and 

ocean imaging could be done from geo. The 

imaging missions would ulilize both the IE and 

visible spectrum at the discretion of the use!' 

depending upon the operational and environmental 

conditions at the iime. The surveillance of space 

objects from spacc would be done solely in the 

visible band. To summarize the potential for 

commonality in the surveillance area, preliminary 

analysis has shown a minimum of five missions that 

corJld be accomplished hy a single satellite design. 

It is expected that a mwe ddtailed analysis could 

sudace even more potential missions. 

As noted earlier in lhis paper, a second level of 

commonality would be to have a common bus 

capable of accepting interchangeable payloads. To 

explore lhis possibility, a second mission area, 

communications, was selected for study. The study 

developed conceptual d3signs of satellites sized to 

provide direct communications support to tactical 

commanders. Design concepts at both SHF and 

EHF were formulated. The tactical users have 

idenlilied the need for small portable ground 

terminals that are lightweight, relatively inexpensive, 

3-3

3-4 

mggd and easily operated. This n~od for small 

ground terminals drives the satelliPe design to the 

use of high powered transmitters and high gain 

antennas. Tho SHF satellite was configured as a 

bent pipa in which little processlrrg 00 the signal is 

&ne on bard the spacecraft. The oommuniciations 

payload simply roceives the signal, shirts carrier 

frctguency orad retransmits it towards the earths The 

EHF sys?em, on the other hand, does much bre processing of the signal on the salellile. The signal 

coF;..rtg inPo the satellite is taken off uf the carric?r and 

shifted down to baseband where the bits the of 

digital message are available. The digital bits are 

routed lo Pheir destination, shilled up in frqudncy, 

put on the carrier ana retransmitted to the grcund. 

The SHF bent pipe system utilizes two 

lransponders each having a nominal capacity of 80 

MHz. A 61 element multi-beam antenna provides 

aoti jam nulling on the uplink and a 19 beam multi- 

beam antenna shapes the downlink coverage 

pattern to the theater. In addition, a spot antenna 

and an earth coverage horn are included in the 

downlink. Throe solid state powered amplifiers are 

incorporated in the design to provide redundancy. 

The spare power amplifier can be switched into 

either of the two active channels. The resultant 

payload weighs approximately 84 kg and requires 

225 watts 01 power to allow link closure with man 

portable terminals having an antenna on the order of 

0.6 meters in diameter. A capacity of approximately 

2000, 2.4 kbps channels would be possible using 

lhose man portable terminals. 

A 36 channel EHF payload was also sized. This 

payload was designed lo support EHF man portable 

terminals. The payload consists 01 32 low data rate 

communications channels and 4 channels for noise 

characterization/acquisition. Thc sample payload 

has a 61 beam multiple beam antenna with a nulling 

processor on the uplink. The fully autonomous 

operation of the processor represents the only 

design area that may be pushing the state of the art. 

The downlink includes a 19 element MEA, a spot 

antenna and an earth coverage horn. The design 

features fully redundant travelling wave tube 

amplifiers. Assuming there is one user per terminal 

and an average call duration of 4 minutes, the 

nbmber of terminals that can be supporlod can be 

calculated using message switching theory. With a 

5% probability of call cancellation or a 20% 

probability of call delay, approximately 400 to 500 

user terminals can be supported by this 36 channel 

system. The resulting payload weighs 

approximately 1.20 kg and requires 245 watts of 

power. 

In the previous section, we sized 3 payloads; a 

single payload that can accomplish two survelliance 

missions, an SHF communications payload, and a 

EHF communications payload. Payload weights 

ranged from 84 kg 13 118 kg and the power 

requirements were from 225 watts to 300 watts. If 

we now try to design a common bus, one that 

accommodates any of the three payloads, we find 

that the payload governing the design is that of EHF 

communications. It is the heavisst payload, has near 

maximum power requirements. a 10 year life and 

requires 45 kg of maneuver propellant (the reason 

for which will be discussed later). The resultant 

spacecraft weight, including payload, is 635 kg. In 

comparison with a unique spacecraft designed for 

each specific mission, the common bus spacecraft 

represents approximately a 30% weight overdesign 

for the theater surveillance mission and a 7 to 8% 

overdesign for the theater missile tracking mission. 

This basically comes about from the differences in 

satellite design life which governs the amount of 

propellant that must be carried for station keeping. 

In addition, the theater siirveillance mission is 

conducted from lower orbit and does not require tha 

45kg of maneuver propellant. In comparison to a 

satellite specifically designed for the SHF 

communications mission, the common bus design 

represents a 27% over design. This is mostly due to 

the lighter SHF payload weight and reduced power 

requirement. Penalties of this order of magnitude' 

must be accepted to take advantage of a common 

bus design. Not only does commonality achieve 

cost reductions as a result of an increased 

production buy and corresponding learning curve 

leverage, but it promotes the use of standard test 

procedures and test equipment. Payloads can be 

handled as black boxes and thereby, integration arid 

test times can be reduced. It is clear, however, that 

the more the payload weights and mission 

parameters diverge, the larger the penalty that must 

be paid by using a common bus. 

The surveillance and communications missions were 

then used to define the more complete set of bus 

design parameters shown in Figure 3. As expected,

these parameters vary both as function of misston 

and orbital parameters. In the area of Guidance, 

Navigation and Control (GNLhC) the ms1 stringent 

requirements (pointing and jitter) are dictdt@d by the 

electro-oplical misston from GEO. This mission also 

has the largest communications data rato demand. 

The requirement lor autonomy falls under the 

general heading of Command and Data Handling 

(CBDH) and can ba up to 180 days. To achieve this, 

it is thought that connectivity with the U.S. Global 

Pbsitioning System (GPS) would be roquired to 

provide ephemeris updates. The propulsion 

requiremonts are driven by the need for orbit 

reconstitution (on-orbit maneuvering). This will be 

discussed later in this paper. Finally, the bus will 

need to be protected from the natural space 

environment as a minimum. It is recognized that a 

truly Common bus design may compromise these 

requirements but to determine the extend of such 

compromise will require more detailed study. 

TWCI launch strategies have been considered for 

TACSAT application: launch on clemand and launch 

orl schedule. To understand rhe implications of 

these strategies, the launch vehicles available to the 

TACSAT must bo examined. In the currwt fleet of 

United States launch vehicles, the medl,lm launch 

vehicle (MLV), i.e, Delta 7925, is the one thal 

cqmes closest to satisfying tho TACSAT 

requirements. With a solid propellant kick motor, it is 

capable of placing approximately 9OOkg into a 

geosynchronous orbit. This represents a 40% over 

capacity for the 635 kg TACSAT described. Ail 

Atlas class MLV, will place approximately 1500 kg 

into GEO allowing TACSATS to be launched two-at- 

a time if such a launch strategy is deemed to bo 

advantageous. For low altitude satellite 

deployment, the Pegasus lift capability is about 400 

kg; somewhat shy for the satellite discussed in this 

paper. The Taurus, which is essentially a Pegasus 

on top of a Peacekeeper first stage, appears ideally 

suited to this application. This vehicle is, howdver, 

still in the development stage. 

Responsiveness is a characteristic generally 

associated with TACSATS. The capability to ra[)idly 

deploy tho satellite to the area in which it is needed 

is essential. When examining the rosponsivor ess 

of our current launch fleet, however, tho nominal 

tinie lrom the mating of the spacecraft to the launch 

vehicle until the launch can actually take place is 24 

days lor an Atlas II and 7 days for a Delta II. By 

streamlining the process. it may be possible to 

reduce this time down to 7 and 5 days respectively. 

Add to this the travel time to orbit and the spacecraft 

checkout time once orbit has been achieved and it is 

not clear whether the GEO based satellites can be 

responsive enough using a launch on demand 

strategy 10 tried user requirements. On the other 

hand, lor the low altitude satellites launched on a 

Taurus, it appears that, with judicious satellite 

design, response times on the order of 24 to 48 

hours may be possible. It should be noted that 

modifying the launch vehicle alone is not sufficient 

for rapid response. Today's spacecraft can require 

days or weeks of checkout after they achieve orbit. 

If surveillance data is to be obtained in the first orbit, 

for example, design features such as blowdown 

focal plane coolers and optics contamination 

avoidance systems must be incorporated. 

For the GEO based satellites, an alternate means of 

providing responsiveness has been studied. In this 

strategy, the satellites would be launched when 

available or on some predetcrmined schedule and 

stored in orbit. The satellites could be stored irt a 

dormant condition and activated when needed, 

thereby, minimizing satellite life degradation. The 

satellites could be stored at a convenient point in 

the GEO belt and repositioned to the area of interest 

as the need arises. Figure 4 shows that a 600 kg 

class satellite could be shifted up to 30" per day with 

the exponditure of no more than 45 kg of fuel. It is 

doubtful, however, that if several satellites are 

stored in this manner, there would be a requirement 

for this high rate of orbital shift. It seems more 

reasonable to anticipate maneuvers on the order of 

5" per day considering that crises or conflicts do not 

normally occur instantaneously but rather develop 

over some period of time. Under these conditions, 

the 45 kg of propellant could provide 4 to 5 such 

maneuvers per satellite without affecting satellite life 

on orbit. 

In summary, this initial study has shown that 

TACSATs can be used to augment the existing 

backbone space architecture by providing a 

capability that currently doesn't exist. such as tactical 

surveillance, or by adding to an existing capability, 

such as communications. In times of crisis or conllict. 

In this manner, it could also be used to provide an 

3-5

3-6 

interim capability should one or mre cl the 

backbone satellites fail. In order Po mahs the 

concept practical. however, the syc~Zems mist be 

affordable. One method of achieving such 

affordability is through maximization a0 COmrutonalQ. 

It has been shown that commonality can be 

achievod at least on WO levels; a singla Satellite that 

can padorm more than one mission or a common 

bus with interchangeable payloads. Respon- 

siveness, which is another key element of.the 

TACSAT concept, can also ba achioved in several 

ways. For low attitude satel!ites, rapid launch on 

demand is possiblg while for GEO salellfies, storing 

on orbi am on obil repositioning appears to make 

more svnse. To make either of Phese strategies 

work requires that the system has a low infant 

mortalily, i.e., when you turn it on, it works. Finally. 

the systeni hust be responsive to user demands. 

this means user control of the asset and direct 

transmission of data to the user terminal. 

In conclusion, the timing is right for the 

donsideration OS a TACSAT capability. With the 

recent (avopolitical upheavals, the focus shills from 

the anxiety of global nuclear war to regional, tactical 

areas of conflict. Such a shill leads to increased 

demands for information ana capabilities that can 

only be achieved from space. Furthermore, the 

areas of operation, although limited in size, are likely 

to be worldwide. The ability to bring assets to bear 

rapidly will be of paramount importance. Recer,: 

experience in Desert Storm has attested to this 

supposition. The value of space assets for 

surveillance, communications, weather and 

navigation was clear. System shortcomings, such as 

the inability to get some data directly to the user was 

also evident. Desert Storm also demonstrated the 

impact of a cooperative, coordinated, multinational 

effort. This trend is likely to continue in the future 

forcing requirements to be specified on a universal 

rather than a national level. These common 

concerns and needs, along with the severe military 

spending cuts that are facing individual nations, 

provide a greater opportunity for international 

cooperation in the development and use of space 

systems. The TACSAT concept is particularly 

attractive in this regard by providing the means of 

acquiring incremental capability on an as needed 

basis. If the degree of commonality and 

interchangeability discussed in this paper can be 

achieved, the TACSAT can provide a new way of 

deploying and operating space assets, one that 

gives the user direcl amtrol and the ability to receive 

critical data in a direct and timely manner. 

I

Theater 

Mission Surveillance 

Orbit, km 500 

Spctrcsrl 

Bands, pm 0.450.90 

Field of view/ 

scan sate, data 

1.6" x 1.6" 

rate 274 Mbps 

optics 

Focal 

Piano, 

Arrays 

Pointing and 

Scannir,g 

45 crn aperture 

Wigl/blCp and OR 

Wide FOV Vocal plane 

- 3" x 0.5" 

F/7 o ~~-~xIs 

High resolution focal plane 

- 0.16" XO.16" 

- FA5 on-axis 

Aczactionless drives 

p 45" conicil field of regard 

Wide area coverage in 3" swaths 

Envelope 70 I( 900 x 100 cm 

Weight 

Power 

Downlink 

Data Rate 

112Kg 

370 w (600 w peak) 

0.03 - 308 MbIS 

(Mission dependent) 

Fig 1. f+kltknieslon eensor 

500 

Vll?lQU$ 

Commwndable 

0.910.0 

3" x 0.1" swath 

2.5"Isec 

274 Mbps 

Rctvislt 12 Hours for one smtellite 

3-7 

Cloud/ Tactical L 

Space Objact Chmn Missitfa 

Surveillance Imaging Tracking 

500 35750 35750 

0.450.90 

VaPrious 

Commandable 

0.451 0.0 

2.7 

360" swath 18" x 18" 3" x 3" 

1.8"hec 8"/!mC 8"lSec 

20Kbps 70 Mbps 2OKbps 

- 1 

I 

I 

I I 

Continuous 

owr Area 

of Interest 

2 sec 

1 1 1 

Flg 2. Mukkniulon msor performance

OI~UI'IS 

MISSIONS I 

PAYLOAD TYPE 

-.- 

DUS PARAMETERS 

GNBC 

Stabilization 

SIC Puiiitiiig ( SWXJ 

cycles) 

cS001yr 

Stressing 

< 50 PPM 

01.1 1131 

COMM 

(I IIMJ mi) 

NAVIGATION 

3-arir 

.5 tu .I 

.5 10.02 

Noiic 

s. L, u111: 

4Kbp 

c 10.6 

Iiitcniiillciit 

NU 

I no 

Yo (+. .lOdcg) 

No 

No 

Ycs 

5 M I yr 

Mud io low 

< 50 PPM 

- -- 

GEOSY NCIIIUlNOUS EAHTl I OHUITS 

ELECIHO . 

COMM 

01'11 CA L 

3-axis 

.l to .U1 

.I lO.oo01 

Nunc 

X. SIIF. U1F 

up to 274 Mbps 

e 

lDiscussiopa 

Question: To meet stated requirements for area coverage, 

how many spacecraft will be needed, given a 9km X 

9km IFOV? The issue is whether the total constellation 

size needed will drive cqsts beyond affordability. 

Reply: A single satellitti\ takes 9 X 9km snapshots 

anywhere in the acquisitdon area. The number of areas 

to be imaged and the dwell time on each target area, 

as well irs the revisit t1.m requirements and the orbital 

altitude, will dictate tne number of satellites required. 

Tradeoffs have not been conducted to assess afforaabllity 

as a function of requirements, but, as you observed, 

the requirements must be kept under control or 

affordability will be lost. 

I 

3-9

1 Int raduction 

The iiotcntial cxploitatinn of TACSATs 15 lirnitecl by a 

vicious circlc in which users tln not slwcify rc:qiiirrtn,ciii< 

which they hcli:vc til hr infcacihlc and ihc spec inthistry 

docs not nffcr radic~lly new solutions hccairsc it ;.crccivc< 

no dcrnantl. rhis is the Catch 22 of the titlr. 

Thi? papr Hinis to shou come of thc p1ssihililir.s if wc hrcak 

out tif t;int viciitus circlc. A private cic*ilian Enrih 

obscrvatinn nliFrion (ScaStar) is ailiiptccl as a b;isclinc. In 

cvdrr tit illiictratc what niight hc iwssihlc. niilitary 

paylonds for survcillancc. vcrificatian and C31 arc 

suppcstcd. tlcrivrd from land or air h;iscd 5ystcins ih?t cilkcr 

alrcatly cxist or arc known to Ix undcr ttcvclolimcni. It 

must hc apprcciaictl that thcsc are not lirrzriilctl :is iwpictd 

clcsignc. mcrcly as ;I kind of "existencc piiii1" fi ~ ',igIi 

pcrfiirmiincc arid IOW ccirt ~~~tcllitcs, 

I'Y 

CA. EIiioRt 

Sinith Sysrcm Engineering 

Sniitk Assixiafcs Lid 

Surrcy Rcscarch Park 

Guildford GUZ 5YY 

United Kingdom 

It is pissihlc. tin the hssis or thiz "csistcncc iiriwl-', lo 

cxplorc s~)iiic iif tlic iycrational conscqt~:nccs of tllc morc 

gcncriil iize d'1'ACSAI-s 

2 '' T r a d i I i o n a I " s p a ce P 11 i 11 k i n g 

Thcrc has hccn a dcvcltipmcnt in thc space proirt.i~ canid 

out in the USA and Europe from the carly days of simple. 

dcdicatctl and incxpcnsivc missions. thrciueh in thc prcscnt 

pisition where niost missions arc cornplcx. niiilti-purpose 

and cxpcnsivc. 

This is a rcsuli iif a positive fccdh;ick nirchaniwi' which 

systcniatically fLirccs spacc missions io hcconic niorc 

cxpcnsivc. takc lnnpcr to caccutc and fail itr xatisf) thc 

nccds of their uscrs. Thc pnsitivr. fccdhack mechanicin starc\ 

with thc bclicf that space projccts arc cxprnsivc. The 

consciwcncc of this bclicf is that thcrc will not he many 

projects. Few projccts nican that: 

. they miist hc pliiniicd carefully to gct ihc hw out r:f 

thcm; 

- they must hc rcliatilc; 

- they nccd to he largc to achicvc a lot from cach 

projcct: I 

. 

thcrc will bc liitlc compctition (not only r.itiiimcrcia1 

compctiticin bctwcen supplicrc bui thcrc i. :ilso litllc 

room for compctilinn of itlcas). 

Each of these brings conscqucnccs for tlic ctwluct of the 

projccki. Planning C~IISCS dclays. High rcliahiliiy wticn not 

building many systems mcans that intcgrily must whicvcd 

by design. This prccludes the usc of the Iate

0 

e 

t 

1. ..- .. ' 

I 

I t 

I ' 

.I... . _J 

This no- points towards the rev~rl*Jtionnry approa\h. 

Miltory rpace missions could cnploit suh.~yatcms nlrcady 

dcvchpcd lor air or land based use and u.l~icvc i1:icgrity 

through rcclundnnry (many missions) nnd through thc 

hcncfits of a prmluction run :ather L!M onc-ofr huild. The 

rcduccd cu t of Ihc missitins would allow thrni to hc. trcared 

as tactical. rathcr than strategic. assc~s. The rmt of this papcr 

will look at snnir possible militnry iiiisric,ns for 

survcillnnce. verification and C31. bawd nn P strndard 

civilian Eort h nhccrv at ion bus. 

3 Wasdine for military m6ssions 

Olackgrou nd 

The SeaStnr misslnn. king cxeciitzd hy (hhiial Sclenccs 

end Hughr. Aernspnce provides a reference on which to 

hose polrrrl~le military missions'. It is n civilian eorLh 

observntion mission. designed to monitor the ncean colour. 

a rnrnsurrmcnt that is considered to bc nf Rrcnt value to 

cnvironmcntrl research and pssihly to bc of commercial 

value. 

ScaStnr is hascc1 nn the I'cgdtnr bus which olfrrs: 

. 

. 

. 

- 

. 

. 

. 

3 oxis stahilisaiinn to *I0; 

at Icost 170 W mean electrical power; 

up to 5 year life; 

up to 70 kg pnylovd moss; 

peylond

indicated hat an IR vcrsion of the 12" telescope is being 

considered. 256 element linear detector snay would 

allow imaging a strip -2.5 h wide with - IO m sp?tirl 

resolution in the 3-5prn band. This would dlow detwtion 

of, for exaniplc. thermal signaturcs on runways where 

aircraft have taken off or the detection nf hot spts on 

armoured vehicles causcd by the hiat of heir engines. 

Verlflcetlan 

Space-hascd vcrification system? rnny be used to cue 

ground or overnight inspections. A systcm with modcrate 

spatial resolution hut with 111c . flcxihilily to image 

frequently 2nd without warning might be +rll cffcctivc 

dctcrrcnt to brcachcs of a treaty. 

Thc opticnl systcrn tlcscribccl in Annex B would allow 2 km 

sqiiarc iiiingcs of any pnint to bc ohlaincd with n spatial 

rcsolution of 1 m. This is adcquatc for the clctcction of nll 

and rccognitioa of most ~ypcs of targct.7. TI^ s:ircllitc may 

he taskcd with a list of pints nf interest :incl can then 

autonomously collcct thc imagcs and eitticr hro;dcast thcni 

to a local rccciver or storc thcm on-board ani1 down-load 

whcn next passing ovcr hcadqu;irtcrs. Thcrc :ire several 

opportunities pcr day to image thc point of intbrcst with 

0 one satellite. 

C31 

Thcrc c c many aspects to C31 which might hc :idtlrcsscrl hy 

rnenns of satellitcs. Annex C considcrs thc fcacihility and 

performancc nf a rrtlar ESM systcrn usccl 111 tlctcct and 

idcntify pirlsc antl CW cniittcrs. Thc hasclinc cystcrn. 

Kestrel. is dcsignecl for airhornc usc :in11 cnn offcr 

significant tactical capability. pirticulnrly iC tlic satellite 

vcrsion of the multi-pon antenna has tiighcr gnin than that 

employed in thc airhornc version. 

One possiblc use of this systcm would bc tarticiil ESM. Thc 

systcm on-hinrtl thc wtcllitc would inclutlo tlic rapiihility 

to dcintcrlrnvc and track r:id:ir c1iiittcr.i :iii~I would 

broadcast its track table (possibly including radar 

identification) to tactical ficld units. Although ESM only 

gives an estiniatc of thc dircction of thc threat from thc 

rccciver but not its rangc. the rapid motinn nf thc satcllitc 

might make it possihlc to locatc tlic transmitter hy 

triangulation as the satellite passcs. The UFC of two or more 

satcllitcs has not bccn considcrcd hcrc but clearly this 

could providc morc irnmcdiatc antl rcliahle location. 

0 An cvcn more powcrful way of using two satcl:itcs 

coopcrativcly would hc to compare the time of arrival of 

individual pulscs at each satcllitc rather t!lm to compare 

the charactcristics of pulsc trains. This would not howcvcr 

bc within the capability of a conventional airhornc ESM 

systcm likc Kcstr-I. 

5 Operational implications 

The possible rnilitary missions suggcstcd indicate what 

might be possible. Thcrc arc two iniptirtani operational 

i m p I ic a t i o n s : 

- it is assumed that the satcllitcs would be launchcd on 

Jcmnnd to provide covcr nf slxcific pints of intcrest; 

- thc satcllitcs can communicatc dircctlv with Field 

units. allowing Ihc data hat is collcctctl 10 hc relaycd 

in real-tiiiic to uscrs and allowing thc USC-B to task and 

control the satellites. 

Launch on dcniand of a constellatiain of naiellitcs may seem 

. 

I 

to be an expensive option. However. it should be seen in 

the context of the COSIS of conventional survcillancc assets 

such as stnnd.off survcillance aircrnfi. It is clearly not 

appropriate to cnmpare directly the COSIS of TACSATs and 

aircral't srncc they offcr diffcrcnt capabilitics but 

surveillance hitcraft illustratc thr sums of moncy that cm 

bc allocated to tactical survcillance. vcrification or C31. 

The cost os operating a surveillancc aircraft is of the ordcr 

of S5000 . : irour. Thus, thc cost of 24 hour cover for onc 

year would bc of thc ortlcr of S40M. To this must be addcd 

the cffcctivc cost of tlic finitc prohahility that the aircraft 

may be lost duc to cncniy action. 

A constcllntion of 5 satcllitcs would providc covcr many 

h c s pcr thy and not hc wlncrahlc to air;to-air or groundto-air 

missiles nt a cost of no morc than S60M for one year. 

Thc financial cecc for satcllitcs is stmnger if the operation is 

rcquircd 10 continue for longcr than one year. For example, 

a drugs interdiction sQppnrt operation could use 3 satcllitcs 

to vicw Central America and thc northcrn coact of South 

America morc than 15 timcs per day at a cost of S30M per 

>;Car. 

Uircct communication with ficld units rcprcscnts a 

rcvolutionrry change in the operatima1 managcmcnt of 

spacc ~~SCIS. It rccogniscs hat TACSATs arc ti~~tic~ I asscu. to 

be dcploycd and exploitcd under the control of tactical 

commanders analogous to any otlicr tactical asset. 

It is inconccivahlc that spacc asbrts could hc considcrcd 

tactical unless they wcre much cheap-' to purchase and 

operotc than than current stratcpic asscts. Howcvcr. it is 

exactly this approach. which would lcad to protluction runs 

of satcllitcs comparable to thosc of. for examplc. fightcr 

aircraft. hat would cause h e spacc as.wts to be chcapcr. 

6 Con cl usio ns 

Thc argument has run full circle. This paper has picscntcd 

an approach to the provision of TACSATs based on three 

premises: 

thc use of an inexpensive standard bus; 

payloads using military sub-systems; 

dircct control and tasking of the satcllitc from tactical 

commanders in thc ficld. 

If these thrcc rulcs arc adoptcd. it is nrgucd that it will be 

possible to brcak out of the Catch 22 and achieve 

inexpensive opcrational TACSATs * which convey 

significant military advantagc. 

7 Acknowledgements 

references 

. and Acknowledgements: 

The author would likc to thank thc following fnr their 

assistance with thc prcparation of this paper: 

- Intcmational Dcfcncc Review. UK: 

~ 

. 

Gulfsmarn Aerospace Corporation. USA; 

Orbital Scicnccs Corporation. USA; 

. Qucstar Corporation. USA; 

- Racal Hadar Dcfcnsc Systcms Lid. UK. 

Re re r e n re s: 

Rcf 1 Elliott CJ. "Cost drivcrs - why do conventional 

satcllites cost s!i much?". Symposium on "Systcms and 

scrvices for small satellitcs". CNES. Arcachon. June 1992. 

4-3

0 

4-4 

Ref 2 Lyon K G and M R Willnrd. "&con color rcrnotc 

sensing tlnin for Ihc 1990s", First Thcniatic Confcrmcc on 

Rcrnotc Sensing lor Mnrinc nnd Coasinl Enviroiirncnu. 

New Orleans. Louisiana June 1992. 

Rcf 3 Wnlicrschcid R L. "Solar cycle. cffccts on thc 

upper ntrnosphcrc: implicntions for sntcllitc drag". J 

Spacccraft 26. 6. Nov-Dcc 1989. pp 43Y-444. 

Rcf4 Wcriz J R nnd W J Larsori. "Spncc mission nnalysis 

nnd dcsign", Kluwer Acndcrnic. 1991, ISBN 0.7923-0971. 

5. pp153-1-55. 

Rcf 5 Rcsl C and W Swceirnan. "Fighter radar in the 

1990s". Intcrnntional dcfcnsc Rcvicw 8/1992. pp 744-747. 

Ref 6 Cjcssing D T. J Cljclrnslad pnd T Lund. "A rnul1i- 

frcqucncy nctnptivc rndar lor dcicction imd idcniification 

of objccts". IEEE Trans AP 30. 1982. pp 35 I 36-5. 

Rcl 7 "Minimum rcsolvcd ohjcct sixcc lor ieingcry 

inicrprcintion". STANAG 3769, Change 1. 

Ref 8 "Electronic support mcasurcs cquipmcnt lor 

rotary nnd fixed wing aircraft ~ Kcstrel Mk 11". Ref DRI 133 

lssuc 3. Rncnl Rndnr Dcfcncc Sysicrns Lid. Chcsiington UK. 

I i 

t

a 

0 

Annex A Radar system 

A. I Background 

It is possible to establish the feasibility in principle of 

opcrating a radar on a TACSAT. by examining in outline 

the pwcr budgets and hence signal/noisc ratio that might 

be achieved using an advanced airborne radJr. The model 

that will Dc uscd here is the Advanced Tactical Fighter 

(ATF) radar currently under development. A tlcscription of 

the this development programme5 included thc following 

quotations: 

- The USAF has pursued X-band AESA [Active 

Electronically Scanned AnayJ technology since, the 

early 1980s for three main rciuons: pciwcrlwcight rlitio. 

agility and rcliahility. With more than a thousand 

transmitlrcceive (T/R) modules. each capable of 

generating around IOW of powct, Ihc F.22 has a peak 

pwcr in the megawatt range. should that hc rcquircd. 

- 

Ultimately. a maintenance-free life of 20.0(N h . the 

lifetime of the airaaft - is possible. 

Synthetic apcrtiire radar (SAR) ... is not in ttic baseline 

but he hardware can do it ... 

A.2 Radar equation 

The following assumptions will be made: 

- number of T/K modules: , 4000 

* module plwcr: IOW 

- square anay. half-wave clement spacing 

- . wavelength: 30 nini 

Th,is indicatcs nn antenna gain of -39 dR and an cffcclivc 

anicnnr area of - 1 In2. If \he spacecraft is at 400 km 

altitude and a target of cross section Im2,is located 300 km 

from the satellite track. then the received power will bc 

-165 dRW. If a receiver noise figure of S dR bntl dctcction 

threshold of 10 dB arc assumed. then the integrating time 

will nwd to be - 3ms. 

The bcam width will hc - IS km at SW km range. An area 

of SO0 km square will cornprise of the ortlcr of 1000 

resolution cells. A transmitter power of 40 kW and 

integrating time of 3 ms pcr cell will r6quire - 0.1 MJ of 

transmitted energy. The total energy available ' to the 

payload is of the order of 50 MJ pcr orbit. 

A ;3 Operational modes 

AI; surveillance 

Any look-down radar suffers from ground clutter and the 

system dcscribcci here will be particularly badly affcc>cd 

bccsuse of the relfltivcly widc beam widh. Two techniques 

thai might be employed to improve the dctcclability of 

airborne targets are: 

- DopplCr hlTli 

- mntched illutnination. 

Doppler MTI may bc employed provided that thc radar is 

directed across track to detect targets with a significant 

velocity component towards the satellite. The pcrfnrmance 

of MTI with the widc beam of this 'radar needs further 

analysis. 

Matched illurninatibn uses modulation schemes matched to 

the characteristic dimensions and resonances of the target. 

This has been u:.cd to idrntify specific aircraft typcs6. No 

trials have been reported of the use of this technique to 

reject ground clutter but the selectivity shown'in he 

identification trials suggests hat it might be effective. 

Ground su rvelllnnce 

Ground surveillance to detect and locate vehicles could be 

carried out using spotlight SAR. Typical performance 

would be to form a SAR image of a single 15km diameter 

region (corresponding to the beam width) on each satellite 

pass. A synthetic apcrturc of 15 km (corresponding to 2 s of 

illumination) would allow a SAR image of I m resolution 

to be constructed. 

Current real-time SAR processors capable of this level of 

processing have a mass and power consumption suitable foi 

airborne use and might feasibly be carried on-board the 

satellite. Alternatively. the raw data could be broadcast for 

ground processing. 

, 

4-5 

:. $1 

* 

: I

44 

Annex p1 Optical system 

B. 1 Background 

This dcsign explorcs whnt might be achicvrd tising existing 

space or military quality subsystems to build a high 

rcsolution imaging systcm. The spacecraft has a space- 

qualifird vcrsion of a commcrcial tclcscopc rnountrtl such 

that it can bc rotatcd about an nxis aligned within - lo of 

the dircction of travcl. A lincscan imager is niountcd at thc 

focus of L)ic tclcscope. aligncd so that it swecps a swath 

along he direction of travel (puslibroom). 

The dcsign prcscntcd hcrc can provide 2 kin square imagcs 

with a spatial resolution of I m. The image region is 

selected by rotating thc tclcscopc for tlic acrosk-track 

dimcnsian and sclccting thc tirnc of rccording for he 

along-track dircction. Thc position of the satcllitc nlust be 

dcterminrd to - 50 m in all thrcc dimensions and the 

orientation of the tclcscoF to - I mrad in thrcc dirrctions 

to permit the centre of thc irnagc IO hc sclcctctl to an 

accuracy of - 0.5 km. 

a 8.2 Telescope and sensor 

The primary optical systcni is a spacc-qualirictl vcrsion of 

tile standard Qiicstar 12" telcscopc. Thc kcy piiraiiiclcrs of 

its specification arc: 

0 

-. rcsolution: 

. focal Icngth: 

- apcrturc: 

0.38 arc scc 

4.57 2 ni m 

30.5 iii rn 

- dimensions: -I ni long. -3.50iiiiii tliamctcr 

- 

~ 

mass: 

vibration tolerance: 

-SSkg 

I0g 

I ' 

- moterial: invar 

. price: - 5 200 k 

It is undcrstood that this tclcscopc has hccri iiscd on US 

military spacecraft. 

Thc baseline dcsign is to use thc Kcticon KAZO4HJ chargc 

coupled dcvicc (CCD) detcctor opc'rnting in timc delay 

intcgration (TDI) mode. It has to he'configcirctt so that its 

long axis of 2048 sensors is pcrpcndiculnr to tlrc track of 

thc spacecraft and the clock frcqucvcy in thc transvcrw 

(short) axis of M dctcctors is synchronous with t!ic velocity 

of he spacccraft. 

The signal'iioisc ratio of thc dctcctor. D. is giwn hy: 

D = r a A T s/N 

v/hcrc: 

r is thc radiance of the Earth. assumctl to be of thc 

order of I00Wm-2sr-1. (This figure is sufficicntly 

conservative la includc largc sun txriith anglcs 

cncountcrcd at high latitudes.) 

a is thc, area of yound ma pdd onto one pixel of thc 

dctccror (nssiI.,Icd to tx I ni $ ) 1 

A is the solid tin IC wbtcndcd by thc telescope 

aperture (0.45 x \b-f2st at an altitude of 4(H)km) 

T is thc integrating timc. dcfincd as the limc taken for 

1 

I 

the spacecraft to fly 64m (85ms) 

s is the smsilivity of the detector (480 nV I-') 

N is the detecm noise level (200 pV RMS) 

The signalhoise ratio is thus - 1OOO. 

The detector pixels arc appoximately 2Spm square. This 

requires the focal Icngth of thc optical tclcscope lo be 1Om. 

A sccondary lens will be nccdcd but this docs not have to 

be of particularly high optical quality. Thc type of lens 

used as a a2 tclcconvcrtnr for 3Smrn SLR cameras would 

probably be suitable. 

R.3 Navigation and positioning; 

If it is assumed that the nominal 2km square image must be 

ccntrcd on the target position with an accuracy of f 5OOm. 

it is necessary to know the orientation of the tclcscope to an 

accuracy of the order of 0.5 mrad. 

Navigation information will be derived from a GPS 

rcccivcr and oricntation is obtaincd from a star sensor. 

A possihlc iniplcmcntation of the GPS rcccivcr is to carry 

out thc signal acquisition ~ t l 

processing in software within 

the on-board proccssing system. A baselinc dcsign using a 

singlc.transputcr cxists and would mcct the rcquiremcnts 

with a power consumption of 4SW. It is likcly hat a more 

approprintc proccssor could he used to rctlucc his. 

The star scnror is mounted on thc tclcscope to cnsurc that 

thcrc is a constant angle betwccn the two. If it is assumed 

that the prapcrtics of the star scnsor are: 

. ficld of view: 25O 

- niimhcr of stars for rcliablc fix: 6 

(hcncc ncrd to iisc stars of 5th magnitudcj 

- spacccraft roll ratc: IO rnrad s.I 

(= - I revolution cvcry IO minutcs) 

. integration he: SO ms 

- flux from 5th magnitude star: 2.5 x IOl4 W 

- detector sensitivity and noise: as Kcticon abnvc 

- sensor apcrturc: 40 mrn diamctcr 

~ dctcctor 

array: 500 x 500 elements 

then it will bc capable of meeting the targct of 0.5 mrad 

accuracy if it is possible to intcrpolatc to onc half of a pixel 

with a signal/noisc ratio of around 70. This is considcrcd to 

bc well within thc pcrformnncc of currcnt interpolation 

algorithms. I

Annex C ESM system 

C.1 Background 

An airhornc ESM system might providc a suitnhlc basis for 

a tacticnl communications or radar monitoring satellite. 

The basrlinc that will he assumcd here is he Kcstrcl Mk fl 

madc by HncalR. This is a radar ESM. capablc of dctcclhg. 

drintcrlcaving nnd tracking radar emissions hetwecn c and 

1 hnnd. 

C.2 Detection capability 

Kestrel employs a six port amplitudc comparison recciver 

to nicnsurc signal bearing. The standard antennas givc 360' 

covcrngc in azimuth. 25O covcragc in clcvnlion. a typical 

pulsc scnsitivity of -60 dRmi and bearing nccuracy of 4.5O 

RMS. This would dctcct the main lobc of a 10 MW E\tP C- 

hnn:l rnclnr nt n rnngc of SO0 km. It would also hc pc";sihlc 

to locatc thc radar to nn accuracy of approximatcly 5Okm 

h; uackinp thc hearing of thc radar as thc sntcllitc pas?:s. 

Antrnnas with grcatcr gain could hc uscd ut, thc ci:st of 

sncrifiring thc 360° capability. This would, hc ninrc cnsily 

achicvcd at higher frcqucncics antl it might' bc appropriate 

to rcplacc thc Rand 3 antcnna (I !o J hand) $id1 a multiple 

fccd horn and rcflrctor. A rcflcctiw of thc ordcr of 500 rnrn 

in diamctcr might bc cxpcctcd to givc 20 clR iniprovcmcnt 

in scnsitivity and a factor of Ifl improvcrncnt in hcaring 

accuracy hut would not add grcally to thc mass iir cost of 

the sy

TACSAT @mognd ColpflmU anad Data 

Coktion 

by 

C.C. CocRriPne 

Matra Marconi Spacc UK 

Anchoragc Koad 

Portsmouth 

Hampshire PO3 SPU 


This paper will address the concept of a 

satellite based system serving the needs of 

tactical users for direct access to 

communications and various forms of ' 

surveillance. Such a system must take 

0 account of the most effective methods for 

deplo ment and mainteiiance during its 

inten d ed period of operation. 

In terms of the mission need the Tactical 

Satellite System (TACSAT) is required to 

provide the services for tactical users over 

a relatively small region of maybe some 

1000 - 2000 km diameter. Also the 

concept is likely to involve relative1 short 

periods of operation of about i! to 6 

months for a typical operation scenario. 

The paper therefore addresses a system 

concept in which the emDhasis is placed 

on reducing the scale of the logistics 

involved in the deployment of TACSAT 

elements and simplifying the ground 

operations and facilities necessary for the 

users to - gain access to the services 

provided. 

The apcr will address a number of issues 

whic R arise such as: 

The need for 'launch on demand' 

I 

Tlie ossibility of launches being 

direct P y under the control of the area 

commander 

Operating concepts for TACSATs, 

comparing the approach of launch- 

via-residual-mass as part of a larger 

mission, not dedicated to the 

TACSAT mission with the approach 

of dcdicated, launch-on-demand. 

Identification of information flow 

requirements for TACSAT integrity 

and status evaluation and for 

surveillance data recovery 

6- 1 

- Determination of technical and cost 

B8;ivers inlfluencin the form and cost 

of ground instal f ation and logistic 

issues - Inteption of TACSAT facilities and 

services with other communications 

and surveillance systems available to 

the Tactical Commander 

- Investigation of techniques to 

mihimise the ground control and data 

collection overhead 

Introduction 

All TACSAT Systems are designed to 

provide a Tactical Commander with short 

term operational data in addition to that 

available via stratcgic resources. This 

paper discusses the interfaces between the 

space and ground segments of such 

systems. Because there is such variety 

amongst the various TACSAT systems 

concepts, it is on1 possible in a brief 

paper such as t h is, to discuss the 

roundhpace interface in general terms. 

hevertheless offering a eneralised 

structure around which s eci ic conce ts 

can be detailed is thoug R ' 

t to be use P ul, 

especially where the concepts are unlike 

those of other types of space system that 

designers may be more familiar with. The 

paper therefore focuses on TACSAT 

system concepts that are not like classical 

geosynchronous or sunsync h r o no us 

missions. 

Mission Definitions 

For tactical o erations any system 

em loyed must 73 e able to support the 

mo i ility re uirement and operate from 

unpreparei and unsurveyed sites. 

Communications in difficult terrain, such 

as mountainous regions, coupled with the 

need to co-ordinate ground, air and sea 

forces, presents a corn a lex array of tactical 

communication nee s and information 

exchange requirements in a variety of 

articularly for an extensive 

tactical t i eatre of operation. 

Tactical Imaging missions will be 

targetted on small, mobile platforms (eg 

aircraft and tanks) as well as Qther key 

targets (e bridges, harbours). Mu1 tiple 

sensors wi P 1 be most helpful in enetratin 

camoflage of these targets. 8 or Tactica f 

Communications Systems, voice and data

e 

communications, point to point, point to 

hultipoint and netted arrangements tray 

be all required. The End Usen may wsh 

to call upon any or all of these sewices at 

,my time. In the tactical situation the 

un p r e d i c t a b i li t y of the operation a 1 

environment dictates that 

communications must be instantly 

available, reliable and trustworthy (in 

terms of a low probability of detection), 

have a high robability of timely 

connection,l and i! ave an appropriate level 

of information security. 

It is evident that the introduction of 

complex procedures for terminal 

operation, access constraints and rul :s 

requiring a high degree of user skill to 

understand and implement will detract 

from the usefulness of the system as 

perceived by the tactical user comnunity. 

TACSAT systems can be classified as 

providing either image data derived from 

spaceborne sensors or relay 

communications channels between sites 

on the ground, or both. Classically these 

requirements are met by standardised 

systems architecture as follows: I 

Image Data - High resolution, 

Sun-synchronous, 

polar, circular 

- Geostationary 

Communications - Geosptionary . 

As has already been stated, it is not 

particularly useful here to analyse the 

@ ground/space interface within such 

architectures, beyond stating that 

TACSAT applications in similar 

architectures are possible, principally 

because of excess capacity becoming 

available for tactical purposes within 

strate@ systems. For example, "sparc:" 

capacity sometimes becomes available 

when a spacecraft suffers a partial failure 

and can no longer meet the full strategk 

-equirement. When it is replaced by a 

cw spacecraft of the standard design, the 

degraded s acccraft cm then be operated 

as a TA 8 SAT. In another case, a 

standardised design of geosynchronous 

satellite has been deployed to three (or 

more) stations in the geosynchronous arc 

to provide a global system but strate ic 

conimunications requirements on one or 

more) of the stations do not call for such a 

f 

large s acecraft. "Spark" trmponder(s) 

on suc B under-utilised strategic comsats 

can hen be o erated as a virtual 

TACSAT. Final P y, it is sometimes the 

case that "spare" launcher payload 

into polar orbit becomes 

availab e because spacecraft desi n 

constraints were too conservative for t % e 

actual lamchet performance achieved in 

a parallel development, and small 

TACSAPS can be launched into similar 

polar orbits with this spare capacity. Ln all 

these cases the ground/space interface is 

similar to, if not identical to, the parent 

system. In some further cases, very 

similar mission concepts are chosen for 

purely tactical reasons. However, ic 

general, different mission concepts tend 

to be favoured because of the tactical 

military requirements for TACSAT 

systems, for example: . 

Flexibility under unsophisticated, 

local control 

Low cost 

Minimum revisit times 

Localized area of interest 

Surprise 

Seciecy 

but, most of all, 

Ease of use. 

Other papers in this series illustrate 

instances of this tendency. Here, a typical 

"novel TACSAT" mission may be 

sunimarised as: 

Intermediate orbit inclination, 

optlmised for target area coverage. 

Low altitude, for maximum resolution 

and/or link margins. 

Elliptical orbit, minimising 

geodymnic drag. 

1 iCHigRly manoeuvrable spacecraft to 

mbntam orbit alignment with respect 

+ 

to the target area. 

Pre-programmed payload operation.

&ring the full novel TACSAT mission 

there will be the following, distinctly 

different, phases of operation. 

hunch Preparation Phase 

It is possible that there will be a choice of 

Launch Vehicle configuration. For each, 

there will be a complex trade-off betweed 

orbit parameters (especially orbit 

inclination), payload mass (oat 

functionalit and tar et area revisit 

periodicity. t ere iwill s so be a compled 

trade-off for the phasing of any particular 

orbit beweeh spacecraft constraints (e 

sun angle at injection), operationa 

coverage requirements and spacecraft fuel 

launches, ;is to the nature of the intended 

tactical support, especially phasing over 

t k target area. Finally, there may be a 

requirement to defend the TACSAT 

system against jamming. 

The trade-offs must be resolved and the 

1 au n c h e rl sp a ce cr aft c o n f ig u r a t i o n 

finalised (including programming of 

on-board computers) early In the Tactical 

Deployment when the Tactical Staff will 

have many other pressures to finalise 

deployment plans and logistic sup ort. 

However, since it cannot be assume B that 

these staff will be familiar with spacecraft 

operational constraints and speedy 

decision making may be of the essence, 

0 previous in-depth training in system 

operation will be a pre-requisite of 

successful TACSAT operations. 

Launch and Early Operations (LEOPS) 

Phrase 

Launch services would be provided by a 

specialist supplier requiring minimum 

interaction wth the Tactical IJsers. The 

boosted ascent and spacecraft separation 

will be pre-pro rammed. However, 

determination o B the initial orbit by 

ranging during first apogee will be 

necessary frord appropriately located and 

equipped ground stations. Note that the 

spacecraft ranging transponders may well 

need to be rotected by encxypters from 

ranging, an B /or from jamming, by enemy 

ground stations; hence digital ranging, 

9 

mi'itar 

6-3 

staff and cypher distribution 

channe s Will be preferred. For accurate 

early 'orbit determination, these ran 

stauons would be on a long (> 10o0 

baseline and must pass ranging data sets 

by communications links to a Central 

Control facility equi ped to compute the 

initial orbit. It wi P 1 be convenient to 

arrange €or this Centre to also compute 

necessary manoeuvres, predict the 

subse uent orbit evolution and, most 

proba 8 ly, execute the manoeuvre 

sequence in a manner consistent with any 

requirements for payload deployment/ 

activatiodcalibration. To effect the 

manoeuvre/activation sequence, Trackin , 

Telemetry and Command (TT and 8 ) 

access would have to be provided via 

several, well-distributed Ground Stations 

if this phase is to be completed with 

minimum delay. In short, this entire 

hase could be under the control of the 

Lunch site, rovided with support from a 

network of appropriately equipped 

Ground Stations. 

However, in view of the military 

sensitivity of TACSAT missions, it is 

more likely that all Ranging, Telemetry, 

Manoeuvre Computation and 

Telecommand functions would be 

exercised by a suitably equipped and 

military-staffed Facility. For reasons of 

compatibility with Launch Site and 

back-up orbital support, TT and C 

functions could be conducted at S-Band 

usin the Space Ground Link System 

(SGh standard, but with encryption 

enabled shortly after successful injection 

into initial orbit. Ranging, Telerne 

Telecommand functions coul 

exercised by a 19 m S-Band Telemetry & 

Command Station (TCS , supplemented 

by relative1 small (3 m) b -Band terminals 

co-locate dy with selected permanent 

Ground Stations. Alternatively, the entire 

TT and C support could be exercised 

within the X-Band channel allocations for 

Milsatcorn and Earth Resource Downlink 

channels. In either case, TT and C 

baseband connectivity durin the periods 

of TACSAT visibility must %e provided, 

:. for example via orderwire channels 

'.* within permanent communications 

. accesses. 

7 7: 

*

(i-4 

TACSAT Operations Phase 

The TACSAT system is seen n phis paper 

as supplementin strategic C P rcsources, 

particularly w a ere communications 

requirements peak or imaging data are 

needed at short noiice. The oppoflunities 

to use TACSATS to best effect can 

thereforc only be recognised locally arid 

should put into effect by a local Control 

Centre. 

The Control Centre must be able to assess 

the effects of orbital manoeuvres, execd te 

manoeuvre$ romptly aild quickly corafiim 

the achieve. B new orbit. As has already 

been said, speedy and accurate orbiit 

determination can only be achieved with 

long, ie out-of-Theatre, baselines. 

Certainly for imaging missions, perigee 

will be over the tactical theatre; for 

communications missions this may also be 

true. 

The out-of-Theatre character of the 

control function for some missions is 

reinforced by the need to manoeuvre near 

apogee, where manoeuvre fuel usage is 

minimised and visibility to ground stations 

is maximised. The Control Centre may 

also have to call on spacecraft equipment 

designers and test configurations to 

resolve spacecraft performance 

anomalies. All of this tends to suggest 

that the res onsibility for TACSAT 

Control coul B be assigned to a Military 

S acecraft Control Centre supported byfa 

P 

gobal 

tracking network but with rdn 

excellent co-ordination interface t,o 

in-Theatre tactical operations staff. This 

latter requirement could be met b 

assignment of several specialists (wii. l 

recent spacecraft o erations experience) 

to provide a 24- R our service at the 

Tactical HQ. The Conuol Centre used 

during the earlier Phases could be used ta 

execute spacecraft control. However, a 

knowledge-based system located 

in-Theatre is likely to provide faster 

response and more consistent operations, 

This could be automated to minimise the 

number of operations staff and provide 

consistency during 24-hour operations. It 

would consist of the following elemcnts: 

Automated Mission Builds timeline 

Planning options 

Automated Library of Flight 

Operations Control Plans, 

Planning including Anomaly 

Contingency Plans. 

Computer Assisted Executes actual 

Operations control via Tracking 

Stations. 

Adaptive Training Creates and 

evalua: zs training 

sessions. 

Network Control is also required in the 

case of a TACSAT communications 

mission. It can be assumed that the 

communications transponder will be 

accessed only by in-Theatre force 

elements, using locally-assigned cyphers. 

In order to provide communications 

services compatible with the needs of 

tactical End Users, the way in which the 

network is managed and user access is 

granted and controlled must involve a 

minimum of "overhead" workload 

imposed on the End User. This can ran e 

from avoiding the need to point t a e 

antenna on his terminal 

simplicity of operation o 

to a mem of 

in the integrity of the system, and to its 

ability to provide the services required. 

Optimum use of the TACSAT capacity 

will be most easily achieved by a mture 

of frequency assignment and timeline 

planning issued by in-Theatre signals 

staff. Some tyges of TACSAT 

store-and-forwar communications 

mission will require quite complex 

space/ground protocols which must be 

transparent to the End User. Some 

classes of TACSAT will provide ima er 

or transponder configuration options t P iat 

are selectable by ground command. The 

in-p eatre specialist TACSAT operations 

staff will be best equipped to make the 

appropriate option selections, which could 

be implemented either by a local 

telecommand uplink or by a centralised 

Control Centre. In the case of in-Theatre 

jamming attacks, the former is likely to 

provide a far more successful ECCM 

response than the latter, provided it can 

counter any enemy jamming of the 

telecommmd uplink. 

The final stage of the TACSAT support 

will he disposal of the s acecraft, either 

into 3 higher parking or E it or a burn-up 

during re-entry. Once the in-Theme

authorities have confirmed that TACSAT 

support is no longer re Kired, they need 

have no further invo 9 vement in thc 

manoeuvre se uence. At this sta ’z 

eiecution an1 monitoring of t g : 

TACSAT disposal could be turned over 

to a central Control Centre. 

&)a 4a Coalectiow 

Modem spaceborne imagers produce very 

wide bandwidth data rates which qbickly 

saturate available spaceborne storage 

devices. Hence direct-to-Theatre 

downlinking is very attractk: for small 

TACSAT missions where data timeliness 

is of the essence. These dbwnlinks must, 

for obvious reasons, b,e encrypted. 

Because of the very high burst rates, 

spread spectrum downlink jamming 

rotcction is not practicdble; the on1 

F easible rotcction methods are Doiinlin 

User Xrrninal (DUT) location and 

minimisation of DUT antenna sidelobes. 

Some on-board storage buffers would 

allow greater flexibilitv in the deplo inent, 

and reduce the numbers, of in- -ay 

heatre 

DUTs. These DUTs must be connected 

by telecommunications links of various 

kinds to End Users. On-board 

preprocessing can be used to reduce the 

downlink bandwidth and reduce the 

complexity of the in-Theatre image 

processinf Sfunctions. However, some 

on-groun rocessing, including fusion 

with other ata sets, will be an essential 

element of the image assessment chain. 

In the reverse direction, the flow of 

information from the End Users €or target 

selection must conver e on at least one 

Telecommand Uplink B acility. Instrument 

settling times dictate that, for efficient use 

during each perigee, these telecomrnands 

must be uplinked out-of-Theatre during 

apogee. 

Simulation 

From the above discussion it is clear that 

deployment of a TACSAT system is a 

complex undertaking requiring 

well-trained operators and well-briefed 

operations stxff. AlthouFh the classic 

military process of reducing complcxity 

down to the minimum number of 

l 

6-5 

adequate operations and planning tools. 

Both must depend on comprehensive 

mission simulations for the Launch 

Preparation and TACSAT Operations 

Phases. 

Conclusion 

Clasically, Tactical Commanders have 

succeeded where they have made best use 

of the time available before tactical 

However considerable expertise is 

re uired to o erate any Satellite system 

an 1 any TAC k) AT Mission is likely to fail 

unless an adequate control system is 

created and worked up to a hi state of 

readiness before the Tactica P situation 

develops. An automated knowledgebased 

system, including ap ropriate 

simulation, will be essential to t 1 e success 

of TACSAT support, which in turn is 

likely to be decisive on future tactical 

battlefields. 

STATEMENT OF RESPONSIBILTY 

Any views ex ressed are those of the 

author(s) and B o not necessarily represent 

those of MM Government.

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9

TACSAT-SPACECRAFT BUS CONCEPT AND DESIGN: 

APPLICATION OF A MULTIMISSION BUS FOR TACSAT IN LEO 

FROM A FEW LARGE SOPHISTICATED 

SATELLITES ... 

Bcforc describing thc way, a low carth orbit 

multimission Bus for tactic;rl application is 

dcsigncd, it is convcnicnt t,u ;in;ilysc in soti'c 

dctails w1i;it is a tactical s;itcllitc ns far as sur h 

satcllitcs arc vcry oftcn associated with tlic 

notion of chcap sniall satcllitcs. 

For 30 yc;irs tlic six, thc ni;iss. the coniplcxity, 

and the cost of thc satcllitcs haw hrcn 

incrcasing. Spacc prograninics, cspccially in tlic 

dclcncc arca, tend to usc hcavy ancl costly 

satcllitcs in a too small nunibcr of spccinicns 

comparcd with thc nccds of uscrs, thcy havc 

thcn to continuously monitor priority conflicts 

such as : budgctary conflicts to dccidc which 

programnic has priori!y, opcratioii;d usc 

conflicts whcn programming tlic niissinns of so 

Tcw spacccrafts. 

In thc tnday contcxt of budgctary coiistr:iints, 

raising again is thc wcll known syndrome "oiic 

aircraft, onc tank, onc satellite as uniquc fu!urc 

-equip ni c n t for dc fc n cc'. 

Thc spacccrafis number liniitation is thc 

conscqucncc of an inflationist spiral which can 

bc dcscribcd in lhrcc stages : 

a - unit cost incrcascs 

by 

Gcorges Richard 

Matra Marconi 

Espacc/Dircction dcs Programmes Militaires 

2.1. du Palays-RUC des Cosmonautcs 

I 

31077 Toulousc 

Frnncc 

b - thcn for a givcn budget, numbcr of 

opcrational units dccrcascs 

c - a lirnitcd number of spacccrafts lcads to 

pusch for mission optimitation with : 

- an incrcasc of in orbit lifc timc and rcliability 

rcquircnlcnts 

- tlir nccd lo group scvcral niissions on thc 

S;I 111 c spa cc c ra ft. 

- kxIini:*al sophistication 

- conscrvativc approach includiiig rncticulous 

:l~:vclopmcnt and compicx vcrifications 

- no risk approach, as thc unit cost of cach 

satcllitc is such a high stakc 

All thcsc points lcad to unit cost incrcasc and 

\)ring back to st;igc n iii tlic iiifl;itionist spiral. 

... TO CONSTELLATIONS OF NUMEROUS 

CIIEAP LIGIITSATS 

To brcak this spiral, somc cxpcrts sugcst a 

"Smart small clicap lightsats" conccpt. Thcir 

main idca is to drastically dccrcasc thc unit cost 

of thc spacccraft in orbit, this cost including thc 

satcllitc recurring cost itsclf, (hc launch cost and 

thc ground scgnicnt and opcrations costs. 

This conccp! is consistcnt with a system 

archi~cctiirc using constcllations of nunicrous 

satcllitcs oC liniitcd in orbit lifc timc and low

(1-2 

rcliabiliry pcrfornianccs, both of thcsc 

cliaractcristics should, in thcory, rcwcc strongly 

tlic recurring costs of 11ic spacccrafls. 

Such a conccpt is rcinforccd by advances in 

technology in the ficlds of pcrformances ;knd 

miniaturisation : thcsc advances arc madc 

possiblc by thc research and dcvclopmcnt 

programmcs led by DARPA and SDIO,thb.:sc 

prograinmcs arc also bascd on hrgh 

tcchnologics dcvcloppcd ogt of the spatial arca. 

For cxamplc : 

- digital computcrs 

- mass mcmory 

- ASIC with availability of dcdicatcd algorithmcs 

for digital proccssing 

- siliciuin and Ga As microclcctronics facilities 

whcrc heavy invcstmcnts for civilian or niilir:iry 

airborne applications givc new opportunitics To. 

spacc applications such as : optical detectors, 

radiofrcqucncy MIMIC which arc usuful to 

dcnign phasc nrray antennas for comiiiunication 

satcllitcs or synthctic apcrturc radar 

instruments. 

- ctc ... 

Tlic potcnlial advantagcs of such a 'Smarl small 

chcap lightsats' conccpt arc wry attractive for 

thc uscrs, this is particulary truc for tactical 

applications in low earth orbit : 

- rcpctilivity of thc passes 

- flcxibility in the ch.ricr nf I' A' nctcrs 

- share of risks 0' ~ 

; 

I 

L' inch spacccraft and 

lower vulncrability of thc overall system 

- flcxihility in the way to usc thc systcm. In orbit 

mcam arc fittcd with the lcvcl of crisis with a 

continuum from stratcgic usc to tactical hsc 

- dedicated satcllitc for a givcn mission 

- salcllitc programing and usc dcccntralizcd to 

on the ficld theatcr uscrs 

- etc ... (list not cxhaustive) 

At this point we will not discuss if such a 

conccpt is technically rclcvant in fulfiling the 

rcquircmcnts of a pivcn sct of missions. 

. . 

I-lowcvcr, with thc payload bccing shared 

bctwcen a large number of small satcllitcs, we 

can assume that the total in orbit mass of thcsc 

satcllitcs to fulfil a mission would be obviously 

larger than thc total mass whcn the classical 

approach using hcavy satellites is followed : 

grouping differcnt payloads on a single satcllitc 

always sakes iilass. 

As a conscqucnce, a "Sinart small chcap 

lightsats" approach using sa!ellilcs with an in 

orbit lifc time 5 to 10 timcs shortcr than in a 

classical approach lcads to place in orbit a total 

nuss morc lhan tcn times hcavicr than tlic total 

mass ncctssary to fulfil the same mission on a 

big salcllilc. 

For a niission on a givcn pcriod of tirnc Fig. 1 

shows thc cvolution of thc Iau.nch cost and 

satcllitcs costs with rcspcct to thc largcltcd in 

orbit life tinic for c;ich satcllitc of tlic 

constellation. 

For a consmt launch unit cost, thc lotal launch 

cost (curvc 1) is thc invcrsc ratio of thc in orbit 

lifc timc. 

Thc satcllitcs total cost (curvc 2) is cocsistcnt 

with thc "Smart small chcap liglitsats" 

approach : whcn thc in orbit life timc dccrcascs, 

you savc more nioncy from thc satcllitcs unit 

cost dccrcasc than you loosc from thc incrcasc 

in the nuniber of rcquircd satcllitcs, thc nct 

rcsult is that thc 'otal cost decrcascs. (this 

conclusiolr is less valid for a vcry long in orbit 

life timc ind is no morc valid for a vcry short 

onc). 

With ;I launch unit cost of thc siimc ordcr of 

magnitudc than cach satcllitc unit cost (curves 

in contitiuous liiic) tlic overall cost (ciirvc 3) 

dccrciiws whcn lifc in orbit incrcascs. At 

cvidcnce thc opt,imum is to improvc thc 

reliability and thc in orbit lifc timc: it is thc 

present trend. 

A "Smart small chcap lightsats' approach would

only bccomc pcrtincnt if vcry cheap launch costs 

arc prolmcd'(curvcs in dottcd linc). 

A coI~,ciit way to dccrcasc thc launch costs is 

to aim for a "Smart small chcap lightl:iuncher" 

conccpt cutting dowii thc launc'r cost for a Kg in 

orbit by at lcast ten times. 

Unfortunatcly the cost pcr Kg in orbit for 

prcscnt or near tcrni heavy launchcrs is vcry far 

from this goal, lor -::;:ill launchers of the 

PEGASUS class with a cost der Ky 2 lo 3 tinics 

grcatcr than thc onc ofthc ARIANE V/TITAN 

class hcavy launchcrs it hccomcs niorc and 

niorc difficult to achicvc. 

A WISER API'ROACII I 

With the krck of cmcrgcncc of vcry cheap 

launchers, constellations of nunicrous clicap 

lightsats with short in orbit life tiiiic arc neither 

for thc short tcrm nor for the medium term. 

To opcn thc way io ncw missions -cspccially in 

thc lactical arca - thc only drivini; lorcc of 

intercst is, for a givcn mission, a niodcr:itc 

overall cost, consistent willi the pcrloriiianccs 

offered for a sct of sufficiently high priority 

o!)jcctivcc. 

In other words. tlir today raising of 

tcchnological t~rc;ikthrough i ri 1)crli)rni;incc aiid 

miniaturisation will tx used in two ways IO : , 

I - enhance again tlic prcscnt performances cif 

1argc s;itcllitcs which will rcni;iin hc;ivy and 

sophisticatcd. This i,. iypically the c;isc in 1lic 

rcconnaissancc field wlicrc users pt!t 

coiitinously morc slringcnt rcquircmc its. 

2 - opcn thc door to ncw missions, able io satis-.y 

ccoiioniically new nccds through the usc of 

spatial means. New missions types will he 

offered wliilc reducing tlic mass, the sizc and 

I 

the overall cost ol satcllitc in orbit. This appears 

cspccially pertinent for tactical missions. 

CONSEQUENCES FOR THE BUS DESIGN 

Due to thc rcduccd number of satcllitcs for a 

givcn application, the reduction of the 

spacccrafi rccurrcnt unit cost is no morc the key 

clcmcnt to rcducc the ovcrall cosl.Thc cost 

rsduction has to be niorc focusscd on its non 

rcccuring part than on tlic recurring onc. 

As a conscqucncc, mass production savings will 

not bc eniricd from only onc mission, hut will 

have to bc gained from a multimission 

approach. 

I'issuiiiing that thc small satcllitcs potential 

ap,;!ic;rtiw~s arc not aimed at rc~lacing thc 

prcscnt hcavy nnd complex satcllitcs systems, 

thc overall pcrformanccs rcquircd from the 

spacccraft BUS would bc modcratc. This is vcry 

convenient with a modular multimission BUS 

coiiccpt hascd on : 

- stand;ird pay1o;id iiitcrkiccs 

- oversized rcssourccs for each nic..iulc (for C;ISC 

tlic sake of LI gc!od standardizat;,m) 

- llci!dc xcoiiiwkition of the diffcrcnt modu;.~ 

on tlic BUS allowing on request i:iodulcs 

addition 

Fig. 2 shows thi. niudular multimission BUS 

concept ilcsigncci jcintly I; MATRA 

MARCONI SPACE and its north ;inicrican 

prtncr FAIRCI.1 ILD. 

In order to rcacli somc non recurrent cost mass 

production savings through scvcral applications , 

it is possililc to add tu this modular ap1)ro:ich a 

ncw dcvclapnicnt plan concept based on 

concurrent cnginccring. 

Fig 3 smws the logic of SYSTEhlA . 

SYS'l'EblA is a concurrent cnginccring salcllitc 

dcsign tool dcvcloppcd by hlATRA MARCONI 

SPACE. AI thc center a comn-im data hsc 

contains Ihc current configural, n cif 1hC 

sa(c1litc hccing dcsigncd. At tlic periphery 

A-3

0 

8-4 

specific tools for each main arcas of cngincering 

design arc shown. They can be concurredy call 

on demand by the different experts working in 

parallel for trade off or validation on diflcrent 

fields : clcctrical, thermal, mechanical , orbit 

environment, attitudc and orbit contrbl, 

dynamic , propulsion, payload accomodatidn, 

mission; satellite programmation, ctc ... 

i 

Presently, SYSTEMA is uscd primarily in thc 

first part of the developmcnt process (fig 4). 

from phase A proposals, mission and s.\tclli!c 

layout tradc-offs to the end of ph?, * L with 

dctailcd satellite design optimisation . VI' up to 

proposals for a phase C activity. I 

If additional risks causcd by eventual flaws rjr 

bugs in numerical simulations arc acccptcd - 

these risks arc assumed to bc affordable far 

small tactical satellites with not vcly 

sophisticatcd missions -, phase C validation tjy 

mcans of such concurrcnt engiiieering only tools 

would saw not only thc major portion of the 

environmcntal tcsts costs (thcrmal, kacuum. suh, 

vibrations) but also would rcducc thc schcdulc 

induced costs. 

Such an approach has dcmonstratcd its 

cfficicncy through thc SSOT prograinmc (fig 5). 

S80T is a microsatellite launchcd this sunimcr 

as a conipanion of TOPEX - POSEIDON 

SPACFCRAR on ARIANE. SSOT has 

bcncfitcd from an intcnsivc use of SYSTEMA 

from thc first stage of dcsign to the dclivcry ;it 

the launch sitc. A programme conducted in a 

very short timc for a very competitive cost. 

I CONCLUSION 1 

The approch prcscnted above is far from a 

rcvolution. It is only an evolution. 

To be efficient suck concurrcnt engineering 

tools need to be validatcd and calibrated by 

refcrcncc to the data gathered during previous 

dcvclopmenl tcsts or during in orbit monitoring 

of opcrational spacccrarts. In that sense such an 

approach capitaliscs the whole cxpcrience 

acquircd by MATRA MARCONI SPACE 

through prcvious or currcnt low earth orbit 

programmes : SPOT 1,2,3 - ERS 1 and 2, 

HELIOS - SPOT 4 and Polar Platform. 

The SYSTEM\ usc built-in flexibility givcs thc 

opportunity to quickly update a current design 

and thus allows to follow cvolutions of 

technologics or accomodatc a newly availablc 

equipmcnt. 

SYSTEMA ;~llows a short rcaction timc and a 

quick acconiodntion on the satcllitc as soon as 

cmcrging rcquircmcnts arc formulated by the 

uscrs. 

~ll~iisimiiotts 

Jw rhis Seciion appear immediaiely 

afim ilte Fmrc~lt mnshiion.) 

i.

'DES CROS SATELLITES EN NOMIIRE 

LIMITE. .. 

Avant d'ahordcr la facon dc concevoir unc 

platc-formc multimission pour ' c~cs 

applications tiictiqucs cn orbitc bassc, il cst 

utilc d'analyscr de plus pr2s la notion dc 

satcllitcs tactiqucs qui cst souvcnt :issociCc 

aujourd'hui Q I'idCe dc pctits satcllitcs pas 

chcrs. 

I 

Dcpuis 30 ans on constatc que la t;iillc, la 

miissc, la complcxitf CI donc IC coilt des 

satcllitcs croisscnt. Lcs progrmnics spaliaux 

ct plus particulithcrncnt dms IC dorli;iinc de la 

dtfcnsc tcndcnt 3 utiliscr dcs s;itclli(cs lourtls 

ct codtcux cn nombrc jug6 nfccssaircmcnt 

trop limitc par dcs utilisatcurs qui rlaivcnt 

gfrcr cn pcrmancncc dcs conflits de priorilt : 

conflits hudgCtaircs pour clfcitlcr qucl 

programnic mcncr cn prioritf m:iic aussi 

conflits dc priorit6 cn utilis;ilkin 

opfrationncllc pour progriinimcr I'cniploi des 

moyciis. 

Dans IC contcxtc actucl des compressions 

budgftaircs on voit ainsi rcnaitrc IC synrlromc 

bicn connu 1 AVION 1 CHAR 1 

SATELLITE conimc sculc dotation A tcrrnc 

pour la dCfcnsc. 

Cettc limitation du nonbrc dc satcllitcs est la 

consfqucnce d'une spiralc inflationnistc que 

I'on peut dfcrire en trois ftapcs : 

a - augmcntation du cocit unitaire 

b - B budget 4-onstant diminution du nombrc 

d'excmplaires oiifrationncls 

c - B faiblc nombre d'excmplaires optimisation 

de la mission : i 

. rechcrchc d'une grandc durCe de vie ct d'unc 

haute fiabilitt 

I 

l 

I 

. rcgroupcment de plusicurs missions sur une 

SCUI satciiitc 

. complcxification tcchnique 

. mtthodcs de dtvcloppcmcnt conscrvatriccs A 

basc dc vCrifications complcxcs ct minuticuscs 

. rcfus de pccndrc des risqucs dcvant I'enjcu 

quc rcpttscntc IC coot unitairc dc chaque 

salcl lite 

cc qui cntrainc I'augmcntation du codt 

unilairc ct nous ramenc au p int "a " ... ctc 

... AUX CONSTELLA'I'IONS DE PETITS 

SATELLITES HON kIAHCtiE 

Pour sortir dc ccttc spiralc ccrtains proposcnt 

unc appr:,chc "Smart sniall chcap lightstats" 

dont la caractfristiquc csscnticllc cst de 

diminucr t1r;istiqucmcnt IC colit unitairc du 

satellite cn orbitc, cc cott comprcnant IC co3t 

rtcurrcnt du satellite, IC cocit du lanccnicnt, IC 

codt du mainticn rl poste par IC ccntrc de 

contrblc. 

Ccttc approchc cst cohCrcntc avcc une 

architecture systemc basCc sur des 

constellations dc nombreux satcllitcs dont la 

durCc dc vic cn orbitc cst lirnitfc ct dont la 

fiabilitC pcut Stre plus faiblc (droit A la 

pannc), ce qui cn thforic pcrmct de rfduirc 

fortcmcnt Ics coats rfcurrcnts des satcllitcs. 

Unc tcllc approchc sc trouve confortfc par Ics 

avancCcs technologiqucs en pcrformanccs cl 

miniatiirisation qui alimcntcnt aujourd'hui le 

spatial au travcrs des programmes de 

Rcchcrchc et Dfvcloppcmcnt mcnfs par la 

DARPA ou la SDIO, mais Cgalcment par 

syncrgie avcc !a haute technologic dfvcloppCc 

pour dcs applications autrcs quc spatialcs. 

Citons : 

- IC domainc du calcul digital 

8-5

0 

0

0 

0 

- les mtmoires de massc 

.. les ASIC de traitements numtriqucs avec la 

' dkponibilitd d'algorithmes sptcialisfs 

- le domaine des fonderies silicium ou As Ga 

OD dcs invcstissements trts lourds rent.abilisc?s 

par des applications civiles ou par I'aVior~quc 

militaire offrent au dnmaine spatial soit dcs 

dttcctcurs optiques soit les MIMIC 

nbcessaires pour les antennes reseaux d;:s 

satellites de communication et les radars A 

ouverture synthttique 

- etc.. 

Les avantages potentiels de cette approche 

"Smart small cheap lights;lts"sont alltchants 

pour l'utilisatcur, particuliCremcnt dans le 

domainc tactiquc sur des orbites basses P 

dtfilcmcnt : 

- rtpttitivitt des passages 

- souplesse on choix des paramttrcs dcs 

orbites 

- rtpartition dcs risqucs unitaires dc pcrtc dc 

chaquc satellite et donc moindrc vulntrabilitt 

- !ouplesse d'cmploi : on ajustc scs moycns en 

orbite A I'ttat dc crisc, cc qui pcrmct un 

passagc continu de L'emploi strattgiquc B 

I'emploi tactiquc 

. - sptcialisation des satcllites 'par missiod 

- d~centralisation de la programmatiorl et dc 

I'utilisation du satellite sur IC terrain ! 

- etc ... cette Iiste n'ttant pas exhaustive. 

Sans discuter ici la pertinence technique de 

cetle approchc pour satisfairc Ics 

performances des diverscs missions, on peut 

prtdire que IC fait de rtpartir la charge utilc 

sur un grand nombrc de satcllitcs fcra quc la 

masse totale en orbitc 'des satcllitcs 

optrationncls A un moment dolint sera 

certaincment suptrieure B cclle de I'approche 

classiquc par gros satellite. On a toujours une 

prime en masse pour le regroupcmcnt des 

charges ut ilcs. I 

I 

Avec dcs durtcs de vie de 5 10 fois plur 

courtes il faudra donc s'attcndrc avcc unc: 

approchc de type "Smart small cheap lightsats" 

A lancer une mase globale plus dc 10 fois 

suptrieure pour remplir une mission sur une 

durte dtterminte 

Pour une mission de dude donnte, on a 

reprfsentt ( figure 1 -courbe 1 ) I'tvolution en 

fonction de !a durte de vie de chaque satellite 

du coirt dc I'ensemble des lancements. La 

courbc 2 presente tgalement I'tvolution du 

cost de I'ensemble des satellites (coots 

rtcurrents). 

A coOt unitaire constant, le c6ut total des 

lanccments (courbc 1) est inverscmcnt 

proportionnel A la durtc dc vie. 

L'tvolution du c6ut total des satellites (courbe 

2) rcflCte I'effet escomptt de I'approche 

"Smart small cheap lightsats" : quand la duree 

de vie diminuc, IC gain dc coot unitaire 

compcnse largement I'augmcntation du 

nombre dc salcllites nCcessaircs et IC coiit 

global dccroit (cct cffct n'ftant plus vrai pur 

dcs durtes dc vic trts trts courtc ct 

s'atttnuant pour des durtes de vic longucs). 

Pour dcs cotts dc lanccment de I'ordre de 

grandcur des coots satcllitcs (courbcs en traits 

pleins) IC coot total (courbe 3) dfcroit au fur 

ct B mcsurc que la durte de vie. s'allonge. 

L'optimum est A I'tvidence d'amtliorcr la 

fiabilitt et la durte de vie : c'est la tcndancc 

actuelle. 

Pour quc I'approche "Smart small chcap 

lightsats' dzvienne cfficace, il faudrait que Ics 

coirts unitaires de lancement devienncnt 

beaucoup plus faiblcs (courbes en pointillt). 

Pour rtduirc dc facon cohtrente Ics coils de 

lanccmcnt il faudrait donc une approchc 

"Smart small cheap lightlaunchers" reduisant 

au moins par 10 IC coot du kilogramme lanct. 

Malheureusement lcs coiits du kilogramme en 

orbitc pour les lanceurs actuels ou en projct 

sont trEs loin de cet objectif et on s'cn Cloignc 

d'autant plus quc I'on clicrche A utiliscr dcs 

petits lanccurs de la classe PEGASUS qui

affichent un coot au kilo de 2 a 3 fois 

supCrieur 3 celui des trts gros lanccurs de la 

classe ARIANE V ou TITAN. 

UNE APPROCHE PLUS RAISOWNAQ1LE 1 

Fautr: de. voir Cmerger des lanccurs B trts 1 

coat, Ics constellations de nombrcux pi III 

satellites pas chers B faible durCe dc vie iic 

sont ni pour le court ni pour IC moyen tcrr . 

Lc seul critbe ite!!ement dimcntionnant pour 

voir Cmcrger de nouvellcs mission5 e,t 

particulitrcmcnt dans le domaine tactiqub 

sera plus ccrtaincmcnt d’avoir un coirt global 

de possession raisonnablc pour des 

pcrformanccs jugees suffisarrnicnt prioritaircs 

Dit cncore autrcmcnt, Ics avanctes 

technologiqucs en pcrformancc et 

miniaturisation que I’on voit poindrk 

aujourd’hui pousscnt dans deux voics : 

I 

I 

- P mfliorer encore Ics pcrformanccs actucllcs 

dcs gros satcllilcs qui rcstcront lourds cl 

complcxcs. C’cst typiqucnicnt IC domainc ob 

ICS bcsoins cxprimes par ICS utilisateurs vont 

toujours croissant. Par excmnilc la 

reconnaissance. 1 

- Ouvrir la voic vers de nouvcllcs missions 

pour salisfairc Cconomiquement de nouveaux 

besoins au moycn de systhcs spatiaux, cd 

offrant dcs performances nouvcllcs Ict cri 

rfduisant la massc, la taillc et donc IC dofit dr! 

posscssion en orbitc d’un satellite. Ccri csl 

particuli2rcmcnt pertincnt pour de!; 

applications tactiqucs. 

1 

CONSEQUENCES SUR LA CONCEITION 

DES PLATES-FORMES 

Comptc tcnu du nombre ntccssaicmcnt rCduit 

dc satellitcs pour unc application, la rfduction 

do coCt unitairc recurrent n’est plus I’fICment 

clef pour rfduire le cott global. L’effort de 

,I, I. 

reduction des coilts doit porter plus sur le non 

rtcurrcnt quc sur le rtcurrent. 

En corollaire, I’effct de sCrie n’etant plus 

suffisant sur une seule mission, Ies rtductions 

de coCt lites au effets d’tchelle doivent 

s’obtenir en jouant sur I’aspect multimission. 

Au plan des performances, dans la mesure oh 

Ics applications erlvisagtes sur petits satellites 

n’suront pas la prftention de remplacer les 

systtnrcs actusls utilisant des satellites lourds 

et complexes, I’enveloppe des performances 

dcmandtes B la plate-forme doit &tre plus 

modCrCe. Ceci rend particulitremcnt 

pcrtincnte une approche modulaire mettant en 

oeuvre : 

- des interfaces standards avec la charge utile 

- une surabondance des rcssources pour 

chaquc module autorisant une bonnc 

standardisation 

- un amCnagcmcnt souple favorisant I’ajout de 

modules compltmentaires, a la dcmande. 

Ccttc approche modulaire est reprksentte 

typiqucmcnt par les concepts dc BUS 

MULTIMISSION Ctudifs conjointcincnt par 

MATRA MARCON1 SPACE c,t iiotrc 

partcnaire nord amtricain FAIRCHILD 

(figure 2). 

Toujours,dans IC but de rechercher un effct 

d’Cchelle cntrc plusieurs applications pour 

rCduirc les coirts non rCcurrents, il y a licu 

d’adjoindre B cettc approche modulaire une 

nouvcllc conccption du plan de 

dkvcloppcmento baste sur une ingenicrie 

intCgrCe. 

La figure 3 prtsentc la logiquc de I’outil 

SYSTEMA utilis6 B MATRA MARCONI 

SPACE en ingenieric satellite. 

Autour d’une base de donnCe decrivant la 

configuration courante’ du satellite ttudiC, un

I 

I) 

U-8 

certain nombre d’outils sptcifiqucs pcrmcttcnt 

dc mcncr lcs etudes d’ingcnicric dc facon 

inttgrte dans lcs grands domainrs clnssiqucs 

dans la conccption de satcllitcs : unalyscs 

tlectriqucs, thermiqucs, mfcaniqucs , 

J’cnvironncmcnt en orbitc, bontrdles 

d’attitudc et dynamiquc, propulsion, 

implantation dcs chargcs utilcs, analysc , de 

mission, programmation, ctc... 

Aujourd’hui, figure 4, ccs types d’ouiils 

d’hgcnicric inttgrte sont uti1if;ts 

principalcmcnt dans la prcmiErc pabtic d’)n 

dtvcloppcment depuis la proposition, Ics trdde 

off mission, la phase A , Ics coinprohis 

d’amdnagcmcnt jusqu’a la phase @ ct ICs 

optimisations fincs de la configuration. 

Pour rtduire cncore ICS coots non rCcurrcrIts, 

ct A condition d’admcttrc lcs risqdcs 

compltmcntaircs d’impcrfcction d’unc 

simulation numtrique - risqucs acccptablcs 

pour des applications pas trop complcxcs dc 

pctils sarcllitcs tactiqucs - la validation par 

simulation dc la configuration en utiIis.int 

I’outil en phase C dcvrait pcrmcttrc de rtdulrc 

cncorc Ires fortemcnt non sculcmcnl IC coot 

dcs cssais globaux (vide-solcil, rntcaniqdc, 

dynamiquc ...) mais surtout Ics tcmps dc 

d~vclop~icmcnt. 

Cettc apprcchc a dCj3 416 tcsttc avcc succes 

au travcrs de S8OT (figurc 5) microsatcllitc 

IancC A I’CtC 92 cn compagnon du salcllitc 

TOPEX POSEIDON par , ARIANE. 

L‘utilisation intcnsivc de S YSTEd dcpuis la 

i 

phase de conception jusqu’a la fin du 

dtvcloppcmcnt a permis de mcner ce 

ptogrammc a bon terme en trts peu de temps 

et pour un coot trts attractif. 

I CONCLUSION^ 

L‘approche prtscntte ici est loin d’Etre unc 

rtvoiution, c’cst sculcment une tvolution . 

Elk capitalise au travcrs des outils 

d’ingcnicrie inttgrtc tout I’acquit dei platcs- 

formes multimission dCvcloppCes par MMS au 

travcrs dcs programmes SPOT 1, 2, 3; ERS 1 ’’ 

ct 2 , HELIOS - SPOT 4 et plate-forme 

polairc. 

Ccs outils d’ingcnicric integrtc nc prcnncnt en 

cffct toute lcur cfficacitt qu’h I’aunc des 

cxptricnccs acquiscs et dcs analyses mentes 

lors dcs dtvrloppcmcnts ou aprts expertise 

des comportcmcnts en vol. 

Unc tcllc approchc, par sa s,~uplcssc dc misc 

en OCUYTC autorisc Cgalcrncnt unc conccption 

ouvcrte B I’Cvolution tcchnologique et B la 

prise en comptc rapidc des nouvcautts. 

Ellc pcrmct dc rtagir au plus vile am 

nouveaux bcsoins (ou B leur adaptation 

rapidc) dts qu’ils son1 cxprimts par les 

utilisatcurs.

I 

1 - CONSTELLATION LAIJNCHES COST 

2 - CONSTELLATION SATELLITES COST 

3 - GLOBAL COST 

IN ORBIT LIFE TIME 

FOR EACH SATELLITE OF 

THE CONSTELLATION 

GLOBAL COST OF THE CONSTELLATiON FOd A h4ISSION 

ON A GIVEN PERIOD OF 'TIME 

' 

8-9

n-tu 

T~RUSlER :61 PUOPELLANI IANK (7) 

\ / 

Class It multimission spacecraft 

CAPABILITY: 

SPACECRAFT FEATURES 

SUN SENSOR (41 

Mission life 

3 to 4 years 

Orbif altitudes : 200.1000 km 

Payload available mass : up to 200 kg 

Payload available power : 100 W mean, 200 W peak 

Battery capocity : 9or 1BAh 

28+/-4V 

VakY. 

Ani e painling ' ' accuracy : +/- 0.15 deg 

Data storage an board : 5 Gigabits 

Dolo transmission 2 to 8 Kbits/wc 

Encryplian : optional 

SATELLITE BUDGETS: 

Mass Power 

Payload : 

Platform : ____ 

Hydrazine : 

( 4 years mission ] 

624- ._ . IIOW -.-a. n - 

1 BO Kg 

8 KCI - 

60 Wan 

-. .__ 

Total : 250 Kg 170 Wan 

7 / 

RF ANTENNA I?) 

PAYLOAD MODULE 

/- 

L EARTH SENSOR 

The FAIRCHILD/MATRA MARCONI SPACE 

spacecrah is a light weight, lawcast slructure designed 

to accamadate a wide range of scientific and 

operational payloads . It provides a simple, efficient 

power system with a super-NiCd battery and a 

modular solar array thot can be adapted lo various 

orbit geometries and payload demands . The central 

data processor unit includes an embedded solid-state 

recorder and generous margin far growth . The 

attitude determination and conlral system and the 

propulsion system are bath designed for flexibility 

and long life ,

ls 

FIGURE 3 

6-11

I. !. I. 

...... . .... ...... ............... ..... ................ M.

a 

a

! ' ' I' I 

';, . ..

SYmME DE NAVIGATION PAR SATELLIT'ES A COUVERTURE EUROPEENNE 

1.SOMMAlRE 

Lbhjel de cclle prtscnlalion er1 de proposer un sysldme dc 

navigation lonciionnani suivanl IC mCme principe que IC 

syrldme GPS mais qui ollrirail un service pcrmancnl en 

Eump 5 hide dun nomhrc limit6 de snlelliler. 

H. naranpr, J. Bouchard, T. Mkhal 

Office Nalionrl dEluder el de Recherclier Atmrpatiales 

B.P. 12 

92 322 ChPtillon Ceder 

FRANCE 

L. constellation pdsenJe ici ne ntcessitc que 4 satellites 

comprcnant un gtoslationnairc el his ralelliles sur des 

orhilei gtosynchmnes d'inclinaison el dercenlricilt hibks. 

Ceiie constellahn pcnnct de couvrir lolalcrncnt I'Europ. IC 

Mnycn Oncnt el I'Alriqus. En ouve. I'ulilisalion de raielliles 

nlativemcnl simples ed cnrisageahle. En ellcl. lous Ies 

iacclliles Clan1 visihler en permanence depuir un mCme 

point du Glohc. il CSI possible de laisscr au s 11 I'horlnge 

ulka-slahlc qui lournit Ii rtftrcncc de tcm(~r pour Ies 

mesurer de dislance usagcr-ralellile. 

Ceric constellalion apparaissanl cornme prnmellcuse. une 

analyse plus pnusste est en cnun alin de jugcr de la 

laisahilifi dun lcl syribmr. En parliculier. Ies pmhlkmcs 

posts par la mise et IC mainlien b POSIC dune lcllc 

constellalion on1 dorcs cl dtjb 616 analyds. On prdrcnle ici 

pluricun lolulinnr cnvinageahlcs pnur la mire B pnsle. avec 

Imcemenls uniqucs nu mulliplca. 5 pulir dorhiles de 

transfen ilandard ou non. Alin de lournir une prcmidre 

Cvalualion du coDl de mainlien h pnsle, I'inlluencc des 

principalcs pcnurhalinns dbrhile sur IC service lourni a Cl6 

analystc. Quclqucs cxcmplcs de inailien b posic rnnl 

tgalcmcnl lournin. 

1. INTRODUCTION 

Lcs performances du syslkmc amfricain de navigation par 

salelliles (3's (Glohal Positioning System) mnt dfsormais 

hien cnnnues CI res applications pcwn!icllcs 

puliculikremcnl nomhreuses Ian1 dans le domains civ I que 

miliuirc. Bicn enicndu. I'ohlention dc ces Frfom ancc3 

(muverturc mondialc quasi pcrmancnte) ntcctriie la mise 

en ocuvrc dun nomhrc imporlant de salcllites complexes. 

11 nous a donc paru inltressanl d'examincr a'il csl possible 

Ue cnncevoir der sy&mcs dc navigation lonciionnant 

suivanl IC mCmc principe que GPS. mais avec un nomhre de 

salellitcs beaucoup plus riduit. Lc service orrerc ne 

dilkrcrait de celui lourni pm GPS que pu I'tlcndue de Is 

zone gtographique couverte par ccs syrlbmcr. Noun nnus 

sninmes plus p~~icuiitrcmcnt inlfrcrrfs b cler cwwcllations 

ollrpni une couvcrturc de I'Eumpe. 

Lea rtsultels dune prcmiirc tiude on1 ntnwrC qu'il CSI 

possible dasrurcr un scrvice permanent de navigation sur la 

m+um panic de I'Eumpc. IC husiri mCdilcnas6cn el 

I'Arriquc. wec une constellation d+ 4 tateI\iics. mh 

minimal rcquii pour line navigation de cyp WS. 

, 

Lcr rtsullata prlrenl€s dans cette communication concement 

unc prcmitrc analyse de la laisrhililt dun Iel rystbmc. CI en 

particulicr la capacilt 1 dtployer el maintenir en service la 

conslcllat; n de raulliles ulilistc. 

Tout dabord. nous rappcllcmns hridvemenl IC principe de 

lonctionncment du ryslbmc de navigalion GPS. Puis nous 

prtsenlemnr let principaler cuactCrisliques de la 

constellalion 5 4 salellilcs rclenue pour celle Clude. Lcs deux 

chapiuss ruivlnu wnt consacrtr rwpclivcment h la inire 31 

posle el au mainlien 5 posle de celle conrlcllalion. 

3. FONCnONNEMENT DU SYSTEME GPS 

Lc syrldme amtricain de navigation par salclliles GPS 

(Global Positioning System) perlnct i tout usagcr. dispmant 

du rtccpteur adqual dc delerminer presquc instanlaniment 

sa position. sa vilesse cl I'heurc locale. Ces calculs son1 

ellecluts avec une Meision intgaltc jurqul prtsent par 15% 

nutrcs syslbmea de navigalion. Le principe de navigation 

ulilisd. pu lriangulalion gtomltriquc rcdondanlc. impose 5 

tout usagcr du syrldme delre en visihilitt simullanfc dau 

moins 4 satellites de la conslellalion. Dana sa vcmion 

compl8lc. cellesi os1 cornposte de 14 aalelliles tvoluanl sur 

des orhilei circulairca inclinks dune +rinds de I2 hcurcr. 

Rappslons hritvemenl le principe de limctionnemcnl du 

syaltmc. Chaque silellile de la constellalion GPS Cmcl cn 

prmanencc un signal veri la Tcrrc. Cc signal cinlC criiilicat 

In dnle cxnetc de dfpart du signal. qui CSI dflcrniinfe pa1 

une horlogc atnmique emharqufc. et des Cphtmiridcs qui 

permellent de connailrc Irks prtcirtmenl la position et la 

vilcsse du satellite 1 ceI inslanl. Ainsi un rtccplcur 

appmprit. dolt dunc horloge. peul determiner la dislancc 

qui le stpare du aalcllile parlir de kan entre Ics dales de 

dfpm cl darrivte du signal. La :?:.G radiale du satellite 

par rappon au riceptcur peu~ fgalemcnl elre dttcriiiiiii.c par 

mcrum de IWet Doppler sur IC nignal. En principe. avec 

lmir satellites en visibililt sous un site minimal de 5". 

I'urager pourrail dtlcrmincr par triangulation sa posilion et 

sa vilesse. 

Un rysltme de conlrRle au sol permei de maintenir unc 

crccIIenlc synchronisation des horloges de grlndo precision 

dm satellites. Par con&. I'horlnge de I'mrgcr est hcaucoup 

moins slahla. En l'ahscnce de rccdages fr6qucnl.s. IC lcmpn 

qu'cllc indique fink par ilill6rcr nnlahlcmcnl du lcinpr dc 

rilfrcnce GI'S. CC qui intrwluil une loris crrcur danr la 

dClcrminalion des distances usager-raklliles: cellcs-ci 

dcviennenl alon inexploifahles. 

Lemur sur la dislance CII Io memc p ur lous lei salclliici 

ohncwda nn mEms instant lille peui dunc 8Irc eslimtc b 

partir dune mesurc sur un satellite supplCmcnlairc. Ainri. si 

un urager du syzldmc fail dei mesums sur 4 salellites i un

10-2 

instant donnt, il put dtlcnniner i In lois snn binis dhorlngo 

(par rapport nu temp GPS) ses lmis cmrdondes 

gingraphiques. el iventuellement lcs tmis compmanlcs de 

si vi~essc. Par la suite. il peul dilcrmincr ss pmition el sa 

vilesse ivec 3 salelliles seulemeol pendant 18 CnUrtC Nn0dC 

duranl laquellc son hiais dhorloge rcslc quasi constant. 

Fa dffinilivc. nn considfrcra qu'un usager di4 eke en 

virihililt simullonte d'8u moins 4 salelliles pur pllrvoir 

cmlculcr sa pnrilinn ct sa vitcsrc inrlantantcs. Cer. une 

condition strictc qui assure une exphilalion comctc des 

rignaux Cmis par Ies satellites. quelle que soil la qualitt de 

I'borloge de I'usagcr. 

lln usager est capahlc de ddtermincr sa porilion caaclc s'il 

connait la dirl:incc giomilriquc (mSmc hiairic) qui IC 

siparc de la prilinn dc chaque salellilc. La mcsurc 

de cctle dislancc est cnlachCc dune cmur risuilant der 

imperfections du traitcmcnl du signal, de la pmpag itinn 

almnsphiriquc ct des iphdmiridcs dos salelliter. Sn Ies 

tmun de incsurcs pur les diffirenls satcllitcr titilids rnnt 

indipendantes el de mCme nivcau. la pricisior. de 

Iocalixalion 3n. carclbririe par I'fcan Iypc dc I'crrcur 

d.Lstimatinn de la pition, est C ale nu pmduit dc I.6carl 

typc dcs mcsurcs el du PDoPl 9 I (I'osition Dilution of 

Precision). Ir I'DOP cst une quantitt sans dimension ne 

dipendant que de Is giomilric rclalive usager.saallilcs. 

Ir I'DOI' pcmict d'fludier la prfcisirm de Incaliratinn tlc 

toule constrllalinn de navipalion du typc GI5 

indipcndamincnt de In pricirion des mcsurcs. Aisri on 

considcrc usucllcinent que le service de naviptirm est 

arsuri 6 un inslant cl en un pnint donnfr si 4 rillcllitm rim1 

visihler cI si IC PDOP. calculi en cc pnint. er1 inffricur P h. 

4. cnNsmLi.xrioN OPTIMAI.E: A 4 SATEI.I.ITES 

Dam unc premihe fludc121. nnus awns rccherrhC des 

conrlellntinn~ a faihlc nnmhre de satcllilc* (rnlre 4 el 9) 

p. mellmt d awrcr un service de navipalinii du type GPS 

sur une rigion liniitic dc la Tern. 

A nomltrc de sntcllitci fixe. nnus avnns cherchf B mnxiifliscr 

l'airc de la prtion dc la surface lcrrcslre h I'inlClicut de 

:aquelle IC I'IX)Pcri en permanence infCrieur i h Cc critcrc 

nr6scnte de Irks nomhreux maxima Incaux. e'cst purtluni 

nous awns utilici une mClhnde dnptimiralion glnbalc h t 

le principe crt imc rcchcrchc aliatriirc adaprhc: Adaplivc 

Random Search (ARS). II s'agit d'unc mithndc initialcmcnl 

prop& par Bekcy ct Mnrri en. 19H3)31141. Iillc ne 

ndcerriie que IC scul cslcul critbe ci non celui de son 

gradient. 

hs parninrber oplimisis sonC pour chaque ratellilc. 5 dcs 6 

p8rmCtrt s indfpendants difinissanl son orhiie: crccnviciti. 

inclinnison. argument du @rig&. ascension dmitc du nocud 

ascendant et anomalie moyenne. En cffel. nous avnns choisi 

pour demi grand axe celui de I'orhite ginrtatinnnairc (42 

IM km). De la ronc. la mne survolic par chnquc ratclliie 

est enlihment cantwnCe i I'intiricur #uric fraction dc la 

surface dc la Tcm. ce qui est parliculi&rcmeni inf6rerrmt 

pour ohlenir un service de navigatinn riginnal. 1% 

d6finilivc. ie nnmhrc de parambuss op\imistn CUI cnmprii 

entre 20 ei 45~ 

Pumi Ian conrlcllalioin ohcnius h I'irauc de CCIC Cludc. il 

cn est una prrticulitremcnt iniClsrsante qui permet de 

daliscr une couveI(urc ymanenie de I'Eumpe et de 

I'Afrique a'8ec reulcmsnt 4 satelliies (voir fig^^ I). ce qui 

e11 IC ncinhrc minimal requis. Cette conslcllation CSI 

cunstitule dun satellite giostalionnah et de trois satellites 

siluis sur des orbitcs giosynchmncs inclinier (i=18,3O) CI 

faihlcment ercentriques (e=O.lQ). 

Ln couv~nure permanents dc ccttc conslellalion reprisenie 

15% de Is surface ternstre. 

Lcs quam satellitci itant eonatammcnl virihler de tout 

point de In zone COUVC~C. cela pcrmcl dcnvisagcr un 

ryslkme de navigation simplifii uliliranl une horloge 

atomique nu snl. ICs satellites itant don munis d'un simple 

rip6lcur. 

Couverlure nominale de la constellation 

Indisponbilile journalitire (mn) 

1436' 

360' 

240' 

5. MtSE A POSTE 

la mise b pos~c dm satellite est I'op5ration qui perinct de IC 

placer sur son orhitc de aervlcc 1 parlir de la surface de la 

Terre. Ellc eat gtntralcment r6alisCc en deux Clapcs. sunout 

dana IC cas d'orhiles Clevics qui noun concerne danr celle 

Ctude: 

~ un lanceur injcctc IC salelli;8: sur une orhite inlermidiaire 

qui difkre de t vhik finale socliaitCe. 

- le ratellile effectue uti transfcn J: I'orhilc intcnnidiairc P 

I'nrbite finalc nu mnyen dun mnleur qui lui clil proore. 

Dans IC cas dune conrtcllalion dc satelliter. on pcul utiliser 

des Inncements mulliplcs afin de riduirc IC cntl glnhd de 

I'o$ralion: la premitre Ctape est faite simullsnfment polr 

dcua satellilcs ou plus. 

Ir trvnsfcrl d'un aalcllitc I pnrlir de I'orhite intermtdiaire a 

lnujoun CtC dCferminC dann cctlc ttudc de fagon i minimiser 

In qusntitt dcrgola ntcessairc h I'opiration. i massc finalc 

1'

du sntcllitc fixCe. Aucunc controinlc i1(n CIC prise cii compte. 

h pnrticulicr. In poussie du motcur est suppsic librcment 

oricntehlc. 

Les nianiwuvres nnt 616 modilis6cs par des impulsions. 

Dam ces criiiditions. lo mnsse d'ergols inc coiisoininCe par 

IJn transfcrt s'cxprimc simplemcnt par: 

avec: 

my : masse finale du sntcllitc: c'est la 

masse h I'issuc du transfer:. innssc tlu 

motcur comprise. 

AV: sommc des varintiniis (le vitesse du 

satellite impriinies par Ics divcrscs 

impulsions du transfcrt. 

V, : vitesse dijection du mntcur. 

0 Minimiser la quailtiti d'ergok consomink est donc 

iquivalcnt b minimiser la snmme des vorintinns (le vitcsse 

AV. Cc dernicr crith prCsentc I'iiitirtt d'ttrc intlipendnnt 

des perfnrniaiices du meitcur (V,) et de la inasse du satellite. 

C'est donc lui qui a effectivement 616 cmployi. 

c 

' 

Dans cettc Ciiitle. chaque trnnsrcrt est suppcisi rhlisi uu 

moyen de 2 iiiipirlsinns. ce qui cst le noinhrc iiiiiiiiiial rcquis 

pnur un transfert quclconquc (entre tics cirhitcs non 

sicontes). 

5.1 hlisc B poste du svtcllite R&xtationna/rt 

On suppisc qeic IC satellite giostatioiiiiaire ser.1 mis i poste 

par la prncidure stantlard suivante: 

- un lanceur AKlhNIi iiijecte le satclliic sur uiie rirliitc W O 

(Gcosialinnary Transfer Orhit) dnni les paraii;i.trcs cirhitaux 

sont apprcrxiiiiativeinciit Ics suivants: 

Ikmi grand axe: 

24 372 km 

Exccntriciti: 0.73 

Incliiiaisnii: U," 

hrgciinent du p6rigie: I UO" 

Ascension tlroitc du nocud ascontlant: non rice 

(cllc est fcinction de I'instaiit de lanccrnciit) 

- IC sntellite est placf sur I'orhite finale au inriyeii d'uiic 

impulsinn unitpc clfectuic b I'apigie (le I'cirtiite (ilU. I1 

s'agil de son scul pnint d'intersection over I'orhite 

ghtatinnnnirc. hvcc Ics valeurs fournics ci-clcssus. le cnOt 

du transfcrt est: 

AV = IS09 inls 

Pour uiic viicsse d'i,jcction usuellc Vc= 3000 ink. IC 

thsfcrt niccssitc donc uiic quantiti d'crgcils igalc b: 

65% dc la masse Finalc. 

5.2 hllrc h pmtc cler autrer rrtelllter 

En cc qui coiiccriie In premikrc Ctapc de lo mise b pc~le. 

quatrc rolutionn ont iti cnvinogies: 

I 

a) lcs sntellilcs 8onI injectis initialcmcnt sur une orbitc CTO 

(SCS curnciiristiques non1 celler indiquCcn nu pnrngraphc 

prCcidcnt). 

b) ils son1 injcctis sur unc orbilc didiic h leur misc h pste; 

il s'agit d'une orhitc de paromtires orbitaux identiques a 

ceux dune GTO, B I'exccption de I'inclinaisnn, Cgalc b 

I'incliiiaison de I'orhite finale, 

c) ils son1 injeclis sur uric orhite dedi& i leur mise h poste; 

les pwamttres dc I'orhitc sont ditcrrninis de faqon a CC: 

qu'elle inccrsecte les 3 orhites finales; chaquc trnnsfert est 

rialist au moyen d'une impulsion unique cffcctuie en I'un 

de ces pnints. 

d) ils sont iiijcctis sur unc orbile did;& i leur niisc h poste. 

don1 les paremttrcs sont totalcmerit optimisis; plus 

prCcisimcnt, oii oplimisc coiijointcmcnt la trajectoirc de 

montic du lanceur et les impulsions perincitant de rtaliscr le 

transfert. 

Pour ICS deux prciiiitres solutions. nous awns 

dtudit dciir prtridurcs (le mise i poste: 

- chocun des 3 satellites est inject6 sipnrCrncnt par un 

lnnccur propre. 

Pour I'un des satellites, on ilitcrniinc nlws le transfcrt hi- 

iinpulsionncl opliinni qui perincl dc passer de I'orhite 

d'injection h I'orhite finalc. En rCalitC. I'orhite d'injcctinn 

ii'est pas eiiiiSrenicnt tlCfinie: I'asccnsicin tlrciitc (IC son 

nwud nscendant pcut prendre n'iinpnrtc qcrellc valcur sLlcin 

I'iiistant de tir. La tlitcrinination du transfcrt optimal tloit 

donc ttrc faite pnur toutes les valeurs de SIO coinprises cntre 

3 et ?I[. On peut alms tracer la courhe d'ivtilutinn du coot du 

traitsfcrt en foiiction de f20. OII eii dttluit la vdeiir nptimale 

tlc Q qui coiiduit au transfert "optiinuin optiniciriim". 

Pour Ics tleux nu1rc.r satellites. Ics courhcs se dicluiseni de I:I 

pricitlcnie par un simple tlkalage en no. Ce tlCc:ilagc cst 

Cgal h l'Cc:ir! aiigcilaire qui existe entre IC ntwud asccntlani 

tlu lirciiiier satellite et celui du satellice cnnsitl6rC. fin 

particulicr, IC transfert "optirnurii optiinciruin" a IC niSmc 

coot pnur les 3 salcllites. Pour pcwvriir I'utiliser 

clfcctivcnient. il suffit d'ajuskr pur chaquc satellite la 

valeur de 1% par IC hiais de l'inst~nt 

de Iaiiccincnt. 

- Ics 3 sutcllitcs sont injecth siiiiiiltiinCnient nu riioycn 

cl'un laiiccur uniqiic. 

I1 ii'cxistc alms qi;'uiie sciilc iirliiic tl'iiijcctiiin pour ICS 3 

satcilitcs. caractirisic par iiii rb tlriniii. 11' n'cst clone pas 

possible cl'utiliscr IC transfcrt "optimum crptiincirurn" pour 

chacun tl'cux. 1.3 coiisiiinmatitin tl'crgols est par ctiiisiqucnt 

tiicijours suphiclire iiu Cgalc b ccllc tlu cas prCci.tlcnt. 011 

tinificie par ccintre cl'iin cnOi de loiircmciit infiricur. 

Pour toutc valcur de Q nn pcut diduirc tic In cciiirhc 

ohlenue (lam IC cns pricidcnt IC coot du transfer1 riptimnl 

pour chacun des 3 sniellitcs. Ccs 3 coots permettent de 

cnlccilcr un coot ghhal piur len 3 tronrlcrts: nws ovcins 

chniai le AV du trundcri unique qui ccmsntnincruit unc 

rnosie Cgolc h lo masse totale d'ergols der 3 transferis. pur

ploccr sur nrhite In n ihc masse finale (3 Tois In masse tl'un 

sntcllitc oprLs misc pnstc). [,a vnleur de CC critkrc tltpend 

de In vitcssc tl'6,jcction des motcurs: nnus svcins chnisi la 

voleur Ve=7000 rids. 

Pour Ics dcux dcinikres solutions. scul le 

Inncement siniultenC clcs 3 satcllitcs a 616 CtucliC. 

5.2. I Tran.cjerrs ctcrprris une GTO 

La cnurhc de In figure 2 rrprtsentc IC cofit minimal (AV) du 

transfcrt hi-impulsionncl optimal dcpuis IWC ttrbitc GVO. cn 

fnncticin dc I'asccnsicn droitc Qo du nocud nsynd;int de 

cettc nrhitc. 

2900. 

1600 j V 

1200. - I - 7--l----7* 

0. 90 180. 270. 36 

deer 

Coirt du transfer( dun des satellites 

en fonclion de I'ascension droite du noeud 

ascendant de I'orbite d'injection (GTO) 

[.a cnurhc prtscntc dcux iniriinia si.pari.s tlc IOS" cn % 1.e 

plus petit cst allcint pwr %=lOf . sciit unc valcur p~ chc 

de ccllc tlc I'asccnsicirl clriiitc du ncrutl ascent1;int dc I'orhitc 

finalc (IO?..;i 6"). 1.c coht ccrrrcspintlnnt cst tlc: 

11M mls 

Avec unc viicsse cl'tjcction tlu itititcur tlc 3000 nilr. In III:LSSC 

d'crgols consoiiinii.c serait alors tlc M';c tlc la lli:i.i\c finalc 

niisc a pistc. ('cs rhltats sont trcs voicinc clc ccux tlu 

!.-anrfcrt pftistatic~iir!oirc cffcctui. tlans Ics iiii.nics ciinditiiins 

! IS09 mls. (15% 1. 

['our pwvcrir cffcctucr chaqw tr;insfcrt pur un coiit de 

14x4 mls. iI faut iiitpcrativcinent iitiliscr un lariccur pur 

chaquc salcllitc. l-'iiistant tlu prcinicr lanccnierit n'a itas 

d'imprtaiice pour la inisc a pistc. Par contrc. Icc dcux 

Ianccincnts suivanls doivcnt itrc faits b unc hcurr 

particulicrc clc la jiirirnfc (qui tltipcritl dc lii datc dc I'anntc). 

Si ICS 3 ratcllitcs siint injccttc siiiiultaiiinicnl par 1111 Ianrcur 

ilniquc. cin cvirc ccc cnntraintcs tlc tcinpr tl

0 

0 

' 

ml 

3200. 

2800. 

2400. 

2000. 

1600. 

1200. \ 

0 

I 

90. 18i. 27i. 360. 

deer e 

Coiit des 3 Iransterls et coirt global 

en lonction de I'ascension droite du noeud 

ascendant de I'orbite d'injection 

(GTO dinclinaison rnodifiee) : 

Si par contre Ics 3 satcllites sont injectts sur une nieinc 

orhite h I'issue d'un lanccnicnt mulliplc. la situafioii est plus 

dcfavorahlc que daiis IC cas d'une iiijcctinn stir GIT). II 

existc 3 solutions nptirnalcs. poiir Q = ION", ??R" ct 348". 

Lcs coots correspondents sont: 

2797 mls, 2797 m ls et 1315 mls 

Ir AV maximal c5t trcs ncttcinenl cu+ricur i celui cniistatc 

dans IC cas d'une injcction sur GrO (2707 in/!. au lieu dc 

21fa m/s). lin outre. ~cs tniis AV ne snnt pad du tout t~u 

meme nivcau. 

&I conclusion. I'injcction sur GTO mnlifiGe n'cst 

ihttiressontc quc dans IC cas des lnnccmcnt sfpark. Elle 

+rmcl dc faire uiic petite economic d'crgnls (1601 par 

rsppnrt B uiic injection sur GTO standard. II rcste B ftbdicr 

si unc tcllc orhitc est acccssihle i un lanccur Aviane. 1.3 

GTO standard est en revanche unc orhite d'injeL!tion hien 

supiricun si Ics 3 satellites snnt lnncds cnscmhlc. 

5.2.3 Tmnsfrrls nuino-impulsionnrlr depuis une &tile 

d'injerlion CnriJnune 

Nous avnns recherche uiic orhite d'injcctinn intcrccplniit Ics 

3 orhites finales. de facon a pnuvoir rtaliser chaqlJc tradsfert 

au moyen d'une impulsion uniqoc. On cnnsidkre qcit les 

satellite$ sont tous Ics 3 situ& sur cctte .rirtritc aprts 

injection. ce qiii suppnsc cn pratique qu'ils on1 it6 lances 

cnsemblc. 

Un halayagc cxhaustif de toutcs les orhitcs (circu1air.s IIU 

clliptiques) interceptant les 3 orhites finales a dtC cffeutue. 

Pour chquc solution. nnui avnns calcult la sriminc d-s 3 

AV dcs impulsions. En difinitivc, il est apparu que la 

solution qui ininimisc ccttc soinrne cst uiic cirhite 

6quatorialc de demi grand axc: 

42 755 kin 

II s'agit donc d'une orhiie voisinc de I'orhite gtristatii)niiairc. 

don( le demi grand axe est 42 164 km. 'routes les impulsions 

sont Cgalcs et valent chwune: 

I I24 m/s 

I 

En pratique, on purrait cnvisager dinjccter dans un premier 

temps les 3 satellites sur GTO standard. puisqtie I'orbitc 

optinlate identifite est quasi giostntionnaire. 11s seraient 

ensuite trnnsfircs sur celle-ci ensemble nu individucllemcnt. 

pour un coot AV = IS30 rnls. Le coot global pur chaque 

satellite serail donc dc 2654 mls. snit heaucoup plus que Ics 

2160 mls nccessaires piur une mise h postc hi- 

impulsionnelle directc tlcpis line GTO. llne telle solution 

priscntcrait donc pcu d'iiitcrtt. 

S.2.4 0pirni.tn~ion muplir de Irr lrajerloire du lnnreur rI 

des 3 tmn.fcrts 

Nous dispnsons dun logiciel capahle d'optimiscr 

simultaniment la trajectciirc de niontic d'un lanceur donnt. 

plaqarit un nu plusicurs satelli,cs sur orhitc d'injcction. ct les 

transferts hi-irnpulsioiiiiels permeltant de placer ccs 

satellites sur leur orhitcs iinalcsI51. Plusicurs criltrcs sont 

susceprihlcs d'hc minin\i\

0 

10-6 

Ccst dans ce COS que le volcur mnxiinnlc des 3 AV CSI In 

plus petite. C'cst daiis cc cas Cgolemcnt qii'ils sont Ics plus 

voisins Ics uns tles outrer. Ccs rCsultots cnrrcspnndciit i des 

Pour IC cnlcul de la pression dc radiation. Ics 

caractCristiqucs physiques rctcnucr pnur lcs satcllitcs sent 

ks suivanlcs: 

I11Bsscs d'crgols consommics valant respcclivctncnt: surface cxpnstc: 3 in* 

masse: 500 kg 

cmfricicnl thcrino-optiquc glnhnl: 1.2 

97%. 97% et 918 dc la m a w fiiiale tl'un satcllitc. 

Par ropport B une mise 6 pnstc utilisant line CW) standnrtl. 

on nhscrvc uiic rCtluction d'cnvirnn 8% tlc lo innssc tl'crgols 

m nx i in nlc. 

6. MAINTIEN A I'OSTB 

Lonolysc tle pcrfnrinancc qui n pcrinis dc propnxcr In 

constcllntion Ctutlifc a CIC rdalisfe sans prcntlrc en cntiipte 

Ics principalcs perturhatinns naturcllcs apissaiit sur Ics 

satcllitcs tlc 1;i constellation. La prise en coiiiptc tlc ccllcs-ci 

est cn cffct inutilc pnur analysrr la prrnrinancc tlu systkine 

sur une tlurfe de 24 hcurcs. Ccpntlant. il est clair que le 

service ftiimi r-r IC systtiine cnvisagf n'a d'iiitirCt clue si 

celui-ci CSI dispsnihlc pcntlant unc dur& ncihiiiiale 

ditcntlant sur pliisicuis annCcs. 11 convicnt clc verifier tliic la 

constcllotioii prcipcosCc est viahlc vis i vis tlc cc crith. et 

qu'cn porticiilicr les pcrturhations suliics par Ics siiltllitcs 

coinpsnnt Io ccinstcIIatirin ii'impiscnt pas ties niiiiiocuvrcs 

(IC inninticn i pcistc trop friqucntcs (ou trnp ~riiltcuscs. 

la*6tutle c ~ u niainticn i poste a tloiic itt riiilisdc cd deux 

tcnips: tiiut tl'ahirtl. lcs principiilcs pcrliirhitiiiiis ueissaiit 

sur Ics s:itcllitcs tiiit 316 siniiildcs. et il'iiillucncc des 

ddgratlatiiinr tl'cirhitc siir la pcrfcirinaiicc tlii systi.inc ii iti 

. Cvaluic. Ihiis un tlcirxitiiie tciiips. pniir 1111 cycle de 

corrcctirin tl'orhitc choisi au vu tlc I'aiiulysc pr*:cdtlctite. (Ics 

maniKuvrcs de milintien h pcistc iriitiftf tliteriiiindcs ct IC 

coot gloh:il tlc in:iinticn i piste :I 616 iv:iIiid. 

Is satcllitc gCostatinniiairc n'a pas it& pris CI cciinptc pwr 

cctte analysc pour lcs raisons suivaiitcs: cioiniiic iI n itd 

incliqud cn iiitnducticin. la charge utile (IC riiivigatioii 

prnprcincnt tlitc scra tl'iin voliiine et tl'iiiic iiiaw liinitic. cc 

qui autnrisc soli atljonction stir iin satellite gdtrt:itiioiinairc 

~CVOIII i tine autre iictivitd principalc (tdI~c,~iiiiiiiinicatiliii 

par cxcinplc). Ihns ccr coritliticiiis. IC inniiiticn ii pcikie tlc cc 

salellitc scra fix6 par lcs exigciiccs (le I~iisitioiiiieiiictrt fin tlu 

satcllitc tlc tilfciimmuiiicatioii. Par aillciirs 4 I'on ciivisage 

d'utiliscr tin satellite gfostatirinnairc l~iiic~.1clit tlitlid h la 

missiw- tlc navipatinn. I'ciicoinlirciiiciit tlc I'cirhitc 

gioctatiiinnairc iiiipo.wra i cclui.ci uiic fcliCtrc (le 

stationircincnt Iiiii;tic. la respect t~c ' ccttc fcllCtrc 

nCccssitcra iin niainticn h pcistc cl'iin nivcau cciliipiirilhle i 

cclui tl'uii satellite giostatiotinairc ,(le ti.lCcciltriiiuliie;Itin~i. 

snit cnviron 50 nilslan cn tcrmc tlc vitcssc caractdristiclue. 

6.1 Usiire natitrclle dcs orhitcs 

Compte tencl de la iinturc tlcs orhites. Ics pctturh:ltinns 

principalcs qu'il convicnt de prcndrc cn cniiiptc sont Ics 

suivantcs: 

- dissyiiiflries tlii piotciiticl gravitiititriiiiel terrcstrc. 

- ottracticln gravitntionnclle de la I.irne et tlu Solcil. 

- pression tlc radiation solairc tlircctc. 

Le ptcntiel tcrrcstrc o CtC mcdClisC en prcnant cn cntiiptc 

Icn termcq 71~nniix 

el lcwfraux jusqu'h I'ortlrc cl IC tlegrd U. 

6.1. 1 InfCRrtrlion du Inofti'cmrnf drs sritc.//i~~s 

' L'annlysc tlc I'iisurc tlcs orhites sous I'influcncc des 

perturhntinns nnturcllcs U CtC rdnlisCc cn utilisanl un prcmicr 

logiciel dirvelnppd: B I'ONEHA qui perinct une integration 

rapide ct fiahlc du mouveinent orbital. Cc logiricl utilise le 

fnrinalismc dcs parainctrcs ccntrfs ((ru pararnktrcs moycns) 

qui pcrmct de supprimer lcs perturhaticins i hiiutc frtqucnce. 

qui n'nnt que peu d'influcnce sur I'Cvolutjon :? lnn,g tcrme de 

l'iirhitc. Ccla autnrisc ainsi I'utilisatinn tlc firands pas 

tl'iiitfgration (typiqucnicnt '(le I'ordre de la piriotlc orhitalc. 

snit 24 hcures ici). au lieu tlc quclqucs minutes si I'nn utilise 

les ClCinciits nsculatcurs tlc I'orhite (flimcnts iiistantanCs). 

Ccttc tcchniquc pernict dnnc de rtalixr rapitlcmcnt des 

intdgriitinns tlc longuc tlur6c. 

I'our analyser I'6vrrlutioii de la performance tlu systknie snus 

I'infliicnie tlcs pcrturhatirins naturcllcs, lcs parnincires 

cirhitatrx tlcs trois satcllitcs ccinsiddrfs snnt intCgrfs avcc le 

logicicl prfcfdcmiiicnt tlfcpit. I'dritditlucinciit. on rclkvc la 

valcur tlc ccs parainctres et on Ics utilise pur tlftcrniiner la 

.iiciuvcIle ciruvcrture tlu systkiiic aprks pcrturhation tl'orhilc. 

lin pratique. !:..: calcirls tlc ccwvcrturc oiit dtl rdalisc's lnus 

les 7 jiiurs cl lo duric glohalc tl';iiialysc ciiii?;Ccutive est de fi 

mnis. 1.3 clate tlc tlfpiirt (le I'analyse a Ctd fixdc ;NI I Jaiivicr 

ItNJ. ('cttc (late 'a uiie innuclice tiirccte stir IC rfsultat 

puisqii'cllc fixe la position re1:itive tlc la 'I'crrc et tlcs autres 

astrcs pcrturh;rtcurs. 1 hi: aiiiilysc pliis piussCc clcvrn donc 

Ctrc rdalisce. piiir dwluer niit:iinnicnt I'iiifliicncc tIc Iii (laic 

tlc lanceinerit. 

6.1.2 C'rrlcrtl tlr In coiivrrIiirr 

hfili de pruvoir cciniparcr correctcment la ccoiivcrturc tlc la 

coiistclliition "pcrturhec" avcc la cnuvcrturc iioniinalc. iI a 

it6 prtuitld (le la nianikrc suivuntc: 

- Le contour dc la zone de couverturc iiwniiialc a 

iti rntwlClisC apprcixiiiiativciticiit piir UII polygonc 

sphcriquc. quc l'tin pcut ohscrver sur la figure I. 

- IIn rfscaii tle pciiiits situCs h la silrf'ace dc la 

'I'crrc a 616 tltfiiii ii I*iiitdricur (IC cc pi~ygtinc. ccs 

piints stint rdpiirtis sur des p:iriiIIkIcs tlisprsds IIIUS 

lcs 2:' en latitutle. Sur chiiquc parallclc. Ics points 

snnt 6tlui-rfp;irtk en Iiiiigitiitle ct lcur ntimhre est 

chnisi tle tcllc fayirn que la tleiisiti surfacique tlc 

points soit :ipprrixiiiiativeincnt coilstante sur 

I'cnscmhlc tlu rdseau. 

- I.'aiialysc tlc cciirvcrturc cst rdalisdc cn intCgr;int 

la cciiistcll:iticoli stir 24 hcurrs (piirilnlc tlc 

rccouvrciiiciit tle la t:cinstcllnticiri iiiiiniiiiilc) et en 

tcstunt toutcs Icr 5 minuter In valcur tIu I'IX)Ii en 

chaquc pint du riscau. On tlfterininc ainsi IC 

pourccntoge dca points ou IC service tlc navigation 

cat ncccraihle en pcrmnnencc sur la durCc 

tl'inlCgrntinii. Ir rcrvicc crt clit occcssihli b un 

instant dcrrint? si il y o nu moins 4 rntcllitca visihlcs

A cct instant. ct si IC PDOP cat infCricur i 6. 

Comptr tcnu de la rtparlilinn des points du rSseau. 

ce pourcentage en1 aussi IC purcmtagc de la 

iurfrcc couvcnc. II est exretemcnt dc 9R.M pour 

la cnnstellation nominale. La performance de la 

connlcllatim ddgndCo a loujotin 616 chiffdc nu 

moycn de cet indicc. 

6.1.3 R4sultar.s dr I'annnlysr 

La figure 6 reprtrcnlc IYvolutinn du pi~urccnlagc

10-11 

I,'nnolysc du coot de meinticn B poste dnit 2trc rdallsi, en 

deux temps: tout tl'ahod il convient de ditcrminer quels 

sont les parmctrcs qu'il est ohsnlument niccssaire de 

cnrrigcr: iI cct en cffct pnssihle quc In scnsihilitd de ccrtains 

paromi.trcs sur IC scrvicc snit suffis:iinmcnt raihlc pwr quc 

I'm piissc sc pcrmettrc tlc ne pas Ics cclrriger sur tiiutc lo 

durfe du service. linsuitc, IC cc101 ilcs ccrrrccticiiis a rialiser 

doit 21rc cnlculi. Pour ccla. IC logiciel d'optimisation de 

manncuvrcs hi-iiiipulsinnncllcs. ddjb utilisi piur I'itude dc 

la mise ii poste. a de nnuvcau Cti mis en ocuvre. 

6.2.2 Mnnrirtrvres cir rrulinricn rt pr~fc 

tine ftiide cxhaustivc des pnssibilitfs dc mainticti i pislc de 

la cnnstcllntinn a 616 rialistc. en tcstant succcssiveincnt la 

nicessiti dc corripcr chacun (les paramktrcs orhitaux. 

Comptc tcnu de la vnlontC dc rialiscr des satellites siiiiplcs 

ct pii cobtciix. Ics prcmitres nniilyscri lint cii puir hut ilc 

vfrificr s'il dtait pnssihle de RC contenter de maiiiiciivres 

effcctuties scliin la vitcssc tlu satcllitc. nu B la rigucur tlans 

'. plan (le l'tirtiite, Is hut dtait .I'fviter si possihlc dcs 

I! 1 wvrcs cle nitdification du idan tlc I'orhitc. qui snnt 

cob,. 'ea ct qui impnscnt uiic pliitc-forme plus wmplcxc 

plwr le *kllite. 

('rq tests on1 iiinlhcurciisciiicii~ nioiitrk quc ccla n'cst pas 

pnssihle. 1.n rigiirc 0 rcprCscntc I'Cvciliititin $c la cciuvcrture 

du systcnic clans I'hypnthbsc tlc ctirrccticiris (Intis le plan de 

liirhitc sciilcnicnt (ctirrccticin tlii deini 1 pr:iiicl axe. tlc 

I'excciitricitd. dc I'argiiiiicnt tlu pirigtic CI clc I'aiiciinalic 

vrnic tlc I'orhitc) On coiistatc tine prtc prciprcssive tlc la 

cnuvcrture noiiiiiialc: ccllc-ci n'cst pas ti:taIi!iiiciit rticiilx!rCc 

i I'issuc de chaqiic maiitwu\*rc et la situation nc fait 

qu'ciiipircr avcc le tcinps. 

' I 

0. 21. 42. 62. 83. 104. 

s em8 i ne 

I 

Evolution du pourcentage de couverture 

en fonztion du temps. 

Corrections dans le plan de I'orbife. 

II s'avtrc time niccssaire dc rialiscr i.l;.aIcincnt des 

cnrrccticvis tlu plan de I'nrhite (inclinaistm et asccnsion 

droitc du nocud asccritlaiit). Iln cc qui conccriic ' ~ tlcrnicr e 

paramttrc. Ics mantvuvrcs rdalisfcs se cnntcntcnt d'assurcr 

~ U C Ics 3 plans d'cirhite cnnscrvcnt la clispositinn relative 

qiiilr avaient initialemcnt. fin cflct. wus I'inflcicnce dcs 

tcrmcs tcssPraiix tlu pitentiel gravitiitioniiel tcncstrc CI sous 

cclle de I'nttracticin luni-solnirc. In vitcsse de riitiitiiin dcu 

plans d'orhitc difkre suivant les satellites. In rcvanchc. la 

rotation d'enscinhle des plans.d'orhitc. due csscnticllcincnt a 

I'nplatisscmcnt de la Tern et qui aitcint cnviron 0.8" aprts 8 

scmaincs. n'cst bicn cntcndu pas corrigCe puiscju'il suffit de 

mcwlificr ligtrement IC dcmi grand tue initial der orhitcs 

pour que In longitude dcs nocuds nscendants par reppnrt b la 

Terre reste fixe. Des manwuvrcs de ce type cffcctuecs 

toutcs les R scinaines perinettent d'assurer unc couvciture 

qui rcste toujours suptrieurc h 90% de la couverturc initiale 

pendant Ics 7 annics de tlurie de vie envisagics pour IC 

systtme. 

6.2.3 CoCti tiic mninticn t3 posit- 

Cornme on vicnt de le voir. le mainticn i poste envisagi 

ndcessite de corrigcr la totaliti des paramttrcs orhitaux. 

Nfani:ioins. la correction des nncuds ascendants ayant 

uniquemcnt pour hut de mairitenir la disposition relative 

initialc des plans d'nrhitc. il suffit de inanneuvrer dcux 

satellites sur lcs trois pour rfaliscr cettc op6ration. L'identitd 

clcs satellites h manncuvrcr p i t Stre choisic de differcntcs 

fapiis. Pour cettc prcmitre analyse, 2 sctnaricis tlc inainticn 

it poste nnt Cti envisages: 

a) on permute rtgulitrcmcnt IC satellite qui ne 

maiincuvrc pas. 

h) oil inanoeuvre les satellites qui perinettent de 

miniiniscr la sommc totalc de variation ;ingulairc i 

rial iscr. 

I'our tester chnciine dc ccs optiniix. I'cnscinhle tlcs lngiciels 

rncnliiinnds julqu'h prfscnt a fti utiIisC: 

- intigriitiiin cn fleiiicnfr ccntrfg des orhitcs (le la 

ciiristcllatiiiii. 

- calcul tlc la pcrfcirinance avant ct aprts lcs 

nianwuvrcs dc ccirrccticin. 

. calcul du cciirt ininimal tics mantruvres de 

ccirrcctioii. iiitwli.lisfes par des transfcrts hi- 

impulsioiincls. 

[)ails IC calcul effcctuf. IC coirt tlcs manrsuvres (le phasagc 

clcs sntcllitcs (affectant I'anniiialie) a it6 nfgligi. II cst hicn 

cnniiu qu'il cst pcissihle d'ohtrnir IC phasagc ddsiri cn 

rfalisant unc Idgtrc mtdification du demi grand axe tlc 

I'cirhite. plapant ainsi le satellite sur une orhitc de derive. 

llne scconde mancviivrc, faite en scns invcrse de la 

prcmikrc. pcrmct de re-stabiliser le satellite uiic fnis IC 

tlfphasagc soubaiti ohtcnu. Le colit (le cctte manncuvre 

dipciitl hicn cntc'ndu tlc la durfe tnlirte pur I'nhtcntinn du 

phiisagc. I.cs prcmitres ivalualinns tdalisdcs tint mnntri 

qu'un tlilai tle 24 hcurcs perincl tlc reiiclrc IC coot du 

phasagc ndgligeahle vis b, vis du colit tlcs autres 

mantwuvrcs. c'cst pourquoi ce coot n'a pas 616 pris en 

cnmptc p x la suitc. 

hpri:s avoir test6 les dcux scfnarins de inainticn h poste 

iviyiiCs prCcCtlcnirnent, iI s'avkrc lngiquemcnt que IC 

second est le pliis Cconomiquc. De plus, c'est cclui qui 

assure la ineillcurc repartition des masses d'crgols 

consniiimfcs par Ics trois satcllitcs. 

1: coGt total du maintien h pnstc a CtC ivalui en rtalisant 

uiic siiiiulatiivi cciinplttc sur 7 nns. Lr.s rfsultats ohtrnus 

figiireiit danr le tahlcoii (le la figure 10. 

On cnnstale quc IC coot dc tnainticn B poste s'mtrc 

relativemerit plus ilevt que celui d'un satellite

giostationnaire (RS mlslnn contrc 50 pour un 

giostationnairc). Ce coat reste nianmoins tolirahlc. II 

convicndro de virificr s'il II'CSI pas pnssihlc. par un chnix 

adCquat de la position des ntuuds asccndonts initiailx. de 

limiter le nivcau dcs perturhatiolis difffrenticllcs afrcclanl 

Ics plans d'nrhitc et de riduire ainsi le COO\ glnhal de 

maintien 6 poste. 

1 

I 592 

1 

I , 592 I 546 

(mls) 

Masse totale tl'crgols 

(% masse Enale) 

22 22 

I 

20 

Figure 10: Coirt du maintien a poste sur 7 ans 

7. CONCLUSION 

Le hut de I'frude prcseiitte dans cct article Ctoit de ridiser 

une analyse de In faisahilitd d'un systtmc de naviealion 

fonctionnant suivant le principe du systtmc CI'S et nssurant 

uiie couverture perrnanente de I'liurope ci de I'AfriqUe P 

I'aide de 4 satellites sculemcnt dont un giostationnaire. 

Les paramttres orhitoux initioux de cctte constellot inn ann1 

issus d'unc itucie ontirieure121 cnnsncrie i la rechcrchc de 

constellations faihle nomhre de satcllitcs. La coiirtcll:itinn 

prisentic ici prCsente plusicurs caroctiristic\ucs 

intiressnntcs: 

. Irks rnible nninhrc de satellites (4 sotcllitcs cct 'IC 

minimum rcquis pour assurer UII service de 

navigation du ~ype CPS). I 

- tous Ics satellites snnt visihlcs cn pcriiiancnce de 

la memc station de cnnlr6lc; il est aiiisi pnssihlc 

utiliscr Ics satellites coinme de simples repdeurs 

d'un message de navigation ilahnrC ou snl. 

- orbitcs rclativemcnt "classiques". 

L'itudc de faisahiliti prdsentic ici s'cst surtniit attachCC i 

analyser les prohliiiies posCs par la mise ct le riiairiticri i 

0 postc d'une tclle constellation. 

L'itudc de la mise a poste a itf faite cii coiisitli-rail1 divcrses 

solutions: 

- Inncement individuel de chaque satelliic. nu lan- 

cement couple des 3 satellites nnii giostatinnnaires, 

- injcction pr-ilirninaire sur unc nrhitc G'TO standard 

(Geostationary Transfer Orhit) dilivrie par un Ian- 

ceur hrianc. nu injection sur uiie orhitc didiic a la 

mise a pnste de ccs satellites de novigatinn. 

II est apparu que I'orhitc GTO standard hrinnc coiistitue un 

Irks bon choix pour I'orhitc d'injcction. surtout si Ics 3 

satellites imn giosiationnaires son1 mis h poste 6 I'aide d'un 

lanccur unique. Dans cc cas. IC cnCt de chaquc transfcrt ne 

dipassc pas 2160 mls en vitcssc caractiristique. II est 

ccpcndanl heaucoup plus ilcvi que celui d'uii satellite 

gtostationnaire (I SO0 mls). Lorbite d'injcctioii qui permet 

de minimiser la consommation d'crgols des trnderts de 

mise A poste finale diffkre peu dc la GTO: elk conduit B tine 

iconomie modcste (8% en masse). 

10-9 

Dons IC ccs tru les satellites son1 injectis sur GTO 

individucllenicnt. IC crdt du transfcrt est Irks voisin de celui 

d'un satellite gcpstionnaire. lliie telle prncidurc de misc a 

pstc est cependant dilicate CY elk impose I'heure de tir 

dcs deux dernicrs satellites lancis. 

L'itudc du maintien b poste a necessiti dans un premier 

tcmps d'analyscr I'tvolutinn de la couvcrturc du scrvicc de 

navigation sous I'influencc des pcrturhations naturellcs: 

Ccttc analyse o prmis de monb-r qu'un mainticii i poste 

rclativcment frtquent s'impos-. (routes le 8 scmairies 

environ) pair assurer la pcrmanencc d'une coiiverture 

convenable. 

Le coot dcs manoeuvrcs de maintien 6 poste nicessaire a 

ensuitc it6 ivalut sur la hase d'une durie de vie des 

satellites de 7 ans. Cette prcmiire analyse scinhlc indiqucr 

que le coat annuel des manneuvrcs s'ilkvc environ 85 mjs 

(contri 50 mls pour un satellite g0ostatinnnaire). 

Pour parachcver I'nnalysc de mission d'un tcl systkmc. il 

conviendra disormais de virificr s'il cst possible de localiser 

de tels satellites avec une pricision surfisante pour fournir 

une pricision de navigation acceptable. 

I). Kromr, J. 1,andk. J. 1)ol)yne 

"Navstar Glohal Positioning Syslem (GI'S) 

Systcin characteristics - I'reliminary Oraft" 

STANAC 4294. Ilraft Issue 1. I August lW0. 

ti. Ilarlrngcr, H. I'ict-l,ahnnier, J. nouchard 

"Glohal Optimization of GI'S Type Satellite 

Constcllation" 

Papicr IAF-91-369.' 

(;A. Bckey, S.F. Mrsri 

"Handom search techniques fnr optimization of 

non-linear sysleins with many parainetcrs" 

Math. Coinput. Siiiiul.. lOX.1. 2.5. pp. 2 IO-? 1.1. 

1,. I'ronzatn,.E. Walter, A. Vrnnt, 

J. F. I ,e Iw ii chcc 

"A gcnerol. purpose glohal optimizer: 

implcineiit;:tinns and applications" 

Math. (:oin,iut. Simul.. 19x4. 26. pp. 4 12-42? 

I,. Zaobi, B. Crirtophe 

'Optimisation de lanceincnts multiples" 

hgard Symposium (Tacsats for surveillance. 

verificotion and C31) 

Bruxellcs, 19-22 Octohrc 1992. 

1

10-10 

Discussion 

Question: Please provide the definition of TACSAT 

as intended in the paper presentation. 

Reply: TACSAT is understood to be a theater satellite, 

that is to say, a system available where you want 

and when you wa,nt., This leads to.consequences not 

only on the space platform bct also on the ground 

support equipment. 

i 

I

0 

This pqxr is dividcd in lhrcc pat$ 

following itcnis: 

lactical Satctlites for Air Command and Control 

- air command and conml functions and dcfficicncics. 

- contribution of TAC'ATS to air command arid 

conlro I, 

- opcrational improvcmcnu duc to TACSATS. 

1. AIR COMMAND AND CONTROL 

FUNCTIONS AND DEFFICIENCIES 

Air coiiiinand ind control functions arc dividcd in fotlr 

thcmcs: 

- survcillancc. 

- rc.wurccs managcmcnt. 

- air activity conlrol, 

- indligcncc. 

1.1 Surveillsnce 

Survcillancc inclutlcs thc g n ration and diss 

of Ihc Rccognixd Air P ick (RAP). Thrcc I 

M. Crochct - JI Cymbalisla - L. Lcvcquc 

AE~OSPATI ALE 

Espacc & DCfcnsc 

RP 2 78 I33 k s Murcaux Ccdcx Francc 

niination 

:y issu$s 

arc linkcd ti this function, thc'dctcction of low obsc1.- 

vablcs and low flying objccts, thc ballistic missilcs 

problcni and thc ndvcrsc satcllitcs tracking. 

a. &&x *tion of lo w obscrvablc. lo w f lvinr!m 

Thc currcnt solution to dctccl low flycrs is to u.sc thc 

contribution of radars on aircraft (AWACS). This typc 

of platform may maintain its position during about 

cight hours. and you nccd four- to fivc of thcm to 

maintain a round thc clock survcillancc capability. 

Thc dctcction of low obscrvablcs objccts is solvcd by 

dcvcloping a scnsing nct. using diffcrcnt frcqucocy rmgc 

capability (visual, acoustic. infrarcd or clccuornagnctic) 

alld difl'crcnt ilnglc of prc.wnlrition vcrsils thc p'ssihlc 

urgci. This lcads to a costly mulliplicniion of scnsors 

that hust bc in position on cvcry possiblc pcnclration 

conitlor. 

b. allistic mi .' . 

1'hi;ncw thrcaeto bc, includcd in thd RAP. In ordcr 

to do so, wc hive to dctcci thc missilcs in flight as soon 

as pclssihlc and uiick thcm during thcir flight. 

A ground systcin likc thc PATRIOT tins ii liiiiitctl 

dcicction capability cohcrcnt with tlic intcrccptor 

guidance. 

A currcnt satcllitc likc DSP (Dcfcncc Supprt Yrngram) 

was dcsigncd to dctcct a long rangc ballistic inissilc 

coming f rm a wcll known arca. It has limitcd capa- 

bility against a short rangc ballistic missilc coming 

from a country involved with missilc prolifcraiion. 

11-1 

c. Advcrscs&Lt& I' 

A thcatcr commandcr has to know thc location and 

covcragc of thc advcrse observation satellites. 

Today this function is pcrfomcd by thc Air Forcc and 

the satcllitcs tracks arc not includcd in he RAP, bccausc: 

this information is considcrcd as a basis for thrcal 

cvaluation or intclligcnce. 

Thcrc is a rcquircmcnt for hc European countries lo be 

ablc to fulfill this function with indcpcndcnt means. 

1.2 Resources management 

Rcsourccs managcmcnt is divided in thrcc thcmcs: 

- forcc managcmcnt. 

- airspacc m,uagcmcnt. 

- C2 rcsourccs managcmcnt. 

a. F- I 

Forcc managcmcnt includcs thc knowlcdgc of our own 

forccs statc, thc planning and lasking of air opcrations. 

Thc kcy issucs about this function arc thc intcrfaccs 

with a multitudc of othcr systcms, thc Air Task Ordcr 

(ATO) prcparation and disscmination 'and thc wcathcr 

forccasting. 

In ordcr to plan hc air opcrations, a thcatcr commmdcr 

has to gathcr a multitudc of informations coming from 

diffcrcnt systems likc: 

- thc cnncmy Ordcr Of Battlc (ODB) gcncratcd by 

intclligcncc systcm. 

,- his,:Qwn lorccs sutc gcncrated by Army, Navy and Air 

Foftc s y s LC m s.. . 

This lcads to a rcquircmcnt of conncction with a 

multitudc of othcr systcms and thc COirWt intcrprclrition 

of thc data collcctcd by thcsc systcms. 

Oncc $his proccss has bccn pcrformcd, thc Thcatcr 

commhndcr has to claboratc and dissemin;\tc thc AT0 to 

all thc rclcvant units. Thcsc units arc scaucrcd on thc 

Thcatcr and may bc conncctcd by National mcons or 

Alliul systems. 

t 

'Thc planning function supposcs for all thc military 

opcrations that yob arc ablc to forccast thc cnncmy 

opcrations, your own opcralions and thc wcathcr. For 

this purposc you nccd adcquatc informations on thc 

wcalhcr on thc Thcatcr and also outsidc thc Thailcr.

11-2 

b. m 

All thc air opcntions USC a common mcan that mhst bc 

sharcd. it is the airspacc. In ordcr to do so you miist bc 

ablc to collcct all thc rcquircmcnt!! in airspacc coming 

fmm thc diffcrcnt units (Air Spacc Rcqucst) and thssc- 

iiiinatc thc Airsp;icc Cw)rdination Ordcr (ACO) lo all 

thc rclcvant unit!$. 

This airspacc planning is coordinatcd with thc AT0 

planning and distributcd thrcc to four timcs a day 10 thc 

uniu, this rcprcscnt a hudgc amount of mcss;lgcs simad 

all ovcr thc Thcatcr. 

c. n 

T5c air opcrations arc pcrformcd usin;! opcrators, 

ground-air-ground communication ncLs, consolcs ... 

All thcsc C2 rcsourccs must bc allixatcd according to 

thc currcnt AT0 corrcsponding to thc Air Dirccrivcs. 

This suppscs a hudgc information cxchangc bclwccn 

the diffcrcnt C2 cntitics. Thc proccss of thcsc informa- 

tions. and thc planning of thc bcsl C2 rcsourccs 

allocation according IO thc Air Dirwuvcs. 1 

1.3 Air activity control 

Air activity control is dividcd in two functions: 

- air mffic control, 

. air inission control. 

a. A ir uaffic cond . 

Air traffic control suppscs first a flight rcgulahn, that 

is to sry an i1lIWtion of the corrcspcmding airspacc and 

C2 rcsourccs to thc traffic rcqucsts. This supposcs thc 

collcction of all thc flight rcqucsts, thc proccss of 

allocation in coordination with thc airspacc ninnagcmcnt 

lunction and thc disscmination of thc flight autorisations 

10 thc rclcvant units. 

In addition, air traffic conuol is in chiirgc of SGwh And 

Rcscuc (SAR) opcrations. mainly based on thc xcuratc 

location of thc fricndly crcws. 

b. Air mission CO ntrol 

Oncc an air opcration has bccn planncd according LO thc 

ATO, this opcration has to bc controllcd by air mission 

controllcrs. his supposcs a good coordination bciwccn 

forcc manbgcmcnt and air mission control funclion. that 

is 13 say a hudgc amount of informalion cxchangc. 

Thcrc is also an issuc linkcd with radioclcctric propaga- 

tion phcnomcna. it is control of low flying aircrafts. 

This supposcs a hudgc amount of antcnnac widc sprcad 

ajong thc thcatcr to offcr thc coinmunication means to 

air mission conirollcrs. 

dncc a mission has bccn pcrfomcd, thc mission rcpn 

must bc prcparcd at thc unit lcvcl and disscminatcd to 

thc rclcvant opcration ccntcrs for intclligcncc gathcring 

.-+ and force managcmcnt planning function. 

1.4 lntelligence 

Intclligcncc function is in chargc of cnncmy ODB 

awssmcnt and forccasting and damage assasmcnt. This 

supposes thc gathcring of all typcs of information: 

visual, electromagnctic ..., the fusion of these diffcrcnt 

infomiations and thc disscrnination of thc rclcvant 

information to opcrating centers or units sprcad all 

dong thc Thcatcr. 

2. CONTRIBUTION OF TACSATS TO AIR 

COMMAND AND CONTROL 

2.1 Surveillance 

For survcillancc function, TACSATS may providc 

qucuing to lhc currcnt Scnwr net by diffcrcnt mcans. 

First ELlNT or COMINT satellitcs may providc informations 

on, cnncmy airbascs activity and trigger thc 

AWACS cakc-orr. 

If thcsc informations arc not availablc, radars or clcctro- 

optics satcllitcs may providc cnncmy raids carly dctcc- 

Lion in ordcr to alcn the Theater scnsor nct and activatc 

thc rclcvanl sensors. 

For thc spccial casc of ballistic missilcs. launchcrs 

dctcction may bc providcd through radars or clcclro- 

optics satcllitcs. Missilc launch prcparation may bc 

dctcctcd through the usc of ELINT or COMiNT 

.mtclliLc:; picking-up thc corrcsponding clcctromagnclrc 

signals. In last rcssort. rnissilc launch dctcction may be 

dctcctcd by infrarcd satcllitcs picking-up llic plunics of 

thc incoming missilcs. 

2.2 Resources management 

For rcsourcc mnnagcmcnt. mctcorological satcllitcs may 

providc rhc rclcvant, information in ordcr to proccss thc 

24 to 48 hours forccasting ncccssary for thc planning of 

air opcrations. 

broadcasting TbiCSATS arc a good mcan to disscminatc 

thc AT0 mcss& .(torcc managcmcnt) and thc ACO 

(airspacc manag$r&t).m 

, 

all Ihc units widcsprcad on lhc 

#?.* 

Thcatcr. 4,;;y:,* 

t:i';...' 

Ground-to-ground TACSATS arc a good man to solvc 

thc opcrational rquircmcnu of: 

'. 

1,*# .' 

- othcr systcm: 'dg$$wc ".;,.. intcrrogation (forcc managcmcnt). 

* , .* *. 

I . 

e;., 

".:+e 

- Airspacc Control Mcans rcquircmcnu diffusion (air- 

spcc managcmen:), 

- C2 ilssct~ availability (C2 rcsourccs managcmcnt). 

Thc tcchnical involvcd considcration arc thc quantity of 

information cxchangc aid the widcsprcad on thc Thca1r.r 

of thc diffcrcnt uniu involvcd in thcsc functions. 

2.3 Air activity control 

Navigation TACSATS (signal location typc) is hc 

most cfficicnt solution for aircraft localiiration. which is 

thc major dcfficicncy of starch and rcscuc opcdons.

0 

Grouad-air-ground communication TACSATS is a good 

mcan to solvc thc opcrational rcquircmcnt of closc 

conuol of low flycrs. that is mandatory IO allow an 

activc. control of low flying aircraft incrudcd in air 

mission conuol function. 

Ground-to-ground communication TACSATS inay 

solvc Ihc opcrational rcquircrncnts oT: 

- flight plans dissemination (air traffic conuol), 

- imrcdiatc airspacc convol mcans availability (air 

traffic control). 

- rapid rcallocation of planncd missions (air mis: ion 

control), 

- rapid atwk asscssriicnt (air mission control). 

2.4 Intelligence 

Ground-to-ground communication TACSATS ilrc a good 

mcan to solvc thc opcrational rcquircmcnt or timcly 

diffusion of filtcrcd inlormotion to thc rclcvant unit or 

opcration ccntcrs in thc Thcatcr. 

ELlNT and COMINT TACSATS arc thc orimary 

scnsors to providc thc cnncmy OD9 for SAM, radars, 

airbascs. FLOT location and activity. 

Radars or clcctro-optics TACSATS arc a complcmcn- 

city platforms to solvc Ihc opcntional rcquircnicnts of: 

- cnncmy ODB asscssmcnt. 

- bomb damagc asscssmcnt, 

- air campaign results cvaluation. 

3. OPERATIONAL IMI'HOVEMEN'I'S 

DUE TO TACSATS 

3.1 Surveillance 

TACSATS givc thc opportunity to implcmcnt il glohill 

cxtcndccl air dclcncc capability hid on: 

- Lctivc(IcicI~, 

- passivc dcfcncc, 

- countcrfirc. 

Activc dcfcncc is alcrtcd through thc dlcrt function 

dcrivcd from survcillancc and thrcat cvaluation, qucucd 

by thc inflight missilc track and controllcd through thc 

intcrccption arca prcdiction. A!] thcsc functions may bc L 

pcrformcd by dcdicatcd TACSATS which pcrformanccs 

m rclincd according lo thc Thcalcr ballistic Ihrcat. 

Passivc dcfcncc is alcncd through thc survrillancc 

function and convollcd through thc impact arc3 prcdic- 

lion. This control is mandatory in ordcr to implcmcnt 

passivc mcasurcs on limitcd arca locations and during a 

limited timc rclntcd with UIC impact timc prcdiction. 

Counlcrlirc is alcrtcd through thc survcillancc function 

and thc wcapon systcm queuing is pcrformcd through 

thc launch zone dclcrminaiion. Thc adcquatc launch zonc 

dctcrmination supposcs dcdicatcd TACSATS which 

pcrformanccs arc fincly tuncd according to thc Thcatcr 

ballistic threat c haractcristics. 

3.2 Force management 

Forcc managcrncnt proccss is a complcx and Icnghtly 

prtKcss going froin "gcncral objcctivcs" to "Air Tisk" 

and "Flight dtxumcnlation" production. 

i 

11-3 

The process that leads from gcl?eral objcctivcs to the 

AT0 is pcrformcd in an opcration ccnlcr using modcm 

mcms likd ;rrtifIcial inlclligcncc and knowlcdgcd bascd 

systems. Oncc thc AT0 has bccn claboralcd it must bc 

disscminaicd to thc different units in the Thcalcr. This 

rcquircs a hudge cxchangc of information bctwccn 

opcrations centers and units. Communication 

TACSATS is a good mcan lo pcrform this information 

cxchangc. 

Wih the ATO. hc pilols in thc units arc ablc to 

pcrfthn thc largct atlack prcparation whilc thc opcration 

officcrs in thc opcration ccntcrs may pcrfom the global 

mission preparation (doconfliction, flight routes ...). 

Oncc thc global mission prcparation has bccn pcrformcd 

thc pilots in Ihc units may procas thc dctaikd mission 

prcpanlion and issuc thc flight documcnts. 

Thcy arc rcady lo cake-off as soon as thcy rcccivc thc air 

lask from the opcration ccntcr. 

This short somnicnt about form managcmcnt shows 

that by using adcquatc communication mcans and 

adcquatc intclligcni prwcss. we may rcducc thc global 

timc rcquircd by thc function. Communication 

TACSATS may providc adcquatc mcans to rcducc thc 

timclincs involvcd in this proccss and drivc changcs in 

opcrational proccdurcs,. 

3.3 Airspace mhagenient 

Thc ACO is a complcx mcssagc that dcfincs thc diffc- 

rent arcas in thc airspacc. This mcssagc includes air 

routcs, transit corridors, low lcvcl transit roulcs, wcapon 

frcc zoncs. air basc dcfcncc zoncs, rcslrictcd opcrations 

zoncs, high dcnsity airspacc control zonc ... 

It is a lcnghtly proccss to claboraic this mcssagc and to 

disscminatc it to thc rclcvant units. TodiIy this nicsugc 

is distributed cvcry six to cight hours und valid for thc 

samc pcriod. Thc conscqucncc is that thc Army by 

cxaniplc hxs a dcdicatrd airspacc availablc for a six hours 

pcriod to pcrform its opcrations,This has bccn a 

problcm in thc Gulf War whcrc thc Frcnch Army had a 

radar on a hclicoptcr (HORIZON) that could not bc uscd 

with iu bcst pcrformancc bccausc of tlic limitcd night 

altitudc. 

TACSATS could providc tcchnical mcans that may 

inuoducc ncw opcrational proccdurcs likc dynamic 

allocation of thc airspacc. 

4. CONCLUSION 

This short analysis has shown that communication 

TACSATS arc nccdcd to pcrform all thc air mission 

comm'and and conmi functions. 

Diffcrcnt typcs of communicaiion TACSATS arc 

quiral: 

- broadcasting. 

- bidircctional. 

- ground - to-g nund , 

- ground-to-air. 

Thc dcvclopmcni of TACSATS may changc thc current 

miliury proccdurcs (cspccially thc timAincs for AT0 or 

ACO). 

1

11-4 

TACTICAL SATELLEES FOR AIR COMMAND AND CONTROL 

AIR COMMAND AND CONTROL SYSTEM FUNCTIONS (1). 

AIR COMMAND AND CONTROL SYSTEM FUNCTIONS (2) 

TACSATS FOR SURVEILLANCE 

TACSATS FOR RESSOUReES MANAGEMENT 

TACSATS FOR AIR ACTWI lY CONTROL 

TACSATS FOR INTELLIGENCE 

OPERATIONAL IMPROVEMENTS FOR SURVEILLANCE 

OPERATIONAL IMPROVEMENTS FOR FORCE MANAGEMENT 

OPERATIONAL IMPROVEMENTS FOR AIRSPACE MANAGEMENT 

CONCLUSION 

[ AIR COMMAND AND CONTROL SYSTEM FUNCTIONS (1) ] 

~7 

FUNCTIONS KEYISSUES 

AIRSPACE SURVEILIANC E 

FORCE MANAGEMENT 

1 

LOW OBSERVABLES. LOW FLYING OBJECTS 

BALLISTIC MISSILES 

ADVERSE SATELLITES 

INTERFACE WITHTHE OTHER SYSTEMS (INTELLIGENCE, 

ELECTRON IC WARFARE -. .) 

AIRTASKORDER PREPARATION AND DISSEMINATION 

WEATHER FORECAST1 MG 

1 AIRSPACE MANAG EM ENT 'REALTIMFALLOCATION OF THE AIRSPACE 

1 'AVAIIABLP AIRSPACE DISSEMINATION 

C2 RESSOURCES MANAGEMENT 

INFORMATION EXCHANGE WITH C2 ENTITIES 

WORAPHl 

\

0 

a 

.. 

. . .I 

AIR COMMAND AND CQNTROL SYSTEM FUNCTIONS (2) 

FUNCTIONS 

AIRTRAFFIC CONTROL 

AIR MISSION CONTROL 

INTELLIGENGE 

J 

i. 

FLIGHTS REGULATION 

KEYISSUES 

COORDlNATlON WITH AIRSPACE MANAGEMENT 

SEARCH AND RESCUE OPERATIONS 

INTERFACEWITH FORCE MANAGEMENT 

ACTIVE CONTROL OF LOW FLYING AIRCRAFTS 

MISSION REPORT PREPARATION AND DISSEMINATION 

ENNEWORDER OF BATTLE ASSESSMENT 

DAMAGE ASSESSMENT 

DISSEMINATION OFTHE RELEVANT INFORMATION 

WORAPH? 

DEF flClENClES I OPERqTlONAL REQUIREMENTS 

LOW OBSERVABLES, 

LOW FLYING OBJECTS 

WSTlC MlSslLES 

ADVERSESATELLITES 

.. 

AI RBASES ACTIVATI 0 N 

RAIDS EARLY DETECTION 

LAUNCHERS DETECTION 

MISSILE LAUNCH PHEPARATION 

MISSILE LAUNCH DETECTION 

COMMUNICATION SATELLITES 

POSITION 

OBSERVATION SATELLITES 

COVERAGE 

TACSATS TYPE 

ELINTAND COMINT 

11-5 

RADARS OR ELECTRO-OPTICS 



INFRARED DETECTION

11-6 

!' 

i i 

[XCSATS 

FOR RESOURCES MANAGEMENT 1 

DEFFlClENClES 

__-I 

-- 

INTERFACE WITH THE OTHER SYSTEMS 

AIRTASK ORDER PREPARATION 

AND UiSSEMlNATlON ! 

WEATHER FORECASTING 

'REAL TIM E" ALLOCATIO N 

OFTHE AIRSPACE 

'AVAILABLE' AIRSPACE DISSEMINATION 

INFORMATION EXCHANGE 

WITH C2 ENTITIES 

DEFFlClENClES 

FLIGHTS REGULATION 

COORDINATION WITH 

AIRSPACE MA NAG EM ENT 

SEARCH AND RESCUE OPERATIONS 

_-- - 

INTERFACE WITH 

FORCE MANAGEMENT 

ACTIVE CONTROLOF 

LOW FLYING AIRCRAFTS 

MISSION REPORT PREPARATION 

AND DISSEMINATION 

OTHER SYSTEMS DATABASE GROUNDTO GROUND 

INTERROGATION COM MU N ICATIO N 

AIRSPACE CONTROL ORDER 

DISSEMINATION 

C2 ASSETS AVAl LA B I LlTY 

WORAPtl4 

[ TACSATS FOR AIR ACTIVITY C~JNTROL] 

OPEWTIONAL REQ U I REM ENTS 

~~ ~ 

FLlGHt PLANS DISSEMINA?ION 

IMMEDIATE AIRSPACE CONTROL 

WANSAVAILABILITY 

AIRCRAFT LOCALIZATION 

RAPID REALOCATION OF 

PLANNED MISSIONS 

CLOSE CONTROLOF 

LOW FLYERS 

RAPID AIR AlTACK ASSESS lENT 

BROADCASTING 

GROUNDTO GROUND 

COMMUNICATION 

- .. . .. - 

TACSATS TYPE 


COMMUNICA i'lON 


COMMUNICATION 

NAVIGATION 


COMMUNICATION 

GROUND/AINGRO U N D 

COMMUNICATION 


COMMUNICATION

ENNEAAV ORDER OF BATLE 

ASSESSMENT 

DAMAGE ASSESSMENT 

DISSEMINATION OF THE 

RELEVANT INFORMATION 

.. 

[ TACSATS FOR INTELLIGENCE 1 

OPERATIOW\LREQUlREMENTS I TACSATSTYPE 

- 

SAM, RADARS, AIRBASES. FLOT 

LOCATION AND ACTIVITY 

A in CAM PAI& N RES U 1-1s 

1 EVALUATION I 




_ _ ~ ~ 

TIMELYDIFFUSION OF 

- 

-1 

I 


FILTERED INFORMATION COMMUNICATION 

OPERATIONAL IMPROVEMENTS FOR SURVEILLANCE 

/ \ 

IMPACT AREA 

PR E 0 I CTI 0 N 

I'

11-8 

I OPERATIONAL IMPROVEMENTS FOR FORCE MANAGEUENT~ 

AIRFORCES 

PREPARATION 

-- 

COMPLEXAND LENGTHY PROCESS REQUIRING HUGE COMMUNICATION CAPABILITY 

PERATIONAL IMPROVEMENTS FOR AIRSPACE MANAGEMEN 

RESTRICTED 

OPERATIONS ZONES 

€3 BASE DEFENSE 

ZONE 

WEAPON FREE 

0 ZONE 

WEAPON FRE 

OF THE AIRSPACE ] 

-

0 

0 

(CO") 

-COMMUNlCATlONTACSATSARE NEEDEU FOR ALLTHE AIR COMMAND AND CONTROL FUNCTIONS 

I 

- DIFFERENTTYPES OF COMMUNICATION ARE REQUIRED : BIDIRECTIONAL 

. II' 

BROAD CASTING 


GROUNDTO AIR 

- DEVELOPPEMENT OF TACSATS MAY CHANGE THE CURRENT MILITARY PROCEDURES 

, 

WORIPHIO

CONSIDER4TIONS FOR NATO SATELLXE COMMUNICATIONS 

IN THE POST-2000 ERA 

1.The National Delegates bnrd of AGARD. upon 

recommendation by the Avlonics Panel of AGARO, spprovea in 

March 1986 ths establishment of WG-13 to study satdllite 

communicdtions for NATO under the direction of Prof. Or Nejat 

lnoq of Turkey. 

2.9me 14 scientists/engineers. from research Rnd indudrial 

establishments of Canada, France, The Federal Republik of 

Germany. Noway, Turkey. the United Kingdom. the United 

States of America as wnll as from International Military Staff of 

NATO and SHAPE Technical Centre, participated,in the work of 

WG 13. 

3.This paper 1s a brief summary' 

of the studies carried out by the group in the 

period 1988-1990 on the type of satellite Communication 

systems which NATO can have in the post-2000 era including 

the critical techniques and technologiea that need lo be 

developed fcr this purpose 

I 

4 In accordance with the Terms of &lerence.the Group 

considered a time period beyond NATO N and other natidnal 

systems now In the implementation or planning stage, wthh 

would cover a time span of 20-30 years, i.e 2CCO-2030 It was 

recognized the1 the earlier part of this period would be 

constrained by the eristing and planned assets but the later 

oart would be. and should be, more technology-driven the 

following assumptions are made which take into accolmt 

perceived trends and desirable attributes for future SATCOM 

systems: 

I) The area of interest for NATO will remain as is to-day end 

will include the polar region 

li) The use of SATCOM will be more pervasive particulerly 

for small mobile users (aircratt. land-mobile. ships And 

submerged submarines) to 6 ~pporC general purpose dnd 

modern 0 1 structures. 

SATCOM will be integrated with the future ISDN networKs 

now being planned and implemented In the nations dnd 

NATO. This may require SATCOM to have ImproJed 

effective performance 4th respect to such parameters as 

delay and echo. 

lv)Yhe need for increased survivability against bolh physical 

and jamming threat will continue. 

v)The use of frequencies In the EHF and optical bands lor 

greater capability (e.g. AJ capability and communicatidns 

with submerged submarine?) and smaller terminals hre 

foreseen. 

d)The future SATCOM systems will be required to be 

cheaper and more affordable. 

vll) Thoro wlll be the usual need for interoperabllity. 

5.The Group agreed that the above attributes could be taken as 

inputs and goals for the system architectures lo be developed 

for a future NATO SATCOM. In fact. these attributes were 

derivsd from the deficiencies of the present system which is 

no1 flexible enough with resped to growth In capacity and 

capabllity. and has a high degree of electronic end physical 

. . , 

by 

A. Nejat Ince 

Marmara Scientific and Industrial 

Research Center 

EO. Box 2 I 

51470 Gchzc-Kmaeli 

Turkey 

14-1 

vulnerability dind does nM provide communications for the 

polar region ' and submerged submarines. TRe system 

development.."in the past has been based on successive 

discrete mstqh in capability and spending and each 

procuremih'?as contained an important cost element of R&D. 

Thsre has been R minimum of joint national RAD and use of 

the NATO system which resulted. among other things, in 

considerable interoperability problems. 

It was agreed that what was required for the coming decades 

which may be characterized by 'uncertainty' and "shrinking 

military budgets" was a very flexible. modular SATCOM system 

whose communication capacity and resilience to ECM and 

physical threat can be modified when operational requirements 

change, however, without having to undertake excessive RBD 

and total replacement of the space segment. 

6.For the development of system architectures to achieve 

flexible and highly cost-effective SATCOM optioris for NATO. a 

technical survey has been made and information collected on 

the satellite system concepts being considered nationally 

(Canada. France. FRG. UK and USA) and internationally (ESA. 

Intelsat. Eutelsat. INMARSAT) for both civil and military 

applications as well as on related technological R&O activities 

and operational aspects regarding threat and environmental 

factors such as propagation and the usage of frequency 

spectrum. 

7.TLe status of the follovring lechniques/technologies and 

conrapls which appear feasible and exploitable by future 

SATCOM systems and whicli are consequently being 

investigated nationally and internationally have been described 

in the report: 

i) multi.beam/phased-array antennas with adaptive spatial 

nulling and multiple transmit spot beams, 

ii) ECCM techniques, 

iii) flexible and programmable on-board signal processing 

and switching techniques and devices. 

iv) multi-frequency payloads. 

v) multi-satellite systems to create spatial uncertainty for the 

enemy. 

vi) USP of tethers in space, 

vii) laser and millimetre-wave communications. .for 

inter-satellite links, 

viii) blue-green lasercorn for submerged submarines, 

Ix)application of superconductivity. aflificial Intelligence. 

neural networks. robotics and of space-borne 

computers/r~ftware for slgnal processing and for manual 

and autonomous control of spatial and terrestrial 

resources. 

x)power generation in space, 

xi) spacecraft propulsion systems, 

xii) launch vehicles and space transportations. 

xiii) nuclear effects and hardening techniques. 

.

0 

0 

. 

14-2 

xiv)physical attack and protective measures against dirocted 

energy beams (laser, particle. RF) and ASAT etc.. 

w)sensitive. light, long-life materials. Component9 nnd 

devices for sensing, power generation. amplilicaticn and 

control. 

&The speed of progress made in the above arras will be 

determined mainly by the urgency of the need for. and the 

amount of resources allocated to, them. These technologies 

and new production methods coupled with basically 

software-controlled processing transponders with a capability 

to continuously adapt to changing requirements are expected 

to lead to more flexible and reliable, lighter and less-power 

consuming and altogether more cost-effective satellites than 

the present ones. Moreover these satellites can be launched by 

a number of different launch vehicles. Further reduction in cost 

may be obtained by sharing the satellites (single an/or cluster) 

between NATO and the Member Countries. 

9.h can be stated generally and with confidence that in the time 

period in question it will be possible to design and build any 

satillite to meet almost any requirement. Technology exists or 

will be available for whatever communications perfcrmance 

and level 01 hardening is required as well as launch vehicles 

with capability to place the resulting satellite of whatever 

weight and power into any required orbit. The constraints will 

be the availability of orbital slots, frequency spectrum and, of 

course, funds. 

1O.The cost considare: ,IS have therefore been the driving loctor 

for the systems reported here. When assesslng different 

concepts for sate!lite designs and system architecture what is 

importanat is not so much their absolute but rather their 

relatlve costs. Accordingly a cost model of the satellite system 

has been established which takes into account: 

band used (SHF. EHF). 

- number of transponders, 

- spacecraft reliability, 

- RBDmSt. 

- power required. 

- weight. 

- launch cost, 

- recurring cost. 

- system availability. 

I - frequency 

11.Several SATCOM system architectures with the potentlal of 

meeting possible future NATO requirements Implied in the 

paragraphs above have been defined using different orbits 

(geostationary, polar, 12-2dhr Inclined at 63'.4 and Low Earth 

Orblt LEO) and a number of satellites with single and/or dual 

frequency transponders (SHF and EHF) whlch rad be 

configurod to meet any operational requirement. Table .l lists 

the architectures considered in the report and gives the 

number of active spacecrafl for full continuous coverage of tho 

NATO area includino the polar reglon as well as the total 

number of spacecraft needed for 7-years and 21-year periods 

for a certain given Gpacecraft reliabllity. Archltectures based on 

the use of LEO and a combination of geostationary and 

pola:-orbit satellites were eliminated from further considerhtion 

on cost grounds and the others were subjected to more 

detalled cost-padormance analysis using the cost model 

mentioned In paragraph 10 above. 

12.Table . -2 lists some twenty different promising architectures 

(Caseo) for a future NATO SATCOM and gives the associated 

RBD. recurring and total msts for differont spacecraft reliability 

and Wntinuous service availability for 7 yearr.The mmmon 

attrlbutes of these architectures are the fol!owing(see Fig. .lI : 

(a) I) The transponders have adapUvs receive (with 

steerable nulls) and multl-beam trsnsmll nntennas (1 

earth cover. 1 Europe m r . 1 polar spot and 2 

steerable spots). 

ii) A flexible channelization technique is used on board 

tho satellites at both SHF and EliF. At EHF. this is 

exploited in an omboard processing concept that 

prevents the satellite downlink transmitter from being 

loaded by the jammer and also to prevent 

unauthorized access to the satellite. For flexible AJ 

processing and ease of interoperability a full 

bandwidth (2 Giiz at EHF. 500 MHz at SHF) filter band 

is provided using perhaps different filter technologies 

to obtain different selectivities required (see Fig. E-\) 

where the channelization can be conlrolled by 

telecommand to avoid interference, to alter the 

satellite capacity allocated to various geographical 

areas and to adapt the specilic requirements due to 

restrictions in the tunability of the NATO cr national 

ground segment. At EHF. where the flexhie 

channelization technique is coupled with on-board 

protessing for AI purposes then switchi;lg between 

high-selectivity filter bank outputs (element filter 

output) will be performed at a high rate and controlled 

by an on-board transec equipment which can be 

programm3ble (in orbit) to support several 

simultuneous uplinks. 

The ground segment would consist 01 both SHF and 

EHF terminals. The SHF terminals would be those 

existing at the end of the NATO IV era and would be 

usod mainly to support common-user trunks. General 

transition rom SHF to EHF is foreseen to take place 

over the period covered In the study to support mainly 

mobile/transportable users many of which may have 

demanding AJ andjor LPI requirement. 

The EHF ground segment: 

i) has preferably non-synchronized frequency- 

hopped (because of its better performance in 

disturbed and time-variant propaoation 

conditions and betler suitability to small 

terminals than the direct sequence modulation 

system) terminals operating in FOMA with 

flexible data rates and redefinable codes, 

ii) consists of the simultaneous accesses (for 

system comparison purposes) given in Table 

-3. 

. #, 

The systems . : 

\) have the virtue of allowing easy transition from 

exlsting to future architectures, 

ii) Have minimum development. recurring and 

launch costs. 

. iii) are upgradable and expandabla on a scale to 

meet operational requirements. 

iv) defective and life-expired elements 01 the 

system are replaceable without man 

intervention, 

v) spacecrafl are capable 01 being refuelled 

without man intervention, 

vi) have virtually zero down-time at low cost, 

vii) make maximum use of orbital slot allocations, 

vlii) allow spatial dlstribv(kn of spaceuaft to reduca 

Uwir vulnscability to jamming and physical attack.

It should be noted that the data in Tables .2 (a) and 

(b) are for a 7-year period. hring the 21-y~ar total 

period, three stages of complete space segment 

replacement are expected to occur, which would allow 

for an update for changes in traffic or other 

requirements. For dual . frequency systems 

development cost will be incurred at each stage.Single 

frequency systems will not incur such costs since the 

Same designs of spacecraft would be used throughout 

the 21-year period: only the mix of EHF and SKF types 

would change. Provided military components are used 

in the design of the spacecraft it should be possible to 

maintain full availabilty over the 21.year interval 

t3.h examination of the data shows that: 

.... 

P 

For geostationary operations the cost of 

interconnection of spacecraft is of the order of 3 % , 

and is not more than 4.5 % for the inclined orbits 

(Tundra as the most expensive case).lnterconnection 

provides significant Improvement in service availability 

probability, ranging from 0.14 at the lower inherent 

spacecraft probabilities to 0.04 at the high end. 

Increasing the space segment availability by the 

amount given in (a] above without. however, using 

Inter-!Satellite Links ISL wou!d require launching more 

satellites and this would increase the system cost by 

about 25 %. 

Operation in Inclined orbits costs about 50 % more 

than the geostationary case for Ihe same sewice 

availability, but gives full NATO coverage including the 

polar region. 

The geostationary case 1 corresponds lo the NATO IV 

satellite as far as coverage and the nuniber of 

satellitcs and reliability are cuncerned. It is interesting 

to note, however, that the 7-year system cost of Case 

1 and that 01 NATO N (about -M) are almost 

identical even though Case t satellites have 

considerably more capacity (in SHF and EHF) and 

significantly greater resistance to jamming (on-board 

signal procebsing in EHF and adaptive nulling 

antennas). 

The system cost changes signlficantly with the 7-year 

service availabllity probability. How many Batelittes 

would be needed for a 21- year period without having 

excessive capacity would depend on this as well as on 

what residual capacity would remain at the end of 

each beven-year period and. how the change in 

requirements is introduced; abruptly at each 7-par 

period or progressively during the 21-year period. In 

the latter case, some reduction in the total number of 

satellites required and hence in total cost would be 

expected. 

14.The architectures which appear cost-affective and promising 

ma ghn In Table -4. 

The following comments can be made about theso 

architectures: 

a) 

b) 

An adequately wide range oef architectural options 

are presented from which the architecture best suited 

to the requirements, as they will be known nearer Ihe 

date of system implementation. can be snlerted 

Based on the assumptions made regardlng possible 

future NATO requirements. reli&bilitles of future 

electronic systems and wsts per kilogram of 

Payloads. Spaceaaft Platforms and Launches which 

have been used consistently for all of the candidate 

architectures. it can be concluded that: 

14-3 

' i) Procided NATO can accept the coverage 

provided by a geostationary only system of 

satellites, Architecture A is the lowest cost 

solution. 

ii) If polar coverage obtained by leasing,from the 

USA. costs less than Cost (H-A) or Cost (I-A) 

then Architectures A or B plus Polar leasing 

would provide the next .lowest cost options. 

Option B gives improved availability and AJ 

capability but at 33 % higher cost than the cost 

of A. 

iii) The lowest cost architecture which pidvides full 

coverage is Architecture H at a cost increase of 

50 %over geostationary only (Case B). 

iv) For a further 5 % increase in cost, an 

improvement from 0.95 to 0.98 in operational 

availability and an enhanced AJ capability can 

be obtained by using Architecture I. This 

architecture is probably the most cost-effective 

option of those considered. to all of the 

assumed luture NATO requirements. 

15.k is likely that cost will be the driving factor in determining the 

hoice of a future SATCOM architecture and it is therefore 

appropriate to consider the lhree dominant cost lactors (RBD. 

replacement and launch costs) and indicate what steps could 

bo taken to bring about cost reduction in each case. 

Economy in R83 costs could be obtained through 

NATO/National collaborgtion and by adopting a 

modular approach to system diversilication. and 

evolution. An effective way of achieving the latter 

would be to devplsp at the outset separate SHF and 

EHF spacecraft and use them, in GEO and TUNDRA 

orbits alike, in a mix delermined by the changing 

requirements. 

The use of smaller spacecraft, even though more of 

them may be needed, could lead to lower system 

costs because of the economies 01 scale. Such 

economies of scale would be further enhanced if the 

same Spacecraft types are used at all stages of system 

evolution over a period of, say, twenty years. They will 

also be enhanced if the aame spacecraft types ate 

bought for national as well as NATO use. 

Launch wsts can be minimized by reducing 

spacecraft mass. in particular through the exploitation 

of new technology. tt is also important to maximize 

compatibility with the largest possible range of launch 

vehicles. 

Interconnection of spacecraft increases system 

reliability and therefore tends to reduce the tolal 

number of spacecraft that need to be launched. 

finally. long-term planning is the key to achieving 

reductions in both RBD and recurring ccsts. 

'. 

t6.The NATO SATCOM systems sa far acquired have been 

based on national d&elopments adapted to NATO 

requirements and the %$tin& of service (not necessarily full 

service ) has been obtai#f.ed. by sharing or borrowing capacity 

Irom nntionsl sysleme. '?he national systems. In turn. have 

relied for continuity 01 service on the availnbility of capncity on 

the NATO system. Each procurdment has contained an 

important element of R&D costs and since successive syster.is 

have been developed almost independently of each other, 

R&Dcosts have been. like the replacement cost, also recurring. 

'-.

14-4 

There has been a minimum of joint national R&D and use of 

the system and each procurement has been preceded by 

lengthy negodations on production sharing which has not, in 

general, satisfied, at least some of the member counlries. As a 

result of having independent NATO and national systems there 

has been considerable intoroperability problems. 

h is believed that this trend, based on successive jumps in 

spending and capabilty wilh a minimum degree of general 

national participation should be mnd can be changed lo meet 

the needs of the coming decades which may be characterized 

by uncertainly and shrinking military budgets requiring 

affordable and flexible systems. 

The member countries have adequate experience within NATO 

end Europe and know Ittat under these circumstances it is 

newssary to resort to joint RBD, procurement and use of the 

system while ensuring edectiveness and compelitiveness for 

keeping the costs down. 

17.hhat needs to bo'done jOintly are: 

a) To define NATO an4 national requirements far satellite 

communications. 

b) To develope and agree on a system architecture. 

c) To delineate those technological areas which are 

critical and require RBD. 

I 

d) To encourage and support companies and RBD 

establishments to form research partnership for 

development and production to be carried out in a 

competitlve manner. 

tt Is believed that the archlloctures evaluated and 

recommended In ibis report form a good foundation 

for (b) above and ensure also that the satellite desigrs 

outlined that are flexible need not change basically 

over 8 period of some twenly years nr longer thus 

keeping the RBD and recurring costs to a mlnimum. 

The report outlines also certain critical lechnologies for 

(c) above which neod %D. Some of these RBD topics 

are common IO miiitary and civilian satcoms: some 

others which are specific to military, are likely lo be 

common lo both national and NATO systems and yet 

another category of topics will be NATO-specific. It 

would therefore be necesarry to make a more delailed 

assessment of the RBD topics and determine where 

RRD is a prerequisite and either can be relied upon 

present/tuture civilian developments or carried out 

iointly by member nations. 

18.Tne lollowing areas appear as first candidates for a NATO 

RBD effort because they would provide solutions to problems 

which are NATO-specific and can be made available within the 

time-frame considered lor NATO SATCOM systems' 

On-board flexible anti-jam signal processing which 

can be controlled by software to meet AJ 

requirements generally and to adapt to national 

modems and new modems introduced during tl,e 

lifetime of the satellite(s). 

Adaptive nu1lir.a AJ receive antennas tailored lo NATO 

needs and to keep costs down. 

Autonomous control of the spacecraft and O&M 

generally using techniques of artificial intelligence, 

neural ndtworks and robotics. 

Ry sporing RBD activities. limited to payload technology, in the 

member nltions even on modest scale. NATO can expect to 

get.a bener insight into and to make an impact on current 

technology developments carried out for civilian and military 

purposos. 

t9.h is believed that the collaborative approach outlined above 

for SATCOM acquisllion in NATO give tasks to all the exlstlng 

bodies in NATO such as NAClSq STC. DRG. IEPG, AGARD. 

etc., arid would probably not necessitate creating new 

structures. Cost and benefit anlysis carried out in Ihe report 

show that tqe architectures recommended can be 

implemented In the manner suggested above and could lead 

to systems which are considerably cheaper and much more 

effective than those we havo had so far.

RX de hop 

a) Non-lransparent satellite wilh aboul 50 MHz information bandwidth h?p&dacross 2000 MHz. All terminals hop 

in synchronism. There will be as many dehoppers in the satellite as th& ‘qe different nets with different codes. 

I 

I 

ACCESS 6 AJ 

COMR0L.L ER 

b) Transparent salellilo (full bandwidth) allowing operailon with nonsynchronised frequency-hoppd lerminals. 

*. 

.. )I 

.’ I 

, 4**’ .; 

44 4 . : . 2. 

Fig. -1 Two promising AJ satelllie designs wilh on-board processing and rOufl.‘iQ; ).- 

8 . 8 

14-5

Architecture 

TABLE -1 

Number of Satellites 

Required for different SATCOM Architectures 

No of Active S/C 

for full contiiiuous 

(a) Proliferated LEO 240 

(c) Indined Elliptical Orbit 

(cl) LOOPUS 9 

(C2) MOLNIYA 

3 x 12 - hrs 

(a) TUNDRA 

2 x 24 - hrs 

2 x 24 - hrs 

(a GEO 1 Baseline 

~- 

~~ 

(e) Svstems of Satellites in more than one Orbit 

(el) GEO + Polar 1 GEO + 6 Polar S/C in GEO are 

(82) GEO +24-hr MOLNIYA 

dual frequency singk 

in Polar orbit 

(a) Dual freq S/C in 1 GEO GEO S/C have 

GEO +single in t 2 inclined EHF and SHF 

Inclined Orbit 

Inclined EHF or SHF 

(b) Single freq in 2 GEO GEO S/C are air 

both orbits + 2 inclined of EHF and SHF 

Inclined EHF or SHF 

(f) CLOUDSAT Receive S/C Numbers will depend 

with lOdB ECCM 20 GEO. 20 Inc. on jamming threat 

advantage TX S/C:- at the time 

relativu to (e2)b 2 GEO t 2 Inc 

I 

No of S/C 

for 7 years 

> 240 

27 

9 

G 

6 

3 

3 GEO 

+ 

18 Polar . 

3 GEO 

+ 

6 inclined 

6 GEO 

t 

6 inclined 

60 GEO 

60 Inclined 

6 GEO 

6 inclined 

(8) M ~ S The basic concapt applies lo all case (c) thro' (f) 

Total No of 

s/C tor 

21 years 

-- 

> 500 

81 

27 

18 

18 

9 

9 GEO 

+ 

54 Polar 

9 GEO 

+ 

18 inclined 

18 GEO 

+ 

18 inclined 

180 GEO 

180 inclined 

18 GEO 

18 inclined

0. l 6 

Table -2 (a) System Evaluation Data lor Geoetntlonary Operations ( 7 years) 

spacmn Pnylond Avallablllty Total No. System Costs 

CIW 

No/Orbll Frequency EMF SHF Connect S/C %Al 

operating 

Spscecran R I D Recur Launch Tolat 

1 2 Dual Y Y No 061 085 2 242 82 76 400 

2 2 Dual Y Y Ye 061 093 2 2C2 87 79 428 

3 3 Dual Y Y No 061 09d 3 242 163 115 520 

1 3 Dun1 Y Y 

Yes 061 098 3 

- 

4 Y V 

0 72 

4 Single NO 076 

4 292 % 92 478 

- I 

4 Y 

SqIlS Y I YO3 :;g 093 

- -- 

6 Sq1e Y Y 

No 

0 72 

076 

096 

6 

.- --.___ -____ - 

e 6 Smgle Y V YCS 9;; om 6 

Y 

/ 

14-7 

- - 

- - 

Table - 2(b) Evaluation Data lor 24-Hour TUNDRA Orbits ( 7 years) 

- 

262 173 118 553 

R6 D Recur bunch I Total 

223 221 126 570 

238 236 130 604

14-8 

Table - 3 : The EHF Ground Segment Assumed lor System Comparison 

Type of 

Termlnal 

_____-- 

Ship- Borne 

- -- -. 

Aircraft 

Submarine 

-__. 

t 

-- 

Land tronsportatle 

~ Dla. 

Antenna IT, pa 

:,n) OIW) 

- 

01 

-- 

os 01 

-- -..- 

----- 

025 01 

-- 

50 lo 

20 05 

05 001 

I 

Transmlsslon Number of slmul- 

Rate (Baud) taneous accesses 

4 x64oOO(') I 15 

(*) 16 W/s COOBCS (adapltve suo-band codlng) exist today with quality whkh equals that 01 the 64 kb/s PCM. I1 IS oxpeclorl that In the 

IlmOfrme COnSkWd In lhls repod lhera wlll be 8 kb/s 01 even lower-rate codecs available lor use In SATCOM wlh qualiiies comparable 

lolhatd64W/sPCMvo(ce. 

t 

1 Le 

J 

Carea No Total No of 

opeding 

rpa cecm n 

e 12 

TABLE -4 

COST-RELIABILITY COMPARISON OF CANDIDATE ARCHITECTURES 

FOR A SYSTEM LIFETIME OF 21 YEARS 

AvsllabllHy 

3 3 D 098 

" . q E I 0 I 097 

RLD 

3 * 242 - 

726 

3 x 262- 

7eG 

3.238- 

714 

3 = 238- 

714 

2ee 

9 I 3 I E €5 I 095 290 5 

- 

370 86 

Coal (21-year) (SM) 

665.519- 313.354- 2755 

1104 667 

I

ADVANCED TECMNOILOGIIES FOW LIGHTWEIGHT EHF TACTICAL 

@BMMUNICATP[ONS SATELLITES* 

David R. McEIroy. Dcan P. Kolha. William L. Cimnbcrg. ad Marilyn D. Scmprucci 

Lincoln Laboratory. Massachusettq htiiutc of Technology 

P.O. Box 73 

Lexington, MA 02173-9108 - USA 

1. ABSTRACT 

'The communicatiom capabilitics prdvidcd by-!iHF satcl- 

litcs can range from low data ratc scrviccs (75 to 2W' bps 

pcr channcl) to mcdiuni data ratc links (4.8 kbps to 1:>44 

Mbps pcr link) dcpcnding on thc payload configuratlon. 

Through thc usc of EHF wavcfonn standards. thc EHF 

payloads kill be compatible with cxisting and planncd 

EHF terminals. Atlvanccd tcchnologics pcrmit thc dcbcl- 

opmcnt 0; '.ighly capable, lightwcipht payloads which can 

bc utilizcd in a varicty of rolcs. 'Ric kcy payload IcAdol- 

ogics includc adaptivc uplink antennas; high spccd, ]ow 

powcr digital signal proccssing subsystcms: liphtwc\ght 

frcqucncy hopping synthcsizcrs; and cfficicnt solid-statc 

transmittcrs. Thc focus in this papcr is on thc sipal 

proccssing and frcqucncy gcncration tcchnologics and tlicir 

application in a lightweight El4 F p;tj.load for tactical 

applications. 

2. INrHODUC'I'ION 

A motivating factor for thc tramsition to EHF corrimunica- 

lions (i.c., 44 Gklz uplinks and 20 Gtf?. downliiiks) is thc 

rcquircrncnt for iinprovcd intcrfcrcncc protcctiw with 

small mohilc prwl rnancportahlc tcnninals for tiictical and 

stratcgic ucr~s. Enicrginp tcchnologics nllow El IF ctm- 

municatiom systcrns. which can s uppi both low data ratc 

(LDR) and medium data ratc (MDR) scrviccs, to tx implc- 

mcntcd in lightweight. low powcr configuration% Sbn- 

dad EHF payloads, utilizc both atlvanccd antcnna systcrns 

and on-board signal gcncration antl prnccssing tcchniqucs 

to improvc pcrformancc and protcction. A payload which 

utilizcs thcsc fcaturcs for a thcatcr covcxigc application is 

described in this papcr. The application of advanccd 

signal gcnnation and proccssing tcchnologics to this light- 

weight payload rcsult in a payload which can bc incorpo- 

rated into sstcllitcs of many sizcs, ranging from large, 

multiplc function satcllitcs to small, augrncntation satcllitcs 

1141. 

3. ANTENNAOFTIONS 

Advanccd antcnna fcaturcs for tactical applications can 

includc thc ahility to providc a variablc covcragc uplink 

spot hain pattcm, an autonomous nulling capability within 

the uplink spot bcam pattcrn, or both. Variable bcamwidth 

EIIF antcnnas can bc utilized in a varicty of applications 

as shown in Fig. I. For payloads in clliptical orbits, a 

variablc barn width fcaturc can bc utilizcd to maintain an 

essentially fixcd covcragc arca indcpcndcnt of satcllitc 

altitudc 141. In a gcosynchronous orbit application, thc 

bcam variability can be uscd to satisfy diffcrcnt covcragc 

and gain rcquircmcnis such as in supporting tactical 

thcatcn of varying sizc and capacity rcquircmnts. Onc 

approach to obtaining the bcam variability is by employing 

multiplc fwds in thc antcnna. Thcsc frcds arc combined 

wirh a vanablc pown conibincr nctwork hcforc going to 

thc rcccivcr. With 7 uplink fccds in thc anicnna. a $to- 1 

*This work was sponsorcd by thc Dcpmmcnt of thc 

Amy. thc Dcpartmcnt of thc Air Forcc. antl the Ihfcnsc 

Advanccd Rcscarch Projccts Agcncy undcr Air Forcc 

Contract FIWI~R-~O-C-OOZ. 

variation in bctunwidlh can bc achieved. whilc 19 uplink 

fccds givc a 5-10-1 variation. Ry incorporating both phasc 

and amplitude co~trol in thc hamforming nctwork and 

including a proccssor, thc variablc bcamwidth anicnna can 

also includc autonomous nulling [5]. 

4. LIGHTWEIGHT SIGNAL GENERATORS 

In ordcr to providc cffwtivc intcropcrability. it is impor- 

tant for all thc EHF payloads to work with thc samc typc 

of uscr tcrminals. S:andard ELIF transmission formats and 

dynamic acccss/configuration control arc important fca- 

turcs in providing Lhis intcropcrability. Thc standard EHF 

wavcform rcquircs thc dchopping and clcmtdulation of 

communications signals on-board thc satcllite. As shown 

in Fig. 2, lightwcight frcqucncy hoppinp synthcsizcrs can 

bc irnplcmcnted using dircct digital synthcsis tcchniqucs 

along with high-spccd. hybridized bandwidth expansion 

circuitry. Thcsc advanccd frcqucncy gcncrators yicld 

alrnost an ordcr of magnitudc rcduction in wcight ovcr 

frcqucncy synthcsizcr subsystcms of thc carly 1980's whilc 

also rcquiring significantly lcss than hall thc powcr. 

Thc kcy clcsign critcria for a payload frcqiicacy synthcsizcr 

arc a low powcr cmifigurati(m which hiis thc aliility to 

gcncratc signals with low spurious frcqucncy cantcnt whilc 

mccting thc frqucncy switching spccdi cquircmcnt. Thcsc 

factors arc kcy in sclccting thc bancbidth expansion 

approach as shown in Fig. 3. A switchcd filtcr bank 

approach is a straightforward implcmcntatiori. flowcvcr. 

film sizc limits thc niimhcr of frcqucncics (N) which can 

bc sclcctcd for mixing with the dircct digital symthcsizcr 

(DDS) output. thus impacting thc amount of bandwidth 

which must bc gcncralcd by thc DDS. This advcrscly 

affccb both thc powcr and spur constraints by rcquirinp a 

highcr powcr DDS and by gcncrating largcr spurs. Tlic 

altcmativc afpoach shown in Fig. 3 was sclcctcd for tltc 

payload frqucncy synthcsizcr. This approach utilizcs a 

high spccd phasc-lockcd loop to gcncratc thc sct of N 

frqucncics which arc mix4 with thc. DDS output to 

expand thc bandwidth. 'Thc widc bandwidth of thr loop 

allows N to bc Inrgc. thus rcquiring a smallcr Dl>S 

bandwidth. Thc rcduccd DDS bandwidth allows thc usc 

of a low powcr, CMOS based DDS and rcsults in lowcr 

spur Icvcls. Thc kcy icchnology chdlcngcs in iniplcmcnt- 

ing thc widc bandwidth loop arc thc high-spcctl countcr 

and thc custim voltagc controllxi oscillator (VCO). 

Somc of thc tcst rcsults from a brcadboard synthcsizcr 

which utilizcs :'IC wick bandwidth loop for bandwidh 

cxpansion arc shown in Fig. 4. Thc brcadboard synthcsiz- 

cr mwts thc switching spccd rcquircmcnt by scttling to 

withit? 7.5" of thc final pha.sc in a littlc nvcr 0.8 pscc. 

Thc goal for spur lcvelr is also mct hy thc hrcntltward 

synthcsizrr. A typic;ll.ob'tpt spcctrum is shown iri Fig. 4. 

5. JII(;lI-SP1.:ED SIGNAL PROCESSORS 

High-spccd digital signal prtxcssing advanxs can bc uti- 

lizcd to providc lightwcight. low-power dcmtxlulaiors and 

signal proccssing subsystcrns capahlc of supporting many 

LDR and MDR channcls. In ihc carly 19HO's. ihc use of

0. 

16-2 

combincd analog and digital proccssing technologics 

providcd thc most cfficicnt implcmcntation for dcmodulat- 

ing thc LDR uplink wavcform. As shown in Fig. 5. thc 

frcqucncy dcmcdulation was pcrformcd by a siirfacc 

acoustic wave (SAW) dcmodulator followcd by a digital 

communications and acquisition proccssor. Now howcvcr. 

thc progrcssion of digital tcchnology has advanccti the 

staic-of-thc-nrt to thc pint whcrc an all digital approach 

is morc cfficicnt. Thc dcvclopmcnt of application spccific 

ICs (ASICs) which proccss thc st'mdard EHF waveforms 

will contribute significantly to thc rcduction in wcight and 

powcr rcquircd by thcsc subsystcms. For furthcr rcduc- 

tions in wcight and powcr, thc ASIC dcviccs c h be 

intcgatcd into multi-chip modulcs to achicvc ths bcticfits 

associated with a wafcr-scalc lcvcl of intcgration as shown 

in Fig. 5. In this comparison of zn LDR signal processor 

using multichip moclulcs with an I,DR signal procbssor 

from thc carly 1960's. an ordcr of magnitudc rcduction iii 

wcight is obtaincd while thc powcr is dccrcasrd by inorc 

than half for thc samc nlirnbcr or chanricls pmccsscd 

The digital Fast Fouricr 'Transform (FFT) dcmodulator is 

implcmcntcd wiih two ASIC dcsigns shown in Fig. 6. Thc 

samplcd signals arc first prcproccsscd bcforc ihc actud 

transform is pcrformcd. In this FIT prcproccssor chip, Ihc 

signals arc windowcd. cohcrcntly intcgratcd for iidjusimcnt 

of frcqucncy sample spacing, and storcd in mcniory. Thc 

hcart of thc dcmodulator is thc in-placc FFT rnip shown 

in Fig. 6. Thc data is storcd in mcniory, thc FrT buttcifly 

opcrations arc pcrformcd. and aftcr the transform is 

coniplctcd. thc 1 and Q sam~!ia arc coltvcrtcd to inagni- 

~udc valucs Tor Turthcr prr-cssing by thc uplink processor. 

Thc F1.T chip is dcsigncd for usc with (lata or :rccluisitiori 

channcls and can pcrfomi a traiisiorrn of up to 256 points. 

Thc ASIC for thc in-placc FFT, shown in Fig. 7,' has bccn 

dcsigncd, fabricatcd, and tcstcd. Thc FFT ASIC is 

dcsigncd to mcci thc priniary rcquircmcnts for a spacc 

applicatitm: radiation hardncss, high pcrfnniiancc, low 

powcr ccmsumption. mid high rcliability. A significant 

dcsign fcaturc in this chip which cnahlcs high pcrfonnancc 

in a low powcr configuration is [tic usc of on-chip rnchiory 

(RAM and ROM) for thc data bcing proccssctl arid fdr thc 

cbcfficicnts uscd in thc FlT. Thc amount of riiciiiory 

rcquircd is mininiizcd by employing an innovativc in-place 

algorithm using dual port RAM. 

Thc Fm chip, thc prcproccssor chip, and a coniniutiications 

uplink proccssor (CUP) ASiC can bc confiuurcd into 

a comrnunicaiions dcmodulator, which is capablt: of 

proccssing up to 16 channcls, as shown in Fig. 8. Thcsc 

ASICs, along with thc supprting chips (AA1 cnnvcrtcrs. 

CUP RAM, and mission ROM) can be packagcd irito a 

multichip modulc which is about 2" x 3" in six. 

A 

For MDR channcls, similar ASIC tcchnology is cxpcctcd' 

to yicld cfficicnt imp:cmcntations for thcsc higher data ratc , 

channcls wcll. A prclirninary dcsign Tor a four channcl , 

MDR subsystcm rcquircs thrcc individual ASIC dcsigns,, 

Four dcmodulator chips arc utilizcd in conjunction with a 

clock gcncrator chip and an MUR prcrccssor chip to form 

thc four channcl MUR suhsystcm. l'hc dcsigris for ihc 

clock Rcncrator chip onti thc MI1R pr(tccs?qr, $hip ollow 

cascading to support additional MDR dcm,wI,ulatyrs for . .. a* 

payloads with mwc than four channcls. , ... . ..' a,. 

.. 

6. EXAMPLE EHF PAYLOAD FOR 

GEOSYNCHRONOUS ORBITS 

An cxample EHF payload, which utilizcs a pair of variable 

beamwidth spot bcam antcmias and bah LDR and MDR 

signal processing, is shown in Fig. 9. For this example 

payload, the uplink spot bcam antennas utilize 7 fceds 

cacli and the downlink bcams arc formcd using 1 ked 

each. Both LDR and MDR channcls are supportcd in the 

spot hams. In addition. the payload providcs LDR c h 

covcragc senticc through a pair of carth covcragc horns. 

The LDR proczssor supports 16 communications channcls 

in each of the bcams using thc EHF common transmission 

format. Thc MDR proccssor providcs a total of 4 channels 

of scrvicc in thc spat bcams with any mix bctwccn 

the two beams. 

Thc main coasidcrations in sclccling a spot bcam sizc arc 

thc rcquircd gain and llrc covcragc arca prtwidcd by the 

ham. Thc 1" :o 3" spot bcam sim in this cxamplc pay- 

load, along with thc 6 W solid statc transmittcr. will 

support 2.4 kbps scrvicc lo a small tcrminal (2'nw) whilc 

in thc widc bcam mode and will support 1 Mbps links to 

a mcdium si7x tcrminal (4'/12W) whilc in thc narrow 

bcam niodc. Thc payload in Fig. 9 is cstimatcd to wcigh 

about 200 Ib and rcquire about 290 W (thcsc cstimatcs in- 

cludc 20% margins). 

Thc 6 W transmittcr and thc 20 spot bcam antcnnas 

providc sufficient EIRP to support both LDR and MDR 

links in a varicty of modcs and daia ratcs with the total 

throughput for thc payload dcpcnding on thc mix of LDR 

and MOR bxnirials in a sccnario. An cxainplc loading 

scciiario is shown in Fig. IO. For this cxariiplc. thrcc 

typcs or tcrminals wcrc assunicd: a 6', 25 W ground 

tcrniinal; a 4', 12 W transpnrtablc tcrminal: and a 2', 2 W 

portablc tcrniinal. Thc ground tcrminal is supported by thc 

carth covcragc bcani in thc cxarnplc. Thc portable and 

transportablc tcrniinals arc supportcd in thc spot hcanis. 

Chc of thc spot bcmns is sct to a 3" bcainwidth (ahut 

1200 milc diarnctcr covcragc at thc subsatcllitc point) 

whilc thc othcr :pot bcam is sct to a 1" bcamwidth (about 

400 milc dianctcr covcragc ai thc subs:itcllitc point). in 

this cxamplc. 27 LDR networks and 17 MDR links arc 

supportcd for a total payload throughput of 3277 kbps. 

A range of payload capabilities can bc implcmcntd using 

the variablc hamwidth aitcnnas. nulling prtxxssors. and 

ttic othcr kcy tcchnologics dcscribd bricfly in Fig. 1 and 

2. Thcsc tcchnologics can bc uscd to implcnicnt small 

EHF payloads as in thc cxamplc prescntcd hcrc. Howcva. 

thc samc tcchnologics can also bc uscd in sccondiiry anti- 

jam payloads or multiple function anti-jam payloads on 

largc satcllitcs as shown in Fig. 11. In addition. many of 

thc smc signal processing and frcqucncy gcncration 

tcchnologics arc applicablc for improving El IF tcrniinals 

as wcll. 

7. SUMMAHY 

A kcy fcaturc fur thc flcxiblc usc of Ihc EHF payload is to 

providc thc ability to configurc the payload to providc a 

varicty of scrviccs. Suppming cithcr LDR. MDK. or both 

typcs of chonncls in a varinlk. hciunwitlth utitcririn ticllm 

provitlc itiis sort of flcxihility to nwct a troiitl raiigc of 

uscr rcquircmcnts. Dcvclopmcnt of the critical technologics 

for use in thcsc typcs of payloads hiLC bocn initiatcd. 

Thc tcchnology arcas includc variable bmwidth antcnnas. 

lightwcighl frcqucncy synthcsi7~~i!.,and high spccd signal 

processors for both LDR and MDR channcls.

0 

a ACKNOWLEDCEMENTS 

The concepts which m firesentad here wem developal 

hough the MILSATCOM concept a d tachnology 

development effaru of I!& lightweight EHP payload 

program 8.t MIT Lincoln Labontq. We thank the lil (li#k :' ' 

individuals who have contributed IO this work. We 

cspecinlly thank John Drover for his work in devcloping 

the FIT ASIC and David Matma for his work in'lcading 

the design of he frequency syntheeizer. 

9. 

1. 

2. 

3. 

4. 

5. 

REFERENCES 

D. P. Kolba. E. L. Jeromin, D. R. McElroy. and 

L N. Weiner, "Complementary Robust MILSATCOM 

Servica: A Significani Role for Lightweight Space- 

craft," Roject Report SC-79, MIT Lincoln Laboretoty 

(28 March 1989). 

D. R. McElroy, D. P. Kolba. M. D. Sanprucci, 

"Small EMF Military Satellite Concept for Augmentation 

and Restd," in AIAA 13th fnt. Canm: Sat. 

SYSIC~ Cod., Los Angeles, CA, (1 1-15 March 

1990). 

D. P. Kolba, William L. Grcmbcrg, D. R. McElroy, 

and M. D. Sempmcci, "Advanced EHF Tcchnoiogies 

for Light- weight Augmcntation / Restomtior, Com- 

munications Saicllites." in 4* AlWSU Conference 

on Small Satellites. Logan, Utah, (27-30 August 

1990). 

D. P. Kolba. D. R. McElroy, and W. C. Cummings, 

"Lightweight EHF Satellites for Augmentation of 

Anti-Jam Communications," in 14* AIAA Intcmation- 

a1 Communication Satcllite System Confcrcncc, 

Washington, JX!, (22-26 March 1992) 

-D. R. McElroy. W. C. Cummings. and D. P. Kolba. 

"Lightweight Adaptive hlCnMS for EHF Payloads," 

in h4Il.COM '92, SM Diego. CA, (11-14 October 

192). 

' 8 

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. 

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16-3

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STRAIGHTFORWARD IMPLEMENTATION 

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FILTER SIZE LIMITS N- LARGER DDS BW 

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LARGE LOOP BANDWIDTH 

FIXED 

FREO. 

* VERY HIGH SPEED COUNTER 

- POWER PENALTY 

CUSTOM VCO 

Figurm 3. Bandwldth Expandon Implementallon Options

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IG TRhNSIENT 

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3 

169

I 

SYNCHRONIZATION TECHNIQUES FOR MEDIUM DATA RATE EHF 

MILSATCOM SYSTEMS 

SUMMARY 

I, rhc LIU or MILSATCUM. cmvlderahlc crrm is 

cvmntly bcing cxpcndcd om Ihe dwhpmcnl of systmr 

opcraling in UIC EHF frequency hmls and employing 

mbwd pmccx

e 

muior, MDR ryp &U nier up Io ud includins TI 

would bc rcquirrd 

Syuhrmiratim is me of the ty arcam of plential 

vulnerability in Ihe design ud oprratim of a 

MIUATCOM ystan. In R& tn met operational 

raquirancnh an MDR EllF MIUATCOM syslcm mu.% 

pvide a syrwhmnixalirm upability hat is 11 ICul U 

robust U Ihe uxnmunicatimr capability it sup- 

Synchmniruim cmsism ot hxh rquiritim d %ti% 

pmrcssm Thc~ p~reu~i involve adjwling the critical 

puuncim or spatial pointing. rmuency ud timing. It the 

g m d cemirul. It vnll k umwd that be payload is Ihe 

spem rcfmmr vi& rcgud to trcquency utd timing. md 

that UK gmund terminal must match iu timing uul 

rrcqumy to che DL roccivcd signals. Similuly it lnus 

cnwrc Ihal the UL signals urivc at the paylimd matched 

in tim uxl frcquency IO thau of Ihe paylord This papa 

cimimn chc systcm &sign consideration* for 

rynchmni7atim of EHF MDR systems u~iliring Tactical 

Satcllitcs (TACSATS). Thc anphmis of thr discussion 

will hr im pvformance capahilltics lo nrcl thcatrc 

rmand qummcnu. 

Thc paw is organi7ml as follows. Sccthm II ciamincs 

d 

rimc of the syricni chuacterirtics and asrumpli~ms which 

imp8ct Ihc dcsign or Ihe r)nchroni7alion pmfcsr. Srction 

111. 1V. mi V rraminc the hign or spatial. iimc a 

frcqumcy syicl~nimim aIpnithm.. mrpstivcly. Srrtim 

VI eranlines paramr~m ~d pcrlammcc mcuurrq kn UI 

ovrrall .ynrhnmiialam aI$irithn. Sccticm VI1 pr~ividcr a 

CorTIUslon to lhc papcl. 

2 MDR EllF SYSTEM CHARACTERISTICS 

2.1 Wavrtorm and Opmllonal Cnnsldrrallunr 

The rmmcd kcy wavcfnrm .nd opcralional characicristics 

thai are peninml io Ihe 

> 

discussion in this papr arc 

outlid in Tahle I. These characteristics were conridcrcd 

hy the Canadian Dcpuune I of National Dcfcnce tor the 

currint MDR EHF MILSAT CM system design (21. As 

dmcusscd ahrve. the uplink h dwidth is 2 GI11 ceiitcrcd 

about 44.5 GHr. whrxas c dcrmlink hanlwdih is I 

GH7 ccntcrcd ahut 21 CIO. hquency lwpping is 

cmploycd to comhat jamming. with the hopping rate king 

on thc dcr of kllz. A typical systcm conliguration is 

illustratcd in Lgure I. in which L grixrnd lcnninal (CT) in 

I given hatrr of operation communicaics with a GT in 

the same or dilfcrcnt Ihcam. A tlravc of opcratim is 

dcfinal by Ihr salclliic antema hcam patton coverage. 

The salcllitc antenna CUI e i h h a fixed w slccrahlc 'put 

beam. or a multihcam antenna that can be dynamically 

slccrcd from one theme to another m a hop to 1 op or 

kame to Cram basis. In order to accommc&tc multiuscm 

and variable data rata. a hybid FDMA/TDMA frame 

svUcturc is employed on Ihe uplink as illur~rated in FsRure 

2. Usen arc rsw~ad capcity in terns or M ~CVSI whlch 

CUI be one or more m)nconcuncnt subtruncr in OK or 

mm uscr channels. The downlink employs a singlc 

channel TDMA wucture. The modulation assumed for 

r - 

UL frequency 

budwidth 

budwidth 

modulation I DPSK -1 

liopping ntc slow frequency hqrpina 

Diu Rates 32 kbm IO TI 

I 

Rocasing fwtim - coding: Mat or 

cmvolutiaul 

- divmily 

. inlcrleaving 

- timc oermutation 

I 11 

satellite abiu ~ 

&lbibiuuy 

payload UItCnN 1 T-5'bcamwidIh 

26-34 dRi 

payload amplifier 5 W SSPA 

nnwnd terminal mcnm I un to 1.R m I 

ground tam;nrl up to 20 w 

bmplifia 

.\ 

Figu:c I: Syslcm Configuraum 

purposcs ol his discussiim is DPSK. No pulx shaping has 

hcn as*umed. although Wmt studies idicalc lhal lhis 

may be useful for MDR applicatim 131. M-uy FSK could 

also he considend however given hat slow frequency 

I

-U 

I 1 

b I l l 

. . . . 

, Figure 2: UL FDMNTDMA f hc sln~clurc 

: :I 

: :i 

hopping is a.9sumed (i.e. he hop rate is lest Oian be G *.U 

rate). a DPSK rype dui.4on it rnwe amcnahlc to 

attaining the MDR data rata 

2.2 lmpalrmrnb 

In or& tn combat various channel impairments Such as 

athlitivc miw, fading. and scintillation LI well L% jamming 

hreau it is atsum4 that communication data pnrcssing 

tcchniqurs such as FEc ding. interleaving. divcrsiiy a d 

tim permutation of data hops arc implemcnicd in thc 

systcm. In acidition to thc above channcl and EChl' thrcats 

drc system must bc crpahlc of operating unclcr system and 

equipment iniluccd imprimcnts such as dopplcr cffctir 

due IO be relative motion bctwcc.cn the payload aod thc 

GT. rrlative payload to GT clock drift. RF pup &lay 

variatim. and RF frrqucncy respo~sc m the hnp-to-hclp 

rmplitudc varia!ion at a func:ion of frcqilrncy. rhcse 

impaimenla arc listd in Table II along with thr assurncd 

valucs for t.k pu'p~ct d discusqion in this pnper. The 

dopplcr effect is ncgligibte for geostationary orbiiq. 

however for non-geostationary. elliptical type orbits such 

as Tundra or Molniya. the dopplcr cffccm can bc ax scvcrc 

as documentnl in Toble 11. These wbi~r would he rquircd 

in a tactical theatre of operation ai northern latitudes. 

pmicularly in the Arctic. 

2.3 Llnk Budget Requlrernenb 

For a TACSAT EtlF system. it is awumal that a 5W 

SSPA is crnploycd on the payload. Largcr amplifiers 

would rcquirc the uw of a TWTA. which wwld irnpsct (RI 

the available si72 and wcight of thc payload. Thz antciina 

is asumcd to be a spot beam with a 5" bcaniwidth. For 

this size of amplifier on the payload, typical rcccivc C/N, 

lcvels at h c ground terminal will vary from 50 to 60 dB- 

k{z 'or a gWSlaliOEary orbit in clcar sky conlirions. It 

should bc noted that thc link budget must also 

accommodate rain fade margins on the UL and the UL. 

Depending on the desird fadc margin this could 

potatiallv restrict Ihe DL burst data rata unda given 

channct conditims. 

2.4 Inltlal Acqulsltlon Estlrnates 

The complexity of the ac.,uisition phaw of the 

synchronization proccw will dcpcnd significantly on the 

J 

Tabk 11: MDR System Impalrmenb 

Group Delay 

Variation 

Fnqumy Rcsponw 

Variation 

+I- ? dB 

laming I channel dcpendcni 

magnitude of the crrm in thc initial GT estimates of 

payload pointing. frcqucncy UKI timing. 

17-3 

2.4.1 Timinu Eshwtc 

The error in the initid time estimate is detmnincd by the 

availability of M accurate time mfemcc and the relative 

rate of drift of the time standard maintained by the GT 

with rc.spcct to Ihc reference time rtandzrd in the payload 

With the availability of single bard GPS rcccivcrs. an 

MDR tcnninal CM easily maintain time accuracies 017 "IC 

ordcr of microstcondq. If GPS or similar time rcfcrc c 

systcm.9 M MI available. the initial error in the cstii :e 

of the timc enor would likcly be on the ordcr f 

milliseconds. Givcn the current level of technology. '1 

MDR terminal ;an catily accommodate a rubidiL:ii 

standard. A typical vallrc of rclative drift rate for a 

rubidium standard is 5 x IO'* per day. Thc resulting cmr. 

evcn aftcr several drys of uncalibrated usc would still be 

less than a miaosccond. For pitrposcs of discussion, an 

initial hing mor is 50 millisccmds is asumcd. 

2.4.2 Spatial Pointing Esfimai:s 

Thc accuracy of the initial spatial pointing cstimall 

dcpcndcnt on three principal parameters; namcly, thc t 

in the GT's estimate of its own location. he initial tin 

estimate, and the accuracy of the GT's ephcn1cr.C 

algorithm. Thc dc~~ndcncy on the time estimate rcwlu 

from he fact that the GT's estimate of the satcllirc 

position is an outpul of thc cphcmeris algorithm. which 

employs !he currcn~ timc estimate as an input. If GPS 

avai!dbk. boUi the initial timc estimate, U well as . 

GT's position will be known to a high dcpe d accuruc . 

Furchcrmore. if the MDR bau station is fixed in a tactic-I 

theatre of operation. thc location of the CT will typicn . 

be h w n 

to within 10's of mclers, either from w r y 

navigational aids and an accurate time standard can

.. 

0 

sdcly assumed In either of thc scenarios dcscribcd abr~vc, 

thc only effective e m will be due to the accuracy of the 

ephcmais algailhm. A wry qconwative estimate is Ihai 

the ernn canpnart in spatial poiwing duc to he 

cphcmais rlgc-ilhm will be known to wilhin O.l* in 

which c m spatial acquisitim may'nd be ncccsar)'. If 

GPS or similar timc stdads ue hot avrilahlc and the 

location of Ihc GT is not piscly knowil. thc conlribulion 

of he .sparid pointing mor due to thc mw in thc cstiniatc 

of the GT locatim will bcwmc significant. In a tactical 

field scenario the GT location will typically bc known to 

much bctter than IO km. mulling in a corilribution to thc 

spatial pinling e m of lcss than 0.1'. Thus the total 

pointing c m Jhould be lexs than 0.2. 

2.43 Frequency Esiitnatcs 

The initial ma in Ihc frcqucncy cstimatc will bc due to 

a combination of the accuracy of thc cphctncris aljiwihn 

in estimating motion induccd doppla cffccl~ and the 

rclativc frcqucncy drift bctwccn the timc standards of ihc 

payload and the ground tcrminal. For thc orhits rcfcrcnccd 

in scctim 2.2. Ihc worst case unrcsolvcd dopplcr crrm will 

be on the order of to 2 ktlz. Again acsuming thc 

prerncc of a rubidium Ftandard in the GT. the frrqucncy 

crror duc to rrlativc cltwk tbift will hc ncglipihlr Tor 

purpcscs of thc.sc discussions. 

3 SPATIAL ACQUISITION 

To achieve spatial wnchmni7ation, thc gmuntl tcrminal 

must he capable of acquiring and tracking thc pinting of 

thc antcnna typically io within an angle corrrywnding to 

a 1.0 dR loss in gain. In M MDR systcm thcrc arc scvcral 

factors that will impact on the spatial synchroniiation 

algorithm to bc sclcctcd If thc initial spatial pointing 

error is rclativcly largc. such as on [hc o rb of onc to two 

3 dR bcamwidlhs. spatial acquisition will likely havc to 

consist of two phaccs. a coarsc spatial acquisition phase. 

and a fine spatial acquisition phasc. Tlic coarsc spatiol 

acquisition phase can consist $.if a stcppcd or continuous 

scarch pattern. normally in srcps of onc 3 dR bcamwidth. 

out from thc hst initial estimaic as provikd by the 

cphcmcris algorithm. 

Siryc in MDR the DL is capacity limited, it is dcsi-abl:. to 

havc an antcnna vvih as high gain as practical. tlowcvcr 

igh gain antcnnns bin: narrowcr bcamwidths. rcsulting in 

larga attcnuatims for iic same crror in spatial pointing. 

Typical UL and DL MICW bcam charactcristics for EIF 

frqucncias arc givcn in Tablc 111 as a function of antcnna 

kunctcr. As discussed in section 2.4.2. the initial pointing 

error for an MDK'tcnninal is usually lcss than O.I", in 

which case a coarse spatial scarch stage is not rcquircd. 

For cxamplc. it can bc sccn that fob a 2.4 mctcr antmna, 

thot 8 pointiri~ error of 0.1' corrcqw)ntls IO thc 3 clII 

bcwnwidth. For a tactical cnvi.onment in which largcr 

initial pointing mm may bc incurred. the antcnna size 

will typically be smalla, on thc nrdrr of 1 mctcr. In such 

a scenario the pointing error of 0.2" discussed in 24.2 wiil 

fall within the 3 dB beamwidth In such caws spatial 

acquisition would only na4 to consist of thc finc spatial 

acquisr ion strgc Thc most commo~l dgailhm employed 

is a cmicd sun tracking loop about a 1 dB contour. Such 

I~ps can rapidly aqrire in AWGN in the order of 

slxdx fmm initial pointing arm within the 3 dP, 

contour of thc antcnna. This is diciert for most MDR 

EHF antmLv U dixu.ssal above. 

Tahlc 111: Typlcnl EHF Antenna Charocterbtlcs 

0.14 DL 

11 0.14 UL I 1.0 I 1.75 

11 1.0 DL I 0.3 I 0.53 

11 1.0 UL I 0.14 I 0.24 

1.8 DL 0.18 0.3 

1.8 UL 0.09 0.IR 

2.4 DL 0.13 0.21 

2.4 UL 0.06 0. I 

If Ihc initial pointing crror cxccds hc 3 dR contwr of thc 

anicnna. or if jamming or scintillation is prcscnt. it may bc 

necessary io cmploy a coarsc acquisition search. Spiial or 

stcppcd scarchcs may bc cmploycd, howcvcr thcre is an 

additional consideration for an MDR terminal. If thc 

pointing crror is mitsidc thc 3 dR region, it is possiblc that 

thc spatial search may point to a sidclobc at the payload 

In a high SNR cnvironmcnt a dctcc'tion may occur. 

rcsulting in a false locking of the spatial pointing on a 

sidclobc. Cmc solution is to collcct statistics from all 

possiblc scarch regions. howcva this impacts thc 

acquisition timc. An altcmatc approach is to cmploy a 

gimbal scan about a larger contour than that cmploycd for 

thc conical scan. Thc proccssing would bc idcntical. If thc 

contour of the gimbal scan is judiciously choscn with 

rcspcct to thc ovcrall search rcgion. thc gimbal scan will 

always encompass thc mainlobc of the antcnna. 3tiicr 

considmations includc the incrcascd scnsirivity of thc 

conical scan to pointing c m duc lo the highcr slopc of 

the bcamshapc in high gain antc~a~, as well as the cffccl~ 

of frqucncy flatncss variation on thc stability of thc 

conical scan proccssing. 

4 TIME ACQUIS;TIO%N 

4.1 Overvlew 

Time acquisition is dividcd into two siagcs; namcly. DL

@ 

& a time acquisition. Due to thc tactical raquirancnt 

that thc MDR EHF systn have a multiple access 

capability, it is ~CCUWY for Ihe p~ylod 10 dphcally 

assip &U hops and theatres Since a GT in a giv’a 

dou no( have knowledge of which hops hive 

actual data until Inc rcquisitim has bacn mpletad. bL 

synchronization is accompluhcd lhrough che usc of 

spccidized synduoruzui~ hops. These hops must ochr 

in known locations in Ihc dowrilink datalink structure. DL 

aquisition is achkvd by cktating the presence of the 

sphrcmizatim bps which vc periodiully transmilted to 

each cheatre of opemion. SiKe the detection of Ihew hdps 

clrtno~ take place un~ess the antema is pointing at ihe 

payropd. he time acquisition procns is perfnmcd 

concurrently with the spatial acquisition proccdhc 

derribod in scctim 3. As for spatial aquisitinn, the DL 

acxpisitia pmcea consists of I coam and fine stage. The 

c w ~ Stage e spchmniza Lhc DL timing to within I DL 

hop, providing the gmund terminal knowldgc of thc 

correct point in thc frqucncy hopping squcnce rclativc to 

the GT timc-ofday COD). A sccond fine stagc of DL 

time acquisition is mquircd to 8ltain the DL timhg to 

within a DPSK chip or spbl period. 

It should be notod that the u e of time pcrmulatinn to 

combat padd time jamming adds complexity and delay to 

he acquisition procxss. The psition of the pcrmutcd 

synchronizrtim hops must bc calculated had on thc 

estimated TOD and the hopping pattcm. Ihc atklitional 

Slay will bc on the orda of the period ovcr which the 

permutation takes place. for example a frm. 

4.2 Coarsc DL Tlmc Acqulsltlon 

Since the DL is in a TDMA format., the SNR in a hop is 

rclatcd to the rcquircd symbol SNR by the following 

relationship 

in which EJN, is the hopencrgy-to-noise-spectraldcnsity 

ratio, yN, is thc coded-symbolcnergy-t~noisc-spcclraldenqity 

ratio. & is coded symbol rate of a singlc channcl, 

q is the number of downlink TDMA slots corrcspnding 

to che number of uplink channels, add R, is Ihe hop rate. 

For data ccxnmunicatiw the specified valuc of Em, is 

fixed by Ihe required bit error rate. and the hop rate is 

typically fixed for a given system. Thus as the nunrber of 

uplink channels and/or the channel data rate is increased, 

the level of E,/No must be incrcascd to maintain thc samc 

level of EJN, Since MDR system. mbst support data rate.. 

up to TI, the rwulting E& it high. A5 M cxarnplc 

suppose a MDR syste.~ has 8 channels, rate In coding. a 

hop rate of 10 kHz and a TI data rate. For a typical 

required system mor rate betwecn 10’ and 1. ‘, the 

requhd value of WO is rou~Jy 7 dB. For the values 

noted above, Lhe resulhig EJN, will exceed 40 dB. 

17-5 

Similar values can bc obtained for a junming envirmcnt 

Detection of the cxmsc DL synchnmiitim hops can thus 

easily bc made bn.& on mgy mcamuanentd. ’he famat 

or 111c c:o= ~~hroni;lwtim hops not be cmp~el, 

bul should be selected to allow 8 high proba6ility of 

detection (PJ, ancl a low Fobability of false alarm (P,). 

’I. is is a common radar problem, and numerous 

*avefonns can be selectad[4]. A simple example is I 

modulated CW tom. 

Fine DL lime acquisitich is nuaxwy to obtain the DL 

timing to within a symbol period, U well m to rocover the 

symbol rate clock. The DL liming ccmacy is dTccted by 

the following factors; satellite motion induced dopplcr 

effccu. relative clock drift bctwoar the payload rcfcrcnce 

clock and the GT clock. group &lay vuiatia introduced 

by che channel or the equipment, and the timing jitter 

intmduccd by the synchroni7ation process iLsclf. As 

discused in suction 2.4.3. the unrcsolvcd dopplcr can be 

up to 2 W4z. resulting in a timing variation on the odu of 

100 nscdm. Furthermore. the group delay variation can 

be on thc ordcr of 40 nut. Given the TDMA nature of the 

MDR downlink. and data rates up to TI, the bvst symbol 

rate of thr DL will typically be on the order of !O MHz to 

100 MH7- dcpeding on the numb 01’ sloc~. In the 

cxmplc given above the symbol period would be 40 nw. 

Fine timing on the DL can be achieved by .sending fine 

synchronizrtim hops consisting of 8 unique word which 

can be correlated at thc GT. The numba of finc 

synchronizotiin hops and the period bctwan arrival of 

fine synchrnni7ation hops is dictatd by magnitude of the 

timing mor lhnt a.rumulat~~q betwaen synchroni7adon 

hops. The numb of DL synchrcnization hops must be 

sufficient to allow for all thcatrcs of operation to be 

visitcd. Thc principal sourcc of timing error that will be 

rcmovcd by the fine synchronization hops is thc 

unpxoived dopplcr error as well as clock drift emr. Once 

fine timing has bccn obtained on the DL. he GT must 

track thc DL timing. Doppla and clock drift rnw bc 

lracked in ordcr Jiat Lhc DL and UL timing of Ihc CT can 

be adjusted to compcrwte for these effccts. The timing 

jitter induccd by the .gynchroni7ation algorithm is a 

function of the complexity of the feedback loop dcsign and 

can be separately minimizcd. 

4.3 DL Tlme Tracklng 

In addition to tracking doppln and clock drift. each DL 

data hop must be contpcnsatcd for the elTects of group 

dclay */ariation. At the M DR burst symbol ratc, chc group 

dclrv variation from one hop to thc next can be air or 

niorc symbol pcriods a5:discusscd in soction 4.2. Thus 

each data hop must Lc rc.uyrichronized to the DL timing to 

ensure that no data symbols arc lost or that Ihe symbol 

timing of the nccived symbols is not misrligncd. This can 

be achicvd by encoding a known pream!)le at Ihc start of 

mch data hop. The GT will correlate ‘the rcccivcd 

preamble against thc transmitted pmamble and align the 

liming to within half a symbol paid 9 dctccting the 

peak of the correlation process. The length of he unique 

word selected for the correlation process is a function of

e 

174 

in which P- is tk prabrbility of bit erro~ at the ohput 

of Lhe dunaJul~a. 

ud P- U Ihe probability of bit km 

of a DPSK modulated signal. U he danodulator is 

followed by divasity cumbining. he value of P, c8n be 

poor, and yet still allow dust performance. For exatnplc 

wuming a basic maprity logic combining approach. in 

which hops arc divcnifiad he RER at the output of the 

diversity canbindon circuitry will be givm by 

in which Pav is the probability of bit error at he output of 

hc diversity combination cui:hy. Plots of P, versus 

EJNo are given in Figure 3. It can be s en that even uith 

a modcst diversity of L = 11, thhpt a BER of less than 0.02 

CUI be obtained at low E& c:en for P, values a5 poor as 

0.7. This PER into a good FIX will give an overall RER 

of less than 10'. In an operational system. other more 

robust diversity combining techniques may be cmploycd. 

4A Unique Word &lectlon 

Qe probability of false alarm in the detection of UI 

cmmcous preamble is dicuted by the si7z of the sidelobes 

of Ihe unique word Unique word. with ideal mlation 

propaties such as Barka type codes can only be fourid for 

a few shorter length sequences. where ideal comclatib of 

8 uniqie word of length M shall is defined as hl for 

perfect alignment and +/- 1 elsewhat. By shortenink the 

decision window of the unique word and considcring,only 

sidelobes within the defined window, it is possible to 

attain a higha processing gain for L!C unique word. The 

widih of hc window must be long enough howevdr. to 

accOmmDdllte nny potential group delay variation and 

accumulated clbck &iR. 

45 UL T h e Acqulslllon and TracklnR 

When the GT initially beginq acquiring. the total :time 

uncertsinty is dominated by the e m in the estimate of the 

range 10 the satellite ud the error in the position of the 

GT. Acquiring the DL timing resolves one of lhese 

pu~metac. In order to resolve the second parameter, thz 

time at which the UL trrnmwsl * '~ocaumustbedjustai 

to uuun lblt the drt. hop urive at the payload wihin 

the pooaahg window far Ibs UL bop. Thir is but 

achieved by a clmd Imp pnrrea~ m which spaidid synchnmizalibn probts lllt tnnsminbd in baa wrvefam 

locations to he paylord Tbc payload detactr the positioa 

of tbc hopl relative to the rmnind loutions Md 

tnnsmirs spocirlir#l responswto IbsCT tb.1 contain the 

requid adj*mt of the GT UL hing in arda to 

ensure that the UL hopr trmmniaal by che GT urive at 

he payload with th m t limine. As is thecut fa the 

DL Liming, Ihe UL probes will coatah Unique words that 

xhould be judiciously dmun to alloar iar m qtinial value 

of P, and P,. relative to he size of the -eh window for 

UL Liming. 

in which T- is the UL timing hop mismatch, T, is the 

e m in the DL timing estimate. TI is Ihe wcust case pup delay variation. and T, is the residual enor in he UL 

timing from the previous UL timc cstimatc The residual 

UL arclr T, is no worn t h the ~ a c c v pvidcd by 

the come 01 h e DL synchroniution faponsu. For MDR 

sysiuns. T, will excad the paid of a DL symbol. 

rquiring that the 'JL dah hops have'prembla with 

unique words to pcnnit hop-to-hop comlation of the 

timing. The size of T- will dictate the size of the 

processing window in the payload and the size of guard 

bands in the UL hops. 

An additional concidaation in the design of an UL timing 

and tracking pro~ocol is the placement of the probes in the 

UL frune structurc. Robes CUI be assigned on eitha a 

channel basis over the entire frame, or on a TDMA time 

sla his, spanning some or all of he available channels. 

Both of lhesc approaches have advantages and 

disadvantagca UL probes assigned on a chand basis will 

provide m m Uuoughput to an assigned user, however. the 

payload must posscss separate frontcnd processing to 

detect pmbcs h m one theam of opcration whk it 

processes data channels from a separate heatre of 

operaticin. In contrast, if probes arc assigned on a TDMA 

time slot basis. the payload can detect probes from one 

heatre while rweiving data communications from another 

theatre 111 within Ihe same frunc. with no additional 

hardware. The disadvantage to this approach is that the 

amcunt of probe capacity available to the GT is more 

restricted than in the FDMA approach. 

5 FREQUENCY ACQUISlTfON 

The principal degradation in system performance due to 

frequency m will be due to ke accuracy of he hit 

timing in the DPSK demodulator of the M DR receiver. ln

6 SYSIXM SYNCHRONIZATION ALGORITHM 

In a mticd en- it is parunount thrt the ovdl 

synchroniutiaa time be kept to a minimum while 

simultaneously providing capacity to synchronize many 

users U axe Thb god CUI be rcannplis! hough a 

combination of judicious kip d the initid pumtu 

cstimatim caprbilitiw of the GT, selectiun of a robust 

synchronizaticm dgcnilhm and optimization of the 

puunetcrs of the synchmiutim algorithm Irrtrtirlg 

synchrcmiuticm limc Tk availability at be ground 

[ermind y~urue TOD urnition. an accunte 

ephemeris algorithm will PI& duce the spatialtemporal 

surch region, alloAg rapid acquisition 

Howeva the algorithm must be robiust in h scnu hat if 

ao~unte initial estimates arc available. the GT will still 

acquire the paylod In addition to minimizing he 

acquisition time, thc algorithm mut also simrlltmeously 

minimi7~ the probability of false synchroni7~tion 

Cansidering the DL md UL acquisition proce*ua 

separately. the overall probability of correct 

synchroniution and false synchroni7+tion ue given by 

in which PdJlL), PD(UL). PpA(DL), md PpA(UL) uc the 

probabilities of dcteaion and fa1.w alarm for he DL hnd 

tJL synchrdzation pmcessu. Figure 4 illusmuid a 

simplified stlie diagrun of the overall synchronization 

process. The design of the synchronization algorithm 

involves choosing the vdues of POL). P W), P,(DL), 

and PpA(UL) so w to minimize thc acquisition lime unda 

the desired tactical operating Ctditim. 

For the ovdl probability of dctection defined in quation 

(5). thc dcla~tion rtquirem~ CM be equally putitioncd 

to the UL and the 3L U a starting point in the design. 

Howeva, it may be dwirable to have a higher P, on be 

DL urd 1 Iowa Po the UL ~ d certain a operating 

conditions. A DL receive only mode of operation is an 

example of such a rrccnuio. T!w DL detectiori procew 

ilself is canyosed of the comae and fine spatid and lime 

rcquisithn ;*recesses described in sections 4 md 5 above. 

Thus P nL) un be pprtitimed into a function of the 

values of PD and P, fa thc individual conrsc and fine 

In aqkdon (6). the fvat tam cm be neglected. since it is 

extranely unlikely lhlt che m wil nrccusfully acquire if 

17-7 

the DL is not proply synchronized The daminant tam 

in the ovadl process is the d term, which is Ihe 

probability of frlse syldumizrtion of UL timing given the 

DL is correaly quid. 'Ibe third tam is d l in 

comph to Ihc Mcond tam if P,(DL) lnd P,(UL) ut 

nrsonably c& It should be noted th.1 cyen hough the 

rust term U negligible. a large vdue of PJDL) will 

significuuly impact llrc acquisition time, since Lhe DL 

acquisition p a s will bc dcpcndcnt on h e UL v s 

to detect false alums. which is obviously a poor design. 

In orda to be robust in the presave of junming, he 

CO= and fure sync dctcction processing will require a 

verification stage. The verification stage in genad will be 

an m choare n type of decision. in which m of n expected 

sync hops will have to be dctcclcd in ader for thc given 

stage of the dctection poce~s to be declued vdid It 

should be noted hac a high P, md low P, for the system 

docs no( neceasuily imply a requiremall for high a Po md 

low P, on individual colvsc or fine DL sync hops. For 

example. if he system requirts npid acquisition. Lhen the 

vrlw of P, ud P, for Ihe individual sync hops must be 

close IO the Po d the wcrlll system, to ennve thu lhere 

lre few Nse &teaionS. otherwise the synchroniution 

process will expaEd limc vaifying false dctcctioru This 

would require m md n chosen to be luge. Such an 

implementation would limit Iht number of sync hops that 

the system could support relative to its d.l. capacity. or 

limit the numk of theatres that the payload could provide 

synchronization hops to. On thc otha hand thc ovadl P, 

and P, could be met by Iowa values of m id n, which 

would result in morc false alrrnu and verification steps. 

md potcntially a Imger acquisition time. The design 

choscn will depend not d y on the capacity of the datalink 

structure to support the algaihn. but the siFe of the 

terminals. Acquisition by larger taminals in clear sky 

conditions can be s*ipported by M algorithm with low m 

of n, however maller taminrls will requirk longer 

acquisition times, pdcululy in a TACSAT enviraunent 

in which thc DL SNR is limited. 

7 CONCLUSION 

This paper has exarnined the systan design coruidtrations 

for synchroniution of an EHP MDR sysm employing a

17-11 

. 

IO" 

. . 

IO' 0 2 4 6 8 10 12 

WNo [dB1 

FiRurc 3: BER U a funclion of P, 

DL coarse yb fine 

acquisition acquisition 

successful sumssful 

UL time 

acquisition 

sucmssfui 

Figure 4 Simplified Synchnmlion Statc Diagram

TACSAT payload. Sptinl and time synchronization 

algorithms have barn pesentai and the tradcoffs in he 

ovadl acquisition md synchronization pdmmce have 

been discussed E 4 on Ihe tactical requirements of the 

lhera of opaation. the aysm deaigner must judiciously 

choose Ihe paramam of the algorithm to mure robust 

opadon while simulmly minimizing he acquisition 

lime. 

R EFERENCFS 

1. 

2 

3. 

4. 

5. 

Ravin, C. J., "Architbctural Trends in Military 

Satellite Communicatiorls Systems", ProcecdingS of 

the J.E.E.E. July 1990, pp. 1176-1189. 

.I r. 'C. . 

Boudrcau, a. E.. ud Keighdey. R. J., "FASSET: A *I 

Development Model for a Canadian EHF 

MILSATCOM SYSTEM'. Canadian Conferact on 

Electrical md Canpuu~ Engineering. 1990. 

McGuffin, E. F.. Clarke. K. C.. "Wavefm for 

Medium/High Rate W Satellite Connnunication..". 

The 14th International Communication Satellite 

Systcmr Canfcrence and Exhibit. March 22-24, 1992. 

WLShingIOn. Pp. 53. 

Banon. D. K.. Modem Radar hilysis, Artech House 

1988. 

'Cwdence with A. h~alarlry of Corn Dev Ltd, 

CUI&> 

ACKNOWLEDGEMENTS 

I wwld like to acknowledge the help of hk. R. Keighlley 

md Mr. W. sead at the Defenct Rcsurch Establishment 

Ottawa for reviewing lhis papa and vwiding suggestioru 

fa iw iqmvanent 

I

, 

1 SURUMARY 

Thispa~rc:.amincscanmunic;1ioJls~vepmgc from five 

non-aemLationary sarcllitc orhiu. 'OAcsr orbits an: 

circulm inclined synchronouc. GPS. Molniya 12 and 24 

hour. d Turidrn orbit. It also shows t6rt itwca... in 

pnpBr?tbn lms dlbe io imgufar tcmioo rnd t k foliagc 

loss at mm wavcs. IS wcll as t k conhid effcct of tcmin 

and foliqe m SoVlliu vicw duration. Po cnmludcJ that 

coverrmqc calculations fcr EHF WICO~ earth terminals 

med to &e into account lcmih and foliqe IOSJCC. 

. drgtce 

2 LIST OF SYhlBOLS 

minuu 

AMSL hvc mcan sca lcvcl 

CIS circular inclined synctirnm 

rt fcrl 

GPS gbhnl positioning systcm 

kft kilo-fcet (IO00 It E 3W.8 m) 

km kilomcot 

mi mile (5280 h - 1609.34 

m) 

Mol I2 Mclniya 12 hour orbit 

Mol24 Molniya 24 hour orbit 

Tun& Tundraorbit 

WA Washington Stale. USA 

3 INTRODUCTION 

Gcwutionuy satcllitcs on cxpcnsive. affnrd pcmr 

visibilityand degradcd performance in ~k nmkm zortcs 

and may bc not have covcragc ovcr a specific theater. 

Lightwei8ht salcllius tactical salcllitea (TACSATS) in 

non-geoscationuyorbiUforuseovcro~iTrc thcataare 

M altanruivc. 

Salcllite "footprint' eslirnatiorl invm hbly ignorcs the 

effcctoftdn oncovcragcand comm"akt?rians'4'.'"''. 

This is justirublc whar the car(h tcrmid is in a bmcn 

hat Idn. and the mtclliu clcvatim' mnglc is high. 

However. lhcn my bc considmbh effect of the 

surrounding irregular (errain (mounmhs), in pmicular 

whcn L)rr mlcllik ekvation angle is mall, on 

communkauims wilh a manpack, B s h i m ur 81 

mnspasPnb!e mind. This paper will anmine the cfk'ect 

of 1-n and foliose on canmuhiccaimc3 covcqa or 

eanh terminals with ncm-geoscoti~ mw91iPer. 

Dr. M. JnmlB Ahmod 

Mm Tcltcch Lld. 

8 M W e l . Way, ~ Bumaby. B.C.. Cansda V5A 485 

, 

I 

16-1 

For w~~cal m m s . LRcrc is a necd for communication 

that is ovhilablc continuously. is secure. hac low 

probability of intctccpt. has nuclear survivability. is 

immunc to EMP. has anti-jam faturcs. and is rcliuble. 

Rcliability is dctcrmincd by sysren ovailubiliry (99.99% 

ctc.) and is dcfincd by he systcm spccifications. 

Although atmospheric absorption loss. cffccr of min. 

nuclcar evcnL jmiming, ctc. arc includcd in he "fade' 

margin. the eflccccu of tcmin and vcgcution arc usually 

ignored. Inclusion of tcmin. ohslruction and vcgecation 

lawswill dcthc sysicm spccificntions morccomplcu. 

so these losses m cxclmincd in this ppcr. 

4 NON-GEOSTATIONARY ORIRITS 

, Thc TACSATS may use polar ortit.

\ I 

..I , .. . . 

U' 

c L. 

rL 

50 

i 

! 

ml12 

781UiSi20 

21.36:m UTC 

3 

63.4" 

275" 

0.73 

-WO 

0.3" 

I. 

I WO 

0.0e +tu 

one . 

2656I.'d9 km 

- 

Time (Hours) 

m124 

78106120 

21:36:0 UTC 

4 

63.4. 

65 " 

0.73 

-90" 

o.oo 

One 

0.oc +oo 

ale 

42164 km 

Fig. 1. Elevation angle voriotion for different orbits. 

! 

I 

n 

U 

Valats rw 

Tundra Orhit 

tundr 

78/05/20 

21:36:00 UTC 

5 

63.4" 

20" 

0.374 

-90" 

0.0" 

One 

O.&+OO 

One 

42164 km

4fi 

2345 hm 

0830 hrs' 2245 hrs 

270. 

! 

I 

. . 

Fig. 3. Azimuth and eO@vation variation for the Molniya 12 orbit. 

10-3

It is IqmmtQlive of the ,wc.sa Cmst' of Nlmh 

America and Northern Eurnpc 

TRC sir has water. hat tarain. c7EIp rwunraimsls 

tcmin (Olympic Peninsular) in iLo vicinity 

Terrain daw (3 orc-second) is nvnikblc I 

The cmdirulcs of Scd Rock. WA FE /39*:43' N 0d 

122':53' W. A map of the ma in thr pnimily of W 

Rock. WA is shown in Fig. 4, and o twcbdiincnsd 

topgraphic plot with on tours is shown in FiB. 5. 

5.2 3-5 Vkn of Ttrrain Arta i 

A 3-dimensional plot of the arca (1 7x20 mi? shown in 

Fig. 5 presented in Fig. 6. Thc nmh-wmt vkw shows 

consmt - elcvation above mean sea kval (AMSL) 

contom. (Note that the vcnicd scdc is injeer, ant! &e 

horizond scala are in miles.) From tap9qical phu of 

Figs. 5 md 6 it cm k sccn hi thcm is water with a few 

isbnds to cast of LRC site, but Imd nmil s!ogp81y rising 

mountain3 to the wca The highcss mmnnim IC U, lDtr 

9.4 Eft?& ad YQ~TCI~Q on Covcrsnc 

The cflccl of Pmppcln mrinh on covcqc is shown in Fig. 

9 at M GWa. A rcghncwnutivc satcllir elcvation of 20' 

nn8 tmhd mlcnna clcva~on of I ft AMSL (e.g. for a 

wuhmauircr tmirind) wcm nssunocd. Radial tcnain dm 

as &scriM abvc was uscd. FacR cuwc is an qui-ficld 

sape~lgih ca;rat~. LSE Idh~ls of &C cmtour me rclativc 

walm in dB'o; lBte &duk volw is meulinglcss. 

Bullingum mtbd wm u.d IO compute the obstruction 

Ims. VOrr a@lh Ims is &Ecrmincd by tk degrcc to which 

obslplcction.~ pmmr tk Frevlcl 7me. Efrcct of tfre 

munuins (Olympic Rninsular) IO thc rranh-wcst of Scat 

Rock on pmpgmlion md coverage is cvidcnt fmc Fig. 9. 

rig. IO is similar lo Fig. 9, cxccpl that the anlcnna hcight 

kc k n irccmwd by 60 ft. A compmson of - 120 and 

-I 14 dB signal COI(NWI in Figs. 9 mnd 10 rcspcctivcly 

shows that signal lcwcl 81 givcn distance incrca.d by 

owximaacly 0 dB with LOIC incrca.. in antcnra hcight. 

AS expcclct9 CDLtrc is r ) relief ~ in propagation loss in the 

ronoI wesaerly diresib. 

YPIC field campmiam in Figs. 9 and IO do not include 

the CfkCls Obi?Iuh@Mh 0.r foliage. The signal pnhhility 

distribution will &pnd on the c;uLh terminal 

surroundings. Indad it is conjcclurcd that as the satcllik 

kgins U) cmc into view and riscs the signal statistics 

will cbngc from 1%-nml shadowing IO Hoylcigh to 

RQian p&ability disuibulions. 

To summarPi*. lDtz distant irregular bamrn lcrrain even 

w h it is s&?p h p m elevstim of IO' only and dots no( 

no~hwestorSealWock.~~someor~~~~~~ 

6000 dwc L)rz Iloacllile wgulav (elevation) view. The 

It high. 

imgular termin however invoduces an obstruction loss 

as hwn in Figs. 9 md IO. Morc impomnl arc thc lcnain 

53 Ttrraia Radiola 

md foliage ckmrr&cs in LRe fmmrdiarr vicinity of 

For the pu-s of propag31ion mlyois it is nwwe 

thz! termsipid ontenria; eplecu of Lhcsc arc considatd in 

appropriate IO examine the lcrrain dam Ucw the relcvant 

Ihc following scclh. 

azimuths. (NoccO'orMO'a.zirndthc~~~~~Nonlh.

Flg. 4. Mmpd 8 d Rock, WA. 

-17-16-$4-12-11 -9 -E -6 -6 -3 -2 0 2 3 6 6 

28 

-16 

-17-~6-14-12-11 -9 -9 -6 -6 -3 -2 0 2 3 6 6 

MlIe#a 

L arm. 

.I 

Fig. 5. Topoanphlc contours ol tho Sod Rock, W11 

16 

14 

13 

11 

9 

7 

ti 

. 

4 u ) 

2 

(D 

- 

4 

' 

-1 

Z 

-3 

-6 

-6 

-e 

-18 

-12 

-13

I' 

!'.

C. 

c 

1-- 

24 

U 

< 

L c 

0 - c 

i 

C - 

,9 

i 

L. 

5 

t- 

7 

e 

5 

4 

c 3 

2 

I 

, I IQ7 

. 0 5 IO I? 20 25 30 

DBSPiIttPt* from Scol Kock. WA (milcw)

v / I 

,p 

,

6x1 Cammm 

To mqienasclz: 

1 P 4 

lln kmmap eolwimmmr tRc useable clcvation angle is 

lmdl0scml 

Dis@ma oPMuanoircwss tamin docs not signifcantly 

dwe lpre M.&!z Bumion of thc wtcllitc 

hesatcc of vqesatitm. mcs specifically and 

WKU~PP~, 

in lDrr vicinity of &e tcrrccvial termid. 

dwc IkE M.&Ec duration of CRC .wtcllitc 

Tree coved rsw#snmimq lcrnin cxxcrbcc Itr. 

e&-c8 d mes by ducing Lhc uscahk duration of 

the wkzllits 

Manwk. Pmnylwn;lblc and Imd-mohilc tcrminals 

err aflccmf by lcrmin and mcs. hut thc airhmc 

!ermidsand shiphmc tcrminals at crpcn wa are not 

Jiectcd 

In h yc.wnccolvecs Ihc fading might change from 

log-ml shadowing IO Raylcigh to Rician a. thc 

moving satcllitc comc. into view and riscs 

Effect of foliage of diffcrcnt kinds and hcightc nccds 

IO bc studid 

7 SUMMARY & CONCLUSOONS 

Eacvlnaim mglcs fa salcllitCS in 5 diffcrcnr orbit* 81 

Scal Rack, WA bvc bccn elamid. Expctedly 

Ilct visibility of lpcE mlcllitcs in the 5 orbits is not 

identical. CIS Ma GPS clcvations anglcs arc low 

md LDEe wasllika am available for shomr duration. 

Molniya 24 has high clcvalion and it is visible lor n 

SUMM pan or ~hc day. 

Tcnain and covcwgc prediction z.,alysis has becn ' 

dlone by cxmtin8 lcrrain from a 3 OIC-SCC d m bacc 

.wd using the Bullinpn rncthod for computing Ihc 

kid. Effect of mmin on propagation loss as wcll 

as the effect of raising (/lowering) thc antcnna 

clevl~tion been shown. 

VPerreisapaecityoPpropgation lcmsdala ingcncrd 

and h g h lolisge in pyricuhr til mm wavcs. 

M-lo d lo ke made (0 dctcnninc Lhc 

pubability dlistribrkm of the signals. Knowlcdge 

OC & BDCLi9ticq ofthe signal will aid in eclablishing 

dimic f& 

low. 

marain lhat is neither m u s nor loo

f 

I

0 

0 

18-1 1 

(91 Mayes. d&ri D.. Dycr. F.B.. nnd Curric, N.C.. 

11-15 &Wcx. 1976. 'BscErwucr from Ground 

Vegcsatkun a Frequencies Beiwccn IO and 1 0 

CWz." in AP-S lnternaiional Symposium. (IEEE: 

URSII. M -S Session 3. pp. 93-96 

1101 tbycs. W&p1 D.. 9-1 I (9cmkr. 1979. "95 CHr. 

WIId Radar Raum.." in EASCON '79. IEEE 

Elrcrroraics 8r Aerospace Sy~tetns Conference. Parr 

It. pp. 353-356. 

I I I I HirnRla-Marchand. P. R., Bcrglund. C. D.. 3rd 

SICVCX~, M. L.. 1980. "Systcm dcsign and 

twRmlogy &vclcipmcnt for an EHF hcam-hoppcd 

salcllite&mlink.' WC.pp. 17.5.1 - 17.5.7. 

1121 McElmy. D. W. itd EAVCS. R. E., April 11 -24,1980. 

'EMF syacms fm mobile u.sm," AIM 8th 

Ct~~t~kgsio~t Saralliic Sysremc Confercncr, 

AIAA-#O-OSAI-CY. pp. 5W-515. 

1131 hbltrcsan. K. L.. August. 19H3. "Srt~llitc tactical 

communicotims 38 high altitudes." ProcrrdinXs 01 

r k IW Sypryo.ciun on Afilriury Space 

Commmirorions ond0prorion.t. Colordo: USAF 

Ac*my. 

I141 Nicsscn. C. W., IYH.3. "Mil.smom vcnds.' ICC. 

CI 3.1 -cl 3.5. 

I151 Ruddy. 1. h9.. JUN. 19Hl. "A novel 

nc~~-ge~tion;ory swllitc conimunicaiions 

sywm.' Cot@rnce Record Inicmuiionul 

Coq!erencr on Commwuraionr, 

54.3.1-54.3.4 

Cok)rado. pp. 

1161 Turn. A.E. and Ricc. K. M.. June 19M. The 

poscnaial in m-gmynchmnous orhit.' Surrllirr 

Commruoicaions. p9.27-3 1. 

9 ACKWOWLEDCERUENT.6

3. IAUWCUU SVSTEM SELECTION CRUQTXOA 

~lhcsats can ci:hcr Prc launched on dcmmt!. Inunchcd on 

schcdulc m primary p~ybdls. or launchd rs payloads of 

c.ppcwlunity(auxiliav payloads f l t w pir?Jkcfr on WpJlilrly 

schcdulcd flinhts) 'I'hc timat mission ntccnohc iswc ofsatisf'yina 

lnunch system dmitp rcquircmcntq thnt TIQY pwibly 

haw not h n satisrid or cmphasi7cd in Ihr p-ct. 'hditionnl 

launch otvj minilc sptcm dcsign driwm con h roughly 

divided into sin ~atcgorics: (a) p.rform?nuc. (h)c.t. 

(c) optmhility. (d) launch rc\pnnsiwms. (c) lwirrh Ikqibility, 

and (0 surviwohility. l'hc mcfnhn of k, tu;cc major 

I;lmilia of mninlinc LIS cxpcniliihk lnurrrh whirlcs; Atlm. 

Iklta. ond 'litnn, an: cxamplcs of pcr?orinnncr4rtvn 

dcsigns. 'I% IIS Spmx: Shuttlc MIS plenncd 111 tw a 

aat-tlrivcn sytcm hat. in wmmon wih nll lrriinch sptcms 

dcvctopcd up to thc prcscnt. did not ncliicm ita p 1 1 of Icw- 

alst G~XS In sp.~. Ihc IJS MvanarP inrinch Sptcm 

(AIS), now rcplaccd by thc NIS. U;LY a)mx.ivcd IH king 

both an qlcmhility-drivcn rind A uwdriwFc0 sptcm. 'I'hc 

solid pnlpcllant ballistic miwiks.such iu t k US Minutcmnn 

111 (IWM-91Q arc cxamplcs of launch rcsprinsivcncssilrivcrn 

systcms and thcrcforc nny spacc lnirnch dcriv:itiw!i of balla- 

tic missiks will inhcrit this dcsian chnrrctcrbtic l'hc 

i,ir-mobilc sptcms. such as thc US Pcgwiis and tlw prnpmd 

Commontwalth of Indtpcdcnt Statcs (CIS) Spacc ClipFr. 

rcpmcnt sptcms that pmvidc thc lriunch hihilily to sclcct 

a hcncficial Imlion for a specific mission a d an all-azimuth 

launch capahility. 

Survivability b an additional dcsign drivcr that hm histori. 

blly bccn of importancc to wapnn dcliwry sptcms. At 

prcscnt. survivability docs not +;car to be impironnt to txsat 

!aunch systems. but this factor could kmme more importtnt 

in thc futurc as morc dcvclnping nations gain ~CCCM to 

sophis!icatcd olfcnsivc wapm. 

4. REQUDREMENTS 

4.1 Mixshms 

The ovcrall tncsnt mission is chnmctcri7rc9 hy the nc:d to 

dugmcnt capital spacc i~ucts during times ofcritis: the nccd 

10 surgc at thc outhrcnk of a major conflict: nnd thc nccd to 

rccnnstitutc spacc srtcms that haw brcn damngcd or 

clcstroycd. ~;icsais satisfy a military nccd to providc spa= 

!iystcms that arc dctlicatcd to support tactical a)mma!&rs 

without inflictirg a hcavy logistic end adminktrntivc rckponsibility. 

Ideally. thc battkcommandcn rpecd theoperational 

control to task wtcllitcs as thcir own awto to ensure dircct 

and timely access to mal-time data and inPomation from 

spacc. Uw of thc spna: systcms should be on intrinsic part of 

nwtinc pacctinic military training mmi?cs and not 

brought into play only to rcspnd to an Wunl mrr-fighting 

emcrgcncy. 

It iswcn from Tablc 1 that thc orbits lor thc various missions 

fa11 into two gcncriil catcpics: (a) gccnynchronous (GEO) 

or highly clliptic for u)ntinuous covcriigc missions; and 

(h) lcw carth orbit ([.EO) sun-synchronous for all inclinations 

(to covcr any ptcntinl target arca) for Earth surwillancc 

mbions. ~f~gh~lt~ludcsatcll~tcswr~uld probnhlybc 

stnrcd on orhit prior to hostilitics. An attcmpt is made to 

quantify launch rcsponsiwncss rcquircrncnts. Satcllitc 

wights arc R;lred on wty prcliminaty tacsat dcsigns, and 

shwkl in no way be considcrcd firm rcquircmcnts. 

4.2 Constallotions 

Taat mnstcllations can rangc from singlc satcllitcs to cornpkrx 

multiple setcllitc global cnnstcllations. such RS an 

9 rirliu m -1 ikc globa I mm m u nicat ions mnstc I kit ion t hot 

includes nsatcllitcs in 7orbital plancs. Sincc thcrc could bc 

accnarim where multiplc t , ~ nccd a ~ to bc launclicd tit onc 

timc. potcntial launch options cannot necessarily bc cnnfincd 

to smell launch systcms. Opprtunitics for payload 

manifcstingmust~cxamincd inordcr to imlirovc cnstcffcctivcncss. 

It is conccivahlc. for instancc. for a whole plane of 

I1 Iridium-like tmats to be dcploycd on a single mainlinc 

launch whiclc. 

4.3 PnyDcaod MnRiksPiarJ 

For rnmtcllations with a larg number of small satcllitcs in a 

large numhr of orbital plana. manifesting on mainline 

launch vehkka io an attractive option. At low-trrmid inclina- 

tionn.tk mateffcctite meensofdistributk)n is to u.worhitol 

m[Jrension. Spacecraft am launchcd into a park orbit sepa- 

rated in allitudc from thc missbn orbit. Earth oblateness

mum (3 ~qnrlra;Og~m.or~~~n.olR6r?Qi"" 

of drin h n fpPrnsbn U? the oititud't (fid k-' 

o&it. Thcq t h diCemntial pe-b r.*plT.' 'rxn lk? t'm 

omits pmit a phcsin3 ob the orbipn to trPm 3 " ' ~ : m~ tine. 

At tlw nmmprintc lime. with plnm fd;bm".!!. n oprn;?n 

&ti& for n erinin rino performs nn inarc-&rit t~nsfcr 

into its mgrccpiw mbbn orbit. R c p ~ TS'C~, h ttszwr, 

n;e r&d at hiah inclination ord. in F.1. >re zero for 

plar orbitq,. Thus. for high inclinotm m-!tdPntbn, Ihb 

appmh k mot prr;ctfrol. 

Lillisttc misilc&rimtivcs offer tlic pneibility of liirinchina 

in n mattcr of seconds if thcy arc mnintaintd on alert statun 

with thc~~tcllilc in thcsamcstatcofrcxdim~. Thisdtxsnnot 

sccm to tu! a ncccssary rcquircmcnt for trctttcnl situations. RI 

kirct in the near-term. sincc thcrc is a low pnhbility of thc 

rapid wntcrfora attack auumcd in t k ww of strategic 

ballistic misslb. A more rcmnahlc qpmh wr~lld tx to 

storc the whklcs umlrr conditions that wkl allcnw thcm to 

bc brought into R state of launch rcsdim in a matter of 

daysthcymldbc launchedondcmnndinomntterofhours 

ifdesircd. 

From the ultimate respnsivity of thc ballistic miwik- 

Ucrivatives, thc nat most mponsivc systcms arc the small. 

fkcd, rc!ocn!3blc. or mobilc launch sptcms. :It is ncticipntcd 

\hat thcserystcmscouldhe launchcd ina maltcrofdayswithbut 

a huge investment. Finally, the current medium and 

large launch vchicles haw long callup tima kmusc tky arc 

not dcsignd for high rcsponsivity or rccycb timcs. Tkrclorc 

itwM take n large inwstmcnt in launch sitc fdcililics lo 

bring their rcspnsivity into thc onc to two mck rang. 

S. MAUMILOWL BAWFJCH SYSTEMS' 

Thcrc arc presently four nation-states tho1 ollcr routine 

global mninlinc spzoc launch scMccs: the llnitcd ~;tatcs, 

Europe. the Commonwealth of Indcpndcnt Stntcs. and the 

Pcoplm Wcpuhlic of China. Tcchnially, hpnn ~lso 

hraa R 

mainline launch systcm. the ti-I. Hcwcwr. this vctkle is 

currently king ph& out in favor of tttc id-2 and mmlc its 

last flight in Fchruary. 1992. Whcn the MI-2 trcwmcs i?#rS- 

IionRI. five nation-stotcs will k oblc to prcivide mainlinc 

launch =rviscs. HaYtvcr. diffmrltic; bziq urpr e n d 

with the IE-7 cryogenic fint-stitgc cnninc ran&! &lay the 

prrdkted 1993 initial launch capability Qnoe. 

19-3 

Q n corn3 r-YI R?Y-Ilbm 

5. U. U Wroifd .''Ea (US) 

Thz amnt LE noh?h IWR& oy&m frmilb imt& the 

Atk. kh, tr:d EpCmn PmPiPies. 'wrz Atlm. kltm. and 

Titon DB me pmdiutn kumC01 GhWm, 4th payW apbiliab 

Qf bCb3lZfl6,~ Old n,m b (am arrd 9,091 kd to 

EO. Wenvkr lift mpbility iil provided by tk Commercial 

Titan KUP and thz Tieon PV, which can lin closc to 48,OOU Ib 

(21.818 kcI) tQ mo. 

This ~ g of launch , xhkb is thc mat viablc for the high 

A second strntcgy is to launch the spmcmfl inlo tkc wmc emqy taxit mixiom, ita0 only kcmuse of payload capaaltitude 

as th mibn orbit. but at a I ~ZP inrlinmttnn. thus bility, but b u x t k nugpted stom-on-orbil stratcgy for 

cstahlishinn a relative regression rnte brrd cm the differen- thz 8E0 mtellitcs b oonsbtent with thcir current low 

tial inclination. n# plnncchange mnmwm to injm t k mpnw tima Titan I1 an currcntly tu flm only 

spncccnn into the mbkm orbit is a high cvtccrgy mnhtuwr, from t k wat amt launch site at Vandenberg Air Force Base 

h.cvcr. nnd the crew rcquircd incrcmo rnpklly re^ t k (VAFy3) in California. lk Dclta I1 an dclivcr Z10D Ib 

magnitude of Ow planc changc incrcam. T k plmtwhnnge (910 k ~ and ) tptt Atlas 11,310 Ib (1,410 kg) to GEO. For a 

mancuver imples tRt use of pmpcllnnt. &kti reduces Lp# 1,OlXl lb(455 Ir&mtcl9ite. this translates into about $25 M per 

number of 5iilcllitcs tho1 can bc manifaWd on D :in@ payW I~uncW m QI n time on Delta or thrcc at a timc on 

launch. A h l a m hstwcn plene chan,v nniJ ccocptmbh Atlas. white for lSIlI 18 (63'2 kg) aotellitcs, thcse numbcn 

rcgressbn time must be established to mahe efkctive use of b m e abut $50 M for a sin&lc satellite on klta and $40 M 

thc launch systcm performam. 

CPSCR for two wtellitcs on Atla. The viahility of launching 

multipk satellita to GEQ would haw to be aucsscd by the 

4.4 IaeoPrDP ClaSp~ori*onesss 

uscm, but it wukl appcar to tx a remnable npproach since 

A funkr n>nsidcration is thc launch systcm wspncivcncs. thcrc arc thrcc GEO mbions idcntifwd. and. in any case, 

For tnmt mL.k>ns. tkrc is an impliciition oPhidh mponsiv- silcnt spam can be dcploycd if suficicnt cxwss bocxtcr 

ityofthcsatcllitcsystcm.hothonthcgmurrisan~loncc it kin capability cxists. Tk benefit of amtrolling satellite wight, 

orhit. In Mition to bunchingthc fin1 sstcllifc ritpdly, thcrc without cornpromking mission capability. is apparcnt. 

is thc issuc of Iauxh rcpctition ratc rquircmriiL5 (thc nccd 

to rcld thc sptcm) This may he sold with dditionarl 

Fiyre 1 summarim the payload apabilitics of the currcnt 

stomp. tcst and launch pad facilitics. or n) id recycling of 

US mcdium and largc mainline upcndablc launch !;hicks 

thc pad. or mat pmhably a aimhination o P kith. In cvcry to various orbib of intcrcst nd xvcral othcr characteristics. 

W. tDrc marc mponsivity rcquid. the hiBhcr tk .such as payload acmmmcdatiofi. rcliability. and cost per 

non-recurring cost for fxilitics and cquipmcnt nnd tk 

'flight. lsunch rate capacity circa 1995 U idso shown. 

highcr rccurnngcoat for manpcnvcr RMI mnintcnnnoe. 'li& 

studics ntcd to tu mdc when launch rcipnsivcncs. 

rrquircmencs arc bcttcr dcfincd. 

A 

a 

,:SI :z I ::E I a* I ::.z I 

Figure 1. Cumnt US Malnllne Launch Systems 

9.1.1.1 lklta /.mi?, of vehicles 

'Thc Dclta family of whiclcs was dcrivcd from Ihc Thor 

lntcrmcdiate Rangc Elallistic Missile (IRDM) by adding scv- 

eralsmall Solid Rocket Moton(SRMs)and thc l')clta sccnnd 

slaae. Deltas arc uxd to launch payloads into GEO and 

LEO from Eastern Tat Rangc (ETR) lnunch complcxcs 

IXJ-I'IA and K-17D; and to polar orbit from thc Wcslcrn 

Tat RmEe (W)spasc launch complex SIX-2 The apa- 

bilitlrn have atorw, through a wries of upgradcs. The primc 

conlrmor for tk klto family of whiclcs is McDonncll 

Douglas, Huntington Beach. California. 

TRS Ik:lla 11 wm wtecld M) the Air Fora Mcdium lnunch 

Vehick I (NUN-I) o d U cumntly used for launching the

19-41 

5.8.1.8 A/Im faniity of whicles 

Thc Atlno is a former Air Forcc Intcmn!iwntal 13allistic 

Missilc (ICBM) wcapn systcm mnvcrtcd foor ux 89 a space 

launch whfck. The Atlas D was man-rntd and flnv four 

suarssful mhions during thc Mcrcury pm7mm. including 

thc first U.S. manncd orbital flight by John Cilcnn. Ihc sys- 

tcm aomyt. now ovcr 30 ycan old. hm gone through a 

xricsofmc#lcrnizatinns and upgradcs. which haw enhanced 

iu paylox! ptrformana: cnpability comkkmhly. Thcrc arc 

scvcral Atlas vcnioru. misting and plnnncd. hut common to 

all is thc USE ofonc and a half liquid propcllant stagcs. bth 

stap ("hnstcr" and "sustainer") arc ipitcd on Ihc grnund 

and burn in parallcl. After thc bc#%tcr enzincs arc jctti- 

soncd. the sustainer cnginc aintinucs burning to orhit. 'I'hc 

prime conlmtor for thc Atlv hmily of woliclcs is Gcncral 

Dynamics Corporation. San Diego. California. 

AtlacE. Tltc Atlas E is a DOD launch vchiclc prcscntly uxd 

to launch smaller payloads to low polar orbit from spacc 

launch complex SIC-3 at Vandcnkrg Air Form Dax 

(VAnO). 'Thc vchiclcs are fonncr Atla lCllMs that haw 

bccn decommissmncd. rcfwbishcd. modikcl. tcstcd. and 

ccrtifird for spacc flight. Tbc Atlas E is primarily uxd tosup 

porl the Don hfcnsc MctcorolqiG?l !htcllitc Program 

(DMSP)and the National Occanic and Atmmphcric Agcncy 

(N0M)satcllitcs. Itcanplacc IRolh(BRl)kg)intokrupolar 

orbit. Only a fcw vchicks rcmain in invcntory. . 

Ailm 11. Thc Atliu I1 is uud for mmmunication satcllitc 

im~idtcs such as ~k rxkw Siltciiitc Communicaiions System 

(DSCS-Ill). It was sclcctcd as the Air Force hlcdium 

leunchvchick I1 (MLV-II)and isdcsigm1topedor.n 110 

and GTO missions. It consists of thc hocntcr and R Ccntaur 

uppcr stagc and can pl,ra 14.1oI1 Ib (6.410 kg) into IJiO duc 

cast. Sen#) Ib(2.W kg) into GI'O. or 3.100 Ih (1410 I:g) into 

GEO using a kick stagc. 

The Atl;~u mnlracttrr is offcring four venbns of thc Atlas: 

Atlas I. Atla 11. Atlas IlA, and Atlm llAS for launching 

NASA and mmmercial payloads. Thc Atlm HAS is an im- 

proved version ol the Atlas I1 that ha! solid atrap-ons and in 

which thc Pratt and Whitncy HI,-10 cngim in t k Ccntaur 

upper sta@ is incrcascd in thrust fmm 16,S!I!l Ih to 20.8aI Ib 

(7.5UO kg t09.4w kp). Thc Atlas IIAS payW to GTO will be 

7.700 lb (3.490 kg) 

Gcneral Dynamics Commercial Isumh !?xrvicCs hw pm 

pasod arrying wc;ilkd "companion" mtcllita ran&ng 

Ib 23% b(W& t~ XWkpJto EO at ~ . s k g 

on 1nuncl-m of pd,mmy p y w 

s.E.il.3 ~itmjkvdy O~L.&~CIU 

rh Etan fCMIJi!g, of whEcks io a of fir Force vehkb 

thct his ev~lved Pmm tk Titan ICBM system over t k pipst 

35 pa *FRP@~ mnin b~rtch whick confiprations pmntly 

&I: 'K%nn HB SpCOi? hunch &hi& (SLV), Titan 111 Cornmcrciral. 

and 'FiPnn w, with vanat.bns of each. All ha% m 

oorc a9t-w wins liquid propellants. a7~t IW IWO usc 

mcntcd SRI% for the initial stage to enhance pcrfonnance. 

Compiteu-2 SWP&(dcsipmA SRA4U)wilI soon replam 

thc ~tc~l-c.ad ~~ltgs (0 prodrk increcbxd ptrformancc. 

/+ddittO.d gXpfXd3 fop im& performancc include the 

UIX of IQuid CV-Wnic propellant hten. more and longer 

SWIMS. end more liquid cngiincs with strctchcd and/or largcr 

diameter core stwc tankage. The pnmc contrnctor for the 

Titan family of whicks is Manin Marietta Corporation 

Astmnautia Gnwp. Denver. ColoracO. 

Titan 11. 17rr Titan I1 spctcc launch vchiclc was concciwd by 

DOD to utilize an aristin~ rcsourcc and, at the same time. 

augment ihc dwindling Atlas E launch vchiclc invcntory for 

launching smaller payloads to plar orbit. Thc Titan 11 

vchiclcs(likc thc Atlas Evchic1cs)arc lormcr ICDM wcapon 

systems that haw brcn decommissioned. rcmovcd from 

thcir sila. ncfurbishcd. madificd. tcstcd. and ocrtificd for 

spacc flight. Thcrc wcrc onginally 55 Titan ICDMs in invcn- 

tory. and the Air Forcc has a continuing program to modify 

and launch thcx vehicles as rcquircd. The initial launch ca- 

pability of the Titan 11 was achicvcd in Scptcmhcr. 1988. Thc 

Titan IIcanplan:upto4,21#)lb(1.910kg)in 1.EOplarorbit 

fie 'vi \, JCC launch complm SIC4 (Wcst) at VAFH. Prop- 

ds for upgrading 'Titan II paformanu: includc dcvcloping a 

Cape Canavcral Glpahility. long duration circularization 

riurnswith addcdpropc;lants. and SRM strapns. Thc;Iddi- 

tion of ciaht Calor 1Vs. for cramplc. would launch 8.90 Ib 

(4.M5 kg) to LEO polar. Configuration studics includc thc 

addition of up to IO GEM solid rocket motor strap-ons. 

Titan 11, in ik ballistic missilc mnfiguration.can bc launchcd 

with lcss than one minutc ofvdrningsincc propcllant can be 

kft for long pcrids of time without dctcrioration of thc fuel 

tanks or the propulsion systcm. 

Cornmtrcial Titun 111. Thc Commercial Titan 111 is dcrivcd 

from thc 7qn WD with a strctchcd xcnnd stagc and a hammerhcad 

(largLrdiamctcr)shroud for dual or dcdicatcd payloads. 

'The tint commcrcial Titan 111 was Iilunc'lcd in 

1)cccmbcr. 19$9, and can launch 32.00 Ih (14.540 kg) into 

LEO. It is cnmpatiblc with thc Mclhnncll Douglas 

PAM-DII. the Martin Marictta Transtagc. and thc Orhilal 

Scicnar Corporation Transfcr Orbit Stagc (TOS) upper 

stagcs to provide WO capability of 40M Ib ( 1,850 kg). 3YK) Ib 

(4,320 kg), and 11.0 Ih (5.00 kg), rcspcctivcly. Performa 

m to GEO is appmrimatcly 5,500 Ih (2,500 kg) using n 

spacccraft kick motor. Marlin Marietta h;u cxamincd a 

number of paylod dcploymcnt schcmcs for hunching small 

payloads, both as auxiliary payloads and U multiplc primary 

payloads. but thcx dcsign options have not bccn cxcrci:~!. 

Titan IV. The DOD'sTitan IV dcvclopmcnt was hcgun as a 

complcmcnt to the Spaa Shuttle. but following the Chal- 

LcnEcr accident. thc program was arpandcd lo accomrndalc 

critical DOD payloads. Thc program was furtlicr cxpandcd 

in 19E17 8) thc full impact of the Shuttle dclays and cancella- 

tion of the Shuttk-Ccntaur propm bccamc cicar. ' 

The Titan IV IWS citkr a 7-jcgmcnt SRM or a 3-xgmcnt 

SWMU. It is now capable of dclivcring 10.0 Ib (4.550 kg) to 

OEO with t k arrent 7-segri1cnt SRMs. When thc SMHU 

b l e w munrkrdeencbptncnt are available. thc Titan IV/ 

Ccntour will k2 abk LO launch 12.7IID Ib (63% kg) to GEO. 

ThC Titan W/OUS is currently operational and is capablc of

- 

.d: 

5.1.2 EMlOP 

Eump is Pcpn:scntcol by thc Arianc 4 famiUy, vhkh pm-kka 

a ran@ of payl& fron 8.01#) td 2l&Q 1b (3.6Krl) to 

9.545 Ern) in IEO %??ere an: six rcrskm aXl Arinlrrt 4. wth (1 

mix of lkpriid ~nd did pmpcllant strapon hntcrs. Tkw 

' arc two !$ukatc\iite WMt'CS. thc SPE16)/4 (f,\NElUTC hr- 

lcusc Extcmc pur Lonxmcnt Ihuhlc Arinnt), Ikdiatcd 

Satcllitc ScMcc (SDSb and the Ariam: Stn~urc fnr Mil- inry PblylD& (ASAPL plus diffcrcnl t~mions Lbf rttc 

SI'ElBA payload fairing. In this wy. it cn?m to R wiilc 

rangc of pnylods. TRE vchiclcs arc launchnl I'rom il launch 

sitc at Koumu. Frrnch Guiana; a launch cviiiiuth rnnec of 

104rkdcgispmsihlc fmm.349.5 to93.Sdcg. TErrmt pcrflight 

for a sin@ GTO launch is bctwcn fMM onrl DSM. 

Fifty satcllitcs haw kcn launched using IgK' !W,ILi (Sys- 

tcmc di: lnnccmcnt Ikuhlc Arianc) or !~WI,l)/\ du:il 

launch copability. which has rcsultccl in B rntcllitc i!cploy- 

mcnt rote of nbut I2 pr.r Far. up from 7 tfi 0 lnunclics pcr 

ycnr prcvtnwly. The lounch limit for thc Arionc 4 is xt at 

IO flights ptr Far. which allom ftbr dclap or prohlcnvi. 

Thrcc mmmcwial micmatcllitcs haw ltcccn fltrm using thc 

ASAP, and nq many ~LP six ASAID iiIt;u!Ibnicnt points c:rn 

nccnmmtrdntc multiplc satcllitcs up t o nhwt 01 Ih (2Ul kg) 

cach. 'I'hc cntirc ASAP structure can Is. n:ww:d for 

hctwcn $7Ol).l##1 ancl WtO.lI)o. In ordcr 10 wtinfy c rstnm- 

cn'dcmands, n shortcncd wnion of S PWM, n:irncd SIX 

(SpckJa Ikdicatcd Satcllitc) is trcipg built by Ihiltsh Acrtr 

spi to mimmdatc a satcllitc in thc LSiln Ib (6.0 kg) 

clixss. plus nn idditional satcllitc orup toRM) !to. 'Thc capnbil- 

ilks of the Arianc 4 arc summarizcd in Figure 2. 

hriancspace. thc commcrcial o>n.wrtium that npcratcs An- 

hnc. predict5 thc minkatcllitc mnrkct (aimmcrcial and mili- 

tary) tooeach U, pcr ycar by 1993. and i's pnl is to cclpturc 

5070 of thc markct. 

5. I .3 Commonneulrh OJ Indquncnt Stutes (( 'IS) 

Thc availabilityofcx-Sovict IJnion lsunchsptcms is wmplC 

catcd by thc political changcs that arc lakinc plncc and thc 

faa that spacc awls arc no longer contrcilkd by a singlc authority. 

At 1ca.t fivc spacc agcncics (thrcc in Piusia) appear 

to hc cmcrgjng and at Icut thrcc mcmhrn of thc Commonwcnlth 

(Russia. Kazakhstan. and Ifkrain) arc laying claim to 

the potcntial hcncfit of marketing spam tcchnolc~ to thc 

wrld. Thc distribution of thc major CIS 8 p x awts arc 

shown in Figurc 3. 

Russia appcan to havc control of mtnt of the cx-.%viet amnal 

of launch systcms. including thc EncrgiiVRurnn. thc #* 

ma. t k Proton. thc Tsyklon. and thz %atO!~gYdMolniya. 

Hmvcr. the 2nit. which is thc only en-Wct whtclc 

built apcificnlly for a)mmcrcial launch om9 mny pmihly :r@ 

launckd lrom the pmpcwd Cnpc Yo& Spa ibrt in 

Ouccnoland. Australia. is built by Yuzhmyc NPO in the 

Ukraine. 'Ihc Yuzhnoye Design Bureau h a h proping 

the air-launched Spacc Clippcr. which isditoiwd latcr. Tht 

launch capabilities af the ex-Smict unmend launch systems 

arc summarind in Figure 4. 

9.U.Q h$a P?.b-!K oj aim (PRC) 

The PRC b repw-erntd by .he lmn8 March family of 

whkk China'oopm Inuncliwviocsdeprndson a numkr 

of inte~in~oqynimtbm, emh of whish is responsible for 

Pp of t k lawnch ~~,owiOn p&a&. Tk China Gnat Wall 

!? rrdllsstsp, Coqmmtinn (CGWBC) k? responsible. under the 

Ministry of hotmn~uticn. for amdination hctwccn forcign 

mtomers and the olhr ekmcnts of lhc launch xrvices 

orpniatbn. Ih launch capabilitics of thc Imng Maich 

family arc alammerited in Figurc 5. 

9.2 Pm m 3opent ricl Plamswd 

Thm natbnQtms. t k Plnitcd Stela. Europe. and Japan 

haw ckarly InM aut plans to d end thcir mainline cxpnd- 

sbk launch whkk f kt. 

J.2.D United .%lata 

Medium Igupcch Vphicle 3 (IW1.V-3). ??IC 1JS Air Fnru: pliiw 

to numl a a>ntmct during fiscal par I993 for thc h4l.V-3. 

which would knmc available in 19% and has. as its primary 

mission. t k launch of GPS DIU& 1IW. 'The M1.V-3 is intcndrd 

to "bfdgc-the-gap" until thc PSIS is availahlc. and 

an:, prformam improvrmccts ..vi11 k financcd by privatc 

industry. This pmsurcmcnl could amflict with thc prtrurcmcntoftRcAI~S.nndsdccisicin 

may havc tohc madc inCongrcss 

to sckt one or tk othcr. Although no charactcristia 

of thc MI.V-IfI arc rclcasnhlc HI this timc, thc prmrcmcnt 

awld p~)~idR an oppwtunity to plan for dixrctionary iiuxiliary 

payload tlsploymcnt. 

National Laiinch .S,v:rtm (NI..$). I'hc NIS is using iin cwlutinnary 

npproach for thc dcwlcrpmcnt of ii family of hunch 

whiclcs and opcrntionnl infriistructurc with the ciipiihility to 

plncc a wIdc rangc of piiyloads into orbit at ii fraction of current 

CM~S. l'hc r)pcriibility gwls of NIS arc to niiikc spacc 

laimch activitks w rnutinc as thw of a long-haul trucking 

ampany. 

T?c NIS vchiclcs currcntly wrvina ns pints or rcrcrcncc 

ran@ from a smiill. twc~tagc vchiclc ciipiihlc of placing 

appronimatcly 2lMfKl Ib (9.090 ka.) into I.EO (thc immcdiatc 

focus); In a one and onc-half stngc vchiclc utilizing a Shultlc 

Extcrnal Tank (EI')dcriwJ tank section (cnmmon corc) for 

modcralc sizcd paybads to 1.EO. and capnhlc of hcing 

upgradcd to a two artd onc-half stag vchiclc (hy ndding an 

upper stage) with GEO cnpahility: to a hcavy lift configuration 

using N5WIWs NI strapon hatcn. the ajmmnn cow. 

and a Gargo transfcr vchiclc ((XV) for wrgo dclivcry to 

Spacc Station Frecdom (SSF). A ncw NIS uppcr stagc. u.xd 

with thc one and onc-half stagc vchiclc for GEO miaions. is 

alsokingconsidcrcd foruscasthcfinalstagc ofthc M.O(X)Ih 

(9.M kg) WlS-3) vchiclc to furlhcr providc common;ility. 

Vchiclcs with incrc,wd payload capability. attilincd vi;) mtdular 

grcwh to mcct heavy lift rcquircmcnts up to 124.00 Ih 

(56.360 kg), arc also udcr study. Payload cstim;itcs for the 

various mcmbm of the NLS family mcct hth NASA and 

DO11 rcquircmcnls Thc primary intcrcst of thc IIOr) in the 

oncandonc-halfstage istoplacc50.0 lb(22.730kg)intoan 

x 150 nm (148 x 278 km)orhit; NMKs intcrcsl is to usc it to 

dclivcr 55.@30 Ib (25.0 kg) of nct payroad to thc SSF. 'I'hc 

DOD plans to usc thc twtagc whiclc to dclivcr M.Oo Ib 

(!IO91 kg)toan 80a 150 nm (148 x 278 km)orbit. 40 Ih( 1.8 18 

kg) 10 GEO. or ci.0 Ib (3.636 kg) to GTO; NA!h would usc 

ittodclivcr 18.01#)Ib(8,1WZk~)ofnctpnyln:wl totlrcSSE 'I'hc 

tw onrl om-half ntow vchiclc wuld clclivcr 97.W) Ib 

(00,~ kg)totk61lx 1Mnm (148 x27R km)orbitor 1S.WoIb 

(4.818 hg) lo GEO; it could also dclivcr 83.000 Ib (37,730 kg) 

of~crcxag payload to the SSlE The HUW option could dcliwr 

135,O Ib (41,360 kg) lo the $0 x IS0 nm (148 x 278 km) orbit 

or 1zb.W Ib (56,364 kg) of g1oM paybed to the SSE

CURRLHT PRowcTKm N DEVELOPMENT 

" 

P 

n 

,, 

i II 

i 

,. 

- 

d U 

U fl . 

U

1 

6.1 Cumt ud NcwTcm, r*n.ri and Proposed 

61.1 United Stam (US) 

Sbk 2 lhcnn the eh.rr(cmciol of a number of mnali (bced 

or rebcllabk U9 hunch vch~b that abt oram in -fop 

mcnl. TheseoVt I.whkh. in anyme. hnrmntlymt ofprodl~nion, 

an only dclivv 8UJ to MO b (181 (0 273kg) 

pmyIw&tothe bwEuthorbi(rdinlercst. Thc Scout Iland 

I k Pcgmur dr.launsRcd boalcr han.appmrimaIcly tk 

am pprbnd e bility lo LRO in lhc 600 IOW0 Ib(273 lo 

% Rpw han the dnnlago of lkribk 

and all-dmuth capability. The Cow 

hunchen pmviaa a range of payload 

adding slnpan boosten lo thc bmle 

fcur-r~cnerhWe. llshouldbepointcdoutthnt thconly 

conrclpruian that ha Ilown U Conuiqs 1. which w- 

ti1111 I*r a suborbiul mbsion in 19BR The Conestoga IIA 

nnim dlnr 2 lo 3 lima the ylod capability of thc 

-1 I at thc m e pria @~O-G& -ding to the manufaaurer. 

The 'RUN* vhkh h urdcr dew.bpmcnl by Orbital 

sdcncu Gorp @SC) fa tk Deferae Mvanecd 

Racareh and Planning Orgnnimtion (DARm), pmvidu 

amidcnbk paybed capbilty U) Leo. In many cunu only 

one salellite pr ring k uid. but ccvcral rings propcrly 

spadtorhknmea wrap may bc nccdal. If ihh 

b the me. the additional capability d the Comatopa or the 

~UNI may b used 10 permit ermying CIEQ( propellant in. 

say. one of two ulellita to boat it to a highcr altilude and 

different indinrlmn in onlcr Io pnnle I diffemntbl nodal 

regmsion behccn Ihe ha utellite plana Nodal rem 

sbnofautellilepbne b b toforraacrledon Ihcutellile 

~uyd by the fMh'rob*temn TIKOC iaoatrnd torn&

.clrc;lih w m iua 

thc orhilot planc c~cctivcly prcces nhmt tl#: plar rmis of 

thc Emh. Wkn thc planc of thc ~~a~r#l oatcllitc Rin, 

mhicvcd thc desired scparntion from that of tbc first. a scc- 

OM! hurn of that satcllitc's ploplaion can Pn: uwd to rcturn 

thc satcllitc to Ihc Sainc altitude and rnclinotion m thc othcr. 

Inth~~~.thccacc~~hcmatcnpahililyoftIPc~Pkunis might bc 

uscd lo launch n silent sparc. It should ttC pbintcd out that 

thr:ljurusaystcm islreingdcsignrtl (11 tw rckntahlc fcirsurvivnhility 

rcxwns sin= it W.LI prilptwd for S;i;ur 1)cfcn.w 

Initiatinr(SI)I)uw. 'I'hc Sl)l-~RtUliit~d rcquircmcnt for thc 

sF1r.m WR~ to hc ahk lo cstnhlish n liiunch site in fivc drip 

nnd lnunchesatcllitcthrccd;~~ IiiW. Awinwryoftrucbcarrying 

tk appropriate cquipmcnt prcwtrkh this rap:ihility. 

Further study is rcquircd to dcicrminc if thh capability L5 of 

any bcncfit to thc lagat miuion. 

Scotrr I. *lk NASA Swiui whiclc hccarnc cipcmtional in 

IWl. ~9 of July 1991 only four vchtclcs rcmainctl. It is a 

four-slagc. solid prqwllant. .writs hurn rttdrct. 'I'hc Scoul 

can dclivcr 146 kp, to R sun-synchroncra phr orhit. Md) Ib 

(22f) kp,) ton 1,EO plar orhit (Iiiunchcd from ViinJcntxrg). 

or 571) lh(2.59 kg) to an c;utcrly(3~.7dcg)or~it Iailnchcd from 

Wallop IhxJ. Virginin. 'I'hc Scout iscascntially phnscd out 

;IS a 1JS launch whiclc nlthough it is anticipotrd that thc Italinns 

will support iin cnhanccd (Swwt 2) prqrani in cmpcration 

with IJS industry. The Italians.will launch from San 

Mnrco. off thc m;nt of Kcnya. 

'I'hc minimum Scout IiiuWh vchiclc-only uat IS quoted ni 

flflb4. which incrcxscr to $12-13M for lull launch wtcrvisC. 

This translaics lo fZ.fJl#) to S37,UIl) pr Ih (a55.tm to M2.m 

pcr he). which dirs not amparc I;lvoriihly with tk currcnt 

industry avcragc of 910.fm) to $1 1.m) pr 111 ($U.m to 

SUdHlO pcr kg) for dclivcring Iitrgc ccimmcrci:il ra;cllitcs io 

(;lo. 

.Ycortf2. An upgriidcd wrSton (Scout 2) has twcn studictl thnt 

can douhlc thc piiyhincl cap:ihility of SWNI~ I. Sirilpon solids 

nnd nn al#)~,cc hick motor ~ddcd to Ihc cmklinn nm whklc 

yrkl ihc CnhRnCCd pcrformancc. 

Tiitnu. 'H'aurus is a DAHBA dcwlopmcnc of ti Standad 

Small lsunrh Vchicle (SSIY) hhrd on the Pcpws with tk 

addition of 8 bcacckccprr fimt stagc. It 410 +:iwr 3.W Ib 

(1.364 kg) to I .EO or HdH) Ih (364 ka) to CIIEO. 'tiitinin will h 

gmuml-lrunckd ~ ml will tlcmcmstratc ik r~pid cstnhlish- 

PER LPW 

lcm, lMI0 

l?B IWU 

1N.D 1450 

1- 1150 

4.1 4.1 

0.9 0.9 

1.3 1.1 

mmo '20 rn 

PRO3 F A 03 

WAKEAO COAHEAD 

mcnt of a ground mobilc launch c;lpahility. A rcspnsc timc 

of 72 hnun From alert to lnunch is thc goal. 

I P.9 

C'orotst~u. '17iis is a cnmmcrcial dcvclopmcnt of Spacc Scrviiccs 

Incnpwstcd (SS?). whkh is nnw n division of EER. A 

NASA-fundcd effort cntillcd thc Commcrcial Elcpcrimcnt 

'f'ranspwlcr (COMET) usina cnmmcrcial husincss practiccs 

is undcrwny at Wcstinghousc Electric Corpration to dcmonslrnlc 

tk cconomical dcvclopmcnt of a rcliahlc launch 

rind pnyload rcuwcrysystcrn. SSI isprcividingthc launchscrqmcnt 

of thc prngram and is using rocket technology 

&@wlopd by Isrclcli Aircnifl lnduslry ( IN). rathcr than surplus 

LIS govcmmcnt moton. to incrcw rcliahility and 

r~duar insurance m(S. Thc familyof whiclcs isdcsigncd for 

cmlutinnary grcnvth. 

Cniiestqa I1 dclivcrs a payloiid of 7Ol) Ih (31H kg) to 250 nm 

(463 krn) polar orhit. or 4Cll Ih (182 kg) to 400 nm (741) km) 

polar orhil. Concstqn IV dc1iv.n paylo;ids of 2.fW Ih 

(W 

kg)md IsUOlh(f242kg). rcspcctivcly. 'I'hc vchiclc kimily 

is dmigncd to uw a rclwatahlc launch site. Iaunch is nominally 

from Wallops Right Facility. VAFH. or Whitc Sands 

Mis!ilc Rangc. In addition. thc vchiclcs arc also dcsigncd to 

k umpatihlc with pn~poecd Hawaii. Florida. or Capc York 

SpaCCprt!. 

Olhital l5pm.u. A contract his bccn awiirdcd to Intcrniitional 

Micr'ipacc. Onc. for launch scMccs for thc SI)IO's Miniaturc 

Scckcr lcchnology Intcgration (MSII) program. 

International Micrth'ipncc. of licrndon. Virginin. is offering 

its Orhital Exprcss ground-hxwd launchcr to dclivcr a pykuld 

of Ib (182 fq) into ii sun-synchronous orbit. 'l'hc 

Orhital Effprcss has cl

0 

0

19-10 

OcazO midm ~ r nof mp htb~rm ~ ~ 

mm thCP FV m&y im jpdudkm imlsdc tlw Bu 

SJ:,X &,:ix:; (E'%) Ari:am Tbchpw~ 

fu4m (MTEP), the F~mh 

in t k mmmcrcial 

Expriment T 88- 

Motre Ponus. the Italian Itabpct- 

Micra30t. nnd tk British Univcmity of Sumy UoSat, 

hilt by Surrey Sotellik RchnoEogy Ltd. 

6.8.2 lgassn 

k4-VSok.r. l?te fir01 of tk M Rmily dwhiclcs wrc eitkr 

lhm- OP fciur-aoge all moiid-propellQnt whicles msBc use of 

mmdyniamk art$ opin-otlabilizotbn oontrol techniques. 

Pnicr wmbm U& 1~~08lcliary Cue1 injection for thrust mor control in mpm to an on-board sutogibt. and eventually 

tRE edpntml opkm ww di@d to imremc control lq+c 

dagn flexibility and to &ucc psurcr ami wight needs. The 

cumnt pduabn .wsbn is thL' M-3S-11. wkmecharaacristics 

8rc listed in Figure 6 

6.U.3 India 

SLVSePieJ. The Aupented Spa02 ~ AIJ~C~ Vchicle (ASLV) 

can lift 330 Ib (1% ha) into LEO. The launch of thc Polar 

Satellitc l ~unth VehCrh (FSlW). planned for March. 1993. is 

mpcctcd to &liver 6.6Q1p Ib (3.000 kg) to IEO. The PSW, 

unlikc the ASLQ, which is crimped of four .solid slap and 

two strapnns. will use liquid sccntxl and fourth stagcs. The 

IJS hasplaccdsanctionoonthc IndianSpacc RcscarchOrganintion(9SWO)for 

buyingadvanccd mkct vchnology from 

Russia. Thecharactcristiaof the Indian vchiclcs arc listcd in 

Figure 8. 

cuznmn IM DEVELOPMENT 

CWCVKm I 

Figure 8. Cwml end Planned Indian bunch Systems 

6.8.4 isml 

Slrcrvit. Thc Shavit (which trandatcs to Comet) is a 

threz-ctnp mlko pmpllant vchick and is a mdificntion of 

t k Yckb P I Dntcnncdiate Ran@ IBollistic MiKqilc (IRIIM). 

Ths Jepicb io claimed to be capable of hunching a MO Ib 

(Sm, kg)wnrhccJ. A satellite. Offcq 2. wns launched success- 

fully on 1 April. 19%) into an clliptic;ll orbit with a pcrigcc of 

12.6 nm (210 hm) an4 an apogee of er#, nm (1.500 km). The 

onteliite weimt io estimated to be 352 Ib (160 kg) The LEO 

copccity in on eetirnoted 400 Ib (200 kg) into a retmgrade 

orbit.

6.2.2 UniEcd Kin~domlNonvay 

I-ii~lc lmimkrfor Low Emh Orbit (l.iiil.k'O}. '?k mm mcrcia1 

IittIXQ program is king undcrtakcn FpII GcRc~;~~ 'lcchnology 

Sptems Ltd and the NorwqianSp,?rrj: Ccntcr(Norok 

Romwntcr) to offcr a kwarrt and mlinhk n,cnnn of plasina 

small p3yln-A~ into hmth polar and sun-oynshrnnrws orhits 

from a Eumpctcn launch sitc. l'hc ljttl .EO i7 m wlid propellant 

vchEck:copnhlcofpliccinan 1,3~Ih((~hn)payIontl into 

a 243 nm (052) km) pilar orhit or 1547 19, (1d3 kc) i 110 a 

162 nm (3w) hm) polar orbit. It wuld trc 1aursI)cd froin the 

Andoya Wmftct RmRc (69 dcg 17 min M. 16 ckg 01 min E) 

Morc than rlM) souding rtrkcts hnvc hrcn I~i~rrchsd from 

this titc. littl.EO aiuY atso inr;;..fh 2.m Ih (312 kg) into a 

162 nm (SM) km) polar orhit fmm Itbly's San Mnrco launch 

site. 

6.2.3 Spin 

I 

C~pricomi~. Thc lnstituto Nacional Dc Tccnica Ac.rtap;tcinl 

(INI'A) has annnunccd a ncw rtrkcl &vclopmcnl. thc 

Caprimrnb. which is intcndcd to prodc Icw-cmt spm 

transportation for thc scicnlific and communicritions community. 

It is a Ihrcc-stagc all-sdid rnckct c:tpnb!s of placing 

I10 to 228 Ib(M to IOkg) into a 324 nm ((100 kti:)p)lnrorbit. 

Tcsu dl ttc mnductcd from El Arcncnilb (iluclm), a d 

thcrc arc plans lo build a future launch cnmplcx in thc 

Canary Islands. 

I 

6.2.4 Comnmtru~rulth of Indrprndrni Siatts (CIS) 

Spacc Clipper. Yuzhmyc NPO. bawd in the Ukraine, is proping 

an air-lnunchcdcnmmcrciill Iilunch Rystcm.spna.clip 

pcr. which is planned to hc availnhlc in 1W4. Thc srtcm 

cnnsists of an An-I24 canicr aircrdft and a chriicc ofscvcral 

thrcc- or four-stagc solid propellant launch whiclcr(krivcd 

from the SS-24 misdc) that arc launched from tl~c cargo hay 

nfthchn-124. Achoiccofsudiffcrcn1u)lid rmkct launchcm 

has bccn propcncd. 'I'hc b,wlinc systcm in cnpnhlc ofdclivcrina 

1,Iall Ih (500 kg) to I.EO and is mtdulori7rd to pttwidr 

six diffcrcnt wninns of thc vc!wlc ;Ind dapt In a wkk variety 

of orbital recpircmenu. Thc maximum tnlrcoff wight is 

392 tonnes. and the systcm is claimed to b phfr to opcratc 

from any sirftcld capabk ofscrvicing a ?kin3 747. 'ki avoid 

techmlolSy transfer reotrictions. thc inntnllafkin of the paykx4 

can bc ptrfwrr~ed on-bird the Antomot t k cu~tomer's 

eirftehs. Yuzhnoye plans to mcnlify two An-la aircroft, 

and them are more than 100 SS-tas in Inwntary. It Lo 

WACE CUPPEW (CIS) 

F M 0. Ab-- WlW Leunch Wkh 

19-11 

7. ~U.U.US'ITU@ MDSSOI&DKW'JVED IAWNCH 

RVSPlEMS 

l$S a mull of IDCe lJSlC9S Stratcgic Arms Hcduction Talks 

(START) a&rcemcnls. tk use of surplus stratcgic hallistic 

missiles for launchin8 12lsa(s nccds to be mnsidercd. Thcrc 

are. ofcou~. many ixsucs that must he addrcsscd in dctcrmininB 

thc prRcticiility and advantagcs of this option. Thc 

fixtors includr thr latcst trcnds in the arms rcduction talks in 

termsofdctcrmining thc Iyp and numhn of strategic bnl- 

Iistk mi%rilcs that might kccomc availablc and ;my trcaty 

rcslriclionson tkirulc twspacc Iaunchcn: the p;iyloidcapi\hility 

to typical orbits of intcrcst and thc payload mmp:irtmcnl 

dimensions; and cstimatcs of thc non-rccurring and 

rccurrina mls. With rcqxct lo Iiiunch rcspmsivcncss, thc 

1and-h.wi ballistic miuilc on alcrt status rcprcwnts thc ultimarc. 

with rcspnsc timcs in thc onlcr of rconds. 'I'hc cost 

and othcr issucs rclatcd to maintaining this typc of caphilit) 

prcrnls the limiling c;w of launch rcsp)nsivcncss. 

Thc trcnd in thc strategic nuclciir wrhcad rcduction tiilks is 

forbnth thc IJSand IhcCIS togo in twophnwsfrom thccur- 

rcnt total count for all thrcc Icg of thc Triad of somewhat 

mom than IO.QM) warhcads to 3.(MTr3.50 wirhcads by thc 

ycar Mn3. Thc first p hw rcduccs thc total numhcr of wilr- 

hcads lo 3,MO-4.2%1 in svcn ycars or lcxr from thc cxccu- 

lion datc of the trciity. Within thw ovcrall Triad limits. 

thcrc arc spccific 1imitsplacc.d on the Intcrcontincnlal nallis- 

tic Misilc (ICHM) and Ea launched Ilallistic Missilc 

(SI.IPM) forces. At Ihc cnd of the first phase. thc numhcrof 

ICIHWs cannot cxcccd 1.2tIO. and thc numhcr of SI.nMs can- 

mit cxucd 2161); for thc sscond ph,w 1hc.w limits arc 1.200 

and 1.756). rcspctivcly. In thc sccond phwc thcrc is illso a 

rcquircmcnt that all thc rcmaining ICHMs cnrty only one 

warhcad cach. whilc thc SLIMS can mntinuc toc:irty multi- 

plc warhcads. 

7.1 United Slates 

Within thc limiuoutlincd abvc. thcrc arc still n largc numk 

r ofpruiblc distrihutionsofspccific misdc rctluctions and 

thcrcforc of their availability for space launch. tlcnvcvcr. TA 

far (09 lis missilcs arc mnccrncd. 'lkhlc 3 show n gcncrally 

scocptcd rctircmcnt schcdule and indicatcs that. hctwcn 

m and thc year 2UlXb2bll)3. thc Minutcman lis (MM-11s) 

and the Navy W idon C-3 and Widcnt C-4 missilcs will bc 

rctimd and may bc available for othcr applications. Aftcr 

that time perkd. tk'Rccnty wll rcquirc Pcncckcepcr midcs 

8o Rs retircd kauw of NJulltpk Ittdritrndcntly-Tar~ctcd 

RcentryVchkk(M1WV) limitations and spccificdc-MIRVing 

rub The cx~ct number of Pcscckecpcn that would be

19-12 

0 'I% whicles must PW: lnunchcd from minting 1csI "nnges 

or apax launch facilitics. including up to ))o morc than 

sewn new launch pds at thc cnirIin8 sitcs. 

0 The vchiclcs cannot bc lnunchcd from mohilc launchers. 

0 'rtw whiclcs cannot hc lnunchcd from on nirplanc or any 

watcrhmc platform, othcr thnn a submarine. 

Iclcmctty must k tronsmittctl uncmvyptcd. and n t.y* 

supplid to the othcr party to t k Pmaty. cxccpt For 

I I mission3 per year using fully rctiml vchiclcsthat may 

rcturn cncry~tcd data. 

Figurc IO shtnvs thc pcrformanck of t k Rnllistic misrilc 

dcrivatim to four typical orbits.. AlthrruQh it currcntly dms 

not appear likcly that the MM-Ill Ik! will bc retired, 

MM-ill data is prcsentcd hccauk thc ammcrcially avnilahlc 

Orhus third stage wnvcrts MM-II performance to that 

of MM-Ill. It is seen that the MM-II and thc Poxidon C3 

havc fairly limitcd performance. whik t k MM-OfIOrRus has 

c7pability that is c k r to thc tam1 ranpp of intcrcsl. Thc 

Pcacckccper has fairly significant capability but may not tx 

amilablc for othcr applicaiions until BO3 and hcpnd with 

the poasibk clrccpthn of thc 50 miwiles mcntioned earlier. 

Thc volumc available for the pnylod is mmcwhat smaller 

lhan that of othcr small launch vchicles. hit prcliminary 

in-house Acrcmpacc studies of small Pcmxkccpcr-launchcd 

s;itcllitcs with no modifcation to the cxtcmr~l dimcmions of 

thc launch vchiclc (so it could still bc launcltcctl frnm a sib iC 

survivability is an issue) indiatc it is fc,?sibk to package 

viable satellites. For casts whcrc survivability is not an issue. 

the payload fairing can be cnlargcd to prraridt morc rmm at 

the cqxnoc of some perfcmnance. Other brctorn that must 

bc studied in morc dctail includc thc fcmibility of dcrigning 

satellites to withstand the morc scvcrc Inuncli cnvironmcnt 

pmduad by ballistic missilcs. that is, the 19 ~ ' mlcratbn 

s 

of Pcaockeepr. Again. vcry prcliminaPpl cstirnatcs indicate 

this should not br a problem. Finally. the rmu. which Raw 

becn prwiilcd by thr Air Forcc Multi-!kkcc lsunch Systems 

(MSBS)organimtbn, are wen th be m!mirkrably Imr 

than thw of the R ~US and Smut 98 ~:hklm preMntcd 

earlier on a dollan per pound to orbit bt3. onsl n h t the 

mmc as tr#: Taupus. Qnrm: again. mntrnlling satcllitc might 

and sim is sccn to pn~vidc largc dividends in Imwr launch 

cclls. 

An option that his not ken chcckcd for viability or cost is to 

laurrch trmats from a submarinc at the South Pole. The satcllite 

m!d be in orbit kforc it crowd thc equator. In the 

ca.%? olSIBMs tk treaty mnndata: (a) retiring submarina; 

0) 

rcducin8 the numkr of warheads ptr tuk; or (c)sailing 

with cmptv tubes. IF thc empty-tuhe option wrc sclcctcd. 

thc empty t ub could pcrhnps bc used for tacsa! launchcs. 

Minitfernan fkriwfives. Martin Mariclln lriunch Systcms. 

Iknvcr, Colordo. hrrrr kcn wmrdcd A S133M Air Force 

amtract lo mtrdify 44 MM-lls for spacc launch. 'rhe basic 

contract is for twr, launchcs at 830M. with optkm for 42 

morc. 'I'hc MM-II hnsthrcc stnacs. Martin Mnricttnwill ndd 

a fcunh slagc (the Orbun. built by Acmjct). bringing itsapn- 

hility up to appmimatcly thc samc as MM-111. and a ncw 

guidance syslcm that would govcrn the cntirc hocater. First 

launch is cxpcctcd frnm VAFlI in 1994. lsunch mts a x 

cxpcctcd to bc about ESM lo UIM per launch. with a future 

reduction to WM pcr launch. 

~afljlTndcnfl.~seirlon Derivatives. Imkhccd Missilcs nnd 

Space Company (I.MSC) has propcncd using thc Pwidon 

C-3 submarinc missile as a small spacc launch vchiclc that 

coulddcli~r7[#)lb(31$kg)toa270~270nm(500~500km) 

70 dcg orbit.. l'hcrc arc ahnut 60 C-3 vchiclcs in staragc. 

Other options includc the Tridcnt I C4 and thc Tridcnt II 

11-5. The C-4 muld deliver I##) lb (545 kg) to I,EO: thc 11-5 

coulddclivcr 2DOOIb(91)9 kg). ltshould bc noicd that. at this 

time. it docs not appear that thc 1JS Navy will make suhmarinc 

mQilcs available Tor mnvcnion and. in fact. has 

plans lo dcstroy any surplus hardware rcsulting from treaty 

negotiations. 

7.2 CQ~IRIQUDQYQ~~~ 

OB Independent States (CIS) 

The CIS hassurplus ballistic missile hardwarc it would likc to 

cxchangc for hard currency. The cr-Swict spacc organizatbn, 

Glavkoamcla. has rcorganixd to market joint Husqian- 

Kazakhistnn space launch scrviccs (uwpcration is ncedcd 

a i m the Dnikonur Cmmtdrome is bmtcd in Knzakhstan. 

which has formcd its own national spacc ngcncy) and has test 

flarn B conwrtcd SI9 missilc; thcre are about 30 S!!-19 

missiles in inwntory, each capabk of carrying six nuclear 

wrkds. TIE smallcr S-25 can carry only a single wark&d. 

but tkre are more than 300 in thc military's inventory. 

The world's mat pcxerful YCDM. thc SS-IR, has also becn 

prqmwl rn n opcrca: lnunch =hick. This vchiclc can lnunch 

up to a doacn rmell (IWm Ih or 45-91 kg) salcllitcs into

7.9 Fmmp 

1.9.1 Unitrd Kingdom (U0 

Malcolm Wilkind, a kfcncc sccrctary in tk Writihh Ministry 

of p)clcrwc. anmumd on Junc 15. 1!?22 thnc thc orly nu- 

clcarwopns nritain will rctain will be a hnnnlful of WE-ln 

gravity bomb (as pan of its commitment 10 NATO) and its 

strategic Folaris misib. Thcre is adcbak cnncrwht. if any- 

thin& should hc about the Polnris-replttcing Trkknt 

program that is schluled to cany 128 nucbr warheads on 

16 Trident misiks. If the Tridcni prc~mm h continued as 

prcscntly sclfcdukd. it is p ihlc that some surplus nritish 

Polaris mkik cnmpnents will kmmc nvaihhk, although 

they will pmhably become pan of thc t )S inmntnry. 

1.3.2 Fmc 

France hm mt rclccucd a policy aiatcment on the futurc of 

any Frcnch surplus ballistic missilcr. 

7.4 mbaa 

It ispcnsihkthat hithChinannd thc(.'ISawW.inthcfuturc. 

markct ballistic missib to dcvcloping nation?. The futurc 

will pmhnbly scc (I prolifcratiim of hallistic mis.qib through- 

but thc vmorld. China, for instancc, has o Iarp invcntory. 

which it has shown M) inclination lo rcduoe. Othcr smtillcr 

muntrics that fccl thwatcncd hy their ncifihbm arc marc 

likcly toadd to. n:kr than rcduce. thcir inwntcrry of ballistic 

miuila. Tk wide a+dilbility of thw weapons cnukl 

cnmuragc the rix of dangcrous dcslwtic rep.inics anywhcrc 

in thc wrld. and establishes a strong case for conducting 

Mctaikd tmat studies. 

8. FAR-TERM IAUNCDI SYS'FEMS 

Thc emphasisof this paper ison currcnt or near-term launch 

systcm options. Hmvcr. taoat studia a b nccd IO look 

into thc next ccntury. whcn the nccd for such systcrns may 

intensify. A numhcr of advanccd systcrns arc king investi- 

gated that may haw application to future tamat misions. 

8.1 United States 

8. I. I Singit-Stagc-To-Orhit (S,'jTO) 

A singk-stage-to-orhit vchiclc hm long ken thc dcsirc of 

hnny space transportation planncn hcause of its potential 

br rctlucirg opcrational cornplcxity and wt. nnd providing 

hunch-onQcmand capability for critical military sy:tcms. 

Thc SDI0 ha5 cxamincd a numhcr nf SSTO a1nfigur3tions 

losatisfy pstulatcd SDI0 miKqion launch requiremcn:s. and 

sclcctcd thc Mcnonncll Douglns Iklta Clipper for further 

study. 'Ihc Single-Stage-Rozkct Tcchndqy (SSRT) Pw gram is now undcrwy at hlc1)onncIl I)

8.3 Uniad KingdodWussia 

Inrtn'm HOTOI,. A joint Ilritish/Husvan dcwlopmcnt to fly 

an intcrim wnion of thc Ilritith HOTOI. on thc Husian 

Antom-225 'MPIR" hcavy lift aircraft is undcmy. Sumssful 

wind-tunnel tats at simulatctl spec& of Mach 10.5 a d 

14 have ken conducted at the Ccntral kmhylrdynamio 

institute(%AGl)in theirT-128wind tunml in [Wmtaw. The 

three orpni7~tions haw signed agrccmenu among thcm- 

sclva (ps wll as with #heir respectin: gmmmcnt.. . nritish 

htmsyax is defining the Acmpaceplanc and airhnrnc 

supprl systems. Ijmitcd TCSOUT~: are awilahk. but the 

Eumpe~nCommunityCom~:,ission hasbtcn appmhcd by 

British Acmpace for support sine the commission has said 

it WM entertain joint Europcan6ovkt (now CIS) BCW 

space nntum. 

Thc vchkk is planncd to carry a paybad of 15.400 to 

17.600 Ib (7.OOlJ to 8.0 kg) into IEO aftcr king launched 

from thc An-225 at an altitude of abut 28m It (U km) Tk 

An-225 quires the addition of tvm extra .%het D-18 

engines. Rolh Roya replacement cn@m 6xrc cnnsideml 

to amid installhg additional engines but wm rejected am not 

R ccgteffcctin' modificatbn. l'hc cnnacpt is illustmted in 

Figure 12 

8.4 Wosr 

Thc assViet Uninn has cnnCucted aidvamrd partia!ly and 

fully hllashk nhick rcsearch and testing Urn many yeam In 

Nonmtur. 1991. for instance. thr Centml Imtitute of Aviation 

Moton. M-,d.ims to haw anr~ucaed the nnt test 

9. RAUN6w 911w: WSODERATUOWS 

The orbit quimmcnts for thc GEQ and [EO missions discus& 

carlkr an h mct by laumhinp fmm thc tw main 

launch sites in t k US, Cap Canaverid in Florida. end Van- 

3tnBsrg in California Fipm I3 ss#pcm tht orbit inclinations 

that ire ahkmblt hm eesh of thz two sitcs. All targcts at 

irrclinat~mo~aaaltoorftrothen573tgcanhc rcached from 

Cape Cenowml. whik ik hiBkr inclination orbits , includingpolar 

end oasn-smhmr#rus. are r;awsibk from Vandcn- 

FQm 12. 'bicumm3rc?tOalo 

ZzgcZtm 

bcr&Tktc Atlrrcrorklte bnatcnvmld launch the GEOsatcliiics 

due easi a t of Cepe Cannwml. while sinek I.EO 

I 

0.2.2 United Kingdm ! 

satcllita could k laumkd on tk small launch which or 

hllistk mksikdcrivaticncs fmn either launch site. large 

Monmld Tdit-Qfl and landing (IIOT(Pl.). 'I'hc original 

mu'!i-satcllitc c~nstcllat~ns. such as Iridium-litc amcepts 

ambitious BBOTOL gqram is currently unfumlcd. The 

cnuM bc launckd by hlta or Atlas II out of Vandenberg. 

cnginc mmpt for tht )POTOl.&vclqd artd patcntcd by 

An Atlas I1 pid is kingbuilt at Vandcnbcrg. For the ballistic 

Alan hd ha ken dcclauifikd. but th !%olbRoycc 

missik4cr;vintives. thc launch sitc at Capc Canaveral wukl 

RWSO hi3n is still kld pmpiictnrg.. Ilk enair# is a 

haw to br re-activated. and dcdicetcd launch sites would 

preumhd. air-hrenthing mckct that utikm air cntcring 

nccd to he atahlished at Vandcnhcrg. Th: cstimatcd 

thrtwgh B V-rvnlgcd intake. Thc air isskEDTd drm t05uh 

a t for an akovc-grwnd hallistic misilc4crivativc spacc 

wnic spx& and p a ! through R rrfts d kilt pchanwn 

launchcr pd is about DSM. Thc air-mobilc Pcgm~s offcn 

and turkmmprcss4m until it reachcs rcrthet chamhcr prcslaunch 

platform survivability and thr maximum flcxibility in 

sum liquid h,vdnqcn and liquif6d air Pucl the fiat phmof 

launch sitc location and omit inclination. An advantagc of 

cnaintflinhtuptoIW~hS.5at nnahitudxoI93.4M)It (Mkm) 

the Bcga.tus i+ that for target nrc,w et latitudcs hwr than the 

Onbd liquid oxygcn and hydrn@n is U& for the rcmein- 

28 dcg of Cap Canaveral. launching at inclinations equal to 

der of the flight. HOTOLsharcs icchnn!qp ntcds with thc 

thc targct latitudc provides an orbit that alltnw thc satellite 

US NASP but its future is unoertain. It is illustrated in 

I 

more mnxcutive p,wcs m r thc targct than thc two tima 

Figure 11. 

pcr day achievablc if it were launchcd from Cape Canawral. 

It should bc noted that a cost penalty is incurred to exploit 

this advantage. 

'lihlc 4 lists the mrdinatcs nf mint of thc spacc launch si:cs 

that mist (or in some cam arc planned or arc inactin:) in the 

wrld. and Figure 14 s b their distrihution. The fluid 

global environment that is bund to exist in the future and 

thc fa0 that tscsat mision will moat likely be multinational 

in naturc (end pcrhap a UN responsibility) rcquire thc mnsickration 

of sharing launch facilities. The Italian sitc at San 

Marax. off tk mt of Kenya. thc French siie i ~t Kourou. 

Frcnch Guiana. and the nrazilian sitc at Alcantara arc intcrcstingbccause 

they affod thedircct launch inclinationorbits 

for h r latitude targcts. The mlocatablc laurus wuld be a 

candidate for using non-IJS launch sitcs but. again. a 

custtffectinncu analyxis would need to bc carricd out. The 

US. Pcgasus. ',he propd CIS Spacc Clipper commercial 

orbital injcction sptcm. thc lJWCIS Interim HOTOL, and 

the German Sangcr could also bc launchcd from multiple 

launch sites 

IQ. @ONCI~USBONS/WF~OMM&NDATIONS 

While it is ncrt to impamihlc to predict with ccrlainty the 

environment oP thc future and what peacckecping mililnry 

capability will be demanded in that environment , thcre are 

some things that. in the long-term, appear incvitabk: 

There will k a pmlileration of high technology weapon 

spa(cm5 mnd thc world in thc hands of nntionatntes 

that hiuf no( prcvbusly had aaxm to such wapons.

Many of thnw splcms and platforms will haw the capa- 

bility to deliver dcvi@cs of mas.. dattuabn. i.c.. chcmi- 

al. bb!ogcal. and nuckar d eb. 

Many of ~ltc countries that ha& such wnp'ns will haw 

national goals Ihid arc in conflict with to#: inlcrcsts c:f thc 

IJS. its NATO alliu. and olhcr nations dcdicatcd to 

wnrkl pew. 

Some of tk awntrics who hitw such wnlwns will hc 

dediratcd to w rU :errorism ahJ/or militilry attack. on 

thcir ncighhon odor intcrnai ciwl strifc dcstructiw to 

thc intcrcsts of wrld peace. 

19-1s

1P.16 

'II-tcx chen@ngcnvimnmcntal conditions which are am@- 

turcd to evolve oyer the next thirty yeem p!%c increasingly 

dcmnndin8 requirements on twtxtiral cwbllnl systcms and 

henot on responsive launch rrvtccs. TIE intcgrotcd hted 

for launch mviccs, mnging from small currcnt launch 

which. such ~1 Scout. to advamd futum Ivunch systcms.. 

in t k linht of tk ntptctcd 

such as NASIP, must trt BSJCS~ ncar-term and rar-term trxtical r+hn quimmcnts. This 

papcr chrpmterizcs the ringc ol'launch ecwiacs that mukl 

satisfy t m t needs and dwmcnts !he hrot o.wilabk information 

on the cornpiding Iaur\ch systernt.. It kcnncludtd 

thi-t tRc twwt missioi.s idcntificd hcrcin con kc Rilcquatcly 

supported by IJS lnunch vchicla In~nckd frnin the amti- 

nentnl US. Hourwr. numcmus other optionn arc nmilahlc 

and lyteB careful study by thc ti?&at dainncr or planner. A 

bibliography is pmvidtd to idcntily addi\kn;il F m n r ma!cri- 

GI on some of the launch systems. 

I.. 

2. 

3.. 

4.. 

5.. 

6.. 

7.. 

8.. 

9.. 

I 

I.rmru ofrk Fimt Space War. lntcravia $paw Markcts 

4419991. 

! 

Fdcwmon. Frank. "Tactical Sntcllitcs". hscntcd ill thc 

North Atlanttc Trcaty Organization (PdA'I'O) Mnuq 

Gmup for Acmpacc Hcscarch end Ikwlopmcnt 

(hGAWD)Avionio Panel Sympiumon TACSATS/or 

Siirwillance, finfiation and C.31. his5ch. flclgium. 

19-uoct. 1992 

Gipn. Mclirula, and Richard nucnnckc; Jr. Mkmspace 

knuuwnce Pasha Publicatiom k., 1616 N. R. 

Myer Dr.. Suite IOOO. Arlington. VA 22209-3109. 1992 

Fiks. W. S.. "IJnitcd States Air Fom spm Systems 

Division launch Roprems." Parer ?AF-92-4?825. 43ra 

Con- of the Intcmathnai astn)nautbl Fcdcration. 

"ahington. D C!. USA. 28 Aug.-5 kp. I!f92.. 

MI-V /munch Slmrqy Siridy I.'inol Nalporl. Prcparcd by 

The Aerrapacz Corporation Spacc launch Opcmtions 

Programs Group for Space Systcms I)i\.isEon. Air Fora: 

Systcma Command. Acrmpaa Report No. 

TOR-~~)I. IS April I992 

Adas rifirrion flanturr Guide. &. I. March 1989. Gcn- 

cral Rnamia Commerciid launch !hvks, Iw, 9444 

Balbos Avenue, Suite 200. San Diem CA 92122. USA. 

Commlcial 11 User Manital. Juty IQRP. Mchn- 

ne11 hglm Commcrcinl Dclta. Inc. 5301 hoha Ave- 

nue. Huntington kach. CA 92607. USA. 

Wmd Uxn Guide Titan 11 Spjcrr ~ A I M ~ Vchulc. I 

Aupst 1986. Titan II Spaa: I ~~nch Vchicle h p m , 

s p Launch Systems Division, Martin Morictta Corporntion. 

kmr Acrospacc. PO. lEoll7'9, Iknwr.CO 

m1. USA. 

'lirgn 111 C~mmrn~iol lrnttch &W!C~S Ctbstomr Wandbooa 

1- No. 1. December 1937. Martin Marietta 

.. ,,.-.-";., .,.,. , .- "I.. 

- 

1. 

Cainsp69mioI Titan Inc. LO. Bar 179. Denver, 

mm USA 

IO.. Etan WUwrs Ppondhk. June 1%7. Titan IV Spa= 

I.aunch ?pterns. Martin Marittie; Denver Aerospace, 

PO. b 179, knw. CO 80231. USA 

1 I.. htemia Space DirsCtoty (Brcviously Janc's Spaceflight 

Directory) 191-92 FAitcd by Andrew Wilson. Janc's 

lnlormetbn Group. !kntinal Mrwsc, 163 Brighton 

Rod. Coulsdon. Sumy. CRS 2". UK. 

12. Intemntbd &femrwe Guide to Space launch System. 

1991 Edition. hpnradbyStcvcnJ.Isakcnvitz inooopcratfcln 

with t k AOAA Space Tlmqxmation Systems 

Tkchnical Committee. published and distributed by thc 

American institute of Aeronautics and &tmnaurk, 

TpIc Acmpacc Ccntcr. 370 CEnfant htncnadc SW. 

Washington. Ipt' ao2A-2518. USA. 

13.. Woglicvina. Robin. et al. "Survcy of Foreign Launclr 

Vehicb" ANSEW. 1215 Jcflemn Davis Highway, 

Arlington, VA 22202 Space Ttchnology Division Note 

SO'DN 91-17. Octobcr 1991 

14.. Anam 4. Ariancsp;Eoe. Inc 1747 Pcnnsylwnia Avenue. 

N.W.. Suite 875. Washington. DC 20806. Arianc Launch 

Vchicks. NC Soljcnitsyns. 91ow) Eny. Francc. 

IS.. .%vir/ 1autd-r Pmton. Cilanxlsmos. 103030. Miacow 

Krasnoproktankaya 4r.. 9. Russia. 

Vchick. Spacc (:omn,:rce Corporation. 69th Floor. 

Suite 6W. Xxas CornmciL- lkr. 600 Travis Strcct. 

Houston. 'Tx 77002 

17.. I.ong Mmh Fami?, of I.armch Yrhicles. China Grcat 

Wali Industry Corporation. 319 hlta Vcrdcs Illvd 0318, 

Rcdonrlo Ikach. CA 90277. IJSA. China Grcat Wall 

Idustry Corpcwatbn. No. 17, Wcnchang Hutong Xi: 

dan. PO. Ikn $47. kijing, Peoplcs Republic of China. 

matsu-cho-2-chomc, Minato-Ku. Tokyo 105: Japan. 

19.. Nationat Laiirrrh System (N1.S) Poyoad Planning Hand- 

W. Volumes I-VI. Prtparrd by Inckhccd Missiles 

and Space Company. Inc Spacc Systems Division. PO. 

ku 3504, Sunnyvak. CA. !MQ83-3504. Rcport No. 

IMSC-~X'I. 17April 1992 

20.. Scoiit Planning &'de. May 1986. LTV Aerospace. 

Vought Mbsilcs and Advanced Programs Division. PO. 

I)ox 65Nl3. Dallas, TX 75265-(1003. USA. 

2 1.. Imkhecd Standard Laiimh Yrhick Misinn Planning 

Guide. 20 Dcccmbcr 1%. Prcparcd by lnckhccd Mis- 

siles B Space Company, Inc. PO. Bor 3506 Sunnyvale. 

CA !34#8-3504. 

22. R?3ipnu 1prrp.road Usen Guide. Mvanccd Projccts Office. 

Orbital Scknecs Corporation. lu00 Fair lakes Cick. 

Fairfax. VA t2833. USA 

2.. Kniffccn. R. J. ond E

25.. NFQ %&myr* Spcrcc Clipper. Camtcn: Y.A 

Srnctonin. Kriprorothskeya Str 3. Dq~pmpetmb. 

3BIl59. Ukmim, SSR. Tcl: (0%)42 29 21. Tckx: 

127 OREKH SU, Far (0562) 4.2 20 21. 

26.. SpcKc CI~~JWC Comrmrriol orbit01 It&crion systctn. 

Mirrcipl Tcchniml Characteristiax "Yurhl,oye" 

kip Offa. 191. 

27.. Neiland. V. Ya., Central Acrohydrdynnmks 1ns;itute 

(IMGI) Zhukowski. Russia. and R. C. hrkinson. Brit- 

ish Aemg;ta Spxe & Cornrnunicltbna ktd.. $ :eve- 

nage. UK. 'Thc An-aS/lntcrim kllotol Ir inch 

Vehfck. Rper No. IAF-91-197, bmted at thc 02nd 

Con- of thc international AstronWkaI Fcfcra- 

tion. Montreal. Canada Oct. 5-1 1. 1991. 

19.1 7 

28.. Eindley. C. A and J. Renn. The Aerospace Corpora- 

thn. El Sewitdo, CA USA. "Combirred ExdEndoat- 

mmpkris'i)snspm Alternatives". Wper IAF-92066J. 

43rd Coriptm of thc International astronautical Fedcr- 

ation. Wmhington, D C. USA. 28 Aug-5 Sep. 1992 

29.. Wertz. James R. a d WIky J. Lanon (editon) Space 

MissiortA&sirmdM~. Khrwzr Academic Publish- 

ers. Dordrecht/Emton/Londn. 1991. 

38.. $pace Tqddion .4dysk and Lkrign. Acmpace 

Corporation Report No. TOR-92(2464>1. Prepared by 

the AEWOSPACECORPORATION. ElSegundo.CA 

90245-4591.7 August 1992 

31.. National Academy of Sciencu. Navy 21 Study.

SPACECRAIT AND I.AIJNCII SIISlT.MS FOR TACSAT APPLICATIONS 

1. SWfbUMARY 

Theabilityofn~ticnlraaUik(TACSAT)apcc~nyr~mto lulfill 

its mission cpplicotion with the deskd cnpnhility. responsiveness. 

rcliability and survivability. while at tb m e lime ochieving 

low cost ohjectivcs. is a trrmendow chdlrnne thnt can only 

be met if 011 of tho system scegmentn - launch ope hnd ground - 

conlrihute to meeting mission unique requiremenlo. Tlte emerging 

CO~KPF~E Pm the dcvekymenf deployment o d bperntion of 

cost-effectiw TACSAT iystems are enpxinlly dependent 

on tab flexibility and operability of their launch lvchklc anJ 

spacccrnn bug systcms. Omital Sciences Cmpotion (OS 

* ' 

' ;! 

2. INlT2ODWCIION 1: : . 

The world today is a different and chdging plecc. charactcrikd 

by dramatic and rapidly evolving new geoplitkol. ecomic and 

national security structures and relationship. In reaponm. the 

United States' and its allies' national militmy ntrategicr and 

nationnl security infmshuclurer that sup+ @cm must now 

depm fm the principks that have shaped ban since the end of 

WorldwarXL Tbs+ :tratcgksandinfrartturerz, whichevolved 

Ir, contain Ihe sped of Communism and &tar Soviet aggression. 

must now shin dramatically to focus on regional crimr and wan. 

The threats of this new world can he hot chorccteri~~d M 

unpredictable andcomplex -where will theywcw. b w fast must 

he the rapre. what will he the sophisticotion lcvcl of Ihc 

wcapons. who are the cornhatants. whnt ure tlae political a d 

militarygoals,etc? TheUni~dStater'miIitcr1,~~orceobucturr for 

employment rgrinrt these threats will ',e chmctterixed by fcwcr 

in number. more cost-effective ryrtcins. fewm forward-basal 

cknmts. and much lower utiveduty manpower. 

hopcrationd iinperatives to aresvd in &,&filoymcntof 

these forces will be chmckritcd by: (I) "ooJn~~'w'.you are" 

conllict wenarioa: (2) renponse to rapidly unPolCk$&im wi!h 

a few critical cngogcments; (3) long-range application of power; 

CRrin Scb& 

GilM D. Rye 

Rolrpm PO. Memr 

OrMtnl Scienccn CorgornibdSpw Systems 

141 I9 suiiyriErf Circb 

P.O. Box IWO 

Cbantfily. VA 22021 

20- 1 

(4) high kvels of responsivewrs and flcxihility for nll systems; 

(5) situationd awvareneoo on n non-linear battlefield: (6) maneu- 

verability: (7) coupling of national and thcatcr lcvcls of com- 

mand. control. and intelligence: and finally (8)joint international 

operations. 

Some of our first insights into this new world of tomorrow's 

conflicts come from analysis of results of Ihc Gulf War. One of 

the most dmmstic wns thc importance of spacc systcms to all 

aspects of Ihc planning. execution. and succcss of this war. 

Current rpocc systema. which had evolved in supprt of the cold 

war and strategic requiremcnLs. were called upn to provide 

direct suppod to lactical wnrfighters. Mnny high-lcvcl mililary 

ond civilian le&s characterized the conflict as thc first "space 

war" - a war in which space systems were ahsolutcly csscntial to 

both the execution of the conflict and its success. 

The copabiliticsof thcse cumnt spce systems to support n broad 

spcctnm of wtical warfare mission arcas was impressive can- 

sidcring their heritage. Rut in many cases. their lack of flcxil~ility 

and msponaivcnesr imprdd their prformahcc. If the six months 

prior to the conflict had not hccn avnilnhlc to significantly adjust 

and mndify their rpncc-hasd architccturcs and ground systcms, 

the level of support would have ken significontly dcgrdcd. 

Also. if the conflict had cxtcndd in time. somc spacc nssck 

would have prohahly necdal iinmedialc rcphccmcnt - which 

would bave hacn very difficult due to the rcspnnsivcncrs and 

availability of spacecraft and launch vchiclcs. 

These and other lessons from thc Gulf Wnr on space systems 

suppod to the tactical user will he the rtimulur for the entire 

national security community to re-evaluate thc warfighting rc- 

quiremcnts for future spaa systems and the infrastructurc nccdcd 

to mcct these requirements. Thc resulting futurc spacc systcms 

will no doubt include TACSAT systems that will ernphasi7~ 

flexibility. responsiveness and cost-cffcctivcncss in mccting thc 

changing US. and Allied national security rcquircriicnh. Mnny 

of the otkr papers in thir symposium will prohohly wldrcss thc 

wchitcctures. rquiremcnts. BEnSOr syatcm. ground sySlCmS and 

employment strekgicr for Uicse systems. Orhitil Scienccs Cor- 

porrlion hae developed two launch vehicles nnd o spacccraft-hu.u 

tho1 will provide flcxihle. responsive and costeffcctive launch 

and on-orbit prfonnnce for future TACSAT systcms. 

3. PBGkWS 

3.1 Uatdcocgba 

XK flight-proven Pegorus air-launched space bster (Figure I ; 

pvides n costiffective. reliable, niid flenihlc means for dcliv. 

hunted at the AGARD Avionics Panel's Sympmium on 'TACSATS I*)R SURVEII.L.ANCR. VERIIICATION ond C.71". 

DNI~I. Belgium. 19 - 22 October. 1992. 

I

Figvn 1. Pegorus kjligh. 

1

c 

Firvn 4. Horimld vrhiclr andpayload inrrpuion. 

3.4 Iruncb OpermlIOlm 

Pcgaiua launch opratinu comhino launch vehicle and Urnan 

oprubnr wilb emphub on iimplicily. flerihilily. and opera. 

timl dlriplinc. The launch location lkrihiiity inhrnl in 

Peguuic.n iignificanlly imue pybd caphilily and orhiwl 

IkrIbiUly by climin.tin# many of UK launch uimulh resVKlioN 

ollm lmpabd by fired launch iita. Afur invgration. maling lo 

aBJZaLIOI I crrin?irrpfl andps.flighlle~tin~.thswhicb 

LcrridbIh.Iaunch~~~hkhunho'vlluallyanydii~nm 

fmm Ih. inte;nlion lq&Ul;. 'or launch. Rguui L carried U, a 

nominal kvel.flight todillon of 12.200 m (40.000 ft) at 

high subaonk vebcily. Afur tekue. lhe whiclc fwc falls U, 

ckrlhourriaaimah whibcrrculing a pilch-upmuleuverlo 

hbw lhe pper Stituds fa mM Ignlhn. Afkr Stage I 

Ignitbn. ~h. vchkb foUun M autommoudy guided. lining. 

mnt ~n)ectau o Omit. Future mluicni will incorporate GPS 

bm Ute CnCUng Ud guiduva iystm of Peguui resulting in M 

w(On0mw nqa cplbilicy. 

4

Wilbpflamed pailbnin6ofrrbkk1mdfrilil*h aPe6um 

launch could bo called up in ham. mt dap . U, new 

operaIbndnahorraauWuIbnolM~hnUL Simm 

pd refurbilhment h requid. quick munwvld in b. ml 

monlba ~ b alwprrihle. Udngmmlbanawr.Rinabaanand 

intcgntion fwility would albw swga of multipb lwncher in a 

single day if quid. All of theu rcnrbs for oprslional 

empbymmlcuuldbc ro~mplbhed byrmallmililry orconlrac. 

Pegasus' Omai-hull~ll~n lunch capbdity (upaWly wing 

OSC'rul~~lM~ecooccp)pvkkI 

unique lkrihilily lo 

mss( miuion mquinmancl md alimlnrs doslegs. thus impmv- 

in6 pybd pfonnmc4 I) dit. mu upahiiity alto p vida 

for llnt pu mvarye of my point on Ur e h . Alu, of key 

opr*bnd impmtncr it cb. minimal impact of weather on 

'Ik Pe.5uut bunch system pvidcr national muily npw 

system ruae&i~U ud plannen wilb unique capahiiilies which 

w h combinsd with evolving undl spacecraft ~ U and R sensor 

lccbnobgies.uo cnahk flcaihie. rcsporuivc.a~il.effective snd. 

in wmecucs.undrumodofsuppt? tothe wutightcn inmeeting 

new ud evolving national ~ urily quirrmcnb. 

4. TAURUS 

4.1 Imtmducllw 

'Ibc Tvl~'" space hoosler hat been developnl lo provide a 

sqmbilily loquickly MdcffiiienUy inregralealounchvchiclc ud 

pylod for the rapd launch of nmoll rutclliter from either a 

remote or rued Iaumh site. %is gmund IranRpo~ahlo louneh 

system is erectable within five days of urivol .I a 'dry pod' 

launch tite .nd. sIler ut-up. respond lo a Iauneh-on&mnnl 

quiremcnl within 12 houn. Initui launch capohility of Ihe 

Thelinl 

fligbl ofthe Tawt SUndrd Small launch Vchiclc (SS1.V) h 

, Tauurl~unehsyslcmwillacurinthe~nthslfof1493. 

3 v

H 

8p~nwmd by DARPA ud will dcliwr8 DoD payload to a bw 

Er(b Ubk Iho lnncb vrbkle nd ryltem devslopd to 88liIfy 

lbor DOD q m n u hu dm bcca designed to repd to 

ammac*lluncb rrvi98&*Yions~g kncrrespnw 

to mss( outet nppontriitka and with ku boltom lim impd. 

Mas capbb T~INI mnflgur*bns me king devobpd In 

Inlrodu*ion io 1994. 

OSC bu e n d u d to develop user-friendly ekcwicd a d 

meeb~icd paybd inhf8as which frililate integ*on of 8 

vido vmiely of pylodr. "he Taunu vehicle's simpk. dust design enums m8aimum rdiihily and signifiunUy reduces 

liuncb site manpvcr lcning 8nd iuppac infnivucture requiremenu. 

llprizonul integntion mclhods greaUy simplify vehick 

-hly ud paylod integra~ion. 

"he Tauus spre hoostcr launch system cunently in develop 

mcnl u I& SSLV for DARPA is a four-slap solid-fuel design 

compd of the fllghl-proven Peeasus motor stack and avionics 

nounledon lopof rTl~il*olTU.~(Peace~eper)rolMmckct 

motor. (AThiukdCutor 120molor.nowmtert. wiilbeudon 

he cnmmcrnalT8urus). 'hTaurw SSLV system is compred 

of 8 llrghl vehicle Md &round bUppon equipment designed for 

cay kulrpruhillty and nfid vtup 8nd launch from M unim- 

pmved aincrete pad or from a modrrl filed pantry. All propul- 

sion ekmcnu of Ihe DARPA Taunu vehicle have heen flipht- 

proven on the Pegasus or Peveknpcrprogrunr. Tlw remaining 

Taws subsystems M vinually idcnt8cal In Ihnu iucccrrfully 

flown on UK Paguus vehicle. 

'Ibc slvldud vehicle design. shnwn in RgllrC 7. inmrpralcs sia 

majorckmcnb: fourniidfueled~taga.8payload rairingandan 

ivionia amcmhly. Ihe Peganus-&rived molora retain their 

Slap I. 2 8d 3 designations from Ihat program: the Thiokul 

Casta 120 is designated Slagc 0. Ihe vehicle is designed to he 

integnted ud lasted at a launch site integration facility afkr 

completion of di ahpc.leni 8ucmhly and testing 81 Ihe factory. 

mi pmcedure Is less compka and more cost-cffectivc than the 

pmeedures mquircd for luger ground-launched vehicles which 

mad Ihrougha full integnted f.ctoty system test fnlbwcd hy 

duumnhly'' Ages fashipment 8nd suhscqucnl reaivmhly 

ud wmnG Inlcy.lcd I~IICM test at Ihe launch pad. With final 

intCg~8lbn ud tuting only it I ~ C I8unrh integration site, the 

T81mu -&sb minimiDs Ihe h8ndling of Ihe miid rockel 

molonwhilcrimullarrolulyrlrrMlining the vehicle acceptance 

Wlpmear. Exvnrivo fvumy testing by hothOSCand iu vcdon 

ern~sllYt8U budwue Lredy f~fli~lonceilrerhnthe~d. 

A complete ICI of sundud uld opcion8l ~crvicu ia 8v8ilahk U) 

suppl specific paybd quiremenu including: inenial orienlalion 

pbr (0 rpmtion: dum duwdink of critical payload 

tekmctry during pelwneb OperaIions 8ml Iauncl?: eieclrical 

pmcrfapayladh.candolhrrpybd oomponcnuduring 

prrbuncb opcnhl; pybd rdring meis dwn ud Radio 

PqvcKy (RF) Windowl; filmd. dilbnod 8k nd dry 

niUDgm fa pge of U* pybd envimnnwnl during launch 

intepnIILm8.

payload upruiun syucm is availnhle. Tb opciorul HAPS 

pmvidu up lo 73 4 (160 Ib) of Nz14 fa ohil rabi3.g and 

adjuskncnl. Wbcncombind wiul theTaUUStlmdudor .bud 

Glohnl Positioning SysIcDI (GPS) h'aeiva. IIAPS p viks nu- 

IDIY)IIKIY erion dit injedion c.phility. she o?lional 

PcgaS~u 

inlcgnlcd sp8aCnn bus wiU ho dbcusud lam. 

IhcTauruavinnlssystom issimple. mhua and rrliahle. Allor 

k hudwlrr cornponenu a idmlld lo lbDE UIcdOn PCgUUl. 

with thc eiccplion or Ihe addition of a ream gym prkag,: to Iha 

bucofSlIge I udhrmcumodirKationsto~)mmod.l~:SUIc 

0. shes~nw~poyrmucidm~iedernpclor~hadd~tionof 

sup 0 function and mhslm pculiu modikations. 

43 Veblck Inlqrm8lm 

Tauus field idcyalion Is skaighlforvud and rcquhs 4 minimumoflaunchsupponoq~~nt(LSE)andfrililicr. 

Alloflk 

ISE b kM~poruhleadcap.hleolselup~ EmOlC 8USlcre SllcS. 

she vehicle is inlcgnlcd horuonldly a1 a mnvcnirnl wotking 

hcighl which dlowsery CWI formmpnncnl inslallalion. le11 

and impclion. lln uu of sumlnnl scrid RS.422 communica. 

tion purob IhNughnuI simplifics vehicle winng. alrcalnlincs 

avionics lcsling andinlcpalion Md rignirKmnlly ndwcs lcsl and 

culkm LSE requirements. The in1c;ratinn and lest pass 

CNURS Ihu dI vehicln compnncnls and suhsyrlcmr uc lhnoughly 

l ~vd kbn and dlcr final flighl cmmclions uc m.adc. 

Several "fly to orhit.' simulations eacrriw 111 ~ I U P aI ~ d 

plcchnic ioitiation oulpuu. Taurus louyuk,n rlivilks us 

eonlrollodbyacom~hcnsiverclofWakPrtages(WRIand 

Rnccdunl Guides (PGs). which Jcurik uddncumcnlindelil 

every upal of inlegrating UK vehicle uul ill paylod 

4.4 launch Opratlon 

TsuuslaunchocanhemndwIed fmmcilkrofthrkpYkIWnl 

or Ddmuc's Eulcm or Wesim Ranges (ERIWR) U well U 

fmn the Nuiond ~nautinuwlSpvc Adn~iniuraliunINASA) 

Gawud Spnce I3rghl fenkr's GWf) Wallqm llighl Frilily 

(WW)Rangc inVir6ini.. IhofinlTauNs Iwnch forOARPAi1 

uhedulnl for Uw fin1 hdf of 1993 fmm Vndmhurg AIB onlo 

&e Westcm Range using only a rimpk concrrIe pad to wt up 

WI VUI~leIauncbsu~r(cquipmenl. OSf'smMncrcia1 

Taum Iauncb w#vk will he codwlcd utilizing a mdcsl 

filed gmky with a muting vrviut slrwim. OX?r primary 

?ipn IO. Taunu ron/ilurufimu'prfloormrrnrr to W' 

indinorinn 

mmmislTaurus launch facilities WillhcrrlnhlirhaJaIlmunch The TnUNs vehiek offers n numkr Or Slmdud ICIVkcs. 'Ibc 

rim optimum for Ihe pmiculr mission king - sIanduJ I .6m 163 in)diunelcrTnuNI~ylo~f~rin~of~alovcr 

Vurlrnhurg AFB. CA Wdbp Irland. VA nd Cape faluvad 5.15m' (17s ft') fur p.yl0.d use. Iho firing U designed lo 

am likely locations. 

encapulalc Ibc psylud rn a pylod integration fxilily following 

cherkoul. A CIMI 10.000 envimnmcnl can k mainlid 

A Taurus paybad inlcrlnce chrcluiul facility U availshk as a inridc Wi cncapulrlcJ cnrgo clemeiii (ECE) I all ha fmm 

slandud K N ~ C a1 OSC's Fairfu. VA cnlinaring facility fur encapulnlion Ihmugh ECI! kMspun vchick inlcgralion ud up 

initial payload lo launch vehicle functional INI nnct chakout. until launch. h I ~IluYInrd ICN~CC. 0% pmviJes one ILinch 

I~OUling~nmginemnglcI(mudcloluleTauNs avioninwmbly 

nnd a complclc YI of arionin nnd paybd le11 cquipmcnl. 

quam ncau dour in ench hdf or Ik fairing. located lo Ihe 

rryuiremcnu of UK pybd. shew dmn pmvidc dI Ur sacs& 

Ihi~VebicleSy.lcmsIn~ey~ionI.M(VSIL)willb.uudfwiha including lale acass on lhe p ~ ~ lo y UK . py bad once cncynudeveb~nlolrniuion 

pculiulauncb vehKk wftwam.quali- Ialionbwmpklcd. ~.noplion.OSCcMrrp~silioniho.sclu 

liemion of miuion pculiu avionics vnias ud vddatim or 

paybdinugntionpaodvrraudflighlchalllsls. 'Ibc rrility 

doors, povidc IMgCToraddihnal rcrssdoon or RF-VMSFU. 

en1 pnela. she payload mahanldly mounl, lo lha sundud 

Will 410 be equippod romnduct launch vrhkk mbsion sirnulahm 

wilb payload badwa ud wham in dn bop. 

Tauul rpnfion syskln vi. 60 futcrm abwt a 38.814nch 

diunclrr bollclck. 

I 

DARPA TauNs 

orbit Capability 

250 nm. 28". 2450 Ibs 

(Orion 38 Slg 3) (1114 kg) 

Geosynchronous 860 Ibs 

Transfer (STAR 37 PKM) (391 k3) 

Fipn 9. NRPA Taunu rapnbiliy.

'ThcTauNt prylodckcoicwl inlnlactt uc cllahlithcd through 

throcconncclon .powcrud tignal, pym. ml RP. 'Thcpownand 

tignd conmlor pmvidct nu pylod putkught (pior lo 

Lunch).eighl pybddimv wmmandh lowpybddimls 

ulkhrkt and a paybd sepr8lion HNing hcakwim. Sbc 

power and tignal conlycuIT a h tuppont an opiond paylod 

RS422 wktn*ry twm. 'Ibe pym conmm can iniliau up lo 

five rcdundatu pylod pyrotechnic cwnu. In addition. he RF 

con- t u r n pybd RF bntmution via Lha eluting 

Taw. nonm tyuem. Dcuilal inlunnation on pybvl YIvice[ 

andpybdcovimnmenltpvidcd hy TauNtcan he found 

in UU TUIM Usen Guide availahlc on requctl lfom OSC. 

4.6 Taurr Opn(bu1 Flcslblllly for TACSAT Applk- 

Ilom 

'ThcTaUNt launch rytum. hatatuihutet fcr flenihle. mtpntiw 

and cotlillr*ive launch lu heyund eaitting launch tytwms. 

With ilt gmund mobilily d cornpatihilily with air usnipon. 

Tawt un yovide rigninunl kvds of tuvlvahdily lhmugh 

disprrul. Thitugzeallycnhmccd hythclwcIhuTurrutcanhe 

~aunchcd from M "unimpmvcd dry p d . i.e.. ihe end or a 

mnway. 'ThcTauNt syrcem hu ken designad and will demontblc 

mecllng DARPA'a requiremenla lor a launch tils and 

vehicle ta.up or kts Ib.0 fin dap ml I8uncha1demand 

within 72 houn dlcrtU.up. Sbcvehukcanlumainuincd in Ihu 

72-hour launch rcdy condition lor mnIht U required lo mnl 

aytwm opnuionrl mqukmenlt. Tummund t h lo erm and 

launch umlk vehicle U meuumd in &yt. MI monlht. pvid." 

ing signikatu awae uphilily. Vinally. ~h Taurut fairing 

encapulation tytkm &owt lor flcrihk plaunch paylod 

inIegnIbn and Ihc capbilily lo tLom Lha encqnulaod pylod 

for Ions prWt awiling UU Lunch. 

- - 

110' 

\ 

All of UU .how caphilitiin can suppnC LEO U wll N CEO 

miuiona. T h ~ ~ T ~ ~ ~ ~ rmiquecaphililiescu l ~ ~ h s y t l lu ~ m 

eaploivd Lodcvclop and wpportinmvative. flcrihk. mrpontiw 

and cottmStive spre aytumt lo meel Lb. new world roquiromcnlt 

or rutum tpre tytcem. 

5. YEGASTARN 

5.1 lntdudba 

In 1989. OSC began work on sewn1 lowca~ multi-purpose 

tpacccraftpmjab. Oncolulcu. Lha Peg.Sluinlcgralcd tpmcrafl 

hi U dcsigd lor w witb Peguut and Pcguw.derivcd 

launch vehickh including TUIM. PcgaSW U a key clunenl of 

Ihe company's ability w, oRer comprcknrive spre launch and 

tuellilo wim. Uting many or (bo tun0 tytuma lhrl opcrao 

IhePcguuiveNcle.Peg.SIuuheinghuih~undthc~irdt~ge 

of Peguut iminlu cho molor which 11 tcpuavd aflr UUining 

orhit) lo pmvllb Ihe "bouse-keeping" tervicct mccsl.ry Lo 

tupporc 0% U cutlomer-povidcd intuumenb. wmmunicatio~ 

dcvicct and other ~CNOII onorbit. In culy 1991. OK enmed inlo a muad witb (bo US. Air Fora Spvc Tctl 

Pmgrvnfatkpoductionola sun-pointing PegaSurtpcann 

lo t u p 1 uwrwl Air bee acicnlik elprimenu. U well U M 

envimnmcnlrl monilodng&uconlraclwitb NASAGoddud la 

chc pmvitionofoccan cobrdala uting an inkumcnlmounted on 

a ndir pointing PegaSW tprcmn. 

5.2 Vehlda Dacrlplba 

OSC's PegdW integntcd satellite (Pigum 12) apprh POvida 

lor mol0 clficient ute of tho volume d mus available 

from8 PoguworTauNt I8unchcomprod lo8 vpvahls tauliils 

dctign. Bycliminuingcho weighludcosl~tuylopmvide 

tepmlo avwnkt. control. ~ ~rue~unl nd &U tytvms on bocb &e 

pylodudluncbwbsb. Pcg.SuwiUmableauterloplrt

APEX 

1993 

247 kg 

375w 

3 Axis, 0.5' 

Tmnsm(nm SEand 

Propulsion None 

mil GPS 

Determination 

Notes 

1 Year Desigr 

3 Year Goal 

DoD HDBK 

343 Class c 

64 mB& Data 

Recorder 

In Test 

Fi#un 13. Prxdtor rpornr@ ropabiiirirr 

SeeStar 

1993 

245 kg 

!%ow 

3Axis, 0.10 

1.23 mrad 

Knowledge 

2 S Band 

2LBand 

Autonomous 

GPS lo whn 

1 OOm 

5 Year Design, 

10 Year Goal 

Fully Redundan 

1.25 GBI Data 

Recorder 

2.6 Mbps Down 

link 

In Fabricalion 

tn UIC lo(d system cksiy, of fulm ape systcmn. Working 

closely wilh the senior &si#mn m develop slrndanl and com. 

paihk inletfwa. lhne m yll"8chcs'lo mnr/spacccnfI 

inteylion wukl hve dranrtic payoffs in Ihc devebpncnt and 

ckploymcnl of Ikxihlc. mpnnsive and cod-cNectivc KPDTC sys- 

knu lo pmvid suppall la lbo wufighler. 

6 APPLICATIONS 

TACSAT syitrms CM pmvnk impor(ml knrfik in rnililuy 

engagemenu ranging from mvul operations to regional and 

gbhd battks. llrro errmplcs arc now provided for lhe use of 

flighl-rcdy TACSAT Icchnolngies in a relstively inexpcndve 

Uelical svvcillnn *yslem. a commercial TACSATcomrnuni- 

ution mlwd and a mmplemcnluy TACSAT fkel lhd would 

workinconcell wilhcxitlingmiliuyaaICllilcs lomllalimpor- 

Unl Lbulcr mlromhgy dah. 

6.1 SuwrUhna 

TrCkd an*5illancc saklliaa inknded primuily lo support

20-10 

(hcntercoaunnndma have ben discwoad for n( Iccot

countries for several years. Coupled with dug@i ccoiomic 

conditions. the U.S. is curtailing militmyenpd~rrs at unprcedrnted 

raws. From a 'good newdhd news. ppcctivc. tbe bad 

news is this will likely duce rignirihncly the Punding nvnilnbls 

for any new system development Md.nudlcction. But che good 

news is TACSAT system wen conceived in port lo meet thc 

challenge of declining military budget8 ad therefore do not 

require signifcant investment lo bring chem to frition. It U in 

facl arguable that lbcse TACSAT system might well flourish in 

difficult economic timcs. 

Second. Ihe widely distributed h a t environment of loday and 

tomorrow strcngthens the case for systcm whirb am responsive 

to MW tical and qtralegicndities. TACSATspvidenotonly 

the focus nbcdod for regional conflict md monitoring. hut the 

low-lkth orhib common to such syitems pinil an nbit-hyorhit 

reallocation of uwta to WOMI for ever changing priorities. 

The pace of technology is such that hth the cnpahilily and 

Discussion 

20-1 1 

c~tyb6adMreos~Idwide hot-~pacrirrvailable from nsponsivc 

spacc systems like Pegaslar. Peguur gnd Taurus. 

FinDly. aa with all new wdighting capabilities. Ule introduction 

ofnovel app~oacbeslomectingtbe~squirementsof the battlefield 

bave onen met with some resistance - such has been the case with 

TACSATs. Now that a few system have been flown and mon 

hportancly now that che commercial market is finding applica- 

tions for such syotems. Ihe introduction of TACSATs into the 

na~ocrdrefurilysystem architecture will rapidly expand. Whereas 

prim to the Gulf War such TACSATs could be ignored as 

unproven. now there isdopmentedevidence of the valueof these 

sptems and tbe users arc beginning (0 identify additional appli- 

cations where an augmentation in capability, or an entirely new 

function, can he fulfillcd with a TACSAT. Just as the hatlle tank 

and the airplane needed lo he proven, CO too must the TACSAT 

e m ib place on the baitlcficld. Having earncd that place. 

TACSATs will hecome essential components of future milimy 

infrastructures and strategies. 

Question: OSC said tt-st the corporate goal is to 

penetrate the coni;?ercial market. Of the 76 PEGASUS 

orders, how many are governmental and how many are 

free market? 

Reply: Until now the priority is governmental (8531, 

but in the future OSC believes it can increase the 

commercial percentage.

RESUME 

Puisque ks futun lanceun permetmnt I'cmprt d'une charge 

utile de plus en plus lourde. il est possible d'imqincr des 

lancemenlr de plusicurs petits satcllitea sur des orbites 

diflfrentcs. Cgndrnt pour diminucr autnnt que possible IC 

coilt des manocu~res de transfert de ces satellites, iI est 

casentiel de dCtcnniner I'orbitc &injection optimalc qui , 

minimise par exemple la masse d'ergolr nCcessaire A ces. 

transleru. 

La mdthode utilise% pour rdsoudre ce probl&me 

d'optimisation complexe est I'algoriil:i?e du grndient 

pmjett ghCralisf. iI pennet de trbuver I'oibite d'injection 

o;?timale et In trajcctoire uccnsionnc:!- mcqmdnntc qui 

rpnimircnt le coJt lout en rcqxctant laa contrainter 

imposCcs A la trajectoirc de month et aux trmsferts. 

rkux excmgles d'application aeront expods.~ Ld premier est 

I'optimiootion d'un lancemcnt double veri deux orbiter 

dinclinaimnr difltrentes. le second conceme la mise A 

poste d'une conatellation positionnCe aur dm orbiter de 

mudr MC~M~S diffCrents. 

Since future lounchen deliver more an8 more payload mass. 

it is possible to imagine multiple Irunches of small 

satellites into noticeable different orbits. Yet. so as to 

dkcreese possible high cost of srtcllitc transfers. it ir 

etsentiol to deiermine the optimal injection orhit that 

niinimizn for instme he ergo1 mass ns. mary to these 

transfers. 

OPTIMISATION bE LANCEMENTS MULTIPLES 

par L ZZOUI et B. CHICSTOPHE 

Office Notikal B'Etudks et de Recherches ACrospalinles. 

BP 72. W22 Chiitillon Ceder. FRANCE 

The method used to solve this complex optimization 

i 

problem is the generalized gradient algorithm. It dlows to 

find the opiimal injection orbit that sotirfies the 

miKelluKous constaintl rpplied to the laurrchcr and its ~ 3 - 

Jeclory. rrd thr minimizer the cost function. At the same 

time control laws and parameters of iacent phase and 

Uuufers ue optimized. 

This method rpplication will be shown on two exomplea. 

tl!e first concerning a dual launch on two differently 

iik:ined orNu: the ulhcr one conc~s I constallation of 

d&emt wending node positions. 

1 INTRODUCTION 

21-1 

Riisque let futurs lanceurs - comme Ariane V,- auront In 

pcisiibilit4 dcmporter de plus en plus de chiu$e utilc. on 

peut imaginer des Inncements multiples de petits satellites 

sur des orbiter diflfrentes. En particulicr, IC lanccmcnt 

sirnultnnd de plusicurs satellites d'unc constcllation de 

radiolocalisation. ou de deux satellites aux missions 

diflfrentcu sur leurs orbites rcspectives; pcut constituer une 

solution intdressantc malgr6 IC coGt prpbablcment important 

der manoeuvres de transferts aprEs I'injcction. 

En consfquen-e. il est essentiel de dftcrmincr I'orbite 

&injection qui minimise lei masses d'crgols ou les 

incrbments de vitesses nbcessaires nux irnnsferts des 

s.mllites sur lcurs orbiter. 

La mfthode ulilisfe pour rfsoudrc ce probltmc complcxe 

d'optimisation fonctionnellc et paramftriqac est 

I'a!:orithme du gradient projett gtnfrnlisf [ 1 J. Cette 

mfthudc. dfveloypde A I'ONERA. permct de favnriscr la 

sntisfnction des contraintcs lots der ittrations, et donc de 

trouver une trajectoire optimale les rcspcctnnt mCinc si la 

trajectoire initinle en h i t loin. Ccs contraintcs pcuvcnt 

3trc courantcs (flux thermiquc mrximal). intermfdinircs 

(retomb& dun &age) ou finales (paramPtres orbitnux). 

dfgelitf ausi bicn que d'infgalitf. En out:e. unc fonction 

coOt est minimisfe cornme la masse d'crgols ou les 

incrfmcnts de vitcsses nfccssnirer nux manocuvres dc 

traderts des ratellitcs. Lcs lois de contr6le du lnnccur ninsi 

que des parunPtra p t ~ sur t le trajectoirc dc montfc et sur 

les manoeuvres des srtelliks son1 optimisCs. Ces 

manoeuvres peuvent atre mono ou bi-impulsicnnclles et 

elles induiscnt lcurr proprcs contrainter. 

La DrmiPrc partie conccrne lo reprCscntntion utilisCc pour 

cc probkme physique: modflisation du mouvcment du 

lanceur et des srtellitcs. lois de contrfle ct pararnktrci 

optimisbs. coot A minimiser et contrainks A setisfnire. La 

deuxiPmc pnrtie i!lustre Ics potentialitfs de I'outil 

doptimisation: lanccment double vcn~ des orbiter de mZmc 

altitude mnis d'inclinaisons dillCrentcs; mise ?I poste dune 

constellation doni les orbiter ont des noeuds ascendants 

diflfrcnts. Drru cltaque cas, I'intCr2t de I'optimisalion de 

I'orbite d'injection acra dCmontrf.

21-2 

2 POSI'6"ION DU PROBLEME 

2.1 Mouvcmcnt du lrnccur et dos satcllltcr 

2.1.1 Mdiirolior, du mouwnenl ah Ictu.w 

mu-q 

Lea loio de commrnde choisics pur dftcrmincr 

I'oricntotion du lanceur wnt l'assictta 0 ct I;aziniut v. 

exprirnts d m un repbe inatiel. On suppone que le lanceur 

vole sann dtraprge, I'mgle de roulir 0 est &nc fonction de 

8 et r. PI est clair que Ir connaisrance da I'oricntation du 

lmeur prmct la dCtcrminrtion complPte do In direction et 

du module &E forces .frodynamiquc et propulsive. En ce qui 

crmccme lo phase rtmosphCrique. IC vol s'effoclw A azimut 

incrticl constant et i incidence quosi-nulle aprh IC 

buculcmcnt du lmceur. Le mouvcmcnt du lnnccur dons 

I'aunosphtrc est donc dCterminC par trois paramPtres: 

ozimut incrtiel. vitesse de brrculement et dude du 

hwhment. t 

uc sysbme diffkrentiel p6ccdent put donc IIC mctue sous Ir 

forme suivmte: 

X(t) - f(X. U. A. I) 

oh U est k vecwur de commmde et A lo vac(eur constant du 

parunltres optimisrbles. 

2.1.2 ModClisation du mowcmen~ des .t&cIIitcs 

Le mouvement des srtcllites est cntibcment dCtcrminC par 

la six purvnLtrcs orbitaux sriivants: IC dcmi-grimd ale nod 

a. I'excentricitC e. I'inclinaison i. I'rrgumcnt du nocud 

wendant n. I'ugumcnt du pCrigCe (0 et I'nnorhrlie 8 raie v. 

Cu paunhrcs obciuent aux lois de Kepla. 

2.2 Cbronologle 

Lc vol du lmccur CM LmrillC d'une dric dYvtncmcntr 

particulias comme le lorgage des Claner vidu ou de la 

ad'fe. inooduisant des dimtinuitb dnr Ir muse et Icr 

fma propulsive et rtrodynunique. De plus, Ir chrono- 

Ioaia de ces 6whementa a t I priori inconnua. Pour traiter 

ces discontinuit&. il eat nbccrsoirc de considCrer des 

rcctionr de urjactoirar. ts pmsoge d'une section i I'ruue 

est &tamin6 par le changement de 6ig11C d'un ccrtun 

criQrc. diffhent suivmt les Lvtnemcnu. 

2.3 Fonctlon coot 

Etent donnC que leo cornctCristiques du lanceur. les 

conditions initinles et les ClCments orbitaux finaux son1 

connus. si I'on nfglige le temps de rtpnse du syrt&me de 

contrble d'rltitude du lanceur. le probllrne consiste b 

dCtermincr Ics lois d'rssiette et d'azirnut optimales 

procurant IC coiit minimal tout en respectant lei 

contraintcs. 

23.1 FJpressicm du corir 

Le cool b minimiser p ut Stre I'incrbment total de vitctses A 

roumir pour [XrmCttrC ICs transfcnr: 

oh AVi cst I'irnpulrion du ihmc setellitc. 

On pcut nwsi choisir de minimiser I'impulsion maximale 

dcs motcurs d'npogCe de chaque satellite: 

V, = Mpx I AVi I 

I 

Dons cc TU. IC programme tend A fgrlcr Ics difffrentes 

impulsions rlc trnnsfcrt. 

La fonctiu:! pcut aussi concerner lcs mosses d'crgols 

nkessnircs Four cffcctucr les trmsferts d'orbites. masse 

dagols rccl:'isc pour In i'me mnnmuvre est: 

05 mi CSI 11 mosw furale du ibme srtellitc. 

lspi so-. impulsion spkifiquc. exprimkc en sccondes. 

Lea caractiristiqua du moteur d'apagbe correspondant. 

capable dc lotirnir -tie impulsion gricc A sn masse d.'crgols. 

scront ccllcs tfc la gnmme de motcurr MACE (Isp de 310 I). 

En outre. ufin de simplifier IC calcul de la masse sPchc du 

motcur. on considtrero un coefficient de structure constant 

de 109b (rnp;w)rt de In masse dchc sur In masse d'agolr). 

Comme prfcCdcmmcnt, le coGt peut Ctre exprime pu: 

1ntCrcoronr.nous maintenant le crlcul de I'impulsion de 

witesse dnm IC cas de manoeuvres mono ou bi-impul- 

sionnellc.q.

. 232 CdcJ du IIIOIWYHI?~ 

Mmoeuvm mono-impulsionnelle 

.\fin de dbterminer OD r'cffcctue h mmciivro sur I'orbite 

d'injection. un parimbtrc 

-- 

supplfrhentnire optimiscr est 

pris en compte: le temps sfparant I'injection de la 

manoeuvre. 

\ 

- Figurc 1- 

Iinj et Ir;, sont rcspcctivcmcnt Ics vcctcurs inclinnisono sur 

I'orbitc d'injcction et finalc: Vinj CI Vfin sont 

rcspcctivcmcnt let vitcsres sur I'orbitc dinjcction et sur 

I'orbitc fin& au point de mmoeuvre,M (w:r figure 1). 

Pour unum quc le point M appnrticnt prkisCrncnt A I'orbite 

fin& deoirc'e. deux conuaintcs hqqh5ncntnircr doivent 

Cue rjoultes conccmint l'altitudc et la latitude de M. Si 

clles ne m t pns srtirfaites, I'orhitc finale CRI modifife de 

!IUJI~&~C !I pouvou calculer le codt (voir $2.4.1 1. ' 

Aprbs In modification Cvcntucllc $, .I!prl>itc finale. la 

; :*a: 

vilasa Vfin et donc AV son! facilcrnoni,~~,eulablcs. 

:,;:.:. ..i 

*'b*6% 

Manoeuvre bi-impulsionnclle I 

Contraircment A la mmoeuvre mono-impulrimncd. une 

manoeuvre bi-impUlSiOMClh est toujours possible. mais 

requiat un plus grand nomtne de parambtru A opiimiscr. 

aQbuyIcrrn 

- Figure 2 - 

I 

21-3 

Le rateIIite eoi injd ea €41 &pia I'mbitm d'injection sur 

u1t2 orbitdl inlePma8iaias &ante A I'orbita finale. Au point 

dintcrsection M2. uno 00conde impulsion est donnb pour 

placa le rntellita sur son orbite fide (voir figure 2). 

Afin de dffinir complblement ce h.nrfert, trois parunbtru 

mnt optimisbs: 

- un pnrametre ~OMIUII lo position de M 1 sur I'orbite 

dinjcction. On choisit I'rscenrion orbitrle vraie. qui est 

I'~,gle brisf: 

v1 =SA1 +a1 +VI 

OD QI cst In longitude du noeud asccndant,ol est 

I'nrguhent du p6rig6e. et VI I'rnomalie vraie du 

satellitb sur I'orbite dinjcction. 

- un param&tre doMan1 la position de M2 sur I'orbite 

finale. ~2 

- un punrnltrc dftcrmhnnt lo formc de l'orbite 

inturmddiaire. joignnnt MI et M2. Par deux points non 

alignfs nvcc IC ccntre de la Tcne, passe seulcrncnt une 

orbitc KCplCricnnc de paramhe fix6 pr. pr sera choisi 

cornme troisibme p~nmPtrc. 

Dcux nuires parnm&trcs pounont aussi Etre pris cn compte 

(s'ils nc son1 pas conlrainls): I'argumcnt du p6rigCc et dli 

nocud asccndnnt dc I'orbite finale. 

Connnissont la pisition dc MI CI M2 et le pnramPtrc pr. il 

est possiblc de dCtcrmincr Ics autrcs tlfrncnu de I'orbitc 

intcrm6dioirc. nfcessnircs pour le cnlcul des vitcsscs Vi2 et 

V21, rcspcctivement nux points hll et M2. En particulicr. 

il existc dcux solutions iT et -iT pour IC vcctcur inclinnison 

dc I'orbitc inlcrmfdinire. concspondnnt rux dcux scns de 

pnrcours. et donc chnngcnnt v 12 el v2 I en kurs opposfs. 

La solution edoptfc sera cclle conduisant A une impulsion de 

vitcsse minimale. 

2.4 Contralntcs 

Lcs contrainto L rcspcctcr concc:ncnt nusri bien Ir 

trajcctoire de monlee que les divases manoeuvres. Eller 

sont donc de dilftrcnu types. 

2.4.1 Controintrs ~ ~MICS 

Conlraintcs sur le lanccur 

La contrainter finnlcs sur le lnnceur pcrmeilent &assurer 

que I'orbitc dinjcction est attcintc nu temps final (dCterminC 

pnr I'Cpuiscrnent des ergolr). Une premiPre contrainte 

d'inCgnlil6 porte sur I'rltitude du ptrigfe de I'orbitc 

d'injcction nfin qu'clle soit viable pendant plusicurs 

rbvolutions ($2 200 km). 

Contraintcs sur ler salelliter 

Un jeu de contrainter dfgalitb impose IC rcspcct der 

ClLmenu orbitaux finaux (a. e, i et dventuellement n. a, et 

v) des diffhenu satcllitcr. 

Dcr contrainter d'intgalit6 suppltmentaires sont lctivter 

rekm k type de mmoeuvre.

214 

Dens le cas ."un aanslen bi-impulsiohnel. scu'~? unc 

contrainte dinfgrlitb est njoutCe pur assurer in vintilitf de 

I'orbite intermMiaire (altitude de phi& supfricure A 200 

km). 

2.4.2 Cmraituu cowantes 

Unc seule contrainte courante scrn'prise cn compte. Ellc 

pone sur Ir eojcctoue uccnsionncllc du lonccur. ct assure 

que le flux thmique maximal rep pm In chnugc utile aprts 

le Iargrac de In coiffe n'cxckdc par 1135 W/m2. b flux 

lhemiqw est modClid de fnpn simplifite par: 

3 

W n P V , 

oil p est la dcnsitt ntmosphfriquc et U, Ii vitesse 

rtrodynmique du Imccur. 

2.43 Cotulrainirr interddiaircs 

Les contraintes intermCdiaircs prfvucs dons IC code. tellc 

que In contrinte de rctombCe dun Ctrge (121). ne scfont par 

prises en compte dans Ics cas Ctudifs rfin de rirnplificr le 

probkme. I 

3 RESULTATS 

L'outil pitsenid prfcbdemment pcrmet de trouvcr la 

"meilleure" trajcctoire dc montfe (nu sen, dun COG:) rinsi 

que la "meillcurer' manoeuvres. grke k unc optintisotion 

cauplfe. De plus. il est possible de considtrcr lo mise A 

poste simultanfe de plusicurs satellites sur des orbites dif- 

Itrenter. 4.' 

. i . 

-8 

La cappcitb du code A trniter dcr problbmes 'varifs sera* 

dCmontrCe tin let deux excmples suivnnts: le premier 

concerns deux satellites k injecter sur des orbites 

dinclinaims diffCrentcs et le second le mine A poste dune 

Constelluion de uoir srtcllites sur der orbites de mCme 

kliruWn mait dont ks noeuds ycmdantr mnt rtpubs de 

120'. 

! 

Considboru deux ratclliter dont le8 C8r8CIbnsliqlieS sont 

la SUiVMtes: 

- satellite 1 : mnsie: 250 kg (motcur drpogts compris) 

orbite vide : 7aOf700/98" 

- satellite 2 : muse: 1000 kg (motcur d'apogte compris) 

orbite vide : 700~Ct0/8O0 

Le lnnceur considkrb est Ariane 44LP tquipe5 de si coiffe 

longue ($15 kg). du rupport extane Spcler (420 kg) et de 

I'adnptateur Arime (50 kg). 

Plusieurs solutions peuvent itre envisigCes pour effectua 

cc lancement double. 

La premibre consistc A injecter direclement I'un des 

satellites sur son orbite finale ct deffectuer une manoeuvre 

pour le second. Dnns cc cas. la masse nfcessnire pour cctte 

manocuvrc put dfparser lcs cnprcitts dcmport des motcurs 

dapogfe existant actucllcmcnt. 

Une autre solution pcut donc Otrc d'injcctcr lcs deux 

satellites sur une orbite de transfert et d'cffectucr une 

manocuvrc pour chnque sntcllitc. Cctte orbitc d'injcction 

scre optimisfe ou scns d'un coat (pnr cxcmplc. la mini- 

misation des masscs dcrgols dfpcnsfs). 

3.1 .I Vrbite d'injcction f ie 

Puisquc Ics orbitcs vish de chnque satellite 01 et 0 2 ont 

mtmc nllitudc (700 km). I'impulsion dc vitcssc nfccssaire 

nu transfer: d'unc orbitc h I'nutrc requiert uniqucmcnt tin 

rattrappngc d'inclinoison dc 18'. sous rfscrve quc la 

monwuvrc oit licu A I'un des nocuds. La valcur minimalc de 

I'impulsion est dims CC cas 2350 m/s. On suppose que lcs 

deux sntcllitcs sont bquipfs du mhc type de motcur 

dnpogfc dont lcs caractfristiqucs son1 bnsfcs sur ccllcs de 

In gnmmc MAGE (Isp = 310 s. rapport dc la masse skhc sur 

lo masse dcrgols de IO %). 

La table 1 donne lcs mmscs nfccssaucs A mctac h poste sur 

I'orbite dinjcctian pour lcs dcux types dc manoeuvres (01 

vers ct @ vcrs 01) compnrfcs avec l a pcrfOfmMCeS 

dAriane 44LP. 

Masses (kg) 

orbitc d'injcction 

Spcltra + adapwtcur 410 470 

Sntcllitc positionnf 2500 1000 

Satcllitc A positionner 1000 2500 

masse dergols nfccssairc 1165 2910 

3.' 

I 

Muse h I'injcction 5135 68HO 

Performance Arinnc 44LP 5520 6065 

comprenant Ir masse &he du motern d'apogbe 

- Table 1 -

En rcvnnchc, m ce qui concemc la pernitre strattgie. lo 

pmformnnce dArianc 44LP est suffisonte. rnnia le lransfen 

du sntcllite 2 vets son orbite finale regriiert un moteur 

d'apcrg6c puvant contenir 1165 kg d'cr8ols, moteur 

n'existmt pas jusqu'l maintenant., 

3.1.2 Opthisation de I'orhilr dinjnchn 

Le scul moycn de rfalisa cc Inncement double est donc 

doptimisa I'orbite d'injection de tellc fqon que lu deux 

setelliter soimt tquipts de moteum depolgb r6nlistes. Deux 

colculs d'optimiration raont cffectuCs avec des cohs 

diffkrents. 

Le premier indice de coot A minimiser est le maximum des 

impulsions de vitcsre. Ct CIU dc calcul fvident ne fait que 

dbmontrer Ier capocitfs du code. et par consCquent, on ne 

tiendra p compte des rCsuItats concemont I'cxistencc des 

moteura d'opogtc requis. Avec cette fonction coOt. 

I'rlgorilhma tend A fgola les deux impulsion$. en chcrchanl 

A miniism la plus grande. 11 est clnir que I'nrbitc dinjcction 

optimola dcvra tire inclinCC A 89". Effcctivement. 

I'orbita d'injection optimale @ lrouvCe pa I'dgorithmc est 

la suivonk: 070/720/e9°. On peut notcr quo Ics mnnocuvres 

ont lieu aux noerrdo UCC~~MIS des orbites d'injection et 

Tu, des. ce qui minimise le cott puisque seul un rollrepage 

saictement en inclinison est A effcctuer. b)E plus, I'orbile 

d'injection s'est dtformCc par rapport B I'initielisntion 

(700/100M)"). diminuant son Cnergie En cffet. puisque l o 

manoeuvres iont mono-impulsionnelles. elles on1 toutes 

lieu A 704) h daltitude. L'incrfmcnt de 4tessc est minimal 

ti IC module de la vitcssc sur I'orbik d'injection I une valeur 

ICghement infkrieurc h celle sur I'orbite finale. 

Ler figures 3 et 4 prbscntent respectivcment les tvolutions 

au cours &a itkratioru des impulsions dc vilesscs et des 

masses dergob nCcessaircs aux manoeuv'reo. Qn r'aperqoit 

qu'A putir de I'ittration 50, I'optimum est presque rtteint. 

bim que I'initirlisation m roit loin. 

"1 #or1 

t ~--.--u1~ ' 

- Figure 3 - 

IA table 2 donne le dcuil de 1. muse ntcessaire aur I'orbite 

d'iajcction w. 

i 

- Figure 4 - 

Ce Inncement est possible avec Arinne 44LP puisque sa 

performance sur cette orbite dinjection est de 5680 kg. 

La seconde fonction de coiit prise en compte est le 

maximum dcs masses d'crgols nfcessaires nux manoeuvres. 

coGt qui permet d'bquilibrer les masses dcrgols des deux 

moteurs d'apogie. L'orbite d'injection optimale 04 obtcnue 

piu IC code est la suivmte : 695/100/92.3". 

Cctte valeur de l'inclinaism plus forte que prfcfdernment 

est due nu fait que. puisque le, deux satellites doivent 

dCpcnser autant d'ergols. I'orbite d'injection est 

naturellcmcnt plus proche de celle du satellite le plus lourd 

(ici I'orbite inclinfc h 98'). 

La figure 5 donne I'fvolution de I'inclinaison de I'orbite 

dinjection (initialisCe P 90") nu cows des itfrations. 

b' I 

- Figure 5 -

21-6 

,...-. ".._ . + . I.. 

0 8 IO IS 10 

! /f&s:'ans 

- Figure 6 - 

J--fI-{ 1 

'--e e 

- Figure 7 - 

A I'initidisation. les muses dergols n&cssaires Ctnicnl dc 

9500 kg pour le satellite 1 et de 5650 kg pour le satcllite 2. 

Grice A I'optimisation de I'orbite d'injection. ccs valcurs 

on1 Ctt considCrablemcnt rCduites pour lniver L des masses 

rCdistes (700 kg). 

L table 3 fournit le dtuil des dilfCrentes mwcs sur I'orbite 

Sinjection 04. 

-Table 3 - 

La capocite dkmpori d'hime 44LP pur cette mission est 

de 5512 kg. 

I 

D~5.10 CM du Immeslt double. I'optimisstion couplk & 

lo trnjectoire de mmr& el des manoeuvres 1 conduit A una 

orbite J'injcction qui prnnct de metue h poste ks deux 

satcllitcs avcc des ~ UKS dergols dmlistes. 

3.2 Lancement d*uk constellation 

Conoidkrons une conotellnlion de rodiolocalisrtion 131 

composfe de uois sotcllitcs. de 500 kg chacun, dont lea 

orbilcs finales ont pour ClCmcnts orbitrux : 

n = 42164 km 

(hp = 27733 km et h, 0 43840 km) 

e = 0.191 

i = 18~345' 

o = 254,887' 

plus unc difftrcnce de nocuds ascendants de 120" entre 

les orbites. 

Le lanccur utilisf pour CC lanccmcnt uiplc est Arionc V. 

&qui# dc la soiflc courlc (IR70kg) et du support exteme 

Speltrn (900 kg). Lei trnnsferts sont dc type bi-impul- 

sionncl ct Ir fonction coht A minimiscr est la sqmrnc des 

impulsions de vitcsses des trois manoeuvres. Comme 

prckctdcrnmcnf on considPrcra tout dabord une Ics transfcru 

A partir d'iine orbite d'injcction fiaCe qui sera IiMrCe par la 

suite din dobscrvcr les nrnfliorations apprtfes par le 

cdc. Enfin. dnns l o deux cas. unc contrainte supplt- 

mentoire pouna irtrc activfc afin dusurcr un bcn fquilibre 

massiquc entre Ics satellites. La satisfaction de cctte 

contraintc moteur pcrniet de limiter A 5% I'Ccart entre la 

masses d'crgols nCcessaircs A chaque satellite ct lcur valeur 

moycnnc. 

3.2.1 Orbitc d'injection fude 

L'orbilc d'injection considfrte CSI une GTO classique 

inclinfe A 7' d'oltiludc #rigCC 280 km et dopogfe B 35786 

km daltitude. 

Choisir une orbite d'injection dfjA inclinfe A 18.345' peut 

scmblcr au prcmicr abord plus intfrcssant en tr.rmc de colit, 

puisqu'il nc rcslcrait plus qu'un rottrapagc de noeud 

ascendant A cffcctucr. Nfanmoins. lei changements de 

nocud ascendant entraineraicnt obligrtoircment des 

modifications d' inclinaison (sad pour IC sstcllite don1 

I'orbitc finale a le mSmc noeud ascendant que I'orbite 

dinjection). ce qui conduirait h un colit uti important. 

Cette orbite GTO scrvira d'initialiaation pour Ics 

optimiwtions suivantes. 

Dcua colculs on1 ftf mcnCs pour la mise A poste h pnrtir de 

cctte orbite J'injcction. la contraintc rnotcur n'ftont sctivte 

quc dnns un dcuaikme Icmps. Ricn entcndu, In coht cst plus 

important dims ce cas (7071 m/s contre 6631 m/s). 

La tablc 4 ~ OMC Ics rfsultats de I'oplirnisation dms IC cas 

ot aucunc contraintc n'est imporCc sur lcs masses d'crgolc. 

II est A notcr quc Ics valeurs des nocuds asccndnnts ne son1 

que relatives. En cffct. IC tcmps initial corrcapnd arhi- 

traircment nu moment oh y50 pasac A Crecnwich. Pour 

modifier le nocud ascendant de I'orbite dinjcction. il ruffit 

donc drjustn I'heure de lir.

Lea masses d'ergoh pour les trois ontalliiea sont trbs 

diffkntes. Pour &ita ces Ccuts. on ectivc Ir contrrinte 

moieurr. 

Orbite rmde 1 

- Table 4 - 

LJ table 5 rCsumc Ics modifications induites pu I'acdvation 

I 

de cette contrrinte. 

Orbite finde 1 

Du fait que Ics maws dergols dcs deux dcrnicrs sn;cllitcs 

Cioicnt du mCme ordre de grandeur. I'elgorilhrnc n'a foit que 

&grader Is oafit de Ir manoeuvre du premicr saicllite. 

3.2.2 Optimisation de I'orbite dinjecrion I 

Contraink moteuis dfsaciivCe 

b poini de dfpan de I'optimisoiion est ifsurd dnns In inblc 

4. En pnrticulier. la somme des incr6ments de vitcsse 

nfcessaircs mux transfcrts dcpuis iinc GTO 7' est de 6631 

mls. Aprir 300 itfrations. clle esi possfe A 5934 mls. ct 

I'inclinaison de I'orbite d'injcciion est pasCC B 13.8" ct 

I'argumeni du noeud wcndani A 147,3O. De plus. I'fnergie 

de lbrbite r eugmeniC lcs sltiiudes de @rig& et d'apgte 

pusant rcspectivement de 280 km b 61 I' km el de 35786 

lun A 40586 km. I 

On peut noter qu'ou court des itfrotions. I'dccvt rclatif des 

noeudr u~mdpnts der orbites finales demeure Cgal A 120'. 

cet~ conurinte reitant rrtislniic plv In suite. 

La table 6 compare Ics orbiter &ire I'iniiialisntion ei Ir 

convergence. 

I 

1 Masse J'crgols I 414'588/614 I 385/280/773 I 

(kg) 

1 I 

coat 663 1 5934 

-Teblc 6- 

Les figures 8 et 9 lournissent plus de dCtnils sur les 

changcmcnts iirtcrvenus au -ours des ittretions. Elks 

prbscntent respectivement les Cvolutions des ncseuds 

rsccndants et des inclinaisons des orbites d'injection. 

intermfdiaires et finales. 

"i 

0 &e--- 

-* ---- * ---.- -__m 

N I O ~ IM too aw 100 

I1)nllons 

- Figure 8 -

21-8 

Cea finurea montrant qul le convmognncn. leo orbitintemedliaina 

et h ~ Idu e srkllitc 2 on1 grrsli7uement mtm inclinaioon et nwud rscendant. conuoiroment A l'initinlitetion. 

Ln fip~e 8 monbe en particuliei quo CQ noed 

ascaidnnt commun nux orbites intmMdlinire et finale est 

aussi celui CL? l'urbite dinjeclion. ce qui expliqiie 1s foible 

coDt des mnnoeuvres cffcctutes par la sotcllit: 2. La 

trnnafert est en fait quasi mono-impu1sionnc.l (lhe 

impulsii?: 1278 ds, 2nde impulsion: 77 YPJO), lo pernih 

impulsion permeltmt un rrltropage glow en &neri:ie et en 

inclinaison. 

Pow le sntcllite 1. on constate unc Cvolution relal .vement 

minime des orbiter finale et intermCdinire ei,.tre ler 

itbrtbno 0 et 300. russi bicn en t ern &a mud ascendant 

que dinclinnisan. Comme pur le satellite 2. le trmfert est 

qunsiment mono-impulsionncl (lLre impulsion: 1662 dr. 

2nde impulsion: 75 ds). 

Enfin. Ics ecoru en inclinaison CI en noewf ascendant entre 

Ics orbite dinjcction. intcrmtdiaire et finale du sntellite 3 

on: smoiblement ru8mcntC au cours de8 it6rations. Pnr 

cons&pmt. CC uansferc est bcnucoup plus coilteur que les 

deux autres (773 kg dcrgols rcquis conwe 385 el 280 kg 

pour les ratelliter 1 et 2). L'fvolution den matscs dergols 

est illustree sur la figure 10. On ubtcne la diminution des 

masses d'ergols du salcllile 2 pennettant unc mdiorrtion 

du COOL aimi que la dtgrdrtion de Ir menoeuvre du srkllite 

3. 

Coneainte motcurs activfc 

Les rtsultats pfcfdcnts montrcnt unc sensible diminution 

du cost global. mais au dfirimcnt dc IXquilibre entre les 

masses d'ergolr des difffrents satellitco. Pour asrurer Ir 

symEtric de Ir constellalion, A partir de I'idrntion 390. unc 

strie de 300 itCrntieia suppltmentaircs I et6 effcctde en 

rctivant Ir convainte motcurs. 

La table 7 compore les rfsultats des deux converqcnccs 

ruivwit que lo contraink motcurs CII active OLI non. Comme 

on pouvait le prfvoir. IC tespcci dc.cctte contrainte cntrnine 

une augmentation du coir1 total. Ceite valeur obicnue est A 

cornparer In avec celle concspondant nu C'LP de I'orbite 

dinjxtion Fixfc h UM GTO 7", contrninie moteur active 

(13.2.1). 06 I'on constate une nette mClimation. le coot 

passmi de 7071 m/s A 6526 m/s. 

AV (ds) 1737/1355/2842 2095/217812233 

Masse ergols (kg) 305/280/773 49615241549 

- Tlbl~ 

7 - 

Lu figure 11 donne le8 t%olutions des masses dergols de 

chnque satellite nu cours dcs iterations. 

On note que sculcs 50 itfrations sont ntccssaires A Ir 

satisfaction de le contrrintc motcurs. les misses dergols 

rquises gardrnt quasiment lea mCmer vrleurs par Ir suite. 

Io0 1 

i 

- Figure 11 - 

Lei figures 12 et 13 dtcrivent respectivement les 

fvolutions des noeuds ascendants et des inclinaisons des 

orbites d'injcction. intermtdiaircr el finales. 

'O t 

....**-*.e .-............. 

... 

- Figure 12 -

- Figure 13 - 

Les orbiteo intermedirite et finale du sntellitc 1 ont mhc 

inclinaimn et noeud ascendant. ct on1 tr&s pcu varit! par 

rapport A I'itbration 300. En revanche, I'incrtmcnt de 

vittrse a augment6 du frit l e la plus grande difffrcncc entre 

les inclinoisonr des orbiter d'injection et internitdinire 

(voir Figure 13). 

En ce qui conceme le satellite 2. C t ~ donnt t quc son 

emsfen h i t aupnravnnt IC moins coiiteun. I'octivation dc 

la conaainte ne pouvoit que le dfgrader. Ainsi. alors qu'A 

l'itdrrtion 300 Ics orbiter intcrmtdiaire et linnlc avaicnt 

m6me inclinairon et mud ascendant. Ics 3 0 itdrations 

suppl6mmtnires ont conduit A unc dilfdrence de 72' sur Ics 

nocuds orcendanlt et 12.8. sur les inclinaisons. En 

condqucnce. et de mmitre A rattrrppcr ccs Ccarts. la 

reconde impulsion n'est plus ntgligerble (le transfert est 

ettc fois rkllcmcnt bi-impulsionncl). Lc cott du trcmsfert 

est donc mieux rtputi enme les deux impulsions. 

En revanche. la sydtrie entre Ics trois salellitcs impsfc 

par la contrminte motcurs conduit A unc baisoe du coir1 dc 

transfcn du satellite 3. Comme IC monrre la fiaure 12. d&s 

IO SO premitres ittrrtionr. Ics orbiteo d'injcction et 

btermMirirc ont mLme nocud ucendnnt. qui pw le suite se 

rrpprochc de plus plus de cclui de I'orbitc finalc. Quant aux 

inclin.isons. ccl!c de I'orbik intcrmtdiaire 5e ropprochc. au 

COLTS der ittrrtions. A Ir fois de I'orbite dinjection et de 

~elle 

de I'arbite inteddirire. 

Bien Cvidemment. le respect de la controinie motcurs 

impose que Ics masses d'agols des trois satellites soient 

sensiblcmcnt identiqucs, comme l'illustrcnt lei valcurr 

porttU duu la table 7. 

Ler figures ruivmtes prtsentcnt des &volutions globnles au 

cours des 600 itlrrtions effectuCer. le rnccord A 300 

ittrationa rnarquant I'activation de la convainic motcurs. 

La figure 14 dhit IYvolution de la lonction coGt (c'est-A- 

dire de la somme dcs impulsions de vitdre). 

110 

bo00 

IO00 

moo 

1 M O 

0 

i 

IP 

- Figure I4 - 

21-9 

Lc co5t dfcroit rdgulitrement jusqu'A I'itfrrtion 300. touter 

lcs contraintes tiant dfjA satisfoites. Puis. B I'activation de 

la contrainte motcurs. il augmente rapidcmcnt puis dfcroit h 

nouveau rtgulitrcmcnt une fois que la contrainte est 

shfaite. La valcur uouv6e aprts 600 itfrations est bien 

cntcndu supdrieure A cclle de I'itfration 300. 

Les figures 1s et 16 donnent rcspcctivemenl I'fvolution de 

I'tncrgie et de I'altitude de p4rigCe de I'orbitc d'injcction. 

i 

- Figure 15 - 

CIans la prcmikre pnrtie (de 0 A 300 itfrations). Icr valcurs 

de I'altitudc de pfrigfc et de I'fnergie de I'orbitc d'injcction 

croissent afm de se rapprochcr de cellcs des orbitcr finales. 

ptrmcttant ainsi BU coot de dirninuer. Lorsqu'on activc la 

controintc motcurs. I'fncrgic dfcroit fortement. en porallklc 

avec I'augmcntntion du cotit. Cctte baisre d'fnergic pcrnict 

de dfgradcr les mnnoeuvres Ics moins co0tcuscr (sotellitcs 1 

et 2). Cependant. elk n'cmpiche pas pour rutant 

I'rmfliorotion du trnnrfcrt du satellite 3. due 

easenticllcment A In diminution des rettropogcs en 

inclinnison et cn noeud Prcendnnl A cffcctuer (voir figures 

12 et 13). Unc fois la controinte sotisfmite. la valcur dc 

I'dnergic revient b son nivcau prfctdent. et I'optimisation 

~f pursuit avec une diminction du CoGt global. Notons que 

I'dtitude du pCrigCe de l'orbite d'injcction n'r cor6

21-10 

d'iugrnmter nu cours des itdrntions. favorinant ninsi une 

baisw du coat au dtriment de la masse totalc de chugs 

utile p ldc tur cette orbite. 

4 CONCLUSION 

-Figure 16 - 

Ceo deux cxemples ont monvd l'inttrit doptirniser de f40n 

couplh lo rnontte et lei manoeuvres dons le cas de 

1.ncanmu multiples. 

Dms lo cas du lrncement double. I'optirnisation a pcrmis 

deffacw la mim A poste de deux satellites dobscnation au 

moyen de motews drpogte rdilistes. 1 

Pow 10 hnmmnt b la amtcllation. on a pu gngner. grke 

h Ibptimisntion. mLtT& 7 et 10% par rapport A la mise A 

posle depuis me CiTO 7' Clansique. 

Grb b la divereit6 des contrninteg -fncilernent activablcs- 

er nux nomhuscn fonctione collu. M grand nomhe de cas 

peuvent Ctre trait& pnr le programme. Linttrit de cctte 

mtlhode dopimisation repose sur le fait qu'elle put gtrcr 

un grand nomh de porm&tres (pticulihement dans le cas 

des manoeuvres bi-imgulsionnellcs). Cvifarit ainsi un 

balayage futidieux de IOUICS Ics combinaisons possibles. 

111 

(21 

[3] 

C. Aumrr~son. Ph. Landiech: "MCthodc itCrative de 

type gradient projet6 gCnCralisC pour I'optirnisation 

pnrarndtriquc et fonctionnelle de systkrnes 

dynuniques soumis B des contiaintes." 

N.T. 1988-9 ONERA 

Ph. Landicch. C. Aumasson: "Month optimale du 

tnncew Arione V-W avcc contrainte de rciomMc du 

prrmim Ctnge." 

R.T. no 21/61 15 SY - ONERA 1986 

H.Bnmng.er. 1. Bouchard. T. Michal: "Systkrne de 

nrvigntion par srtellites A couvcrtuie europCennc." 

Communication AGARD 1992, B~~ellci Session 

111: TacSrt applications- System 

Question: My question concerns the eqtivalence constraint 

you use in order to limit to 5% the gap between each 

satellite propellant mass and their average value. 

Is it possible to minimize the maximum value of the 

propellant masses instead of activating this constraint? 

Reply: The cost index (.i.e., minimizing the maximum 

of the propellant masses) may be considered as it 

is presented in the paper, and could have been Lsed 

in this case instead of trying to minimize the criterion 

(sum of the delta v) while activating the equivalence 

constraint. Never the less, the 5% margin allows a 

respective balance between the three satellite niasses 

without making them exactly equal (which might be 

too strong a constraint in this complex system where 

the launcher ascent phase and three bi-pulse maneuvers 

are simultaneously optimized).

SVMMARy 

- 

rution inonly I5 monh. 

Quickstar 

System Design, Capabilities and Tactical Applications 

of a Sinall, Smart Space System 

hK QuitStr pgun rrpcmu a Miqua Crppommiry b 

puf0rmcritic.l mission, whik uing tho crecuclp.bili$a 

Of ~p~0ming McDOM~U CUU@U DelU 11 ISW~S. 

QUiikSlu, 7hc Compku SyUm-, povidu a hishly 

clpable. lowa~l ~pIceCru\ immmnlinr a llicht-woven 

kiln la fus reliibk YSUI IO &ace afiaUn;h cdu. much 

below the capeclcd m. 

'Il!oma, P. Gnrriwn. 

Kcal T. Andason+ 

Ball Spnec Syslems Division 

P.O. Box 1062 

Bouldcr. Colado 80306 

USA 

- 

Small amrc .yawnu CUI rcvolutimiw the way govsnment 

md mmnaxi.l intcruu implonat muuch strategic, mid 

The QuickSllr Syitan b MI a mnapt-it is a flighbpnvm 

desi@. QuickSta is a andl highly cqmblo. bwask light. 

weight s v h uiq modem desi;" whdqva thu cm nm ustical space ryaIcM. To && tho implcmcnution of 

cq ~lic~~~incospace~.umhorhamt~rc~~~ 

such system hu bocn inhibid by ha widely hcld 

much Mer .nd mom d y rpre ryrrsnr. Syrm daim PsCcptDn Ihr small rytmnu IC IY)( likely lo be useful. 

rrlevMt tahmlogics, pybd uplbiitier (mm, power. dum rrlilble. 01 eodcffslive. Thia negative plccphn hut 

rat+ pointing, volume). .nd tactid mission rFplicatioru of small systems cm only bs mmxai by a ryslcmUic apprh his light.wcighl salcUilc at described. AI pan or the overall which dbuw specific omcam ud pml~ mission 

rmdl srlcllitc sywm uchitsnuo. aporuble. hwcost multi- utility. To r k c thin d. Bdl Amspace in 1988 initid 

ppwe gmund swion to support palu~tia~ VIL launch m inurnally funded cfTffl cded TECHSI'ARS. The 

ud abit opentionr of tho spec segment U dm availabk. objective ol ha TECHSTARS proRrm wu UI ermine tho 

The vnwtilify ud truuponabiliry buiit into the pund syrvm uchiMWa .uociued wilh amdl ryrlemr md b 

rution allow plsccmrm U my govemmmt inudlation a 

- 

hrporue the advured Icchnologia required lor the 19901 

field rite. 

lo pduce light.wcight rpve ryrtem h t ue highly clpable 

md yet cM be poducd U bw mrf 

The pr~type QuiikStu spye segment wu dcvclopal to 

ride U a uarnby pybd on a McDomell Douglu Delu ll Quickssu is a pogm thu ylcs Ihe qprh md knowledge 

aeries capendable launch vehicle (ELV). With lht eau8 rn rm cha TECH~TARS erroh 

prformmce pvidcd by the Dclu II o( o k ELV of aimilr 

configuration. U mmy U four ruellita could hc orbited U 

om lime In addition, tho pqm dcscriba a QuickSW 

ratclliv diguruion, incorgorating he ruw subs)nlcm 

TIE QuickSur daign is a derivuive of the U. S. 

ud caplbiliticr U he pololyp QuickStu. dctigmd fa s~ldom ELV (Scout or Peguus) launching#. 

(iovammcnt-lundcd pl~yp rpscandk LOSAT-X. 

Flgun 3-1 U a piclure of LOSAT-X in thc clem mom U 8.U 

jut pior 

The pogrun schedule far tho daigh 

UI rhipmcnt lo Cqc Cuuveral Air Face Station 

fabrication, md test of 

a QuiikSur riullite syum rcflecu the lut.pccd 

Delu hunch Complea 17. LOSAT-X wa~ the result of a 

mvimnmmt ol a bvsou p~m. Minimal p'pr ud 

much amcumt engineering gar into a schedule hi pmidca a fliphlu-rudy spxcraft urd rupprting pud 

22.1 

pvcmmml push lo dncbp. lab lumch ud operate rMll 

apaacrh ud complemrnury tahnologiu. 

Designed by Bdl Aercapsce, tho LOSAT-X spsccndt 

included M integrated avioniu suite built murid two 8x86 

pmnwn. a 0.25-Gbit rryy memory. Bddcvebped 

rculpn w k k ad a new widc rKld-ol-vicw (WR)V) SUI 

umc~ hip &ivm diculsd Ihu lhir mmplicavd 

rpvOmn fii within a vay :null envelope on a McDomll 

DOU& Dclu n mcka U L vcondpy paylod ud still be 

mphiskatcdcnw~o*ranplihmL*mlcimcc 

ObjaCtiW.

I - 

- 

AI with Ihr cue of LOSAT-X. OUikSta U I~unchal .I a 

12-1

I 

f igun 5-1 QulrUfar spcun@ syslrm conerpi 

USUAL SMALLSAT 

LIMITAllONS 

QU!CKSTAR 

CAPABlUTlES I 

COMMENTS 

I I 

lrmrpndvr mnd dmpb 

Io bulld. 

Conlrdlmd by Ihm 

1 N.M mallon *I& 

c.

Thc ADACS provido *ti!dc &lamhh ud rOnCm1 for 

the QUK~SW rprscnh Ile ADACS udsu of I sur 

caner& a 3.uU gym puk.ge, WO sun YM* I 3.uu 

magneromcter. three reaction whl nmbliea ad drive 

elecuonia. ud hrm que mdt. Attitude dctrrminui.m b 

wcomplihd =in; inpuu from a undl. vidr4lcld.ol-~ icw 

(WFOV)rol~-sutsswc~vn(viaIhcAfCPmd DMA) 

when in the inulial pointing nIode ud the 3.uis WO 

prkqe during uuking opetitiom. AttitUds conuol U 

achieved usin; the nrtion vhcels while magnetic loquin; 

U u d U) dump uod momentum in the whal. 

The WFOV aur cuma yea reecntiy nncqing Ccchnoh~gica 

in WFOV I-U md r=al piMC naitcning. n= resuit is 

greatly simplified d bwscost IW Camera. Using the 

marc eipbh IIU canen in lieu of E d nd sun M~OR 

rcsulu in a simplified attitude determinition ami conuol 

aubsystrm. With the rcluively simple ch.r;cd couplcd 

device (CCD) 111 camera along with a mmpki loftwuc 

pgrsrn he five brightest 11u8 ue send in the ficld,of. 

VKW uul mavhrd ton m-boucl (tu cualng in cmpuie M 

attitude solution. Usmi the new WFOV camer% the ADACS 

ea wide wit& hwledgc to brtter thm 0. I degrees in 

dl aaci. In additim. ita WWV capability allow he on. 

bud UI caulog 10 bs under JW stus. t:ss minimizing onbnud 

ilorsga and pnu rtq.liremcnu and rdurin; 

processor biding. 

During mrmal operations. QuickSur U maintiid in i Sun 

Poiit MO& in which the molar panelr are positioned normal 

IO he mn.linc for optimum pwcr outpu. In hi mode the 

%UT cmwi is used f r ptimuy attitude deiaminaim. 

Durinl main prcdctamined times, however. the Ipcmdt 

ca k commuded Io on of wvad pointiw mode type, 

such U 7rwk- or "Inmid-. In Track-. tho sprccrdt slevs 

w hit the +X lab kvkr 8 pnlctennincd Erth fiacd or 

orbitd pitia Win; Wi tima thc 111 c u ~ dua a U 

unsvailsbk so spccnrlt attitude ia dctermiiud by using the 

~ym 

is a refnmcc. Attilde munlainlies mtinue to 

~umulrte due 1O ~yro drift until (he end of he slrw and a 

stu mncra updatc becanes available. The Trrk mode 

opcrra with any good** laah vhclhcr m the fwc d Ihs 

W w U ahiul altindr In Inertial: Ihs spcmllt is 

pointed abng a mnnundsd lied bvnial VCMI. During hii 

mod* the gym munairu M bodyaais raw. Aft- each 

Trrk'a Inaid' maKuver. QuickSlr iC rnumal to 'Sun 

Wit'. 

Brk-up inindc determinuion U available using i 3-iais 

~;neIometer uul tho IW nun sensors. Using Mual Eah 

Tuld lii nJ aun dimtiau. sprecrdi hrfyub ittirudo 

mluhru vi& uxuma on Ihs ordm or I Io 1 de;- y. 

available. 

An 0Pion.l clement of Ihc QuickSw ayalms b d m 

m*li+yld rcqukemmu, is a lightweifit poprlsim 

&pm dui@ 10 pufwm delu-webci~ mmers io 

FIpun 6-1 QulekSWoprmUoonolgroro~nd station

?- I

.- 

I

* Snull ground conlrol VMS 

1s.a.a 

FIgm 7-6 VHFISUFIEHP eommmlcadonr 

22-11

12-11 

Spacecraft Family 

Carrying Typical 

hvw 

QUICKSTAR 

SCOUT CLASS I PEGASUS CLASS

.. 

1. INTRODUCTION 

Attitude- and Orbit Cootrol Subsystem Concepts for TACSATS 

The technical pcrforrnancc spccifications ;ind 

rcquircrncnts for Attitude- and 01 lit Control 

Subsystcrns (AOCS) for satcllitcs arc Jictatcd by n 

large numbcr of boundary conditions: 

- The payload rcquircrncntS (c.g. poiiitiny accura- 

cy, LOS-stabiliLy) 

- Thc perturbation cnvironrncnt. Imh caernal 

and intcrnal, i.c.: 

Gravitational-, solar prcssurc-. air dras-, rna- 

gnctic disturbancc torcjucs 

Rcaction jets, whccl wobhlc, payload opcra- 

tion 

. - Easc of opcrability (command structure and scqucnccs) 

- Onhoard autonomy (cornm;ind-. clilta and cornmunication 

links) 

- Opcrational lifc tirnc / rcliabilitv 

- Maintainability, storahi!tv ant1 so on 

For the class of spacccraft undcr discussion hcrc. 

mass limitations. which will not allow major orbit 

changes. and thc diffcrcnt typcs of pny1o;ids for 

survcillancc. vcrification and C31 as well 3s str;itc- 

gic aspccts call for cxtrcrncly high flcnbility ol' thc 

AOCS-concept IO enable: 

- 'Last minute * sclcction of the opcraiional or- 

- 

bits according to the actual nccd 

Adaptation to the rcquircrncnts of diffcrcnt 

typcs of payloads (passivc: Optical. infrarcd; 

active: k-wave) 

- Compatibility with a Iwgc dynamic rangc oi 

plant pararnctcrs (e.g. largc / small solar arrays 

and structural flexibility dcpcnding on clcctrical 

power requirement) 

H.l'!ittner, E.Briiderlc 

MSvraucr, MSchwcnde 

DASA/MIBB 

Space Comm. and Prop. Syst.Div. 

D 8OOO MUNCHEN 80. P.O.Box 801169 

Modularity of the AOCS in tcrms of typc and ar- 

rangcrncnt of cquipmcnt. (sensors, actuators), 

control laws and operational scqucnccs (OBC-capa- 

city and algorithms) thcrcforc has to be a prcdo- 

rninant fcaturc. It is cxpcctcd thar the flexibility for 

adaptation to spccific mission requirerncnts and thc 

rn.duluity of thc AOC subsystcm cnvisagcd will 

contributc to a low cost but still highly efficient 

tactical satcllitc systcm. 

On thc basis of cxpcricncc in Attitudc- and Orbit 

Control Systcrn dcsign, analysis, acccptance tcsting, 

and in-orbit opcrations support for communication 

satcllitcs (INTEISAT V, TV-SATRDF, TELE-X. 

DFS-KOPERNIKUS. EUTELSAT II), earth OIJSCr- 

vation satcllitcs (MOS-I. ATMOS), and scientific 

satcllitcs (ROSAT, EURECA. ASTRO-SPAS). 

suitablc AOCS-concepts arc discusscd in thc papcr. 

2. REQUiREhlENTS AND CONSTRAINTS 

In addition to scniccs alrcadv gcricraliy available. 

tactical satcllitcs of the typc in quc::ion hcrc arc 

supposed to provide on sbon noticc and particular 

rcqucst irnprovcd and cfficicnt scrviccs in at Icact 

onc. prcfcrrably scvcral of thc following fivc mi;sion 

arcns: 

- communic:itions, e.g. from. to md bctwccn 

mobile units on ground or bctwccn satcllitcs 

- wcn:hcr, i.c. dctilcd actual wcathcr conditions 

and prediction in dcfinitc local weas 

23-1

23-2 

. 

- missile wnrninq, e.g. against tactical h\Iistic 

missilcs, to possibly improve thc cfficicncy of 

dcfcnsivc actions 

- nnviir.ntion_ to contributc to thc provision of 

- 

highly accuratc navigation data 

ohscrvntion. survcillans and verificatinn, c.5. to 

chcck disllrmamcnt trcaty tiolation or - in a 

battlc ficld sccnario - to monitor [orcc dcploy- 

mcnts and to provide target rccognition. tbcatcr 

targctins and vcrification 

As a conscqucncc of thc gcncral mission objcctivcs 

oiillincd abovc, opcratiod rind performancc rc- 

quircrncnts. cncironnrcntal conditions and son- 

straints arc imposcd on thc Attitude- and Orbit 

Control Systcm. which arc subscqucntlv outlincd to 

establish thc gcncral framc for thc AOCS. 

2.1 hllssinn rind Faylaad Kcquiremcnls 

For varinus rcisons likc launch cost. in;m in orbit. 

imasc rcsolution or powcr rixpircmcnls of obscrvntion 

payloads thc spacecraft undcr discussion 

will hc injcctcd into rclativciy low cnrth orbits 

(about 300 to 1Mn) km). In gcncrd near pol;ir. sunsynchronous. 

cirulw orbits arc prcfcrrcd, which arc 

charactcrizcd by thc condition that lhc .product of 

three orhit paramctcrs, i.e. orbit scmi-mnjor ;~l(is. 

cxccntricity, and inclination has a spccific numcri. 

cal vduc. cntrining thc orbit node to rotatc t\ith 

onc rcvolution pcr ycar. For optical obscwation 

pavlaods "dawn orbits' arc particularly suited. In 

this casc the S/C will always view thc surfacc of thc 

carth at any given latitud: at thc siunc local time 

(sce e.g. rcf. 1, p. 68). A graphical rcprcscntation 

of thc orbit pararnetcrs 'inclination" (in dcg.), rhc 

"orbit pcriod" (in minutcs) ;ind thc "SIC velocity" 

.(in rnfscc) as a function of altitudc (in km) for 

circular sun synchronous orbi~s is givcn in ligs. 

2.1-la to 2.1-lc of Anncx I. r,:spectivcly. 

For such orbits thc revisit period of spccihc tcrrc. 

strial locations in equatorial regions or ot law earth 

latitude for ;I sin& S/C m;iv bc unaccctahlv long 

for tactical earth obscrvation rcquircmcnts. whcrcas 

the rcvisit pcriod in mostly unintcrcstiny polar 

regions in principle equals thc orbit rcvoltltion 

pcriod. This situation can tic improved as follows: 

- For obscrvation of a particular re+n on earth 

the SIC is launched into n dcdicatcd orbit. thc 

revohtion period of which is an intcgcr fraction 

of 24 hours. Thc revisit limc will then bc at 

lcasl mcc or cven scvcral limes a clay. For in- 

stance (ref. figs. 2.1-la and -1b) a satcllitc in 

- 

sun-synchronous orbit of (about) 570 km altitudc 

and 97.6 dcg inclination will have an orbit pe- 

riod of 96 min aid p~ over the same area 

cvcry 15'" revolution. 16 orbits per 24 h (orbit 

period ol M mh) would cvcn allow to revisit the 

same targct cvcry 12 hours (in thc descending 

N/S and ascending SM orbit crossing) but rcqui- 

re an altitudc of 275 km (inclination 96.56 dcg) 

and the S/C would experience sigificant air 

drag as wil? bc discussed latcr (fig. 2.1-3, AMCX 

1). 

A numbcr of payloads can provide large ranges 

of "sidc looking" capability, cnabliag observation 

of a local arc3 undcr different aspect angles in 

succcssivc orbits. Exccpt when phased am/ 

antcnnas arc crnploycd this generally rcquircs 

nicch;inical slcwing of optics, mirrors ;rnd/or 

rcflcctors and in turn inay givcn risc to sipifi- 

cm intcrnnl torques and associated attitude 

pcrturb;itiocs. 

- Selection of low inclination orbits instead of 

quasi-polar orbits with inclination angles covc- 

ring the rqc of gcographical latitude of parti- 

- 

cular intcrcst. 

Pkicing ii sufficicnt numbcr of satcuitcs into 

appropriatcly inclined. mutually synchronizcd 

orbit to cnsurc r,hc dcsircd covcragc probability. 

Thc rchtionship lictwccn thc numbcr of satcllitcs 

rccjuircd to cnsurc continuous coveragc from any 

point on thc carrrh undcr a local elcvatim andc of 

at Icast IO dcg as a function of circular orhit dtitu- 

dc is shown in fig. 2.1-2 (rcf. 2 ) of Anncx 1. Pro- 

per sclcction of orbit inclin:ition and phasing of thc 

cirbitiny satcllitcs is rcquircd. Particular cxamplcs of 

Low Earth Orbit (LEO) Communication Satcllitc 

Systems c.g. MOTOROLNIRIDIUM or TRW- 

ODYSSEY rcquiriny 77/19, satellites at 735/10350 

km dtitudc arc schematically indicated in this hgu- 

rc. Thc numbcr of satcllitcs Jccrcascs, of course if 

poliir covcraqr is not rcquircd. In any casc orbit 

inclination ;ind phasing of individual SIC forming 

p;irt of a satellite syctcm hnvc to bc rclaincd or 

respectively corrcctcd in c;rsc of dcvintions from 

nominal during opcrational lirc timc. 

For thc asscssmcnt of the amount (m,) of rnono- 

propellant hydrazinc rcquircd to maintain a circular 

orbit of givcn, rclativcly low altitudc, rcfcrcncc is 

made to Eg. 2.1-3 (Anncx l), where thc drag factor 

(9 pcr day (d) and unit cross-sclcctional iirca (0) 

of thc S/C is plottcd. The propellant mass is thcn 

givcn by

m, = f*U*d 

Whcn liquid bipropellant cngines providing hi&r 

spccific impulse are used, thc propellant mass is 

:rbut 23 5 lower. In addition to altitude corrcc- 

tions inclination corrections may ham to be pcrfor- 

mcd. The inclination drift at allitudcs bctwccn BO/ 

km and 3'90 km amounts to about 0.2 dcdycar U?$,. 

requires approxhntcly 27 dscc velocity incrcmcnbi,; a 

for corrcction. 

:;$:' 

I ;.\ 

22 Sprtcecnft Physicul Chnmcteristics , 

:.;,*.!$ 

' .: . ' 

It is, of coursc not the objcctivc s)f this papct to 

claboratc on TACSAT rncchanical, struct~ral. 

powcr and payload dcsign Ccaturcs. In vicw of.thc 

fact, however, that thc AOCS is thc S/C subsyskrn 

with thc largcst numbcr of funciion:rl ;itid hardwa- 

rc intcrfaccs with othcr subsvstcms ;is wcll ;IS siitcl- 

Iitc opcraiional prcxcdurcs. it is rcprtlcd ncccssa- 

ry to cstnhlish at least a rouyh framc of thc cxbcc- 

tcd SIC physical charactcristics: 

- Thc S/C mass targctcd Tor ccmsidcratiod in 

TACSAT missions is bctwccn 200 and 70(1 kg 

i.c. within thc payload ranpc of dcdicatcd Iiiun- 

- 

- 

chcrs like YEGrISUS. TAURUS etc. 

Onboard clcctrical powcr gcncration capabilitv 

of about 1 k W is rcgardcd necessary to ;daw 

for half orbit cclipsc pcriods and 

opcration of microwave pavloads (SAH typi- 

cal avcragc powcr 500 W. peak powcr about 

10 kW/pulsc) 

Conscqucntly a solx array surfacc ;ma of 

about X to 10 rn' will bc rcquircd corrcsponding 

to a mass contribution of about 16 to 20 kg if ;I 

tlTicai weight factor of 2 kgtn' and usc of convcntional 

silicon solar cclls arc assumed. 

solar cells providing about 30 '.T incrcasc in 

power output per unit surfacc a m will Iiavc to 

he cxcludcd for cost rcasons. 

S/C gcornctricd configurations arc gcncrallv 

detcrmincd by the constiaints irnposcd by 

thc launchcr cargo bay hncnsions. shape 

and acceleration load. . 

thc payload rcquircmcnts (including poucr). 

If thc fundamental configuration shall bc riqained 

for thc diffcrcnt mission applications as 

outlined under section 2, thc gcometrical requircments 

associated with 

optical observation payloads i.e. telcscopcs 

of sufficicnt f d length, operating in the 

visible and infrarcd region, and requiring 

cooling of the detector mays (e.g. Liquid 

helium dcwers) andlor 

microwave payloads (SAR) with large area 

(p,-wavefecd or phased array) antennas suffi- 

ciently cnended in long track direction 

arc cxpcctcd to be the dcsign drivers. Some 

squarc-shaped. modular ccntral body truss struc- 

ture with triangular, rectangular or hexagonal 

cross-scctional area seems to be principly ade- 

quate and will provide the necessary free surfa- 

ces for the housing the folded solar arrnys and 

cnsurc unobstructcd field of vicw for flttitudc 

measurcmcnt scnsors and frce spacc for attitude 

and orbit control rcaction jets. 

Ouitc 3 numbcr of clcisting dcsings (e.g. LAND- 

SAT 6 - ref.3, MOS-1, sec sccrion 3.2) are 

cquippcd with a single wing solar array giving 

risc to Iargc (solar) disturbancc torques and 

clisturbancc torque changcs during cclipsc tran- 

sitions. due to thc unsymmetrical configurat ion. 

From the AOCS point of view a symmetrical 

configuration as generally adopted for gcosyn- 

chronous communication satellites is of course 

highly dcsirablc. In vicw of thc rcquircd flcxibi- 

litv for frcc sclcction of thc orbit inclination 

according to thc tactical rcquircmcnts thc solar 

array is assumed to be oricntahic not only as 

usunl around its axis of spmciry, but aLco about 

an axis pcrpcndicular to the first iixis of rotation. 

hlotor drivcn dcployrncnt mcchmisrns iis for 

instancc implcmcntcd in EUTELSAT I1 can bc 

casily modificd to allow scrvo-controllcd uticu- 

lath of the solar array at the yokc junction to 

cnabk oricntation of thc solar array surfacc to 

thc sun for a largc rangc of orbit inclinations. 

Morcovcr by controlling thc solar array rotation 

about two axis, solar pressure torque compcnsa- 

tion tcchniqucs can bc applied to irnprovc attitu- 

dc control pcrfarmancc and onboard angular 

morncntum rnanagcmcnt. - 

In lis. 2.2-la (Annex 1) such a variable solar array 

configuration cap;ibility is schcmatical!y indicated. 

Unsymmetrical dcflcction of oppositc solar arrays 

w.r.1. the sun dircction will gcncrrrtc solar prcssurc 

torqucs about an Luris pcrpcndicular to thc sun 

incidcncc plmc, counter-rotation as shown in Fig. 

2.2-lb will give risc to "wind mill torques" acting 

around the sun line. 

23-3

234 

L -'*. 

f . . 

23 AOCS Opntioncrl und Perl'ormtlncc Rc- 

quircrntnU I 

From thc mission and payload requirements the 

detailed functional and performance rtqukements 

are dcrivcd. 

Typical attitude control accuracy and linc-of-sight 

stability requircments for the missions out-lined in 

scction 2 iuc sumarizcd in table 2.3-;1. 

Furthcrrnore AOCS relatcd Data Managxncnt and 

Control (DMC) tasks havc to bc pcrformed, in 

particular: 

- Surucillance and control of subsystems likc thcr- 

mal- and powcr monitoring and control 

Fault dctcction. isolation and rccovcry 

- Mission- and operational tclcmctry and tclc- 

command data handling . 

Operational tasks to be covered by the AOCS ;ire 

for instancc 

- provision of complctc onboilrd autonomy during 

periods of no gound station contact. 

- orbit corrcctions on time tagcd commands. 

- updating and propagation of orbit modcl para- 

mctcrs ;md corrclrrtion with instantnncous atti- 

tudc data. 

3. ATTITUDE- AND ORRlT CONTROL 

SI'STEhl CONCEPTS 

Subscqucntlv the chuacrcristic fcaturcs of cnnucn- 

tional A0C.S for communication- and application 

satcllitcs wiU be outlincd. altcrnativc equipment 

and conccpts for attitudc measurcmcat and control 

will be discusscd and thcu fcasibiiity for applica- 

tion in TACSAT missions will be i~~scsscd. 

3.1 Typical Conventional AOCS Charrtcteristics 

AOCS tcchnology and conccpts of most S/C prcsenti? 

opcrationnl or in production arc very simihr. 

In particular the thrcc-axis attitude stahilimtion 

principlc is ycncrally applied. primwilv in vkw 

ol thc growth potential of ttjcsoiiboard power. subsystem. 

For casc of rcfcrcn$e the discussion of 

convcntionnl AOCS charaCtei)hljq..to follow wil 

k based on satellite families.d6i .which the AOCS 

design authority was with DASA (Deutsche . aero- 

, 2 

. :

sensors, gyros) intorporated in the AOCS. the 

3-axis stabilization tcchnology fo: transfer orbit 

operations aod during (repeated) apogec boost 

maneuvers has been established using for the 

fist time a died Liquid bipropellant propul- 

sion systcm for attitude control, orbit control 

and Apogee Boost Maneuver (ABM). Furthcr- 

more these SIC arc equipped with a coarse 

bodv control and M additional antenna fine 

pointing system based on RF-sensing and con- 

trol of the TX-antenna beam orientation \k.r.t. 

it ground beacon to an accuracy bcttcr thatl 2 

0.025 dcg cach axis. Spccial reacquisition don- 

ccpts in case of attitudc loss or battcry fa!!urc 

(recovcry after ilipsej havc bccn incorpor3tcd. 

All attitude mcasurcmcnt. data updatinp. for- 

matting, monitorinv, mock scqucncing and 

control futctions, cxccpt antenna (struclbral 

flcxibilitv) stabilization havc bccn implcmcntcd 

in ;I ccnlral. diytd. intcrnallv rcdundant onbo- 

ardcornputcr. TV-SAT FM1 had to bc dcor- 

bited bccausc onc solar array wing failcd to 

deplov in GSO and simultancously hlockcd dc- 

ploymcnt of an antcnna rcflcctor. Thc rotut- 

ness of the AOCS dcsign upcrating then utndcr 

most ahtiorma1 conditions,. was. howcvcr, tin- 

intcntioually dcmonstratcd. as wcll as its flc:5bi- 

lity offcrcd by in-orbit rcprogamming of thc 

onboard computer, whcn for dirfcrcnt attempts 

of rescuc maneuvers. additional control modcs 

and scqucnccs have been implemcntcd. 

DFS-KOPERNIKUS a smaller class S/C family 

of different geomctricd conligurat.icn ("rabbitear. 

antcnna arrangement. liquid bipropcllant 

tanks in ABM dicction) is 3-axk stabililcd in 

TO and GSO. the solar arrays being fdlv deployed 

drcadv in transfcr orbit and during 

(repeatcd) liquid bipropellant Apogce Boost 

Maoeuvcrs. For this operational motlc the 

AOCS dcsign has to cope with panel oscillations 

and proFcUant sloshing phcnorncna in 

ovcrlappin): frcqucncy bands. the sloshing dynamics 

cxpcriencing pole-zcro inqersion during 

thc mancuver. Concepts and provisions for in 

orbit gyro calibration have becn.incorporated to 

also ensure compatibility with midnight launch 

conditions. 

As compared to the previous communication 

satellite in the EUTELSAT I1 AOCS the follo- 

Wiag innovations have been incorporated: 

The capability to acquire thc earth MY time 

of the day 

A S/W safe mode for minimitation of outage 

duration in GSO 

An optimum Nutation and Angular Momen- 

tum Control concept to ensure higher yaw ac- 

curacy (as compared to WHECON) io pre- 

sence df high disturbace torques (NM row- 

yaw control) 

The capability to perform orbit corrcctions 

with yaw refercnce from gyro, i.c. my time 

per day (also io colinearity regions) 

High pointing accuracy during station kee- 

ping maneuver (SKM) trmsients 

In-flight recording of the thruster firing . 

history for propellant budget monitoring 

3.12 Eodt obseniarion und scientific application 

satellites 

World wide a lrtrgc variety of IOW carth orbit satel- 

lites for all typcs of tcrrcstrial and environmental 

obscrvation as wcll as scicntific and research pur- 

poses havc hccn dcsigncd. dcvclopcd and lawched 

within thc national progams of the rcspcctivc 

countries or by intcrnational agencics (c g. LAND- 

SAT. SWSAT. SPOT, ERS ctc.). Thcy arc cquip- 

pcd with dcdicatcd, optical. infrarcd. multispectral 

or microwave payloads, their AOC being tailored 

for thc individual requirements. Subsequently a 

short rcvicw of thc typical AOCS characteristics of 

this type of SIC will be given on thc basis of satelli- 

tc examples. the attitudc and orbit control subsy- 

stems of which have been developed undcr DASA 

rcsponsibility. 

Table 3.1-3 gives a rcvicw of these satellites, their 

dcvcloprncnt pcriocl and launch schedule. Tablc 

3.1-4 summarizes their attitude control conccpts 

and performances characteristics 

- The AOCS for MOS-1, the fist Japanese Mari- 

ne Obscrvation Satellite was designed and dcve- 

loped up to and including the levcl of dcvelop- 

mcnt model hardware implemcntation and clo- 

sed loop subsystcm functional- and performancc 

testing in a joint GcrrnidJapancsc development 

and training progm. Engineering- and flight 

modcl manufacturing and acceptance testing has 

then been performed under responsibility of 

Mitsubishi Electric Cooporation. The SIC wcre 

launched into about 900 km circular sun syn- 

chronous orbits. Orbit correction capability (and 

back-up wheel unloading) is provided by B set of 

hydrazine thrusters. Normal mode control is 

performed by two momentum wbecls in V-codi- 

234

i3-6 

yuratiori. Whcel desaturatioo is nominally pcr- 

formed usiog magnetic torquers in quarter orbit 

cycling. 

- ROSAT, dcvcloped within a German, UY US 

scientific satcute program operates in a 5% km 

circular orbit, inclined by 53' w.r.t thc equdtori- 

a1 plane. Attitude reference is established by 

high prccision star Sensors and a set of 4 inte- 

grating gyros (one skcwed). A coarsc SUO sen- 

sor asscmbly with 4-w FOV providing two axis 

attitudc rcfcrencc is used for initial and einer- 

gcncv sun acquisition. For thc scicntific migsion 

two operational mcdcs are forcsecn: 

In scanmodc the S/C rotiitcs about tllc sun 

linc and the telcscopc mountcd pcrpenUicu- 

I;ir to thc axis of rotation performs witbin o 

months a completc sky suncv for dctcction 

cif ncw X-ray sources 

In pointing mode thc tclcscopc is rotatsd to 

dircctions sclccicd by thc groundstatioh ior 

dcdicafcd sourcc observation 

In both n;odcs of opcration ,inertial attitude 

refcrcncc is dcrivcd from star scnsor rneasurc- 

mcnts and star identifications with i\n ooboard 

storcd stnr cataloguc. A sct of 4 rcnction wheels 

in skcwcd arrangement gcncratcs tlic ncccssary 

control torques. A thrcc axis magnctomcrcr 2nd 

3 mqnctic torqucrs arc urd rcspcctivcly for 

- 

- 

dctcrmination of the carth mnbmetic ticld vcctor 

and whcel uiloading. Duc to'cquipmcnt f7.1 ,i urcs 

emergency stratcgcs for attitudc gcncration 

from mapctomcter mcasurcmcnts and an 

carth mapctic field modcl onboard of the S.'C 

had to be dcvclopcd and implcmcntcd. 

EURECA. the EUropcan P.€tricv;lblc CArricr. 

dcvelopctl by DASA under ESA contract. shall 

be the platform for 5 diffcrcnt scicntific missions. 

whcrc thc first mission (launch and rcturn 

by shuttic) performs c,xpcrimcnts under ,U-y 

conditions. Thc AOCS (a coopcration bctwcen 

DASA. MATRA. GALILEO. LABEN) is able 

to pcrfoim orbit chmyc mancuvcrs (boost-up. 

boost-down, inclination corrcction) suo and 

earth acquisitions with a. hydrazine thrustcr 

systcm and is suo oricntcd in normal opcration 

with a low level cold gas system supported by 

mapnetic torquers. 

ASTRO-SPAS is a reusablc satellite platform 

built by DASA udcr DAM contract. which 

shall fly once per ycar, beginning in 1993.11 w i l l 

be launched with the US Space Shuttle. sct frec 

in orbit ind also berthed from the snnie shuttle. 

Its ACS is equipped with a rate integrating gyro 

packagc, d high precision star sensor, a GPS 

rcccivcr and a sct of cold gas thrustcrs. Similiar 

to the ROSAT mission two principle modes of 

operation can be performed 

In pointing mode the telescope is oriented 

into ground selected orientations 

lo scanmode earth atmospherc observations 

arc performed whcrc the earth refcrencc 

information frame is obtained from the GPS 

receker. 

As io ROSAT, in both mides inertial attitude is 

obtaincd from star sensor measurcmeots and 

star catalogucs. 

32 AOCS Alternatives, Trade-offs and Trends 

Whcn discussing AOCS altcrnativcs for TACSAI' 

;ipplications. the ;ispccts associatcd with attitudc 

rcl'crcncc gcneration. forcc- and torque generation 

and attitilde control conccpts including thc relatcd 

cquipmcnt and software havc IO bc adrcssed. 

32.1 ..lrti!ude rcference generation equipment 

The gcncral rcqucst for low cost solutions irnplics 

th;tt attitudc mcasurcmcnt equipment should bc 

uscd. which just satisfics the subsystcm performan- 

cc necds. In vicw of thc large vnricty of mission 

objcctivcs and associatcd pcrformancc requirements 

(sec tablc 2.3-I), however. equipment of cquivalcnt 

mcasurcmcnt quality standard\ (and costs) has to 

bc sclcctcd. Conscqucotly the AOCS concept niust 

providc thc ncccssary flexibility to tie-in different 

kinds of mcasurcrncnt dcvices as rcquested by the 

application case. Thc typcs of cquipment io quc- 

stion arc of coursc Infra-Red earth Sensors (IRS), 

Precision Sun Scnsors (PSS), STar-Sensors (STS) 

and Ratc Integrating Qwos (RIG). Apart from 

convcntional dcsign performancc chxractcristics. 

ncw dcsiys arc of particular interest. For the typi- 

cal performance data. rcfcrmce is made to table 

3.2- 1. 

322 Force and torque generation rechnolom 

Spacccraft dircctly injcctcd into targct orhi:s with 

Limited orbital accuracy deinands and/or or rclati- 

vely short operational lifc time may not rcquirc 

orbit corrections anti conscqiicotly also no propul- 

sion subsystem. In gcocral, however, orbit COITCC- 

lions will be nccesmy to ilchicve and maintain the 

desired operational orbit. In view of aspccts likc 

inherently different propellat utilivtioo efficiency, 

I

th: burn-our (or dry) mm and subsystcm complc- 

xity, the most appropriate solution prim;:rily 

dcpcnds on thc total velocity incrrment to be 

gcncratcd for the &ion in question. 

In tablcs 3.2-2 and 3.2-3 characteristic parameters 

of catalytic, monopropellant hydrakc- and liquid 

bipropcllant thrusters respcctivcly arc summarizcd. 

For casc of rcfcrcnce. again equipment available 

from DASA in-house manufacturiug has bccn dscd 

as a basis of comparison. The parameters of the 

liquid bipropcUant rcaction jcts rcfcr IO "sccbnd 

ycncration" thrusters. Thcy diffcr from prcviious 

snd convcntional design in that thc combustion 

chambcr is made of Platinum-Rhodium dloy, 

which allows highcr opcrational tempcraturcs and 

bettcr cfficicncy than thc classical rcgcncrarivc 

chamber cooling principlc. High pulsc rcproducibi- 

litv is cnsurcd by the swirl iitomizcr injection in- 

stcad of cnnc injcction principlc xed. 

The diagrams of fiy;lrcs 3.2-1 and 3.2-2 show thc 

spccific impulse and impulse hit sizc rcspccitvclv 

of thc DASA ION and 4N 2"' gcncration thrustcrs 

in pulscd modc of opcration as function of thrustcr 

ON-time in cornpanson to convcntional rcaction 

jcts. Smilll minimum impulsc bit six (and ;iccurim 

rcproducibilitv) are particularlv important fcaturcs 

from thc AOCS point of vic~. 

Figure 3.2-3 shows the graphicai rcprcscntation of 

tradc-off rcsults, performed to idcntify thc bcncfit 

of liquid bipropellant propulsion subsystcm total 

mass including tanks. propellant. piping, and thru- 

stcr systcm for a satcllitc with 8 small AOCS-thru- 

sters as compared to mono-propellant tcchnoloq. 

It turns out that thc liquid biprooctlant tccli~iolog 

is alway supcrior and offcrs incrcasing m m bcnctit 

ovcr monopropellant systcms for incrcasing total 

impulse (Ss) to be gcncratcd. 

While during orbit corrcction mancuvcrs thc di- 

sturbancc torqucs cncountcrcd during AV-genera- 

tion duc to SIC ccntrc of mass offscts arc usually 

rclativcly high and ncccssitatc countcr;iction by 

(thc samc) IhrJstcr systcm in ON- or OFF-modu- 

latcd operation. cacrnal torqucs for attitudc con- 

trol or momentum manayemcnt in normal opcra- 

tion may also be gcncratcd by magcto-torquers. 

Thc rclativcly high magnctic ficld strcngth of thc 

ewth at low orbit altitudes is particularlv suitcd for 

magnetic torquing. 

Table 3.2-4 summarizes the most important para- 

metcis of torquc rods as manufacturcd by ITHA- 

CO. I-iigh pcrformancc attitude control anti stabili- 

zlltion of all SIC axes in the neccssary dynamic 

range is bat accomplishcd by angular momentum 

storsgc deviccs i.c. rcaction- and momentum 

wheels. Fig. 3.2-4 givcs a small selcction only of 

possible wheel arrangements and combinations for 

gcnerathg (idternid) control torques about one or 

several S/C 3x6 andlor bias momentum perpendi- 

cular to the orbit plane. As already mentioned with 

the typical AOCS concepts of section 3.1 the bias 

momentum principlc offcrs particular advantagcs if 

attitudc reference about all thce S/C ruciS is not 

continuously available. Therefore momcntum-/rex- 

tion whccl combinations arc expectcd to cover most 

applications. A summary of characteristic paramc- 

tcrs of off-the-shclf cquipmcnt (manufacturer: 

TELDIX) is given in tablc 3.2-4 of Annex 2. 

23-1 

323 Fcusibilify assessment of control co..tcepts for , 

TACSA 7 missions 

From thc prcdous discussions of mission objcctivcs. 

control concepts, altcrnativcs and cquiprncnt trade- 

offs and thc AOCS rcquircmcnts as summarized in 

tablc 1.3-1 it becomes obvious that 

- thc classical bias momentum systcm with two- 

rvd.; attitudc rcfcrcnce and WHECON control 

can only satisfy thc nccds for communication 

missions. whcrc no particularly stringcnt rcquirc- 

mcnts arc imposcd on thc Linc-of-Sight (LOS) 

stability. 

- In thc case of wcathcr satcllitcs, for thc limitcd 

periods of ..:arming or picture-taking adcquntc 

LOS-stability must bc eacurcd. absolute attitudc 

pointing accuracy is not so critical 

- For carth obscntation missions. depcnding on 

thc obscrvation payload concept (push-broom. 

dctcctor array, scan mirror, mul!i-spcctral dc- 

compnsiiion) and ground rcsolution both accura- 

te pointing and LOS-stability bccomc incrca- 

singly important. Payload operation'will have to 

he intcrruptcd during orbit coh?ction ;i'nd trnn- 

sicnt pcriods. In normal modc whccl control 

about 311 three axcs accompanied with high 

prccision altitude rcferencc has to bc forcsccn. 

Suntcillnncc and vcrification bciny also carth 

obscrvntion tasks ncccssarilv imposc at Icast the 

siunc rcquircmcnts on the AOCS pnrtlv cvcc in 

prcscncc of payload-induccd perturbation envi- 

rocmcnt. p-wavc payloads additionally rcquirc 

highly accuratc orbit data (GPS), LOS stability 

and accuratc attitudc rcconstitution ovcr lor: 

pcriods (minutcs). Payload data proccssing and 

payloadhttitudc data fusion is gcncrally rcquircd 

cotraining high dcmanh on onboard computa-

23-8 

tional and storzge capacity aad TM-lwiority 

during ground station contact. 

4. AOCS BASELINE CONCEPT 

In the past SIC design has oftcn been pcrformed 

with thc emphasis placed primarily on mecltankid 

and structural configurdtion aspccts wit bout taking 

into account thc impact on othcr subsystems to the 

ncccssary cxtcnt. As far as the AOCS is concer- 

ncd. it is of course understood that its SIC intcrnal 

and cncrnd communication- and ~CCCSS capahili- 

tics can providc the ncccsary flcx&ilitv for adapta- 

tions to a givcn environment hut disrccarding 

ccrtain demands from thc AOCS on thc S.'C hus 

and cquipmrnt configuration would entrain thc 

nc+cssiiy to establish a dedicated A( ICS-concept 

;ind mnkc ;I special dcsign hir cnch misTicm Ihicc- 

live and associatcd payload undcr cliscussion hcrc. 

Thc approach outlincd suhscqucntiv .time ,I! rna- 

king hcct possiblc usc I)! the inhcrcnt Ilcubilitv 

fcaturc\ of thc AOCS for Ihc bcnctit id thc ovcrall 

systcm and is c.rpcctcd to rncct thc different mis- 

sion rcquircrncnts without rn;ijnr modifications. 

tkncral Ccaturcs of the concept in cluestion arc: 

a The AOCS shall hc dcsiuncd to incorporatc 

scnsor and actuator equipmrn! altcrnalivclv o r 

in cornhination as rcquircd to mccr the pointinp 

and LOS sthilitv pcrform;incc of labl:: 3 - 1 . 

The Data ,Managcmcnt and Ccintrol (DMC) 

functions of section 2.3 shall he intcarntcd with 

thc AOCS (Intcgratcd Control and Data llrrna- 

- 

- 

pcmcnt System - ICDSI. 

Data transmission within :hc SIC shall 1% pcr- 

formcd hv mcans of a tiiy.itai scriai iI:ita hus. 

HAV and S/W implementation shall bc b:iscd. 

Thc capability of pcrforminu ortiit c!orrcctions 

shall be prcwidcd. 

Payload Ja~a managcrncnt (and prcproccwnc). 

which rnav nccesitatc cxtr-mclv high cornputd. 

tional and storage efforts is rcpardcd ;IS ;I lark 

complctcly scpruatcd from the ICDS. 

4.1 Srnsnr Conngumlon 

It is undcrstood that the wholc scale id ni. *ssions 

under discussioo hcrc cur bc best scmcd. if the 

highest pcrformancc attitude mcasurcrncni quipmcnt 

is xlcctcd. i.e. prccision star scmors a1.d ratc 

inlegratin8 gyros in strapdinvn mdc of opcration. 

This will. however. bc thc most cxpcnsive 

solution and rcprcuni M ovcrdcsip Cor less omhitious, 

e.g. communication applications. Subscqucnt- 

i 

ly the attempt is made to dcfme a sensor configu- 

ration. which could cover dl situations, but incvita- 

bly imposes restrictions on the system layout. 

It is assumed that TACSATS on request of strate- 

gic demands shall operated in bctwcen near polar 

(sun synchronous) down to near equatorial low 

earth orbits. the sun incidence mgk with rcspect to 

thc orbit normal also possibly varying between zero 

and M". If it is furthermore iusumcd that thc array 

dcsign provides thc double axis orientation capabili- 

ty discusscd earlier, an orientation of the solar 

array axis of rotation approximately parallcl to the 

dircction of motion is favourable (see fig. 4.1-la) 

for vcry low altitude orbits (e Soc) km) due to 

- 

air drag (sce fig. 2.1-3) 

if the sun is in 3 region around the normal fo 

Ihc orbit planc (say 2 45 dcg) 

- hi low inclinations of thc orbit planc w.r.1. thc 

cqu;l(Or 

An owntation ol thc SA. xis of rotation pcrpcn- 

ilicular to thc dircction of S/C motion (parallcl to 

the earth surface) is more favourablc (sec fig. 4.1- 

Ibl 

- for high altitude. high inclination (near polar) 

orbits 

- lor low sun incidcncc angles w.r.1. the orbit 

planc 

Thc highest flcxibilitv would bc cnsurcd. if - for 

rcspcctivc application orbits - the SIC orientation 

w.r.1. flight dircction could be sclcctcd cithcr way 

.id thc payload (pointins in nabr dircction) alter- 

nativclv rotatcd by 'XI dcgrccs around its line of 

si*t in the S/C. 

A icasiblc uranpcmcnt of all (optical) ;il!itudc 

rnc3surcrncnt cquipmcnt. is schematically indicatcd 

in fig. 4.1-2. The S/C axes arc dcnotcd bv x. y, z 

(roll. pitch. yaw). whcrc the yaw-axis is always 

nadir-pointing. Thc schematic of optical scnsor 

;irranpcrncnt on thc S/C body surfacc of fig. 4.1-2 

shall not postulate that all scnsors indicatcd hmc to 

hc available simultancouslv in thc s;imc S!C. For 

ccimmur.ication missions e.g. thc cxpcnsivc sensor is 

not rcquircd. in hi@ performance missions with 

stcllar-incrtial rcfcrcncc on the other hand thc IRS 

is obsolctc. 

Thc conical scan IRS points 'into S/C y-direction 

(or opposite to it. depending on thc sun incidence 

angle w.r.1. the orbit). which is tbc dircction of 

motion in fhc CSC of fig. 4.1-la and scans thc earth 

undcrneath wdcr 0 JS dcg cone angJe. Thc star 

sensor is mounted on the -z face (nwoy from the 

earth) inched into the pducction (or opposite IO 

it) scanning the sky as the S/C rotates around its X- 

23-10 

between the modulator output g md the thruster 

activation 3 are stored in the on board computer 

memory accordhg to t;iblc 4.2-2. 

Forcc Gencration 

According lo figures 4.1-1. there are two diffcrent 

S/C orientations in orbit. Fur 50th cases, table 4.2- 

3 summarizes the nominal and redundant thrustcr 

sets. which are used for orbit corrections in normal 

and tangential direction. 

423 Momennrm and -reactioa whee, 

The preferred wheel arrangement a. shown in fig. 

4.2-2 ronsists of 

Two flywhcels in a V-configuration in a plane 

rotated about thc y-axis by an ;ingle q 

Two rcilction whccls alonq thc x- and L - ~ C S 

In the nominal contip~ration only ohc tl~u.hccl 

(cither FMW I or FMW 2) and hoth rcaction 

whccls ilrc in opcration. all running ;it bias speeds 

such that a residual bias angular momcntum Gector 

is nominallv perpcndiculx to the orbit pland. 

In cse of a failure of one reaction whccl thc resi- 

dual rcaction wheel and hoth flphcels udll bc 

used. 

If 00 the other hand the ‘nomind‘ flywheel fails. 

the cold redundant futcd momentum whccl id acti- 

vated. 

43 AOCS HIW and SnV Impletneatation 

Prcsentlv. based on a cooperation agrcerncni bet- 

ween DASA. Acrospatialc. md Alenia Spado joint 

ciforts arc bein8 undertakcn io devclop and qualify 

an ‘Intclpatcd Control and Data Al;ina~cmcnt 

System’ (ICDS) for nem gcncration communication 

and application satellites. within the so-called ‘Spa- 

ccbus Improvcmcnt Program‘ (SIP). This prayam 

also incorporates devclopmcnt and qu;ilificaiion of 

advanccd components like the precision sun sensor 

(tablc 3.2. I), second generation liquid bipropellant 

thrusters (table 3.2-3) and in particular aLw ;I po- 

werful Onboard computer Unit (ORCU) and the 

associated operational and application SW. The 

ICDS in question (see ref. 10) is to the largest 

cment directly suited or easily adaptable for the 

case under discussion here. The main difference to 

the concept favoured for communiwtion SIC ap- 

plications consists in that for TACSAT missions a 

‘two computer solution“ insicod of a nnc ctnval 

compute approach is regarded absolutely necessiuy 

in View of the flexibility- and computational requi- 

rcments of thc different payloads. The amount of 

payioad data to be transmitted to ground within 

short ground cantact intervals will furthermore 

necessitate direct priority link to the telemetry 

system. Subsequently only the AOCS part of the 

ICDS concept, which then can be regarded largely 

indcpcndcnt from the payload data management 

systcm will be shortly outlined. 

Hardware 

Fig. 4.3-1 shows the ICJIS hardware configuration 

(without rcdundmcies) i.e. not only the AOCS-, but 

also the DMC hardwarc units are represented. 

Thc functional sharing of these units and comments 

on thc notations within ligure 4.3-1 arc listed in 

table 4.3- I. 

Thc serial OBDH Data Bus is Ihc link within a 

modular cxpanda1)lc t\OCS. 

As Iar ;is newly devclopcd cquipmcnt and signal 

conditioning clcctronics arc conccrncd (e.g. sun 

sensor clcctronics. UPSE), t hc intcrfaces are de- 

sipncd such as to directlv match the data bus IF 

rcquircmrnts. Thc signal conditioning for classical. 

off-thc-shelf equipment (earth sensors. gyros. 

whcels. star scntors) to thc OBDH data bus format 

is performed in the Platform ‘Interface Unit 

(PRU). 

The ccntral component of the ICDS hardware is 

t’lc On Board Computer Unit (OBCU). It has 

functional interfaces with the ground scpcnt and 

all on-board S/C subsystems for the distribution of 

commands and thc acqi:isition of data. Figure 4.3-2 

shows the blockdiagram of the OBCU. The 

functional units arc: 

- processor Modulc (PM) 

16 bit processor. MIL-STD 1750 A instruc- 

tion set ruchitccrurc 

processing power at least loo0 kips lor DAIS 

MIX (Digital Aeronautics Instr. Set - 

ZOhlHz) 

RAM 123 kwords of 16 bits 

ROM 96 kwords of 16 bits 

- Telccommand Dccodcr bModulc (TC) 

- Tckmcrry Modulc (TM) 

- Reconlipation Modulc (RM) 

supports autonomous satellite failure detcc- 

tion. isolation and recovery (FDIR) 

functional elements: Alarm Level Manage- 

ment, OBCU Reconfiguration Commands. 

0 B D H - bus R e c o n f ig u r H t ion CO m m a n d s, 

Thruster On-Time Control 

- Safeguard Memory (SGM)

contains thc H/w systcm configuration data 

,and dynnaric S/W pcuamctcrs 

- Prccisiou Clock Module (PCLK) 

. Powcr Converter Modules (PCV) 

provides necessary voltages for the OBCU 

modulcs 

provides central on board reference time 

countcr 

Sofnvarc 

Thc complctc AOCS and related DMC-sofdvarc 

(SIW) will bc cxccutcd in thc redundant ICDS-on 

board computer and runs fully automatic and 

autonomously under normal circumst:inccs. 

Bcfore thc mission. the S/W will bc (prc-) stbrcd 

in the PROM and copied into the RAIM ;iftcr.itk 

first activation in the orbit. This allows modiii+. 

tions - ;is fat as thc 3ppticatii)n SAV is concertrcd -" 

;it any timc via tclccomrnands ("mcmorv load'). It 

is also possiblc to adapt important svstcm t,hlcs 

and the S/w configuration from ground. 

Telcmctry and tclccomrnand S N parts arc iniplc- 

mcntcd according to thc Est\ "standard p;ickct 

TMITC'. 

A ccntrai rolc within thc on hixird S/W plavs ttic 

XtOSES I t operating systcm, an updated vcrsion of 

thc MOSES opcrating systcm uscd in thc shuttlc 

pallet satcllitc (SPAS)-progsm. It is cspccidlv 

dcsigncd for the I 

- managcment of piudlcl proccscs and ;is!chro- 

nous cvcnts under rcal-timc conditions 

but can also meet the requirements of 

- strictly synchronous operation modcs. e.g. sen- 

sor data acquisition activation of thc UPS. 

The maintainability and adaption capability of Ihc 

SflV-systcm ncccssitatc J transparent modular 

functional structurc. hicrarchichlly oruanixd and 

properly dcfincd intcrfaccs not only within thc 

opcration system. but also to the application S/W 

modulcs. 

The application SN-parts (johs arc dividcd into 

one or scvcral tasks. Additiimallv, ihcrc arc spc- 

cific error tasks. which can be att;ichcd to a 

jobltask. Thcy will bc activated automaticailv by 

the opcrating system in cast of a failurc (exception 

handling), 

4.4 Attltudc- and Orbit Control Loops 

4.4.1 Acquisition connol 

Bemuse of the short visibility periods of low carth 

orbiting S/C from individual ground stations onbo- 

ard autonomy of fundamental opcrational functions 

is cxtremeiy important. Automatic acquisition, 

reacquisition and safety procedures ensuring initial 

orientation and S/C survival (power & thcrmai 

conditioning) ia case of attitudc loss arc such fun- 

damental functions. Classical, well proven concepts 

consisting in a rcoricntation of a prcfcrrcd S/C axis 

(and the active surfaces of thc solar arrays) to the 

sun are dso applicable hcrc and will lhcrefore not 

be discussed in dctail (see e 5. refs. 4 to 10). 

5.52 On-orbit conrml loops 

23-1 1 

In classical satcllitc attitude and orbit control conccpts 

clcar distinction is made bctwcen attitudc 

control during orbit correction maneuvers and in 

normal rrrodc (NM), thcsc modcs of operation 

employing csscntially diffcrcnt control principlcs 

(c.s. rcaction jet control and kW1 wheel control). 

For the ICDS concept under discussion hcre ;i 

common control approach is regardcd supcrior. 

The mcst obvious advantagcs arc: 

- lnhcrcnt back-up c:ipabilitics uing diffcrent 

types of actuators if rcquircd. 

- Modular 3wis attitudc mcasurcmcnt cstimation 

- 

and rcfcrcncc ycncrntion principle throughout. 

Smoot h transitions bctwccn diffcrcnt operation31 

conditions due to continuous statc propagation 

of cstimation and control vafiablcs. 

- Activation of combined actuators c.g. for fccd- 

forward cornpcnsation in case of hcavy prcdicta- 

ble (payload) disturbanccs 

A schematic blockdiagram of thc on-station attitudc 

control modc is shown in fig. 4.4-1. 

Thc raw srnsor data from sun scnsors and earth 

scnsors (in casc of low accuracy pcrformancc mis- 

sions) or star sensors and ratc intcyntinp: gyros for 

high pcrformoncc mission3 arc procc.zscd to'gcncra- 

te attitudc information (I$*, 8'. 9'). Based on 

systcm modcls orbit paramcler updatcs from 

ground and additional mcasurc:ncnts (whccl 

spccd), optimal cstimatcs nf systcm statc variables 

H, (prop. ~r), E!, (prop. 4). e. w,, U,. (w., prop. 

U,), H., H, and 8 are gcncratcd. In application 

cascs. whcrc attitudc rcfcrcncc is gcncratcd from 

earth and sub scnsors onlv. during cclipsc rcpions 

yaw attitudc is propagated by means of the obscrvcr 

equations of tbc angular momentum in orbit 

coordinates Jupprcssing the nutation by adequate 

fdtering. 

Under normal modc conditions attitude stabilizaticrn 

is pcrformcd by controlling the flywheel and 

rcaction whcels in torquc mode. in order to com-

23-12 

. 

pcnsatc for thc imbact of limitcd rcsolution in the 

torque commands as wcll as unknown iotcrnal 

whcel friction torque. contribution of cross-axk 

aogular momcntum components and cxtcrnd disturbaocc 

torques undcr eclipse conditions, a rnodel 

following loop is incorporated to match the 

wheel control torqucs to thc corrrcct valucs. This 

tcchnique as used for closed loop AOCS dynamic 

knch testing with red hardware at DASA is well 

provcn. In vicw of tbc fact that in thc whcel control 

conccpt in qucstion hcrc the whccl spccd 

variation cxcccds thc usud rmgc considcrably, a 

nonimcar friction torqac compensation loop is 

additionally superimposed. Iqordcr 16 imprtwc thc 

pointing accuracy and stability to the lcvcl rcquired. 

disturbancc torquc cstimation and cornpcnsalion 

is applied. Thcsc cstimatcs Curt hcrmorc cnsiirc. 

that thc necessary yaw attitudc prctliction accuracy 

during cclipsc p:issagc is achicvcd. 

Stcllar-inertial attitude rcfcrcncc gcncration tvhcn 

using r;itc intcgnting g~osc(ipsc in str:ip-down 

mode and updatcs from &yo drift Lornputcd by 

onho;ird Kalmm liltcr usiny obscncd star transit 

times h;is to rcly on upto-d;itc satcllitc cphcmcris 

and rclcrcncc star catdog data storcil in thc onhoard 

computcr. Thcsc data haw to hc pcriodic;ilIy 

uplinkcd togcthcr with corrcctions of the onboard 

timc rcfcrcncc. A typical cxamplc of ;I star idcntification 

pattcrn ovcr a period of 12 min. ;:s Tor instance 

cncountercd during ROSAT mission in sun 

modc is shown in fig. 4.4-2. lo wsc nf largc payload-induced 

disturbancc torques feed-fonvard control 

has to be applied to ensure thc ncccssary 

pointing stability for high performancc missions. 

JS Prcliminnry AOCS hs.c und I'ower Budget 

For th; AOCS conccpt and implcmcntation appro- 

ach outlined abovc preliminary mass and powcr 

budgcts for thc individual I-LW-itcrns ha\v bccn 

summarizcd in tablc 45-1. Assumins th:rt ftir 1 

particular mission r.01 all but only the necessary 

equipment will simultancouslv be intcgratcd into 

thc SIC (31 principly thc locations indicatctl in tig. 

4.1-2) the total AOCS budpcts for rcspechc application 

C~SCS can be composed. 

For typical mass of a propulsion systcm dcpcnding 

on thc totd LnpuL~c to be provided rcfcrcnce is 

made to figure 3.2-2. The burn-out mass including 

12 four Newton bipropcllmt thrusters. tank. piping, 

residual Helium in a blow-down sysfcm amounts to 

approldmntcly 18.5 kg. 

5. CONCLUSION 

On thc basis of morc than 29 years of cxperience in 

AOCS dcsign and development for communication- 

and application SIC in the papcr undcr discussion 

here the attempt has been made to identify the 

configuration, the cquipmcot and tcchnology of rn 

AOCS, which cm provide thc necessary flexibility 

for :,crving the large variety of TACSAT mission 

objcctives ond the associatcd performance requirc- 

mcnts. 

6. LIST OF REFERENCES 

I.R.Wcrtz: "S/C Attitude Dctcrinination and 

Control', Kluwcr Acadcmic Publishcrs, 1378 

DASA-Study: "Networking Rcquircmcnts for 

Uscr Oricntcd LEO Satcllitc Systcms" 

ESTEC Contract No. 973U!VNURE 

E.W.Mowle ~1.31.: "The LANDSAT-6 Satclii- 

IC: An Ovcrvicw", IEEE AES Systcms Majy.inc. 

June IWl 

H.Bittncr ct.31.: "Thc Attitude and Orbit 

Dctcrmination and Control Subsystcm of thc 

INTELSAT V Spacecraft". EFA AOCS - 

Conicrcncc, Noorclwijk, i977-ESA SP- 1 W 

H.Bittncr c1.d.: "The Attitudc and Orbit 

Control Subsystcm of thc TV-SATTTDFI 

Spacccraft'. Proc. of thc 9th IFAC Symposium 

on Automatic Control in Spacc, Noordwijkcrhout. 

July 5-7, 1982 

W.Schrcmpp et.al.: "Design and Tcst of the 

ROSAT-AMCS'. IFAC 10th Tricnneal World 

Conycss. Munich. FRG. 1987. pp 81-NI 

P.Bourg etd: Thc Attitude Measurement 

and Control Systcm of EURECA". IFAC 

10th Tricnncd World Congress. Munich. 

FRG. 1987. pp 49-56 

H.Bittncr ct.al.: 'The Attiludc and Orbit 

Control Subsystcm of the DFS KOPERNI- 

KUS'. lOth IFAC World Congress. Munich. 

I9R7, 

H.Bittncr ct.aI.: 'The Attitudc and Orbit 

Control Subsystem of thc EUTELSAT-2 

Spacccraft', 11th IFAC Symposium on Auto- 

matic Control in Spacc. Tsukuba. Japan. July 

1989 

MSuraucr c1.d.: 'Advanced Attitudc- i d 

Orbit Controi Concepts for 3-Axk-Stabilired 

Communication and Application S;itcllitcs". 

12th IFAC Symposium on Automatic Control 

in Acrospncc, Scpr. 7-11. 1392. Ottobruno. 

GcrlDWl;

Figs. 2.1- la-2.1- IC: 

Parmeters for sun-synchronous orbits 

figs. 2.2-1a/b: Principle Sic-solar rurav 

configural ion 

I 

i 

-w w 

fig. 2.1-2: 

23-13 

IO0 1001 

-(Y 

100000 IOOOOOO 

Number of LEO satellites required for 

global coverage (10" elevation from ground) 

Fig. 2.1-3: Drag' factor versus altitude 

100000 200000 100000 400000 500000 600000 

Fig. 3.2-3: Trade-off mono-hipropellant thrgster 

cfficicncy versus total impulse

23-14 

e I w 11 n IS n n a 41 U 9s M 6s n n m II w,*s IN 

-1- Id 

Fig. 3.2-1: Specif~c 

bipropellant thrusters in pulsed mode (comparison) 

impulse of 2- gcocration liquid 

I /' 

Ad--- - * 

Fig. 3.2-2: lmpulse bit of 2- generation liquid 

bipropellant thrusters in pulsed modc (cornparisoo) 

Examples of momeotum-/rextioo u-eel anmgcmcou 

f "q.-c)

Fig. 4.1-1 a/h: SIC orientation U2 in orbit 

4 '* f 

Fig. 4.1-2: Schematic of opiicd sensor arraogcmeot Fig. 4.2-1: Location a d onenlation 01 reaction Jcrs 

I 

23- 15

23-16 / 

Fig. 4.3.1: ICDS principle block diagram for scpuatcd AOCS and paylaod DIM 

Fig. 4.3-2: Block diagram of the OBCU

4 

2 

0 

-2 

-4 

t 

. 

. 

. 

I "W 

Fig. 4.4-1: Schematic block diagrm of on-orbit control loop 

: b 

:. .: 

b 

4 . ............................................ . , ................. 

&' 

. . . 

60 63 66 69 

star identification in scan mode 

stars in orr-board catalogue 

+ stars not in on-board'catalogue 

Fig. 4.62 

Star identification pattern in (ROSAT) scan mode 

X 

I 

- 

- 

23-17 

ww w-- 

Wheel 

I \ I 

1 

+ 

I 

7 

z 

Fig. 4.2-2: 

Y 

p 

/ I 

#' 

57- \.; t - - - - - 

Momentam- and reaction wheel arrangement

23-18 

Communication 

Weat her 

- 

Operational Pbase 

Orbit Correction 

Scan Phase 

Normal and SK-Mode 

Normal Mode 

Enlironmcntal 

Monitoring Re- Positioning 

High Rcsolution 

b .- . 

'Normal Mode 

Re- Positionina 

Tablc 2.3- I: Typical AOCS perforrnancc rcquircments 

Geostationary Communication Satcllitcs 

SMYPHONIE 

INrELSAT V 

TV-SAT 1, 2 

TDF 1.2 

TELE-X 

DE-KOPERNIKUS 

EUTE~AT t 

2 flight models 

IS flight models 

13 Satellites in operation. 

FM 9 Rr FM 14 1031 due to launchcr failure 

2 flight modeh 

FM 1: one SG failcd to deploy, dcorbited 

2 flight models 

1 flight model 

protoflight model 

FMZ FM3 

PFM = m1 

ma m3, m4, FMS. 

Table 3.1-1: Review of geostationary communication satellite examples 

Dewl. AOCS 

Fhf Qual. 

1- - 1970 

1976 - 1987 

1980 - 1987 

17110 - 1987 

1387 

1983 - 1989 

19P6 - 

Launch Dims 

A: 19.12.84. 

6: 27.08.72 

mil' : 7.1290 

FM2 : 24.05.81 

FM3 : 15.12.91 

FM15: 27.01.89 

FMl : 21.11.87 

FMZ : 08.08.90 

m1 : 28.10.88 

FM2 : 17.07.90 

FM1 : 29.03.89 

PFM : 05.06.89 

FM2 : 17.07.90 

FM3 : .12.10.92 

FMI : 31.08.90 

FM2 : 16.01.91 

FM3 : Dec.91 

FM4 : 10.07.92

Control Accuracy 1 Control oncep pis 

! Ideel 

I I 

Half Cone Yaw (dcgl 

INTELSAT V 0.12 0.52 . Wheel control in Pitch NM 

. Whccon control in RolVYnw (rued bias momentum wheel) 

- Spin-stabili7.cd apogee hoost manc.t:cr 

1 1 TELE-X 

Beam 

TV-SAT. 0.22 1.2 - Wheel control in Pitch (NM) 

TDF I 

- Coarse body control in RoWaw (Whccon with fixed bias 

DFS 

ELTELSAT 11 

Pointing 

Tx *-' Rx 

momentum wheel) 

- Fine mtema pointing system using RF-sensors . 

- h c c axis stabilized apogce boost maneuver with partidy 

Whcel control in pitch 

- ibhecon hody control in RolVYaw Ihcd bias momentum wheel) 

. three-axis stabilized apogee host maneuver with fully deployed 

sblar pcncrators 

- 

. Wheel control in pitch Kht 

. Fine body control system NAAMC (Optimum Nutation dlr angular 

rhomenrum control) for riormd modc RolIRaw 

. thrcc-yris stabilkcd ipoRcc boos[ maneuver with partially de- 

dioved solar gcncratnrs 

Table 3.1-2: Communication sntcllitc AOCS features QL performancc (DASA-AOCS) 

Low earth orbii ObscrvadowScicatiTc Saiellites AOCS Devclopmcnt & Launch dates 

Qualification 

MOS-1 (Marine 1 cncjnccring modcl 1983 

Obsenwion Sat.) 1 fligbt modcl Fhll: 1987 

FM2: 1990 

ROSAT (Riintgcn- 1 cnginecring dodel i9M - 1986 01.6.90 

Satcllitc) 1 flight model 19% 

EURECA (Europe- 1 flight model 1988 - 1310 31.792 

Retricvablc Carrier) , 

ASTRO-SPAS (Shuttlc '1 flight modcl 1988 - 1992 June 93, carly 94 

Pallet Satellite) 

Table 3.1-3: Review of low ciuth orbit satcllitcs (DASA-AOCS)

23-20 

r - .-_ -- - -. --_.._ I 

U 

i 

Lw8:tt?l riccuracy 

.----- -- ---I- 

-- 

. __- 

Normal Modc Control Cunccpls 

- 

MOS-1 ( Mu~c Pointing Dircctioa: 0.1" Two bias momentum wheels in V- 

Observation Satellite) Stability 0.00l0/sec arrangement with magnetic unloading 

of accumulated angular momentum 

ROSAT Pointing mode: 3' Reaction wheel control with ma- 

(Rontgen-SateUite) Meas.Accuracy: 10" gnetic unloading of accumulated 

San Mode: 3' angular momentum 

ASTRO-SPAS Pointing moue: S* Riorf body control with cold gas 

(Shuttle Pallet Satellite) Scan Mode: 80" 1.' : of GPS for Earth ref. frame 

determination 

EURECA 0.9" cach axis for Cold gas control supported by 

normal mode magnetic control with disturbance 

torque compensation 

- 

Tablc 3.14: EartWscientific satclliie AOCS fcatures and performance (DASA-AOCS) 

Tablc 3.2-1: Typical characteristics of attitudc mcasurcment equipment 

Pouw 

4 .J 

Manufact wer 

FERRAKn 

+ 

A 

2.1 - 2 TPD 

GALLEO 

DASA 

WO. baffle 

DASA

0.75 - 0.2 

2 - 0.6 

6 - 1.85 

IO - 3 

24 - 7.2 

350 - 110 

.-- -- 

0.19 5Rs 

0.20 St1 

0.22 SI337 

0.24 5/24 

0.35 ut3 

1.80 301- 

! 

Table 3.2-2: Characteristic parameters of (DASA) catalytic monopropellant hydrazine thrusters 

Table 3.2-3: Characteristic parameters of DASA T generation liquid bipropellant thrusters 

Table 3 24 Characteristic parameters of magnetic torquers (ITHACO) 

23-21 

'Wwn o ainile winding ir used. power doubler.

23-22 

I .a * .o.s 

8.2 

am3 

c 0.012 

a..? 

s60 

163 

7s 

2.7 ... J.4 

ne..a 

0.2 

mm 

c 8.013 

2.J 

c&b) 

2a 

w 

3.5 ... 6.0 

14 ...a 

8% 

mm 

c 0.013 

2...10 

c 100 

Jw a 

120 

5.0 ... 8.0 

Table 3.2.5: Chdrxlcristic paramctcrs d momentum and reaction wheels (TELDIX) 

- and z-componeot 

Tablc 4.2-1: Thrust levels. thrwcr locations and orientations 

Location 

w..m '\ 

.02 

6006 

c 0.m 

3...15 

c Is0 

500 

1% 

7.5 ... 12 

1on the corners of the ccn- 

trd cube 

on the edges of the 

padcl to tbc S/C y-axis

abic 4.2-2: Corrcspadaucc bcwccn torque requucmcnts and thruster activation 

raidd pitch dircrtrb.acr loqm rmp-ed by c 

Table 4.2-3: nYutcr activation for orbit corrections 

I 

23-23

PRW mrms lottrfrsa : 

UDir 

Bnterfscc A[prdm lo AoCS 

sensors 

OdOff distribution for PF wits 

Acquuitioo d PF uaiu tcmpzra- 

tuues 

Panr &ribunion and praccrim 

nf PP U& 

e n of the wWe SIC 

LF with KU (Power Condih- 

&q Unit) 

Bnatery poteaion HW 

BF beater (relays) 

Power distribution and prmec- 

tion of Pt'L wit 

PA unit temperature acquisition 

P.2 beater relay 

Onloll diurihtioa to P:L unit 

fable 4.3-1: Fundwcrl .sharimg and notation of ICDS W units 

Equipmat 

1 OBCU 

1 Prrm 

1 WSE 

1 PSSA 

1 PFDU 

1 IRS 

1 RIGA 

2FMw 

2 RW 

lsrS 

Torque-rob 

0 

Supplier Remarks 

H E High Level 

Priority 

Re~~aligurr. 

[ion Commands 

SADA Solar &ray I Drivc k m . 

DASA intcdy redundant 

SEXTANT iotcmdy redundant 

AL internally redundant 

hmB internnlly redundant 

SlEXTANT ialedy redundant 

GALILEO 

m 4gyra& one & 

TElLDLx reduodant set 

TELDJX red- set 

DW. 

FOPMER 3 coil& inc redundant, 

t 350 Am'

lpnpQR rOYi0WS the QdVOUItQ~OQ and 

liaitoeiom OR OlQCtriC pnowlalon for 

1 iqlhemaa che roctar i zed by o nnunch inam 

ln tho DO0 to 100 Rg ran$@. 'Bna coneidyra?d 

dyotooa include ion propuioion, nrcjvee, 

and ntotionary plasma thruntorn eor 

Bitfornone applications GUC~ ne drmg 

coopnnneion, orbit raisinq, Pdnrlr ?rimming 

of orbital parameters, and variauo crbit 

tranofors. 

ElQCtrk propuloion provldaa nubstnntiel 

oann onviqo nm3 turna out eo bo on 

onablbmg tochnolbgy for ceetnln I lightoat 

aiseiono. TRO conatrainte reoirlPIn9 eron 

DC ~ V O R linitations onbomrd small 

@gtolllktQQ QrO dincuseod, QlOw W i t h the 

inplicotiono on candidate tochnoloqios and 

systoa aolutlons. A review ol nenr terra 

prooptivoa of lou power ion Phrueatero. 

lor lightmats applications, concludes the 

paper. 

1. I~WCTIOW 

Rscont adtvencsa in electric propu?sion 

hsvo finally lad to consider Len une POP 

coanorcinl qoootationary communication 

satallitss etationkeeplng. For rsuclz 

function, ion thrusters, statlonary pleme 

thruotera (SpT) and arcjete ore currently 

boing planned on board uavnrel now 

setollitea. Tho main at?rtiction of 

eloctric thruitoro lice In their hiqh 

OXheU8t VQlOCity which 15 aovorel ti%iiOS 

that oP convent.iona1 chemical thrurstero. 

"he najor benefit is represontad by tho 

gropllant mass reduction for orbit 

control eaeko. I 

Eleceric propuleion is QAOO being 

tonnidlorad for other near earth propulsion 

bpglicotions, 000 n.9. (I], in pareicular 

for orbit tranefer .and manoauvering of 

large spcecraftr and for scientific and 

interplanatary BiO8ione. 

Tor what concern8 the ulectrlc propulsion 

appliceelona to liqhtsats, norno initial 

work raoulto from the open literature, BB)B 

e.g. [I], but no specific plana ora known 

to tho authorQ about actually inplononting 

electric propuleion onbomrd lightmato. 

Thio io quit0 surprising bocmuocr, in viov 

of tho specific conetreinto of s~all 

satollito@, electric propulaion may be 

conoidorcpd an *enabling* eochnology 

without which a number of appltcatlonm 

would br alnomt unfoamibla. 

Ubat:erfc Propuleion for Lightoato: 

A R~MIoQ! of ?$plicotionka and Mvantaqes 

6. mrrotea 

Alhnbo 8pQXiO 8.p.A. 

via BQCCO!PUPO a4, 00131 w-, Italy 

C. Cirri, C. Matticeti 

Proel Industria 

v.10 Machiav$illi 29, 5017q ril'enze, Italy 

24- I 

Tho paper rsviown the koy features of 

oloctric peopuloion in the specific 

context bf DC-power limited liqhtsats 

cheractorlzod by a launch mess rnnqe in 

tho 300 to 800 K9, which is most 

eppropnieeo for Q number of 'professional* 

applications, including clvil and defense 

ones. 

Tho nein reason to consider electric 

peopuloien le to reduce the total 

oubnyeten mass for propuls1m-related 

tnoka, tho iaaximizlnq the payload to 

leunch DblDQ ratio while stayinq within the 

leunch mas8 bounda otated above. However, 

oloctric propulnion can be a viable 

appeoach only Lf the power requirements 

aPQ 8100 compatlble with tho DC power 

lioitationa, conoiderinq that the liqhtsat 

pow0r plane is normally dcslqned to 

oupport the payload operation in normal 

ado. WO will llait our conelderations to 

throo E. R. technologies: ion propulsion, 

Stationary Plasma Thrusters, and arcjets. 

Yn tho low-power ranqe of Interest for 

lrghtoats, typical performance arc given 

@ in Table 2.-1 which envelopes the 

characteristice of a number of existing 

devicoo. WO main Electric Propulsion 

applications are considered: 

- orbit kaeping, which incluCos drag 

conpnaotion, fine trimming of orbit 

prnraooeoeo and, for liqhtsats in 

oynchronous orbit, etation-keepinq. These 

gropuloion tasks are normally concurrent 

with payluad oporation. Therefore 2. P. 

oppllcotione aro mainly power limited, 

bssides being a100 mass limited in order 

to rsoult conpatitive with chemical 

propulsion. To exemplify, we will assume 

to slloceto 30 Kg and 300 W to such E.P. 

functionmi 

.'+- orbit lbnoouvering, which includes orbit 

s!~jr8ioing, 

circular to e1 1 iptical orbit 

.tronofer, and orbits c!rcularization. 

Thooo . propulsion tasks are performed 

outoido payload operation. Therefore the 

full lightoat DC power, normally used to 

supply tho payload in normal mode, can be 

wade availabla, for Eloctric propulsion. 

TypiC8lly, ono pay allocate 60 Kg and up 

to 1200 W of DC p e r to E.P. functions.

24.2 

CJ6Qh ion pl'b;pPelaion tho applied thrust 

IWs'olO QPG Cl000 to the drag force 

avoragexi durinq one orbit porlod, i.e. 

k?lroo 3 eo t5 aM Pot B typical mall SAR 

aoeellieo ineondodl to Ply at orbit 

aAt6tudw km low eo I00 M. Thrusts of 

thio ordou can $s modularly achieved by 

puttinq low power (< 10 mN) ion thrusters 

in parsllol end implementlnq throttling or 

on-off modulatlon accordlnq to the 

requ I red duty . 

.-----.I --.--. --cons~dcring 

typacnl values from Tnhle 

2.-1. it can bo necn that , lor orbit- 

Orbit Drag f.cs Delta-V Delta-V 

keeping teaks. nrcjctn 

height avgd. ov8r 

Rrn S C I V ~ P C power 

6 mo. 5 years 

~ ~ 

limited nnrl are ttrrthor pennli7wl by the (Km) 1 orbit(nN) (m/s) 

poor lop value. SfTe qc~d f.vntc?n*.lc.rs 

a) b) a) b) a) b) 

to ion thruntarr, in that thcry cin provide 

hlqhor thrusts for the snmo I#: pc>wer at a 

lmor moo, but the lover lop valuo can bo 275 30 15 1155 185 11550 852 

critical for long-duration whnnlono. For 300 2l 10.5 815 272 8150 2721 

orbit ~nnoeuvaring tho cpvn61rrbis OC powor 350 14.2 7.1 551 184 5508 1840 

&a juot at the llait where ~rcjoto bacon0 aoo 11.7 5.9 457 152 4752 1522 

intonooU~ng: but SPTn nlno orpear to bo 4 50 8.9 4.4 145 119 3452 1152 

qodl cautaidlmtsrP, In vieu oe eho bettar Iop 

500 7 J.5 270 90 2700 902 

they con offer. Other coneidorntione. ouch 

an tho tine to transfer./ muo?. then b@ Asounptions: 

taken into account, in t.h@ nygtcn trade- case a) : s/C crosmction 4 m"2, 

OfPS, e0 choose the riqht 

drymirnn 400 K9: 

PQChnr)ltwly. 

cane b): S/C croeoectlon 2 rn-2, 

J,TII!fC&L-E,P., AP_F_LI.ICATI O?tS*.TU I.fC.tfTSATS_ 

drymaso 600 Uq; 

Q worst year nun activity: 

>,a, ~rlpqla- co?Jng!>-on. - for- . Obn@rvEAk?!~ 

seeollitso- 

Cone-olfoctivs observat ion mission:& can bo 

concoivod with individuinl ncit.eII itcn, 

leunchd on-dcmand, or bancd on emall 

ontollitao conatellations c?rr)'inq f.AR [I] 

or optical sensors. In both C.PBQPB the 

oioaion roquiroa very low orbit mleleudos, 

ooy in tho 200 to 600 Kn rmgo, to 

onhowce tho optical ground rooolution or, 

in the SCUR cmo: to reduce tho transnitted 

per compatibly vith ehca limited 

resources available on a small ~neolllte. 

At thene altitudes tho residual 

stheongheric drag beromen the Ilmitlnq 

factor for thO mlssion duration. Even 

aasualg o slender platform daslgn and an 

orientation of tho appendaqen (I.e. solar 

arrays, antenniao) such as to axhibit a 

mininun cross omtion In the dlrecsion of 

tho flight path, tho dolta-velocity 

recpirQd to counteract the roaldual drag 

becowo rapidly unmanageable with chatnlcal 

propulsion for dosion dureeionn greatarr 

than a Pew months: see Tablo 3.1-1. which 

is rolwent to two typical liqhterat 

configurations. The determining fmtor 

bscowa the propellant mass, given the 

launch maes limits. 

Tho high specific impuloo of ion 

propulnion allows reducing, by a factor of 

about 10 w.r.t. chemical propuloion, tho 

propallant nasn required to inpart a given 

tots1 volocity incremont. AS a 

consewonco, mission lifetinan of 'J year0 

can ba achieved, which is inatrummtal to 

iwplesnant small satellite conneallationa 

for sprnanents observation ninaione. Itn 

coaperiaon, the other E.P. tachnologion do 

not porform woll in thia Qgglicetion 

cheractorized by very high required 

velocity increments. 

Table 3.1-1 Drsq forces vs. altitude and 

rcqu i red del tn-volocit ies for 

their compensation 

Table, 1.1-2 qives propellant mass and DC 

power requircmants OP ion propulsion vs. 

orbit altitudo lor a prospective small SAR 

oaetsllite. For the consldered thr?rst 

lOV015, tho CC powor requirements are 

coapatiblo with spacocraft allocations. In 

concluoion, ion propulsion has to be 

conoidorod an enabling technology to 

isplonont long duration observation 

missions in vary low Earth orbits. 

W0VorthQleeQ the operating time, Of the 

order of 40000 hours, is OP concern and 

ohould bo properly addressed by further 

dovelopmonta. E?'orts to further Improve 

tha efficiency OK low power thrusters are 

also strongly raccornended. 

Orbit Propell. Thrusters N'/ AVge DC 

heiyht mass avqe orb.duty power 

(h) (K9)(1) (W) , (2) 

- 

275 90 248m~. 1.94 450 

300 62 248mN/0.66 320 

390 41 8NW/0.88 240 

400 34 8mM/O. 7 4 200 

450 25 0mN/O. 55 150 

500 20 0mN/O. 4 4 120 

Nota 1): boo0d on 2800 e. Isp 

Note 2): based on 30 W/mN 

Table 3.1-2 Dtag compensation ion 

propulsion requirements for 

system b) of Table 3.1-1 

.-

3.2 P A tuimira ~ ok c~,~~a~aellonaorbiea 

po~a~oto~o 

An inceoonlng numbar of omall oatollrtoa 

conaeollationo IQ being propcowl (a] for 

advancod comnunication and renoto noneinq 

applicntiono: aost conotollatlono havo 

nultlplo natollltes in ono ou Rultiplo 

orbltoll plonoa: low altItubo onbito, 

typically 000 to 1900 Km, Q ~ O 

noentally 

envioacgod, with a few c e~eo conoidoritq 

altitudloe, as hlqh as loOD0 Kn. 

Wi8nag!?Q thQW.7 COmpl€?X SyUeemS Will 

xoquirs copylng vIth tho launch nystenn 

orbit injoction disporniona, 8s wQlt ibo 

m$intainingl eh0 satallitao relative 

pRoobng durIngl the orbleal lieeelno 

atpinot oneornnl distuubsncna. Tho 

qhntiaation of these eefacea, in eerrns oe 

propolllone amso, doponde stroqly from tho 

launch wohicle cha~actoriatico, orble typ 

and oloalon duration, and vlbll not bo 

nttorslptcd ~QE~P. Tho gush towouch launch 

coat sduction ~lqht probably lqly, in 

tho nwor Puturo, the usa of looa nccueaee 

L.V. a d groator injection Bioporoiona. 

There Lo a100 a clear trend to require 

longer orbital lifetinos. 

-eh Pnceoro vi11 tend to Incr@ase tho 

propellant mass allocated ffor orbit 

control: ehis vi11 impact nqcntivsrly tho 

oyatoa ocononico, also in view of th0 

multiplying oeeoct due to tho Iti~ge number 

oc ooeolliesa In those conotallations. 

Clectrlc propulsion may be connldorod in 

alt~rnetlva to chamlcal propulalon for tho 

potsntlol masdl naving it1, can provldo, 

spoclollly in presence ol hlqh orbie 

Injoction dloprolons and loncg orbital 

'ilotimo. ConetollatIon phaobncg is not a 

tino-llaitod propulsion task, whlch will 

enablo uah9 low thrust, high speclfic 

iFiYpI1b0, C.P. syetoms. suitable neraeogiee 

for conneallation phasing msineananca can 

be concoivod, poesibly aided by nutonomous 

navigatlon systems, to fully exploit the 

E.P. characteristics. 

Stuall oetollites in qooetationary orbit 

can poreorm useful1 conntrnication, 

meteo~ological and observation mlnsiono. 

Clusters of two to four npacncraft can 

form a Bietributed satelllte syatem havlng 

enhanced performance w.r.t. 61 single 

Aatollite of an identical total mass. 

Assuainq the availability of a launch 

vehicle capable of d:rectly injecting the 

saesllieos in synchronoue orbit (such as, 

Q.Q. tho Ruesian Proton rock&) small 

sgacocrale relying exclusively on E.P. can 

be concoivced. 

The absence of a bulky apoqee motor 

greatly ex>anda the spacecraee design 

freodon, including the positioning and 

orisntaeion, or canting angle, of tha E.P. 

thrustera. Spacecraft incorporating 

eevoPa1 ne6111 thrusters may impl@nent both 

orbit Control and entornc;lll torquo. 

cospnsation for attitude control. 

Tabto s.3.-1 qlivoo tho eeorontisls oP em 

Bniithol ccancopt Pou a high prfonaanco 

onell goootaeionery eatallite. Basic 

Boaturea nra tho low potfer/lov thrust ionthrustera, 

tho reouleing overall low E.P. 

OY~P~~PR moo, tho high ach'wable payload 

to oatslllte launch mass ratio, the 

eboonco of any kInd of .chemical 

propulsion. 

Satollito launch mass (Kq): 

Q Payload aass (Kg) 

* Payloed/launch,mass ratio : 

Orbital lifetime, years : 

Wqrd. total velocity 

incromene (ra/n) W-SIS. K. .: 

E-W/S.K.: 

Ion thruotors nurnbQr 

'FhrUQt 169VelS(W) w-s/s.E(.: 

E-U/S.K.: 

Q Total prop.rncPse (Kg) 

Avge dayly thrusting time 

N-S/S.K.: 

E-W/S.K. : 

4 E.B. oyoten einm (K9) 

* E.P. peak DC power (W) : 

Q Deyly e.rergy nosdsIKWh) : 

Foaoiblr! control torques 

in pitch,roll,yev 

600 

240 

> 0,4 

15 

700 

70 

10 to 12 

OmN (2.4mN) 

4mN (2.2mN) 

< 18 

2.66 hour8 

32 min. 

YO (est.) 

240 

0.7 

48 iao 

4.b 11 

8.2 19.3 

26.5 88.6 

C l e 1 

76 178 

51 iao 

11 50 

190 

17 

29.6 

100 

c1 

270 

100 

75 

--.- .-_ 7- 

1) 400 ~ fn initial circular omti 2) 600 KQI opa.:ecraft 

3) thwot lL.** la: ion- 40 Rw: 

SPT- 60 mP(: 

arcjote- 150 nM: 

4) 1ogr2QO a: 5) 188-2806 cut , 

6) XQBp 1500 S; 7) Isp~500 

0: , 

Tablo 3.4- 1 kloctr ic Yropulolon-oyst@mo 

for OrbIt Raising 

---.------- -I, .-I -.- 

roble 3.4-A ShWS that IOU powor arcjots 

OPO goad candidates for Rlcgh altiruae 

d! eeoroneioio, provi~ing 9~ ROW OSV~~JO 

with aoanonable, tranofor ticno. On tho 

conerany. ion Phruetorrs , and !;mu arc? 

Dorqjiml and can bo only conaidered tor 

aooAl oleleudo Lncromenro, oehoarvieo too 

10- eranror t1r;tao will nonult. In 

concluoion. IOW Phruet olectnic propuleIon 

can $3 ccnoidarod for circular orblt 

rnioirrogl of amell metolllt~o whan (P short 

tranetor ti- Ia not mandatory. I 

Whoer oabie ralolrrcg must b@ laplononeed in 

a vouy mort tiao, as for ~~o~-ple with 

aotollitao launched on-demnd, 'thon 

chaoiccal propulmion 1s still tho preferred 

approach. 

Circular toalliptical orbit tranefero 

tlliptic~l Inclined orbits nro being 

conr~ldord with increasing interoat for 

numrwo applications, and thoro arQ plans 

to roalino omall satellite conatelletionn 

olrpploiting tho gsrtIcular foaturm of such 

orbito. However, the injection capability 

of anal1 launchera in elliptical, hlgh 

onorgy, orbits is ncrmally rather pQor, 

and one has , again, to rely on boost 

mtora to Inploaent the final vrblt 

tranofor, for which two inportant 

considerations apply. 

h .( 

@ -' 

ti"k00, V€#q high d@l~-VOlWitiQU are 

mp i wx-1, mm Pig. 3.5-1. SOCORB, 

C@L29311Q 1 Q 1 comuwication ustolliten 

iRj&cd tn olligtical orbltm can ba 

t33~1n~Od ah AeulrPchod mlZ in advanco of 

ma0 ~c$dGitO. Pn>q tnip times aro, thua, 

wlotbbdly uninpogtant but 8i8SiOn 

cacplorziity, cooto, reilabil lty and 

opaationol conoidorationm may put an 

upwr RmuM to the maxiBus accaptablo trip 

eim. 

Eloceric Propulsion alternatives to 

chooicol arb SBTa and arcjets, with the 

oow chartceoriueics given in Table 1.4-1. 

!3i~plbfid conputatlono POP transfers of a 

500 Kg opdscocralt. in trsnsfer orbit from 

an initial 400 tta circular orbit to three 

Qootinetbon alliiptical orbits of 8, 12 

and 24 hour6 priodn were porformod. 

c~oae-idecai trenoeor vas uimulated by 

firing ~RICUS~OPO eor a/4 oP the orbit 

p~pho61 awue eh@ prigses until the final 

opqoo wan reached, ehen firing the 

Phpuotora Sou 1/6 of tho orbit period 

until tho final prigoe WQD also reached. 

aropollant Q~OB required by SFTs and 

arcjots are roported in Table 3.5-1. 

- DOltQ'V. 

- T.O.neoe/ 

** Id001 Tranfor: 

Dastination Orbit (1) 

a) b) Ci 

(WO) : 2350 1550 3450 

peopolA.maoe 

(W) (1) 1 

cPIoaical 1157/657 1:'; !,'*I43 1714/3214 

arcjet 800/300 R '/3J2 996/496 

SPT 379/78 '. '06 620/120 

- T.O. DBBD/ 

propoll.taaes 

44 !ion-Idoel Tranmfer, A rc '*t: 

(K9) (3) : 

- Trip ti- 

058/358 B93/399 l105/605 

(days) 36) 334 530 

- 

Characteristics of Destination Orbits: 

a) Apaqoo:32430 EOsr Perigoo:8107 Km; 

Porlod: 81 hours: 

b) Apocaoe:45150 #m: Perigee:7968 Km: 

Poriod:li! hourQ: 

c) Apoqoo:59030 KIP: Perigee: 25298 Km: 

Period: 24 hours: 

Moto 1) Starting orbit: civ Inr, 400 Km: 

2) Satellite drymass: I O Kq 

3) Inzluding Delta-V 1i':rement (15%) 

for non ideal transfer 

- 

Tablo 3.S-1 E.P. alternativrs to chemical 

peopuleion for circular to 

elliptical orbits tranfers 

POP ths arcjet cane, a non-ideal transfer 

wan ala0 oimuletod, and tho propellant 

mu@ recomputed taking into account a 15 8 

worsening in tho delta-voloclty required 

duo to the non-idoal tranfpr conditions. 

A@ can Bo moon the trip tlrms are quits 

high in all caaoo: a 30 8 rclucticn can be 

achlsved incromsinq the arclnt thrust to 

220 L", which would nevertheless imply the 

availability of 1.8 Kw @C power. This 

sight necceeitete an auxiliary array in 

the E.P. boost section, impacting costs.

Thoro are sovoral additlonal positive, and 

neqativo factors, to bo V.T)ten ' into 

acccrunt, vhlch may affect thn trip time: 

but in conclusion the PMslbiltty of usinq 

low power arcjets irl potmr limited 

liqhtante Cor lov altitudo circular to 

elliptical orbits coplanar trennfers ha0 

to be considered still problemntic. 

3.6 o~b_lc~-ci rcu la r i LA t Ion- 

Thio propulsion task refers to sdtellituo, 

injected in elliptical transfer orbit by a 

I..v., whom final dentination otbit is 

circular with a radius normally coincident 

vith the T.O. aygee. Typica1 cases are 

goostatlonary orbits anti medium altitude 

circular orbits of about 10000 Km as 

envlSm$@d, for example, by TRW's Odyssey 

and ESh'o MGSS-14 constellntion [5). 

Electric propulsion is ~onpnrcd to 

chemical in Tnble 3.6-1. for thnno tua 

typical mlsnions. Arcjetn nre found to 

perform acceptably well in this case, 

olnco trlp tlmos around 200 dayn cnn be 

achieved lony with niqniflcant mass 

oav,Inqn w.r.t. a chmlcal propulsion 

alternative. The bQttQr mnsn envinq 

achievable with SPTs Is, Instead, piid 

wlth an excessive trip t inn dur;rt Lon. 

___.I_____.. --_.--.-. ..."..-. . - -.- _.-.I 

4. T.0. chnracterlstlcn: 

- Periqee (Kn) C679 6778 

- Apqao (Kn) 42164 I 7 2 M 

** DostInation Orbit 

characteristics: 

- Radius (Km) 42164 16728 

- Voloclty incromont, 

idartl trnnnf.(a/s): 1476 1174 

** T. 0. mass/propel 1 . miss 

(W) (1)(2): 

- chnnlcal R44/144 '1 G o/ 2 6 0 

- arcjet 700/200 655/155 

- SPT 555/55 544/ 14 

*4 Trip tines (days): 

' - 

- chenlcal /1 1 

arcjet 227 1R2 

- SPT n.a. 453 

Note I): Satellite drymase 500 Kq; 

" 2): Including a 15\ increnno In delta 

velocity due to non-Ideal tranfern 

Table 3.6-1 E.P. alternativee for Orbit 

C1 rcular I zat ion , 

4,RE;'XEW OF SYSTEM NEEDS 

Prom thip ovorviev two E; P. technologies 

appbar to have a future 'on power limited 

lightsnts: 

- small ion thrusters for drag 

compensation, limltod orbit raining, orbit 

circularization and fine trlmming of 

orbital parameters of small satellites. 

The required thrust lov0lo ara in tho 2 to 

10 mN range. a modular approach anablinq 

parallol operation oP thruetcra is also 

required. Full thrust control, over a 30% 

to 120 a range of the design thrust leveA, 

is an important design requirement. An 

Ovorall specific power of 40 w/mN maximum 

(30 W/mN as a goal), and a spoclPir: system 

mass of less than 1 Kq/mN maximum (0.7 

Kg/mN as a goal), including power supply 

24-5 

end lgic should be sot as near tern 

dovo~oprnont objectives. Isp valuos bettor 

than 3609 sec., and very .on9 lifetimes, 

aP the ordar of 40000 houra, are also 

pr imary roqu ironenta: 

- IOW QOWQr arCjOtS in the I to 1.2 KW 

ranqe. for orbit mnnoeuverinq tnnks. For 

such UOVICQS oflorts should tn! dcvotcd to 

possibly brlnq the Isp closer to 600 sec. 

for thrusts in the 150 to 2r~0 nl.J ranqe, 

vith an overall speci:ic pover better than 

8 W/mN includinq power supply. 

On the other hand stationary plasma 

thrusters do not Seem to have a clear role 

for liqhtsats, at least in their present 

power and thrust level ranqe. Scaling down 

SPTS to lov thrust vnluos (say below io 

nl'), while keeping unchanged thnir 

ex:ellent parformance, in particular 

efficiency and simplicity, is yet unproven 

but miqht be worth beinq investlqatcd. 

For the considered thru-t ranfin, new 

devices bused on tho Electron Cyclotron 

Resonanco (ECR) (2) are presently under 

evnluation, nimfnq to further improve the 

1 on thruster's per formancc . 

The ECR tect iiquo nllowe oporatinq over a 

vider thrust ranqe by chanqing the mass 

flow rate in tho diocharqa ch;imber 

enhancing the electrlcal efficiency and 

qaa conoumption over a widor pressure 

ranqo than tho conventlonnl RF nnd Knufman 

techno 1 oq les . pn r t 1 cu 1 n r 1 y 

ECR appears 

indicated for sinal: sIz@ Ion thrusters, 

for which it io aloo onaler to achieve the 

optimum static maqnotlc flold necessary 

for resonance. 

The ECH technique consists in applying a 

ntatlc magnetlc field I orthoqonal to the 

direction of an oscillating RF field, so 

that electrons are forcod to rotate within 

the thruster's discharqe chamber, around 

the magnetic field lines at a cyclotron 

frequency givon by: Fc- eB/2nm. The mean 

energy per collision, transferred to an 

electron, is: 

Wc- (e*E1/4m)(1/(4nI (F-Fc)+(l/il)), with: 

0- magnetic Pield; e- olectron charqo: 

m- electron mass; E- applied electric 

field peak amplitude: 7- mean time between 

two consecutive collisions, inversely 

proportional to gas pressuro; F- frequerlcy 

of the appliod RF field. 

At re60nance F=Fc, and the quantity WC 

assumes its maximuin value: Wc - (cEi)'/4m, 

which depends only on collision interval 

and electric field peak value. Clearly the 

maximum bonoeitn of tho ECR effoct is 

achieved in the low presouro ranqo, being 

the col~ision fi-squency proportional to 

the operating qas pessure. 

For a ion propulsion system in the 

millinowton range a RP excitation in the 

V"p range proves advantageous for the 

rollovinq considerations:

I 

I 

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I 

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- it is possible to use 8 low level static 

magnetic field to rench the resonance 

condition, e.g. 36 GausB for resonance at 

100 me. A lower thruster mass can be thus 

ach ieved : 

.. slnco the ~avelcnqht 10 much hiyher thar 

the chamber dimensions, problems arisinq 

pram energy propagation into plnsna can LU 

avoided. In case of VllF oxcitation, plasma 

generation Is infact achieved through a 

"noar field" mechanism so that no cut-off 

frequency exists: 

- it is possible to use coupling 

olactrodeo. for the VHF RF field, outside 

the discharqr? chnmbcr, clue to the lini'ced 

rwor losses for irradiation > 1/~, i.6 about 2 UHZ connidcrinq 

a pressure of 10'-4 Torr and nn alcctron 

energy of 13eV. This condltion ensures 

that electrons turns around the magnetic 

field many times between consecutive 

collisions: 

2) R 1 cm, whore R~is the qyration 

radius of the electron in presence of a 

magnetic field dirocted nlonq tha chamber 

axis. This condition enquros that the 

electron trajec'ories are conta,iriwl in the 

# 

+ischarge chamber; 

3) EM field wavelcnqht >' 3+5 cm. Tnis 

condition avoids propnqation problems in 

the plasma. 

In summary, the ECR technique IR expccted 

to provide substantial Lmprovenenta in low 

power ion thrusters pcrformanca, enhancing 

the advantages of traditions: RF tcchnlqes 

in combination with qthers typical of the 

Kaufman technoloqy. The main fotsturcs of 

the ECR technique are summarized as 

Io1 lows : 

- ECR sources do not have components 

subjected to wearout, as cathodes or 

accelerating electrodes, l.n the plasma 

charber. I , 

Problems of sputteriny erosion inside the 

chamber are thus eliminated, impac; ing 

positively the thruster lifet ime. 

Moreover, it is possible to realize the 

discharge vessel with materials having 

high secondary electron emission 

coefficients, scarcely sensitive to 

erosion and capable of reducing electron 

losses from plasma towards tho vessel 

walls. 

- T:.e plasma produced by the ECR 1s hiqhly 

uniform, both in density and t-mperature. 

Achievable ulec'ron densities ar@ of the 

order of 10'12 electrons/cm'3 at pressures 

in the range of 10--4 + 10A-5 Torr, thus 

facilitatinq beam extraction optimization. 

- The ECR technique is specially 

advantageous for ion thrusters operating 

at' low thrust levels ( 2410 mN) where it 

reduces considerably the Instability 

phenomena inside the plasma. Low thrusts 

ere related to small chamber dimensions, 

which eimpliliee tho realization of a 

uniPom magnetic fielc! in tne dlscharge 

vessel, and requires less Dc power. 

A small chamber also requires small 

electrodes for electroinaqnetic energy 

tranwfer, with lower losses due to EU 

irradiation and vessel walls absorption. 

Furthermore, for constant average beam 

current densities, thruster throttling is 

accompl isiied keeping the mass flow rate 

to beam area ratio constant. A reduced 

flow rat& is associated with a pressure 

regime within the discharge chamber where 

ECR proves more efficient and stable than 

other traditional excitation techniques. 

- Tho yrid extraction syetcn can be 

dcsigncd and optimized on the basis of the 

enhanced plasma characteristics typical of 

the ECR technique. In this direction PROEL 

Is investigatinq also new technoloqies 

(patent pcn-llng) for the realization of 

qrids with a qcnmstry having a hiqh 

transparency factor to ions, while 

maintaining good nechanical rcsistnnce and 

the capnbillty to survive to sputtering 

erosion. 

The USQ of ti hiqh melting point refractory 

material, coa t ed with sui table 

anti?putterlng protcctlon layer, is the 

solution to long lifetime requirements. 

6,CONCLOS IOttS 

Electric propulsion, and in particular 

advanced ion propulnlon. is an enablinq 

technoloqy for the feasibility of very low 

Earth orbit missions, in power-limited 

liqhtsats, where drag in the doninant 

effect. 

Furthermore, low power ion thrusters are a 

good system alternattve for propulsion 

tasks requirinq tho stoady application of 

low thrust levale ovcr extended periods of 

time to implement a qiven velocity 

correction. Nevertheless very lon9 

lifetimes, of the order of 20000 to 40COO 

hours, must be reliably demonstrated. 

Improvements In mass and power efficiency 

of such low power tiiusters wou!d a!so 

benefit the liqhtsats design. 

Lov power arcjets, in the 1 Kw ranqe, have 

also promisinq applications for certain 

orbit manoeuvering tasks, and their 

development s:iould be further pursued. 

REFERENCES 

(11 J. Reale "A low altitude Lon-prop-IIf*d 

remote sensing spiscecrnft ": 27nd 

IEPC; Viaregqio, October 1991:

[ Z ] C. Purrotta, M.Bieconi, A. Bicci, 

H.Capacci,C.F.Cirri,G.M~tticnri: I' Ort ita1 

control and manoeuvering of lightsats / 

synchronous natellites: assecww?t or new 

ion propulsion technoloqioo b m 4 on tho 

Electron Cyclotron Resonnnce pherrsrnanon to 

Improve thc poreormancc of thrusters in 

tho mill iHawton ranqc": 27nd IEPC, 

Viareqgio, October 1991: 

[3) C. Pcrrottn SAR wnsors an tACSATS: 

a eeasibiiity assessment" : this 

Conference: 

i 

(41 C. Perrotto Emerqing new concepts 

for non-CEO satellite networks: a review*: 

ICCC '92; Genoa, October 1992; 

[5! J. Oonodicto, J. Fortuny, P. Rostilla 

PACSS-11: a medium altitude global 

mobilo 133tQllitQ system for personal 

communichtiono at L-bandn: ESA Journal 

Vo1.16 N' 2, 1992.

I . 

Ihfcmc Advanced RcJcuch hojccts Agrncy 

Advanced Systcms Technology Ofkc 

3701 North Foirlon Drive 

Arlington. VA 22203-1715 

Am Overview OP DARPA's 

Adwumdl Space TccBowo~ogy Program 

I. P SP w 0 r) c CT IO s 

In the rhrcc dccdes thmt have clapcd rime the beginning 

of the spuce aae. satellites have incronscrl in prrkirmrncc 

ond cspohility hy orders of magnitutk. Dcniantls for more 

copocity hnve. in many cases. ken met by merely 

increasing the sire and wight of h satclli\cs. with more 

channrls for communication or mote mrmciry or mnrc 

proccsring capability, but still reprcscntotive of thc 

clisring stoic-of.the.ut. In general. the Dire of satrllites 

hns grown sianificantly ovcr the early irail.hla?cr 

vcrsinns with their admittedly limited capobiiitics. Yet. 

thcre are indicaticms that we still hnve n Ion8 way to go 

klt,rc he ultimate limits ue rcochcd in "mating thing* 

small." 

In the present economic climate. it amwar* ccrtnin that 

there will he significant cutbackr in most arras of the 

dcfcnw htljict. including militory rpace ay*!rmq. fhc 

I.kputrncnt id Dcfcnsc (DoD) and thc dcfcntc iritlintry will 

he eapecied to design oncl field more MJVMCC~I and mcirc 

efficient spnre systems. These newer systenu must, mit 

will. make even more use of miniaturircct hifih technology 

components thnn are incorporated in our current stable of 

satel;ites. Using this philosaphy. future syctcmr cnn he 

e~pcctcd to hove cqual. if not grratcr. capabilities thon 

most ol he current systems on a unit wciBht hnsis. Upon 

implemcntntion ol this philosophy of reductinn in the size 

md cost of huth satellites UKI lhcir tnorter rockets. we 

wiil hove made major steps toward synergistically 

satisfying cmcrging national nccds for retponsive and 

reconstitutoblc space systems. 

The Defeme Advanced Research Projccls Akrncy (DARPA) 

is the ccntrnl research and development orgnnir.niion ol the 

DoD and. as such. has primary re*pnsibility lor the 

maintenance of U.S. technological superiority over 

potential adversaries. DARPA's programs locus on 

technology development and proof-of-concept 

demonstrations of blh evolutionary and revolutionary 

epproaches lor improved strategic. conventional. rapiddeploymcnt 

nntl sea ;mwer forces md on the scirntific 

investigotion into adv~ced basic tcchnolngics of the 

future. DARPA cnn move quickly IO exploit new idcar md 

c,oncepts hy working directly with industry and 

universities. 

For four years, DARPA's Advanced Spocc Technology 

PIOgrmr (ASTP) htu addressed various ways to irnpve the 

pCrfO~MCe of small sate~~ites md launch vehiclcs. The 

advanced iC%hnologies lhaI are being md will be developed 

by DARPA for small satellites CM Se used just N easily on 

luge Sakiliter. The primary objective of the ASTP is lo 

Col E. NicatriI and 1. l)nld2* 

2. The Arroqpre Corpornlion 

Suite 7WO 

955 LEnfant Plaza. S.W. 

Washington. 1I.c. 20024.2174 

25-1 

enhance support lo opcrnlional commanders by 

devcloping and applying advanced technologies that will 

provitlc wst.elfcctivc. timely. flcxihlc and rrspcinsive 

spxc systcms. Fundamcntal to the ASTP cffort is finding 

new woys to do business with the goal of quickly ictcrting 

new tcchnoltrgics into DoU space systcms while rcr,ucinp; 

cost. In our vicw. thcw nwthods arc ;wime cxnmples of 

uhat may tw tcrmed "technology leveraging." 

The ASTP is a muliidisciplinary technology development 

cfkirt aimed at quickly exploiting dvanccd tcchnologie3. 

lncludcd in the program ue: 

Sponsorship of the initial launchcs of the 

Pcgarus Air.Launched Vchiclc (ALV) ond thc 

ilcvrlopmcnt of a Standard Small Launch Vrhicle 

(SSLV); 

Dcvclnpmrnt of cnohling tcctiniilngicc 

tubdividcd into sntellite support suhsyetcrns. 

SAlCllile poyloads UI~ 

communication terminals: 

Development and launch of small satellitcs lor 

demonstration to and evaluation by the military 

Services. lncludcd in this area arc the Multiple 

Access Communications Satellite (MACSAT) 

program uid the Microsat program: 

Development of standdired. multimisrion 

common bus undcr the Advanced Technology 

Sundnnl Satellite Bus (ATSSR) program; and 

Development of two advanced technology 

satellite demonstrations scheduled for lnunch in 

the mid-1990s. The Advonccd Satellite 

Technologies for EtIF Communication (ASTEC) 

program will develop and launch two EIIF 

payloads. The Collahorotion on Advanced 

M u I i i s pe c ti a l E ar I h 0 bse rv at i on (CA hl EO ) 

program will develop and launch a multiple-use. 

remote scnsing, multispectral payload. 

The ASTP has initiated ovcr SO technology projccts. many 

of which have been coniplctcd and transitioncd to uscrs. 

The objectives arc to quickly qualify these hiRher risk 

technologies for use on furJre programs and reduce the risk 

of inserting rhese technologies into mojor systctns. and to 

provide the minieturizcd systems that would cnahlc smaller 

satellites to hnve significant -- rather than limited -. 

capability. Only few of the advanced technologies can 

be describcd here. Ihc majority of which are applicable to 

both luge and small ratellites. 

The authors wish to acknowledge &e valuable contributions of LTC Robert J. Bonometti. DARPA. and John bairn. 

Spre Applications Corporation. 

.

I 

23-2 

2. ):SADLISG TF.CIISOLOGY PRo(;wAM\as 

2.1 Subsystem9 

A sigriificant purcion of the ASTP effort is clcvotrd to tho 

dcvclopmcnt of satellite subsystem tcchnologics. 

Suhs)stems such as pwer suppliks. attitude tlctcrminolion 

and control devices. comm,unicotionq. computer 

prcrcessing and memory storoge. propulsion units for 

stnti:,nkccping rnd repositioning ore. of necessity. 

prcscnt on virtually every satcllitc (whrtlirr "light" or 

"heavy"). All of these items contriburc to tlic weight of 

the snteilite nn-orhit; thus. niajtir reductions in wcigltt and 

cost not only hcncfit the soteIIite. hut nIso aid in reducing 

the sire nnd Coli of the booster vchicles that pul t h h in 

orhit. The ultimate ohjcctive is to minimile the six and 

maRioiire the efficiency of launcher vchiclcr and the 

satellite bus so that the "business end" of the the space 

systrm -. thc payload -- comprises o much morc significant 

frat-tinn of the ovcroll satellite weight. 

2. I, I LiRkrwcifihr Rcarrion U'hrzl 

ne Lightweight Wrartion Whccl (LHW) is a magnclicdly 

rusprnded reoction wheel with rrdundarit elcctronics that 

will provide five timer the mnmcntum of erirting units at 

the I me weight, with growth potenlid to ten limes the 

momenturn. hy using rnognctic bcoringr in lieu of boll 

bearings and fastcr rotational speed. The LRW requires 

U percent lcrs power and can hc used nn all sntellite,: its 

higher speed 4 rrduccd bearing vihration pntrntially CM 

hcncfil oprraticin of onhoud scnsors (e.g.. lcss "bluning" 

of a scnwr's imrgc). This cfron is aimal at ihr design and 

delivery of a prototype LKW for testing a?d siihrcquent use 

on a satellite. The prototype LKW will he flown on an 

upcoming Air Force Space Test I'mgram llight. 

2:l.Z Aliniaurc Global Positionin# Sy.strm Rtrtivrr 

This effort ia a technology devclnpicnt project to design. 

fabricate. develop. deliver and demonstrate. in an 

apcrotional cnvirnnment. a spncc.qunlificd. niultic!innncl 

Global Positioning System (GPS) rcceivcr lhan can bc uscd 

to support autonom~us navigation onbnard spacecraft 

(Figure I). The GPS receiver will enahle the simultaneous 

reception of mulliple CPS navigation sipnals. therehy 

providing p:ratrr psition accurory in cottiparison with 

cunrntly ovailahlc rcccivers that sqricntially receive the 

miiltiplc GI'S navi~atinn signals. The IIW cif gallium 

arsenidc (GaAs) tc#:hnology has ennhlctl this morc 

"pwcrful" rccciver to fit in a much more compact package 

(one-tcnth the siic of previously space-qualified 

receivers). The GI's rcccivcr is scheduled to "fly" on 

several space rnissinns hr4;inning in 1993. 

2.1.3 Artitndr Dricrminnlion. Control and Nuvigaiion 

S y.5 tcm 

A single. fully inrcgratcd guidance. navigation and control 

system is hcing dcvclopcd under the Attitude 

Dctcrminotion. Cnn:rol and Navigation Systcin (AWNS) 

projcct. It will IIW low cost stu trackers. fihcr optic 

gyro*. gencric VllSlC space-borne coniprrirrs nnd the 

ASTP-dcvclopcd GPS rcccivcr (sec parogrnph 2. I.?). The 

strap-down star tracker is designed to determine attitude by 

recognizing stnr pntirriis via an acquisition search pattern 

(a slow attitude chnnge maneuver) and mnintnin that 

attitude dctcrmination in ony orientetion via ncorly 

continuous star tracking. Low cost, high!y reliable fiber 

optic gyros provide attitude determination during high 

slew rate rnnncuvcrs. smoothing between aiai sighlings 

wid rnte stabilin~tion. Spocccraft autonomy is maintained 

by using L h GPS lor navigational updates. AdvPnlagCs of 

this' project include a star pattern recognition algorithm 

that r\iminkcr he nmd lor U\ initial altitude acquisition 

scnsor (i.e.. no sun or wth scnsor is required) and generic 

applicability to all three-axis. stabilited spacecraft. 

- \/ 

-LI. .., 

'. 

//. 

Figure 1. Miniature GPS Receiver 

2.1.4 /nJ?atahkc 'Torut Solor Array 'ferhrvhgy 

Solar arrays typicolly provide spocecraft power. At 

present. as the omount of power required increases. the sire 

and wcight of the solar arrays incrcaw _- n situation that 

rieccssnrily constrains the capabilities of poyloads r , 

small satrllitcs. The ASTPs lnflatahlc Torus Solar Array 

Tcclinology (ITSAT) prnjcct amis to ni:ike pssihlc spacc 

missions that are othcrwisc imlwssiblc hy providing 

incrcawd ovnilahlc pwcr while niaintnining vmall launch 

vrilurrie and wright. An inflatnhle. srlf-rigidizing torus 

striicturc ruplwris :he solnr ccll hlonkei. The inodulilr 

design allows for cosy insertion of new solar cell 

tcchnology including thin film arroyq. Thc current ITSAT 

under dcwlopmcnt hog dcsign goals of 100 watts/lcg and 

120 wai.s/m2. 

2.15 Atiniaturizcd, Lav. Pavtr Parallel Processor 

The basic goal of the Miniaturized, Low-Powcr Parsllrl 

Processor technology dcvclopment prajrct is the 

rcduction. hy an ortlcr of m:ignitutlc. of onhurd pror essnr 

sire. weight and pnwcr consuml)tion for s~iarc..h:isc~l 

scnsor systenis. Such proccn.cors must cmphiy niazsivcly 

parallel architrcturcs with lorgc numhcrs or processing 

elements in order to actiicvc thc high throughputs required 

(up LO tens of billions of operations pcr sccond or more). 

The appronch for achieving this goal is to use threc- 

diinensional. hyhrid wafer scale intcrconnect aiid 

pacia~iiig technology. In this conccpr. individual 

modules with multiple. unpockaged seiniconductor chips 

are compactly intcrccinncctcd intq a high dctisity packagc 

with substantial weight and power saving5 over cxisting 

packaging appoachcs (Figure 2). 

2.1.6 hlugnetic Disk Macs Mrmnury 

Hotuting disk mcmory subsystrrns have becn n leading 

technology product for many years. Allhough not widcly 

applied to space applications. they represent statc-of-thc- 

art for high tlcnsity. mechonicrl mcniory suhsystcm~. 

They arc less complex and hnve fcwcr potential mechanical 

failure pints then troditionol spacchornc talx recorder 

systems. Thc objcctive oi thc Magnetic Disk Mass 

Memory project is LO dcvelop a magnetic rotating disk 

mcmory suhsystem that will provide up to 1 Cigobyte of 

high-speed data storage. The effort will rcvicw availohle 

optical and rnibnetic disk equipment. detcrmine the

- 

physical and mvirnnmmtal rrquiremcntr ktr npcratitsn 

ahrud a .p.crcrdt. url design uul fahricarc nn mclnsurr 

suitable lor rpare flight 

1.2 Fm)load lechnoloplrr 

In additton tn providing more rmm lirr payloads nn 

satcllitcs. cc intcnd w increase the nunihrr ul hits or 

pixels per pnund for communicatinn. and optical 

paylods. Se .rial p ~ects have ken inilintcd lo clo just 

hi. In IM mtim. we discurs snmc 01 ow EIIF. UHF md 

kaur mmmuni'atbn initiatives and several i4 our olitical 

tcchnoli~y~cs Inilialiver. 

2 2 I Ellf 

2.2 1.1 Psrylmd ctmctp 

The mnst promiwnK. new. near-trrm ieclindngy lor 

protected cnmmuniralions employs :he EllF hand 

(apprnxm.tcly &I Ctlt uplinks MJ approaimmly 20 Gllr 

duwnlink.). The ASTP hu several tcchnolv&y yrojku 

underway that syncrgisticallv complrmenl and support 

other Do0 work in the ENT arena. including the 

applictlim of advanced technnlngies that ruuld 

significantly rrduce the site. weight. volume MJ p~rwcr 

requtrrmmu 01 exisling EllF sysicms. We ue striving lor 

a hS percent rrhction in quL4 pnwer compunl with the 

present tcchnntopy hase. Within five years. further 

lechnology mdrances should provide an dditiunal 

30 prrccnt reduction in weight MJ pnwcr. hescntly. our 

audoes indt;alc a payload weigh1 01 ipprnximalely 

67 purds br a 15.rhanncl. low data raw (LDR) EllF 

package IS pssihle (compul tn the eai%ting 225.pnund 

package). A highly efficicnl. 2 walls. 20 Cllr 

IrUIsrI.illmg. high.powcr amplifier yields on overall 

eI!iciency ol at leas1 35 percent; it USCI a rsctntly 

deweloped (DARP Spnnsored) CaAs permeahlo hase 

umsism?. AI&# developed for thit pnject ire a 

high-spcrd signal proensor. lightweight signs1 generator 

ud lighlweight scanning anlenna. The U Ollr vulning 

amna hms a variahle brunwidh. making it capable of 

operating in elliptic. U well U circulu. orbits. 

2.2.1.2 Sphrriral Lew AIVewsa 

The Sphcricml Lens Antma prsjcct has as its ohjcclive 

the development of a wide licld-of-view (WFOV). 

elcctmnic scmning. multibum EHF mmna cspahlc of 

nulling interfering sqnds md operating in a vuiciy of 

orbiu. inludin8 those that arc highly elliptical. The 

munna's radiatinp apenure is 8 splm of Mlid dielectric 

Ih.1 provides a graduated index ol refraction la furm the 

ractating .p*tum. Fsedhorru 10 VrMgcd with equal 

~p~:hg on a concwo spherical awfica adjacent to he 

dielectric sphere. TO lorn .n electronically scmcd 

UIVNI% any one of a luge number of fee& b ercited 

hhmugh UI interleaved. switched lrm network, which CM 

combine c l u r of ~ horns 10 perform complex nulling or 

CUI 5c wed for simple swivhcd beam operations. The size 

or the lens dcpcnds on lk minimum gain requirement 

(0.8.. for 2.5 38 minium gain, cha lens would measure 

apparimately 2.5 inches in dimeter at a fryucncy of 

44.5 GHt). The estimated sirs or lk uuenna (lens. 

horns md switch U-) h 12-inch dimeter cylinder and 

rJ inches long. 

2.2.2 UllF 

The mosi widely used d. unfomnutely. most vulnerable 

mililuy satellite communication (MJLPATCOM) frequency 

band is UHF. The Multiple Path, Beyond Line-of-Sight 

(MUBL) Communication effort is aimed at providing 

interference-resistant voice communications among 

affordable. handheld UHF terminds having appmaimatcly 

5 warn of RF OUQul. The concept provides a singlc.hop 

capability (U seen by the user terminal): it may be lhought 

or U M amplifying ionosphere. No salel~ile crntrlinlring 

is contcmplated. When more t h one ~ satellite is in view 

of the communicating terminal pair. there are multiple 

popagation pah. "be modulation nnd coding system is 

designed W sdppon this and resist interference from other 

satellites. In addition UI satellites. MUBL CUI ba mounted 

on high altitude balloons. mountaintops or unmanned 

aerial vehiclh. Successful implementation of these 

concepu could rubsumtially alleviate shortcomings noted 

in che went Dcmt Storm operations. 

2.2.3 SatrlliteiSubmarine Laser Communications 

Initiatives 

A number of laser communicarions studies and 

demonslrrlions are underway or have been completed by 

rhe ASTP. n\ec common objective is U) dcvelop reliable. 

two-way luer communications systems. For submarines 

having OlpMded operational depth and speed envelops. 

laser communications povidcs the plential for timely 

message delivery at wdul umsmission rates. Current 

submuim communications can be enhanced through the 

use of bluegem laser technology. Submarine laser 

communications sysmnu will require small. lishtwcight. 

pime power cllicient laser5 Md nmow spccaal blnd wide 

t3ld.c.f-view optical fillen. The ASTP h u scverd blue- 

]Ireen laser Pmjccts that address these challenges. AI 

pesent. here development efforu focus on he Cesium 

Atomic Relonmce Filter (Cs 4RR md alternste narrow 

handpass filters. as well as several laser umsmitter 

technologies. All cr there technologies ue being 

developed for rapid insertion ino ..aididate spaceborne 

luer communisations systcmr. 

223.1 CeJiwm Alm'c ReJoMnre Filter 

The Cs ARP pm~~ct U desigmd w investigate enabling 

technologies IO support srlellile-to-submarine laser 

communications. Specific ueu of investigation are 

satellite system concrpt delinition and uplink rrceiver 

kcadboud design ckvelopncnl ud testin& The Cs ARF 

raciver a p u h utilims a unique side-znupled Cs ARF U 

h buis fur he 4.rell anay ('igmc 3). This approach 

porrJcs very gomi hoadbmd signal rcjcctinn wtlh 

erc..plionally high mband sipnal throughout. Our 

Iimdings w-date have resulted in an order of magnitude 

improvement in cell efficiency fra 4 percent to over 

47 percent.

124.1 PhwdAwmy Mimv.~tnhbkL.u#eApn(ur. 

Apmure si- of pent space.IHwd oplud systrms is 

limited by c0.t md rrlilabiiity of a vch*k IO launch a 

logr. massive. prim mina. The Phsd Anmy Mi-. 

Eitendahle Large Aperture (PAMELA) project is 

devclqnng Ihe Icchnnlo~ IO build a mim mmpKd of 

lighlwci#hl lcgmenu Ihu CUI be folded fa launch and 

auimatically spacedeployed IO form a luge aperture. 

(5- Filum 4). The rchnology will dwclnp md mtrgrste 

srgmenr Sensors and position 8clunIora with conlrol 

algoiilhms for accuram remote dcploymrnt and active 

N~U. mml. Minimm wnms on dI djaccnt edges 

YI)Y reluive w;ment offwt. %se acNon, CONidnnl 

key IO Ih tochnob#y. have bccn denmnrhmsd 

p- .*.HI -q 

Fipunl. PAMELA 

ML wmiIIIc 

2 2A.2 Inmid PseudoS~w Rr/nrr. Unir 

The lncnid Puud0-S~ Ref- Unit OPSRU) pc:a 1 is 

developing a sin;le unit for pecision pointin; and 

subiliuliol of 0pic.l pqlods. It will uwnp~u for 

nuwhMicd hwa! mov.(~ota. thanby albwin; Ih 

uuorpa.tion or la# stiff and lighter smrtuea. Th. 

, 

LI &-I- 0- 

Fgun5. PSRU 

-. 

2.1 43 Elccmm Turnfin# Se- 

Sensors for a wide range of signals are nf primary 

impmtmue for d v m d lyrtcms in acmspwr RlIihIcc 

rmd conuol. mbotin. tuget imaging and oihcr trnpmmt 

applications. The ultruensitive cl~cvon tunnel .crun. 

recently dcvclopcd at lct Prnpulrion Lahnrsimy. has 

applicalionr in adrmued arcclemmrtcrr. hydmphnnes. 

ma~netometers and rwm.tcmpraiure infrared daccttm. 

The Nnnel smsor is bard an Ihe quantum mcrhanicd 

elwlron tiinncling merhanim used in thc sranntng 

turncling microscope. which won Ihr 198b Nokl Prim 

for Phy-ics. A armpvt ti*mI sensor wilh he size .nd 

mu: of a penny has been micromachid from a silimn 

wafer. Recause tha tunnel arnm can be fabricated ii 

silicon. it is possible to fully inteflaie Ihc tunncl sensor 

6th iu nkmclecmicn in a dithii silicon pekap. 

5.3 MILSATCOM Terdnal TeebmoloBy 

Developmeat 

DARPA’s IMPACT(hmion into MlLSATCOM &duns 

olAdvrPsd Cornrn~~k~~P~ Tahmbgin) Fvogrun is a 

mullidiuipliny tsclaology development clfon limed at 

phased insertion of advanced technologies into 

MILS/.~M tamind syuenu. Tho fundanmid god of 

lhis p orn in IO reduce ha lifa cyclo cost of the 

MLJATCOM U nnid segrnnru with umciited reduciiav 

in unhal sim. weigh1 d pmwr consumption and 

Onhnsenrnu in pcrlonnrra. nliabilily and capbilities. 

lb pOpElI MldTUSel bod IshnolO&y effON hat Ipu, 

dI MILSATCOM terminal po;wna with iechnnlogy 

insation initiatives. reuotiu ad upgrades. as well as 

enabling ucblogy developnonis in sumrt of neat- 

pnaatian Mminals. 

MlLJATCOM qyatems cumally encompass a diverse 

mollind. -I tmnin.l 01.1 ue designed IO inlcrfvo wiUi 

mcrd differem m a of saullita operating in three 

MILSAXOM brdr Eah brstay b.nd offm pniculu 

d~~tagcs ad complmentuy chuvteristics to Ihe 

orardl dormu rpa rchicocm 

In lddition IO his diversity. IIU urminal populatinn 

brapa.us numeroo1 distinn aystcm implementations. 

lncludiy nunpek ud man-porubb Immidr: mobile

IMPACT rill work cbuly wilh thr MILSAXOM lamiul 

community nd with 1echnolo;y devsloprs. B 

conducting m intr;raa coherent C N IMPACT ~ wit 

synergistically bvmage ongoing wak within this 

mnnlmily md Wilkin inbuy IO rh*r*IL* puducc- nd 

vraicrud ;a& d I& mrm. 

IMPUX wiu m e a mm md mte mndtiip0lrnr far 

ths new m of defense rqvisiiim i6 which budgetary 

collruaim messwe raked f&img d m-w I Y I ~ nd 

Ereus anphrU in plued m meach md dnebpnmi. 

This pgrm will pioneer Ih. leveragin# of RAD IO 

uppd.. .o.uin ad modemin existing rrldsd equipwnta 

in order IO nunlain Ih. cnmptilive uhmlcSical 

MIVMII~O that the US. now powasus in defcnse 

capbiliun. 

1. LIGIKSAT COMMCMCARONS 

TECHSOLOGY DEMOSSlRATlOSS 

Amhr driy &ud by th ASR b.h rnul onorbit 

dernoruuah of compln~ rysms. This prwides 

-pof of ttm pdding- far all thc parodivy pha of RAD 

effm in mums sdh. md wWstcm ad eompnent 

developmrml in he form of conclusive on-orbit 

operalions. 

3.1 MACSAT 

The initial wnstellation of DARPA liJlw WP launched 

01: a SFOII hur m May 1990. two- rlh ~ rmpd 

ch. pmm. It includd two UHF nm-ad.forrud 

suellitm Ih. MACSATs. 11 IU p l d IO demm~tru 

thew opr~ion IO ucticd wmmudan b U realistic 

enviromncns U pouible. Th. drmorW.lioru would 

duplay gbbdnwuye relay for mvlpct *ra*u*. IO b. 

wsopmb* with existing guipnem. 

The MACSAT whdula demonnuaid ml accelerated 

mpOnM d developwnl lima wilh more 

convenlional synmn. The Mx performed 

communiuliona operuioru in suppon of Opratiolu 

kvrC Shield md DM( Slan (for th US. Mrin 

capx md were urd in uaining demommliaa far th 

AnnY md Ih. Navy nd fa Anuretic mppon far hr 

N.liorul Science Fotlndrinr Nunemus Clnwnsuatiau 

including Uuumisshn of diaitized phomvaplu hare 

bm -inbed. 7h physical c h d h d Ih. 

MACSAT# m I f0lb.l.: 

I 

The MACSATa am p l d in a nea polar circulu nbit 

(89.9 drpa inclinuion) 370 mlical mile altitude. Up 

to 1.024 'mailboxes may be accessed. The 

wnununiSUi0ns prkage operates with UHF frequency 

shift keying (FSK) receivers and either a IO-watt 

8.mminer OT a Wwm hi;h porn msmitter. The 

nad.rd 3.u rate U 1.4 Kbm allhough dannu~ationr U 

4.8 Kbp hair been .ccomplUhed. 7%. electric F e r 

Nhystcm IIU. a body.moonlcd Y-.olu all may ad a 

144.wUt.h mmmcrrial nickel cuJmiun (NiCd) Luuy 

prk. operuing in ml I8.VOll Dc bus. 

3.2 Mlrraal 

A reumd nm~ellalion of lcvm canmwicatim satellites. 

wei@.hmg 50 pounds euh. wem launched on a single 

Pegrslv ALV on July 17. 1991. Th. saielliua (known as 

Minosus) vac deaiRnd I, vide intra-!heater voice M 

di;iul cm~nunic~io~ don; wih me sune.md.faaud 

digilal &U m-kr. The electric pm sysm includrd 

I8 wlu ;neb I. *. 50-watt-han commercial NiCd 

buuy pet. a 5-volt I ~ regulaIOr U ud a 5/15 volt 

DcW amvmer. The utiiude coruml sysurn imluded a 

uzh swua ad magmomem for reference. loqw mdr 

fur spin-up and a 1.I.liter nitrogen tank for 

U.lidecping. The communications nylm dlnved fnr 

eilher analog or digital communications. A digitally. 

mn~~lled UHF FSK lawrlt umuminer u*l FSK receiver 

allowed voia canmunicatinru or up IO 4.8 Kbps di;ital 

data raw. 0nmidircctim.l b!da mmnu rem deployed 

an ~III sidn or chc npucrdt. Microuu hd chc following churteristics: 

12.silw 

19-kh diuneter. 7.5.inch height 

Dcployahle antennas 

Spin stabilized 

Niww cold gu propulsion 

The Minaam were designed IO bc ejated from Ihe curiagc 

in such I mum. U IO plrc them in a single Mhilal plrne 

with 400 naulical mile altitude ci?culu orbits. Allhough a 

lwrrh vehicle anomaly resulted in a much lower nrhilal 

altitude. !he -I mnclination ud satellite spscing was 

rhievd. A v y suocesnful demauush pogrun was 

canpkted before Ih. sawlliia re-entered !he ~UIIM~~CE 

qp~~imalrly sir monh afm Iatmch. 

4. ADVANCED TECHNOLOGY 

DEMONSTRATIONS 

Cmsiscent wilh lhe new LhD Science and Technulogy 

Sua*-~v. DARPA hu initiued a numb of new pgruns 

IO ~u1~1LIy develop nd apply dvancn( iechnoln~ies inln 

echro1o;y demonsuationr. The purpose of there 

~ V M C tedmology ~ demorutrations is IO ensure we 

Wnlinue to purnue the advancemen1 of enablin8 

uchmlo;ia 

:gv. 

ha may b. requbal in our future wenpns 

r)lIenu #&U, reduce the risk,,lor incaporaying these 

. fuwn sysums. demonstratinu 

Peguq d.T.uur launch vehicles 

nd &.*l IUW pVkU lb b#imonsuale advanced 

wllita uC*lolo;*l fa conmunicuioru ud remote 

u+sing.

Lulrhd durimilr NASA md Navy p*bd on 

8 sinrk launch aiubn: 

hmhed lcven Microuu on I 8- lsnch 

miuion: a d 

- hided 1h8 fir11 damnNuatiOn of a GPS 

receiver operating on a cprcr 

launch vrhiclc during Ih. boai @.U 

U.jUIOty. 

ucmt 

FolWi Ih. rvlt laud of Peg&, umu pdonnnsr 

upgrade8 rm inenparaled for Ih. Lcond bunch in 

luly 1991. Although ch. second Pqaru :aunch 

expaicncd 1'10 8ipliIicm1 inflight nomdiu n8uhing 

in 

- 

a Ima-t)un-inlmdsd orbit injmim aliituda, Ihe faa 

chat it Nmrrfully nbiud UK wm Hianlo 18 8 vbibk 

meum of ch mbusmaa of iu mumemmm pidmce and 

control 8yrlem and ultimate capabillly., Design 

mOdXkUbm ID Ih p b h 8 hrr krd.rebpd 

nd m in Ik prom8 d being qudirak 

4.11 T w u 

The Tamm SSLV will pride the capMlity to Imnch 

appiimmly five linvl Ihe cqaci~y of Pmanr from 8 

~round~IranipuIahle ry.cnm. 11 consiu of P8guu8 

wichoul winE. and a brier Idring nWng atop a 

Perekecpnr fir81 8Inga. Th. mlta lumh splcrn i8 

Umsprmbk nd cm k opcrucd fmm bm bas% lunch 

tile eUaMi8hnunl is complad within five dap d 

i 

p.yloada CI ba 1.rCbd rlw 11 b.n d 1.- 

lolificaticn. 

Tho current TIUW design cm place approximately 

2.000pounds inlo MO nautical mile, 286deyr 

inli Omit. 11 in expectad &a with modirwuh 

(i.e., ddiwnel 81rap.on mown ud a new apogee ti 

motor). Taunr8 will ba able 10 place small 8nle~liler 

(6oo.poud Clnu) inlo gO0.wiony nbiu. 

4.2 Advanced Trcbaology Standard Satrllllr 

Ban 

The ATSS8 pojccl will deiign and devefop 

mul1imis8ia1capble. small. UUrLrd rprrcrah bur hi 

incapam a new -ah CO building utellita hi cn 

accommodnlo differen1 lrpca of 'boll-on" mirsion 

pylodr. The boll.on CO"- cn hell bo dcvrikd U a 

ryltcm having an irulnml payload 8llached 10 8 high 

performance. lightweighl bun employing ndvmd 

lrchnoby h g h a single. rudrd intduc (Rgun 6). 

The ATSSB will br capahk of uceping there Lnli.on 

p8ylod8 from a voicly of candidate mirsion areu 

including meleoro~. commun*aliosu. 8lwcih~e and 

arking. u g a l0cum.r md Nvigah. 

Paybad8 employing Ih 8lMdrd bur w111 he Inmchmblc 

fmm hoch mall nd lrge hunch vchicln and clplhk of 

palming in a ruiefy d ahiu. Thr ATSSR F V ~ I will 

povidc &ri#ns fur a renntile bus hi rill allow rtngc 

c&ly nd cy. in rrcmriiiurim of SF U-. 

Th. key fealura of Ih. common hur mr8 r;vahiliiy. 

.rTadabili~y md kaihili1y. Cqhlity rnnn biainly hy 

mrnploying newer Iechnologie8' enshim; g:rrier 

prfOnnnCa in malla prkJgC8. Autnnnmu8 nht nd 

UtiNdo dnermilution will mabk srrlliu supnisnm. #I 

well U ulalliu maintenonce. Th. nummmms miisim~ 

pluming function will ultimately enable the rylpnt of 

Iuticnl Uler8' immediate larking rcquircmenlr. The 

dlordability of 111 auclliw iyrtrrm is Iar#ely n function 

of mal sa~llite (and alainrcd brmm) weight. U well U 

thm number of uniu procured. Obviourly. the non. 

d g 

00.u will demeum when eah satellite ceua ut 

k a quxid design cue in itself. In additinn. che 

hiibility of Ih. bi1.m COnqN nylwm CUI en8hla quick 

htegration ud chmga out. if necr8ry. immcdinuly 

pia (0 Immch. 

TIN mnrnOn brr paida ckn #uClllrd 8drC with I 

Umdrd ckcuicd inlerfms o m.u rilh a wide r qe of

! 

--- ----FE- 

UICLIEASWO SAIEI Ill€ WkH&!l#! 

Figuro 7. Pnybd Msaa Frmbno. Cunm Spokms 

and Futt~n Gods 

The p dmance requiremenu lor he ATSJCQ indude: ( I) 

suppon to payloads of up to !MM lpounrnb ;requiring: 

400.600 wmo of pnk power. (2) rhmo-anib nltitudc 

canlrol. (3) atadarcl communicatim linlrm. (a) propulsion 

for orbit rnaintmas\ce. nd (5) a three.yem oniaaion lifc. 

The partla uill emphaoire Ihc UDC of c mmm industry 

rtnndmds mal will be scalable to WFpoft OOOO-pnund 

paybods with a revcn-year milrion life. 

4.3 AStE@ QQlOOQO~rOlhn 

This 1)AWPA.led joint DoD pronrnm iate~rotcs the 

advanced EWF communications and satellits suhystcm 

tcrhnoktgico urrdit Cevcbpmrnt m DARPA/W@ md flight 

dcmonrtratco two experimental. lightweight. EllF small 

satellites. T)M ~oals of he program MC to supprt the 

joint DoD Global Surveillance and Communication 

(CSBC) dcmonrtration objectives: I 

Develop. space-quolily and transition lvlvnnccd 

technologies IO support the mid- 1990's 

. MILSATCORI modernization decision milestows 

ud integrated CSBC demonstrations: 

ASWSI the utility of small satellites IO: (1) 

augment IPrp,cr backhnne sr.tcllitcs; (2) cnahlc M 

cvolutionrrylalfordable approach to 

MILSATCOM procurcment/maderniartion; 

(3) provide quick reaction IW~C md specidixcd 

communications ovpporc: md 

Smc 111 m wquisitinn management t ctW rimed 

at towering ccsu md redwing "time to mrkcr" 

fa new srtcliitc systems. 

The gwrd ptDflun approach cdis for Iha 6vakqment. 

launch rid 8cmonstration of two technology ac%,0lites in 

geosynchronous orbits. Satellite 1 incvatcs he 

prototype ATSSB a d the Massachusetts Urnotiauie of 

Tcchb8ylLincoln L.bauory-developsd EMF payload 

I 

4 ' 

2s-7 

Figure I) shows IRr functional layout of he core payload. 

Th corn of koa pnylodo is M EHF communications 

pxkarJQ lhrl pvidea 32 MIL-STD-1582C LDR chmls 

d two MILSITD-1810 MDR chnnrerls. The data rate fm 

the LDW chnnnela io 75.960 bpr and for the MDR 

chmnncls. 4.1-1638.0 kbps. The core EHF 

communicatipna pnckagc will provide a variable 

kcanwidth antenno ant wes a dichroic lens to support 

bth uplink ~scd downlink with a single reflector. Two 

earth covcrogm Promo nrm included. The payloads will 

perform all riBnol paeeaoing rquired to maintain the 

MIL-STD-1512C and MIL-STD-1810 transmission 

formats. As a &sign gool. the pmylods will have a 

dulcu dcsiun bu dbw early l~hrrolo~y uppoder. U well 

00 scalability. for increased channel crpacity and ertra 

8D0l beans. 

Figure 8. ASTEC EHF Peybad 

Thc technology ~ VMCCS goid U a rcsult of the ASTEC 

technology demonstrations will greatly impact future 

MlLSATCOM systems through the introduction of new 

coyrbiliiies. incorporation of new advanced tcchnologies 

and demonstration of new implemcntation altcrnatives 

such t) small sotellitc mugmentotion. The ASTEC payloads 

implement he following new MILSATCOM KIyiciv: 

First on-orbit MIL-STD-1810 (EHF MDR), 

capability 

- Supports 4.8-1638.0 k b data transmission 

- indudes four channels on Payload 1 and 

eight ch.mwls on Prylod 2 

Unprocessed (i.e., transponder). VHDR EHF 

capability (Poylood 1 only) 

- Supports rintillati~-rcsistant lclivcry of 

widebad data Wkom rcmots k ations 

- Supportr &U rnm wp to 274 Mhps from a 

IO-foot, 500-watt transmit terminal. hough 

cha AnEC VMDR WMS@~, 

receive terminal 

lo 2O-fOOt 

!

2s-a 

The paylord concept is distinctly diffmowtt front typical 

"dud UM- approcxhco. Rather Ihw chEaahp n mum LRnc 

CM he wed only for P single purport by "&id w s " (ia.. 

t:loud imaginc for DoD and civil d a ) . Qb goa[gmm will 

develop dvmccd ~ ~lol uxhnology dapcfda U) mnltiple 

plrp0-a by muldipl. usm. 

SgmiTic t esW a%$xJvao m L# 

Dove: '8 and apace.qualify an advanced. 

multiopced. remota payload for small 

satellit6o; 

-trona mh.mimim wage of ATSSB for 

.mina pyb& in tow earth orbil; md 

!&vel& aid dmonrttnta Common Data Link 

(CDL) s ~ i d - d ~Anology fa mall satellites 

end dimst dormlinlt comw4vity to mobile earth 

taminmls. 

OIlr first Ectivity W(U IO identify Ihe DDD and civil remote 

tensing requirements and needs that could bc met best by a 

multispcclrd paylocd. EIistinC DoD requirements urd 

mensurmrenrt rarcds mmcintcd with civil programs such U 

Lartcdan~, NASA's Earth ObPming System (EOS) and the 

Strotegic Environmental Research and Gevelopment 

Progm wew nrweycd, from which emerged clcu area of 

ovnlop in qwc~rol coverage. spectral resolution. etc.. 

hat indicate mmy rcguiremenll could h ~ddresscd using 

an intogratad multisgsctral payload. The requirements 

frrr.cwmk wu U& lo &fine llw general churctcristia of 

a paylord d m in-how atudy wm conducied to define I 

point desion. This design proved feasihle for 

implrmentotion a mall sokllita payload on h e ATSSB. 

runent gmogrfun plan cd!s for system development 

rwuistent with m FYW launch. 

Tk first mo swvcyed w u climnlc rcscuch. The highest 

piority memwemmu for detecting and charactcrixirig the 

global climats change liana1 and the pattern of this 

chanp hove ben well uticulsled by Ihe U.S. Global 

~ a n memuch ~ e propam and many individual pcientista 

uuch M U?. Jim D~anasn. Dirtcta of NASA's Coddard 

htitutc for S~OCC Studies. The core nieasurcment 

requirement cocmiiol to chnractaiting Ihe climate sysiem 

is long-term monitoring of Ihe cmths radiation budpet. 

The00 measurements have not been mode for 

~ X h O V ZIWQ l ~ yEI?PO d lpona We p\fUUWd befote he dqloymmt of 0 rdiation Waet rdiometcr on a Japnnere 

mtellitc, in &a mid-199& SRd he f't EOS system in the 

Iota 109%. Et is eomtiol to undrwtand mm'r impact on 

the climate EYSkm. anthropgcnic climate forcings. 

Spece mcnowemntn of rcroools. omc. water vrpr and 

snsrfnce re9ectivity (albedo) am required. all of which. mi 

pemt. m nnaaowd hcdquatcly or not measured at all. 

hotly. the climate feedback mechanisms are poorly 

understood nnd modald. It is eooeniisl to understand 

whlher mm'o impact on he climate system results in 

hfp? K P changer ~ (e.&. cloud cover) chat positively or 

nqotively reidmca h d towd alobal warming. The 

most important of ;hess requires detailed globrl 

menrwacnta of clod polnre md prrcicle rim. 

P), wcod IPDUMUP~~~I area CanaiQIcd is mvironmentd 

quahy monitor@. inrludinn pornmeters such U air and 

voter pllutioa hnacwdaws waste rite monitoring. wetlands 

- 

cad I d w mitorin EBEB rurvcillance of natural ud 

mmm& dioatero for unerpicy response. Most of 

&em pmamrltro Rave oilplatwe fearares hat emerge from 

multiogtctrol mcosurcments. Although Landsat and 

Sptem0 hoWm d'Gmaw~ion de la Tmr (5m have 

cr9graod many of Ihaaa. heir rpctral bmdr were not 

cphized U) w u m chan and heir spatial resolution is 

\

i 

0

2s-10 

\ 

I 

i 

I 

f

I 

0 

I 

I 

I 

@. 

I 

1 

@uc?otion: You mentioned an JPSRU progiam where platform 

jitter is assessed/eliminated using a.laser. May I 

ask: 

a. If the intent of eh@ program to measure jitter 

(for later post-processing), or to eliminate/compensate 

fox jitter through is slaving control mechanism? 

b. Is litexatuxe is available on this matt-r (open 

or at least releasablelto NATO)? 

Reply-: a) The vnit albnc provides very precise and 

accurate line-of-sighk offset measurements for high 

frequency, low magnitude jitter. When used in concert 

with a fast steering Lnirror, or other closed loop 

syst.em, it can actively remove jitter. 

I 

b) The organization developing IPSRU is Draper Laboratory '.$ 

in Massachusetts. The program manager is Mr. Jerry 

Cilmore. 

meetion: Would you comment on the status of CAMEO? 

Reply: The CAMEO, ASTEC,and ATSSB (standard busi fundinj 

has been included in the President's Budget submission 

to Congress in Fiscal Year 1993 and is in the Five 

Year Defense Plan. The initial technology work (for 

EH)' Comms has been conducted for DARPA by Lincoln 

Laboratory and awaits further funding. CAMEO payload 

specifications have been developed. The ATSSR is . 

currently in source selection. The Congress deferred 

these programs in FY 93, stating their opinion that 

we are premature in starting the program. We plan 

to re-plan tire program for a full start in 1994. 

Que~ation: Referring to submarine laser communication.9, 

where you indicated that the submarine would uplink 

a signal for geolocation purposes to assist in downlink 

laser aiming, what measures do.you propose for preventing 

exploitation of this uplink radiation by hostile forces 

for the same purposes? 

Reply: There will be, in general, euff icient geogrdphl.ca1 

separation that exploitation will not be possible.::",-,. ,., , . 

Use of EHF ensures nhrrow beamwidths. 

25-1 I

~Y!!?w!L 

Tho fnasibllity of installinql SARs on 

board liyhtsats for tactical and otrategic 

oboervat Ion mlsslons 1s dllbcusrred, 

enphaolzing hlqh resolution and short 

rovlsit intervals as moln syoton drlvers. 

Llqhtoat constollations deuign criteria 

are prssentcd for both globnl on4 limited 

latituda belt covoraqe. Pros and cons of 

sunsynchronous versus ncdium 1ns:lination 

non nunaynchronous orbjto are discussed. 

Gross Bystem trJd0 Off3 for tho SAR sensor 

are then arldreoaed, in tho spccific 

context of a resourcc-llmitod liqhtnnt, 

stressinq tho achicvcncnt of *@solutions 

better than 5 n, swaths grestsr than 20 

Km, access anqles of at least 30'. small 

anton?ta dimensions and a reaeonnblo powwr 

consumption. Roth X and C band SAR 

solutlone are outlined. Ditn transmisslon 

alternatives aro also discussed,* In the 

contoxt of tactfcal and 1 stratoqlc 

scenarion, outlininq thcir ' projectod 

performance. 

I 

Conotellation orbits control and plattorn 

attitudo are also addrt-ased lor tholr 

Impact cn mission , SAR Inn70 Quality a.id 

natellita design requircnents. Rsy aspects 

of critical platform subsyetens are also 

idsntified. 

/ 

1 L 1 !?IK~KG-roF?- 

Liqhtsat constellations 'aro rrceiving 

considorablo attention by industry. 

qovernnanta 1 Aqonc I cs and commcrc la 1 

carrlors. Thalr potontial for strateqic 

connunications is well undarntood by 

ailitary planncrs. which contnibutod to 

the rant spinorf of major prnjncta boing 

undertaken by Rome American sytaton houses. 

Less well perceived are the 1 iqhtnots 

capabilities for :emote senninq and 

obscrvation tasks for both civil nnd 

dofense uses. In 1990 , anticipstinq tho 

need for new and unconvcntlonml oolutions 

to observation sateltites, AlonIn Spazio 

started an Intornal ntudy addraoning tho 

feasibillty Of small SAR QatOlllteQ, 

stressing tho achievcment oP ; high 

resolutions and short revlsit Intbrvnls. 

Tho '91 Gulf War provided furthor ntlmuli 

in that diroction, reinforcod by tho 

world-wide trend concernlnq npaco and 

dofenco budget allocatlonn. Flree results 

were publiehcd In [l]. Slnca thon, further 

work on ayatem architectures and trade 

offs hao boen performed, concontretlnq on 

military applications and tho nosr-tom 

foaslbIlity wlth available tochnoloqlras, 

thus avoidinq long and contly now 

developmente. This paper revlauo nom0 of 

the most recent results achleved masfar. 

, 

SAN SENSORS ON TACSATS: 

A FEksIllILIPY ASSEGSIENT 

' C. Porrotta 

Alanla Spario 9.p.A. 

Via Saccomuro ?4, 00131 RODQ, Italy 

I 

2L SAR OBSERVATICIN MISSIONS 

SAR sensors operational value comes from 

their independence from time of the day 

and clouds cover. Achievable ground 

resolutions, swaths and access anqles are 

comparabln to those of panchromatic 

optical sonsors. Nevertheloss SARs respond 

differently to the physical foatures of 

the obsewr' 'cone: thio may be exploited 

to enhancs certain target characteristics. 

SAR and optical satellites can therefore 

complement each other. 

Howover, in a tactical scenario, where 

weather and time-of-day independence of 

the observations are a premium factor, SAR 

satellites outperform the optical ones 

from an opcrntlonal vlewpoint. 

In addition, constellations of SAR 

oatollitee can offer performance 

unmatched by larqer spacecraft flown 

individually, much as Inhorent redundancy, 

mor0 frequent rovislts and an easier 

dCCCGB to in-orbit rOEOUrCO8. If SAR 

u~nscr~ can bo flown on liqhtsnts the 

total syoton cost can be considerably 

reducod, whilo achieving nom flexibility 

in deployinq and managing them. 

2.1. System confiqurntion alternatives 

We will discuss rcpresentatlve missions 

otreoninq tho hi-resolution ones for 

dofonso applications. SAR llqhtsatn can bo 

launched on-demand, for short duratlon 

observation tasks over cpeciflc arcas, in 

the event of qco-political or nilitary 

ctlsee. Alternatively, lonq duration 

mioolons with liqhtsats constellations can 

ba envisaged to porform cont lnuous 

obaorvations within a given latitude 

bolt. 

ThO cost-effcctiveness of short duration 

aissione is ncvertheloss questionable, 

considering the nced for a pormnnent 

ground Infrastructure whlch has to bo 

operated and mairbtainod anyway. and tho 

satellite and launch costs bhich arc 

poorly amortized. Permanent constellations 

car., Instead, otfer, oven batter qlobal 

porformanco at a higher initial cost which 

ia howevor amortized over a much longer 

aorvlco p0riod. Furttiermoro, a pernanent 

constallation can provide shorter revisit 

incorvals and, outside crises perlcds, 

otratwic observation aervlcos as well as 

remoto eensinq functionu for qovernment 

and public une, with specific referenco to 

pot-dioaeter damaqe aceesement. We will 

thus concentrate, in the following, on 

lightsat constellations. 

\

aLRaqy1 rsmnto ,.verviaw 

An incrooairvgly important aoqpirawmt 

cnnc~rno tho rovimit intorval with which 

military rolovant sitae, mat Rxa obaeovdr 

typical value14 from few dmyo to ad hourer 

apply rsinly to fixed aaoota. Obeorvitq 

targeta variable in tino or apcico 

requieoo, however, much ohontor raviait 

Intorvalo, of the ordm 00 ton houro. 

Concariring ground resolutlon, 3 a are 

suffictont for detection, In none 

cases rocognitIon, of fJeIrQteqliC ally 

relevant fixed or low-mobility aoaata. 

Tactical applications nead, howewe, 

better resolutlons down to 2 tn or leos. 

The swath width , or instrntanooub fiold 

ol viow, must be commonoureto to tho 

thoaton: 20 CO 40 Km , depondlppgl from tho 

qround reoolutlon, are likely WQ~UO~. The 

swath m0t also be oloctronicnlly 

repositioned inside tho acconn anyls, 

providiq a high operational Blcnibility 

in gaehoring SAR images of aolectodl opots 

duriq oatollItee* overpassea. WdQo access 

anqlow FAYQ instrumental to :BOCU~B a 

covcrsqlo without *holes* and td n1nirsir.e 

tho con~utallation*o satellites nunhr. 

TIme dalay ninim1ratlon hotwoo; o reqluaet 

for dater and its wailability to tho onduser 

io of utmoot importance, apclally In 

8 taCtaCQl eituetion. Direct aCCOOa to tho 

satollitm~, during sites oworpmssca, 

followodl by 10~91 dnta fux~ooain9 and 

intarprotation by multlple,dmto atatlono 

doployed in the theater, pro nom am an 

ekfectlve answer to auch nemo. 

In a oeacteqic occnario thQK0 in the 

additional requirement of tming &$lo to 

oboorvo dintant nitan with a ohort 

turnaround time. Hclajinq lmegouy data vIa 

a Data Walsy Satollite network bn tho most 

logical and performant solutlon Ito the 

prob lei. 1 . 

3LCCNETELUTIONS DESIGN CRITERIA 

I 

WO must diatinquiah bctvcon syntono aimed 

at providing a global Earth covaraqe and 

thooo Intendod to covar a narrower 

latitude bclt around the equator. 

AD a mattor of fact, most Countrloo whera 

politicel instability is oxpectm! to occur 

also in Pueure are includod in tho SO' U 

to 50' 6 latltudo belt: which m y justify 

tailored constellations. 

3.1. Conetellationn for-qlobal cowsraqw- 

I 

A modul~lr solution &onsiete in injocting 

oquispacod lhqht6atn in olnqie plan0 munoynchronouo 

orbitnr the SAR con bo 

provided virh just ono or two antmnnem 

looking on both sides of tho flight path. 

Multipla raguispaced orbital planma Can 

cop. with vory stringent reviait Intorval 

rof~uirowntm, i.e. less than 12 hours. 

3.1.1. Ljalhtbat C-tolkat Iona u m o x 

sneonns 

The capability of e 6AR to inago tarpot 

oreas inaddo a wide oarth strip is 

proportional to the a-xoaa an910, dof1n.d 

polv tho alninun and rwximrr ole-nadir 

nerglleci. TRQ conetol lat ion daml@n -cr'itorib 

ohould peoi*ida for a contigypad, iarth 

covorag~, wIthIn the above'~on~trhinis. To 

thio and, the fundaQental inteeval is 

divided into U oubintarvala whose vidth 

corraaponde to the SAR antenn8 access 

angle projected mto the evator. If the 

ainimum and maximum off-nadir anglos 

cstiofy tho conotraints of Fig. 3.1.1.. 

then tho strips accoroiblo to tho U 

astellitom vi11 bo contiguous. 

FLg. 3.1.1. SYSTEM GEOYETny 

right antenna 

accoee angle accoee anglo 

I i 

In ono orbit period, the N satellites vi11 

have covor-ed an Earth slico as vide as the 

fundamental interval, and the cycle will 

repeat providing a continuous Earth 

coverage up to a latitude close to the 

munsynchronoue orbit inclination. 

with tho constraint of keeping ha 

rainimum and maximum off-nadir angles close 

to 20' and 50' roapaxtlvely, the number of 

setallites N depends frota the orbit 

altitude and acceoo angle, as shown in 

tIp.3.1.2. and Table 1.1.1. 

* . . . . 

'I * U. .ll.I..ll. .*I. 

* . 

*. .

c_- 

XZiiK matelT. mloy ka>r*can 

h.ipht(m) per plan. two S/C rnnooo(.) 

------ 

270 -150 lo 10.3-20.3 i r 

?oO-BQO 8 23.9-29.4 * 

4 4 3-700 6 3x.1-3a.Q * 

* 100 4 49.5 

(b) for two-antonna SARS 

------I_-- 

Table 3.1.1. satsllieon nunbor vn. 

orbit altjtude 

- -, 

W i t h thin atrarqwnont, :tho co+opt 00 

ropoat cyclo Looooo partld Ieo cnohrlnq: in 

otner words s1n.a a cQntiguouo onrth 

covorago can bo achiovod daylp and SARQ 

are 900 sensitive to dun illumination 

condition;. orbit rcpcat',cycl@o of 1,2,3 

or aore days can be choscd. Thio providea 

mor0 Proodcm in choosing tho orbit 

altitudo, which ie a critical Pnctor for 

SAR dimnrloninq duo to'lightantri powor 

tiaitationa. On tho other hem%, tho 

variabllley of tho incidence aqlo, with 

which D oito can be obocawcrr0 during 

subsequant days in tho repeat Cyclo, nay 

bo CQnObdOr@d a pOSitIV@ f@l3tUFO In ViOW 

of tRa WaoLbilLty of implemontiny B olow 

sanplirpq rata Irrcidonce angle divarmity 

eystoa. whlch may or ance the rocorpition 

of cixod aaaots. 

Since Smn can oporato day and night, tho 

ono-orbit plane configuration O C ~ ~ O Va Q ~ 

noninal 12 houre rovloit intowal over 

nont altos. If revisit intervrlo nhorter 

than 12 houro nro roquirod, H oqlulopacod 

orbit planm can be inploncntod, and the 

averago rovinit interval will bo 121~ 

hourn. Tho price to bo paid io nn ~ - f ~ ! d 

increane In tho satellitos nurhr. 

l 

,I 

' ! 

--I--- 1 

I 

26-3 

Xuaot~allkmg Uho SkiR antenna on the left 

oddlo dloclcoaoao olightly the maximum 

ob~orvshlo~ lc~titudoa, a feature common to 

011 rretrogrsdo orbita. Fig. 3.1.3. also 

alhowo tho rowinit intervals VS. latitude: 

tho 12 houra velu0 is confirmed, with 

ninor dovhationo above 60' due to the 

inclination oP tho orbit plane combined 

wIth the okientation of the SAR antenna. 

Tho aystem go or not^ in Fig. J. 1.1. is euch 

that the acc@so angles, and the gap in 

batween, dubtend identical arcs on the 

oguator, Correspdnding to 1/Nth of the 

fundamental intehal. Aftor 1/Nth of the 

orbit period, the previously unaccessible 

otrip iQ now visible ,by the 2nd satellite: 

after 2/Nth of tho orbit period, the strip 

accessed by the left antenna on the 1st 

natellite iu now visible by tho riyht 

oneonna on the third satellite. Each strip 

can bo, thus, accessed twice by different 

ooeolliton with a tirno delay of 2/N of an 

orbit poriod: uoo Table 3.1.1. In summary, 

the presence of two antennns does not 

chanqe the nurnbor of hatrllltes required 

to achlovo n contiquous Earth coverage, 

but allows looking at the same target with 

difforont incidence angles after a rather 

Ohort time dolay. This allows implementing 

(3 fast oamplinq rate incidencr angle 

divorolty ayotem, for target detection and 

recognition enhancement purposes. Desides, 

target ohadowing effects ulll be lessoned, 

slnce tho O B ~ O arm ca'I bo observed from 

both righe and loft directions. With 6 

two-antenna SAR payload, stereo SAR 

inaqlng In lat?ral viaion could bo 

ulti~atoly implemented, providod that 

ouitsbla proceaeinq techniques will be 

developed. 

Obuorvstion ,oyotoms for Iinitcd latitude 

bolt c0*~0~cp90 oxploit the chnracteristics 

of lcw to modiun inclination non 0unnynchronous 

orbits.! Thiu ia poesible due 

to tho 5AR indlpendcnce from sun 

illumination conditione. Lou orbit 

inclinatlons give soveral advantages. 

Pirnt, tho number of satellitos required 

to contipuouoly covor' tho fundamontal 

ir.eerval io 108s than with sun-synchronous 

orbits. Thio is ohovn in Tablo 3.2.1. 

ropoae/ inclin. hoiaht H' Sat. 

orbLee ('1 !#tu) per plano 

1/15 30 482. I i 

e(. 

m w 

40 480.4 4 

50 696 5 

2/31 30 328.4 5 

m w 

m e 

40 334.4 6 

50 342.7 7 

3/46 30 378.9 4 

e n 

m m 

a0 380.9 5 

50 392.9 6 

- 

Table J. I . 1. Won aunoy&hronouo orbits 

conoes~lotionor satallit.aa 

VQ. altitude and inclinatlon 

-

264 

giving tho nunbor of oaeollitnn wrt Plana0 

Vn. em txbit inclination CIM eltltwdla, 

with aiditional constraint oinioun 

ana aaximllm oft-nadir en9100 of 20' and 

50' 

c,:-nd, ai latitudes cloeo to tho orbit 

inclinatior the ground track0 Blro rfc?nnGr 

and DOVO onst-west instead of northaouth. 

This feature may be very uaefull in 

certain regional sceiiar loa. 

itowever, if all satellites are in thO setae 

plane thoro vi11 bo a cluntouing ol 

revielea every 24 hours. To achiave an 

even upreading of the revisita trough the 

day, it is essential to redintribute the 

satelliten in t4 orbital planoo, with a 

proper phasing (riqht ascmnion and 

satellites' true acomaly). An oxample of 

application way presented in (11 and is 

also mentioned in a companion paper (21. 

Third, ono m y combine orbital planes 

having Biglorent inclination0 and same 

fundaaental. Coverage continuity n mds a 

propoe phaelng of satelliton orbital 

parPmoeorm, achiovinq also B roduction of 

tho rovioit intewaln at irrtitudas 

corrooponding to each orb': planQ 

inclination. This approach rducoa the 

oproad in tho averaqo rovlolt intorvalo, 

typical of constellations with one orbit 

plane inclination only. 

.;ne orbit plane oriontntlon playn a 

fundsnQnts1 rolo in liqhtn@t deoign. 

sin910 plana down-dusk nunoynchronous 

orbit0 aro vory convrnicnt for SAR 

satellitas: infect fixed solar nro-ayn 

be- uod since thoy aro always LIIuminated 

by tho Dun. This fncilitntcn continuouu 

SAR opaetion, unrestrained by battcrics 

capacity. Solar array wlnqo arc) parallel 

to tho orbit planc ninlnitinq tho 

drag allact. One nido of the opacocralt 16 

alwaym oxponad to cold npaco pravidlnq an 

ideal haet aink for thermal control. 

Mult Iplo plnnes sunsynchronous oabitn can 

be oriented nynmetricnlly w.r.t. PRe 6 A#- 

6 1% plnno implying nu!)-tracklnq nolar 

nrrayo. Earth shadowinq IJr nhout 501 of 

the orbit wlll, anyway, rcfiult rquirinq 

to augport the EAR operottop Pron on-board 

battorion. Aooldes, the ' vanimblo nun 

vector incidence on tho sntelllta, during 

the orbit, complicates tho thamal 

contrcl. Novrrtheloss the eunnynchrcnlclty 

and eyotoa oytnmetry , tho lattar only in 

cand oP an even number of orbit plenea, 

will holp in controlllnq tho growth in 

system complexity. 

Thia w111 not bo so in case iP non- 

ounoynchronoua inclincd orbits. Tho dayly 

nodal oAiPt wlll cause a slow potion OP 

the orbit plane w.r.t. tho clin vactor. Tho 

syntoa daalqn muat, than, cow with 

orbital lporiod timo-varylng phoncrnona as 

well a8 with Slowly ct.angin9 omn. 

Thie may considerably affect tho aatolllee 

d-i9n, SAR operation and minaion 

planning. With medium Inclination orbits, 

-r-------- . 

-liiui7: 

tho nolor onnny doaig? bocomee even more 

critical, rotpiring a I-DOF sun-tracking 

nachanilzn. Tha nsceasity for continuous 

oolcpr wing13 roorientation will cause a 

tlma-changing satellite cross-secti In , 

adding #NIO?.hQr variable to the problem of 

drag compensation. Basides, variable 

cxtornel torques may Impact the natellito 

0ttitudo control, speclal ly at, low 

altitudes. The thermal control also 

becomes mor0 critical due to the full 

variability ol onvironmental conditlons. 

In summary the complexity and ccst of SAR 

lightseta increases qoing from down-dusk 

to nultiple planes sunsynchronous orbits 

and, eventually, to sinqle or multiple 

inclined non sunsynchronous orbits. The 

increased tlntcllite complevity necesarily 

reducos ; the payload nccomodation 

capability Por the samo launch mics. These 

considerations must be borne in mind when 

evaluatinq tho mission benefits 01' various 

orbit alternatives. 

41SAR-CakRYrNcL!_C1(TSATS 

4,l, CApabilities and ljmitotlons OL 

1 iqhtAats 

The doetqn of R SAR-cnrryinq liqhtsat must 

follow a bottom-up approach starting from 

a cot of constrainta and defining which 

(wrformance cnn bo reaasnnbly achieved. A 

liqhtsat cnrrylnq a SAR scnsor for 

pruleeetonai uses cannot be; too small: a 

500 to 800 Kq launch macs ran90 Wa6 

c3onun. bolnq ulthln tho injection 

capnbllltIti?s, in 1.EO. of scveral planned 

anal) launch vehicles. For a 5 years 

1 IleLime, draq conpcnaat Ion is the 

dcmlnnnt factor In sizinq thc propulnlon 

systom. A conpanfrn pnpcr [I1 shows that, 

for long mlnnion duratlonn, electric 

PrOpUlGiCIC tc mandatory to keep t.he 

proprJllnnt mass within 100 Kg at very low 

altitudoe. Tho ansociated IC power 

consumption must bo considerad in 

satelllto power plnnt oizinq. 

Tho SAR antcnnn cannot be too lnrgc: when 

Poldcd and ntoucd it must fit tho limfted 

volumc ineide thc shroud cnvclopo: its 

mnoa and area muot bo compatihlc vith thu 

attitude control cnpabllitlcs and should 

not contributa niqnificnntly to drno. All 

antenna lcnqht of 6 n and n width of 1.5 m 

were definod as upper bounds. 

Tho SAR will normally operate lor a 

frzction ol the orbit period, so that two 

paramotere aro of concern: tho nverncp 

onorgy por orbit and tho required pcnk 

power. [loth Increase with orhit hoiqht, 

thoreforo SAR-carrying lightsats must 

preporably fly rather low. 

Tha avornqo enerqy col lcctod by tho 

li$htoat dopcnde from tho chosen orblt 

plana oriontation w.r.t tho sun. 

Typically, it can be in the 0.7 to 1.8 

C(UR/orbit ranqo. Considorinq the cnnrgy 

conaunad by ossmntial platform Iunctlocs, 

that available to payload io between 0.5 

and 1.3 KWh/orbit.

, 

i'or a typical 708 operating duty, m SNR N 

peak powsr conaumption of 1.3 to 4 KW 

could bo fittad fron puro anergy 

c 3ns id@ PCP t ions. Neverthe lson , th k a woil ld 

aply to rely heavily on battarlam. Woro 

conservntlvely, a MI powor to SNR 

allocation in the 0.5 to 1.9 KM rplngo wan 

retainad for system trade-ofPR. Concerning 

data rates, an upper technology bound of 

200 ~bit/cec. was also assurnad. In viow of 

the abovo, a SAR payload mann allocation 

in the 150 to 250 Kg range reoulto, ear a 

500 to 000 Kg spacecraft launch mass 

range. 

4.2. SAR SENSORS F~LIG11TSAT~- 

We rovlew the main trade-offs impacting 

tho SAR desiqn in presence of conetraitits. 

Tho SAR will normally operate in the 

STRIPPVIP node: the swath will be 

electronically repositioned, inside the 

access onglc, by beam steering in the 

elevation plane only. Thin operating mode 

wa-s found to be adequate for tho intended 

hiqh raoolutim missions, given the 

lightsats constraints. Other SA$ operating 

nodes, ouch as SCANSAR, are also available 

if required by the mission. I 

4.2.1 xmnqe interpretationj tarqet 

cha racto+?iel.: ice, a&S/N 

! 

For extenckd targets hinh 'rasolution' 

images intcarpretation is nore rolatad to 

pixol sizo than to radiometric renolution. 

A singlo look S/N of 5 dB was choaon for 

.;q'. dimensioning. SAR opernting at 

fi!.rrsnt frequencies respond difforently 

i > '.he physical chaidctcristica of tho 

Earih surface, in terms o€,bachocntterinq 

coofficiont vs. the incidenco angle. For 

tho OB~O backscattor coeificlonte and 

swath width tho average tranmitted RF 

power incressos fcurfold from S to X band. 

Ncvertholess the average backscottsr from 

typicel ground surfaccs also increase by 6 

dR from S to X band, so that the two 

effects conpensate nnd it could bo 

possible, in principle, to transmit the 

same power at both bands. For discrete 

targ~ts, however, the determining factor 

is the contrast ratio against the speckled 

clutter. The relative merits of X vs. S 

band are still unresolved duo to th0 large 

variety of possible scenarioe and the 

scarcity of experimental data at X band. 

Assumimql frequency independent ,target 

Radar Cross Sections, the SAR ohould be 

denigned for the same S/N indipendontly 

from fraquency. This criterion ronulte in 

an incredse of the transmitlad RP powor 

with tho operating frequency, pannlizing 

the X-band choice. In tho following 

referenco is made to a sigma-nought of -15 

dD indegondent erom frequency and offnadir 

angles. 

4.2.2. Frequency choice, accoas anqle, 

andresolution 

In sizing tho SAR access nnglo, too low 

oPf-nadie angle values should bo QVOided, 

not to look at targets with n om vertical 

incidonco. Too large v2luee ohould almo bo 

avoidad to reduce shadowing aSUects and 

oxceesivo image distorsions. 

26-5 

~ddem e'hooo Walitatitrcr considerations 

nor6 graciee limtts are set by both 

roqulatory and lightsate accommodation 

rotatreinto. The upgar value impacte the 

trcnnsvorpla antonna dlm~nsions, as shown in 

Pig.4.2.1. showing the antenna width vs. 

tho neximua off-madir angle, operating 

iroquency and epacecraft altitude to 

ewath ratio H/Sv. 

, / 

1 20 30 40 50 

=IN. otf-nadlr angle. des. 

Fig. 4.2.1. Antenna width vs. frequency 

band, maximum oef-nadir angle and H/Sv 

ratio. 

This Figure shows that, at X-band, a 50' 

off-nadir an910 is both feasible and 

compatible with the assumed antenna 

constraints even increasing the tl/Sw ratio 

to 20 (e.g.: H-500' Km and Sw-25 Km). 

At C-band, one ha0 to superiorly limit the 

maximum oef-nadir angle to about 40', 

loosing in coverage: alternatively a 

maximum H/Sw ratio of about,12 could be 

chosen implying however an altitudo of 

only 300 Km for a 25 Km swath. 

S-band antennas can hardly be accomodated 

on lightsats at all off-nadir angles and 

orbit heights. 

JOO 

10 '. . . 

Pig. 4.2.2. Chiri, bandwidth vs. range 

resolution and off-nadir angle. 

Y I

0 

I

Tho ]Lo~ton boU& Of the Dfb-UFfliTf if3 

dggomAnod by tho SAR chirp bndj'g'dth. 80 

ohown in pig.b.a.2. for romp roaolutiona 

betweon 2 and 5 m. 

The inotmtanaoue SAR bandwidth mot bo 

conp~ltdbll~ with international bmndwldth 

allocationn Por Wedat nyntancr o,wratingl in 

the various (Iroqu~ncy banda. Ht turn0 out 

that, considering the 100 Wla bandwidth 

allocation eOr C-bend S ~ ~ CPGICR~BO, Q 0 5 a. 

rango roaolution limi* ,nuet bCJ ~cc~ptd, 

or 8 oovera rootriction in tho ninimum 

offnadir angl0 to about 40' would result, 

impacting negatively tha covorrega of the 

numbor of oatelliteo in tho CoPaUto~lation. 

On tho othor :..a?, a 2 m rnnqlo eaaolution 

at 20. .nimua offnadlr nnglo Is 

cornpiatib.r ;th both X and S-band choices, 

sinca bsnuuitho cf respectivnly 300 and 

200 me are available lor this aarvlce. 

Azimuth rooolution, in tho 5h.R etripmep 

mod0, dlopcmb, from antenna langht and 

lookn numbar. It is betWeen 2 ond 3 m for 

antenna llonghts in the 4-4 m range, with 1 

look. 'PRO situation is surnmvrizod tn Table 

4.2.1. which identifies two possible 

syston altarnatives: 

--a nodliun-high reaolutLon C-bond SAR lor 

conmtollotione in low to mdiun altitude 

orbito: 

- a high resolution X-hand SAR. for 

constollotiono in medium altitudo orbits. 

The 5-b~nd alternative ia rejoctcxl being 

incompatible vith typlcel I lightsat 

accommodation constraints. I ! 

Freq. Avail. Range Azim. Mmnlnun 

band @:I reool. resol. tt/I;w 

(mi21 (N (m) (Q) 

s a00 2 2-3 ! 20 

c Cl00 5 2-3 4 12 

X 3GO 2 2-3 I not compa:ib. 

(*) at 50' off-nadir, Nloaks-1 

Table 4.2.1. Impact of frequency band and 

lightsats constrainto on SAR 

feaeibility 

I 

4.2.J X-band SAR: Swath, datarates, and- 

RF pow0r 

This section focuses on X band SAR trade- 

offs. The swath, off-nadir anqloe, 

rosolution, pulse lenght, orbit height, 

and av0rage RF power are closely 

interreAated. 

At a nodium altitude or 360 #n and naximum 

off-nadir anqle of SO', achievablo swaths 

and averago RF powers v5. qround 

rosolotion and pulse lenght aeo plottad in 

Fig. 4.2.3. Increasing the puloo lenqht 

one loonoo in swath width b.it &wok powero 

deCrarl60 too. #Ore epeCifi\!i.lly for PUlOQ 

lenqht greater than 20 mi:ronac. peek 

powero bolow 1 KW are faar iblo, whilo 

belov 15 microsoconds multikiltmatt poak 

power lovelo result, inpactittq HPA 

technology choice and relisblli.ty. 

Fig. 4.2.3. Average tranaaitted RF power 

ve. swath width, azimuth resolution and 

pulse lenght. 

0 - L 

- n 

51 

e - 

0 

L 

a 

c 

0 

0 I ' ' /. 

Swrth mldth. K. 

Pig. 4.2.4. Data rate vs. swath width, 

azimuth resolution and pulse lenght. 

Orbit height: 360 Km: off-nadir angle: 50' 

Fiq. 4.2.4. shows how the data rate varies 

with swath and qround rssolution, assuming 

to transmit 4 bits/sarnple, which is felt 

to be adequate for most tactical SAR 

imaging applications. The data rate 

increases with swath and even more rapidly 

with ground r0solution, and is therefore a 

linitinq factor for such satellite 

oyetemo. The assumed 200 PIbit/sec upper 

Bound jq compatible with a 20 Km swath at 

2 U reoolution, or a 35 Km swath at 2.5 m 

rosolution. Lower data rates would imply 

narrower svatha, and viceversa. 

\, 

?

280 65.0 63:6 40.1 

360 84.6 81.8 56.7 

a\ 60 108 104 , 72.5 

560 127 123, 80.3 

660 157 143 103. 

-I 

Table 4.a.a. AVerngQ trangnittad LIP power 

vs. orbit sltitudo, nrjnth and 

renolutim at 50' off-nadir. 

This confirms the desire Tor flying, SARs 

at rathor low altitudes, compatibly with 

covorago and rsvislts goalo. Once the 

swath is chosen it is kept conntant, 

independantly from its rapooitioning 

inside tho accom anglo, and 00 io the 

peak powor for obvioun hardware 

constrainto. HOWOVO~, from: 50' to 20. off- 

nadir, tho antenna beam in tho alavation 

plane must be broadened to cuv?r the 

svath. An a result the pulsa duration must 

be gradlaally increasod to r'ocovor the 

beambroodoning lossea Thus, at 20' ofI- 

nadir, 'tho avorage tra smitted RP power as 

well as the absorbed DL1 power, Is 'about 

1.5 times that at 50' off-nadir. 1 

Other ShR modos can be inploriianted 

according to mission needs, trading off 

goomstric with radiomatric raoolutionn 

(multi-look modee), or azimuth rooolution 

with swe:h widths ( SCANSAR raod'~), or 

rango roeolution with avornge, powor, 

adaptively changing the chirp bandwidth 

and peak pulse power and/or pulse 

duration. The spacecraft design lo anyway 

determinad by the most demanding hi- 

resolution tasks. 

C-band SAR trade-offs results 

Parametric evaluations were also perform2d 

at C-band, achieving similar roaults in 

terms of swath widths, which aro anyway 

superiorly limited by the antenna width. 

Substantially lower RF average trnnenitted 

powers, as well as DC pover requirements, 

are needad consistently with tho lower 

range reoolution feasible at C-band. A 

SCANSrW mode would equalize tho azimuth 

and rango resolutions while nearly 

doubling the width of the imaged ground 

strip v.r.t.. a hi-resolution X-band 

implementation. In this way a eimple 

mediun reaolutkon SAR could h m +mplm-ntcd 

for wide area eurveillonce tasks. 

4.2.4. SKantonna requirements 

A phased array with electronic scanning in 

the. elevation plane will poeltirn the 

svath within tho access angle. Beeidos 

providing beam steering in n +-15' w.r.t. 

the antenna normal, phaoc control munt 

also provide beambroadening in tho 

elevation plane to match antenna beanwidth 

to the swath position inside the access 

angle. 

26-7 

[ha0 to thd o.p~rtuao ovorobzing factor of 

Q ~ O U 2.l:l ~ at OihimuQ off-nadir anglo, 

lbnitod boomo;sopimg in tho slovation plane 

cm bo also inplanento8 to squalize the 

mtanna gain through tho awath width. The 

Righor boanolo@on outeido the swath will 

inprovo ran90 ambiguity control, which is 

particularly important at low incidence 

snglan. Booidss, nadir echo suppression 

roguires putting a beam null at nadir. 

Achieving ouch Paatur0s with phose control 

only ( conratant amplitude illumination 

lboing proforrod to reducm antenna width at 

maxfraum off-nadir angle) may be an 

untx-ivhl task, But it is feasible. At X 

bend a paaalv0 single polarization design, 

using multiple panels of radiating 

waveguide olots fed by power dividers 

carrying embodded phase shifters, can be 

realized starting from already proven but 

simpler design 15). at a specific weight 

of 10 to 12 #g/mA2 with less than 1.5 dB 

losses. A probably lighter technology can 

also be implemented at C-band. 

5. DP.TA TRANSMISSION 

Data transmission capabilities are very 

imp.xtant to fulfill the observation 

miasions herein considered. Two main 

approacheo were considorod: direct data 

transmission to ground and the use of ,data 

rolay satellites. On board storage with 

subsequent data dump was not considered 

practical and affective, also due to 

expected near-term technology limitations. 

5.1. Direct transmisiion to ground 

The simplicity of this approach is partly 

offset by coverage limitations, which 

render direct transmission unsuitable when 

performing SAR observations over sites too 

far apart from the data etation. 

In a tactical scenario, however, opposing 

forces are normally dep!?yed within a 

circle a fow hundred miles wide. Data 

receiving stations deployed within, or 

close to, the theater can easily access 

the satellites of the constellation during 

overpasses and get real-time data for 

inmediate, on-site, ground procossing. 

Table 5.1.1, summarize8 the projected 

characteristics of a direct trasmission 

system at X-band. 

- 

** Satellite terminal 

- Frequency: e CHZ 

- Antenna: mechanical nteerinq', driven by 

on-board navigation system: 

- EIRP : 27 dBW (Ant. gain:21 dB: 

Tx pwr: 10 W) : 

- Data rate: up to 7"> ?fbit/sec: 

- #odul./coding: QP. ./ > 4 dB coding gain; 

-'Mass and DC power: 10 K9, 50 W 

** Receiving Station 

- Antonna: traneportablo, with tracking: 

- C/T: 16 dB/K' (Ant. dl8rn.r 1.8 m)i 

- Slant rango: up to 2400 Kmr 

- syutem margin: > 3 dB 

Table 5.1.1. Direet Data transmission to 

grobnd: System performance

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For tn ainglo plane oun-aynnclnmnmn wbit 

conotallation, mooting tho dloni~n critorh 

diocucanod Ln 3.1.1., tho ncce-nbhla Broa 

from tho oitallite pacaoo in vioibili.:y of 

a data rascaiving otstion ham boon 

paraDotrically evaluatod for n nininurn 

olevation angle above tho horlnon of 5'. 

It DUO^ bo noted that tho ~bovo aroa can 

be ~XXCIR~Q~ two times per doy and ~ Q P 

orbit @ono: aultipla orbital planoo 

conntollationo will increaoa Lhe dayly 

nurabor of such *events*. Tablo 5i1.2. 

shown tho nunbor of uoofull oatellito 

passoo and total accsssibldl arm vo. Orbit 

sltitudlo. Tb. total availeblo Bccors tine 

is botwoon ~430 to 3100 SOC., ~por *ovcnte, 

during which 500 to 600 imagoQ, typic':aliy 

30 by 30 kn wido, could be uado 8vai:able 

to tha data station. Such vsluaa may, 

obviouoly, ba reduced dua to real-time 

ground processing limitationo. 

- 

Orbit Wumbor of Acceeoible Total 

altitudo satellite area access 

(W) pasoes (10.6 Ita-2) time(s) 

268 10 4.9 2500 

362 9 7.6 to 

460 7 9.8 3100 

Table 5.1.2. Direct transmimion to ground 

miusion related porformance 

5.2. Data transmission v i a m& Rels]L 

SatellitQQ 

For atmtopic observations ovor sites not 

in diroct visibility of ground atatlone, 

tho uno of a D M network will bo a costeffectiva 

and performant nolution. Our 

studio8 have shown that , in vim of the 

severa lightsate volumo Qnd ma00 

limitations, Inter-Orbit Link0 should 

preferably be carried out nt 60 CHz. 

Efficient coding scheme3 provldlng > 4 dB 

coding gain moot also bo used to further 

decroaoo antenna size snd power 

requitomants on both user tonainal and 

Data Relay Satellite. The DE3 repeater 

will Lsature onboard donodulationremodulation, 

while decoding io performed,. 

on ground. 

*: 8 dB 

POnoVQ1 during ground proceasing will be 

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onaior. Undlor thooe aooumptions, a 0.1' 

Table 5.2.1. Data trGofor to grround via ottitudo omor !- roll control and lees 

Data Relay Satellitote 

than 0.08' in pitch and yaw control can be 

met as reasonable goal.. 

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NovorthdanfS high frograonq CIQBfi~Uda 0r-r 

conpnornen, 810 might Fm hducadl By 

fioxiblo oppndagdo aubjoctad BO eranniont 

forceo, auat bo minilsiaod duo to tho be8 

effect they may have on iInQq0 gyslity. 

6.3 Spacecraft platform rewironants 

WO outlino some3 platform aubnyatona design 

aspecto ROB~ relevant to SAR performance 

and operation. 

Low orbit altitudes will raqludra oloctric 

propulaion, which must be cosmaidlalrod an 

enabling technology [J] for thoso SAR 

lightnats missions, as alroady discussed. 

tJevertho1ese. flying satelhitan at lou 

altitudo has also positive offmts, in 

pdrticular concerning the more benign 

environment (5). 

The stiucture design, departihg from 

conventional, should adopt a highly 

integrated aQprOxh where a t avmt~ frame 

utilizoa important SAR payload copponents, 

like tho antenna or big boxm, ab part of 

the structure itself, in ordar to save 

mass. Since the bulk of tho heat is 

produced by the SAR HPA, heat rejection 

shc*ilci be by direct radiation Fo spaca as 

far as practical: this is certainly easier 

on down-dusk orbits. I 

The solar array design ia ntrongly 

dependant upon the SAR payload operating 

duty. Infact, since the SAR will normally 

operata for short intervals totalling 5 to 

10 8 of tho orbit poriod, payload supply 

can normally be from battgry, the solar 

array merving mainly for battery 

recharging. The orbit plane cholce, and 

the percentage of time spont In Enrthshadow 

p ~r orbit period, will alno impact 

the OOlkr array siting t0 provide the 

required energy. Bosidos, electric 

propulsion DC power requiresnnts, will 

also increase the solar army siting. 

Accordingly, the solar array hype may 

range Prom a fixed wings' configuration, 

suitablo for satellites in' sunaynchronoue 

down-dusk orbits, to a sun-tracking 

configuration for Spacecraft :n low to 

medium inclination orbits. 

On the above grounds, long lifetime 

operation of mass-efficient battories, 

subjected to rathor deep and pariodic (up 

to 30000) discharge-recharge cycles is an 

oustanding issue for. such L.E.O. 

obsorvation lightsats equipped with SAR 

sensors. 

Spacecraft tolocommand must bo oacuro, and 

possibly jam-proof, to avoid unauthorizod 

entries to the satellite nyntam. Data 

encryption must be also implenontrd, in 

SpacecraPt telemetry and SAR data 

transmission to ground, to prevent 

eavesdropping by unauthorized uners. 

! 

Lightreto in tho 500 to 800 Kg range can 

carry CUI nQnaora for high resolution (2 

to 3 m), short rovisit interval, tactical 

ObQQFJatiOn missions. Medium resolution 

(order of 5 m) missions, tor strategic 

and, in genaral, international law- 

onforcement applications, are also 

Poaeiblo. Such spacecraft can form 

priaan@nt constellations of, typically, 6 

to 8 satallite8 per orbit plane to provide 

global cbverage. Multiple orbit planes 

constellations can offer enhanced 

perfomanbe, allowing also a gradual 

system build-up. Smaller constellations 

of 4 to 6 spacecraft -can be alno 

implernentgd to cover a narrower latitude 

belt akound the equator, while 

eignif icahtly Improving the average 

revisit intervale at sites close to the 

orbits inclinations. 

In summary, SAR lightsats constellations 

can offer certain performance unmatched by 

existing, or plarlned, single and larger 

observation satellites and can provide a 

valuable answer to specific operational 

military needs in both tactical and 

strategic scenarios. The required 

technologies exist, with few exceptions 

needing an early in-orbit demonstration of 

d@vices being now developed. Nevertheless, 

advances in few fields wili certainly 

benrfit future generation lightsats. 

REFERENCES 

(1) C. Perrotta " SAR sensors on board 

small S8tQllitCfJ: problems and 

prospectives"; Proceedings of 1991 

International Conference on Radar; October 

1991, Beijinq, china: 

[2] F. Borrini " The Italian approach to 

tactical use of space": this Conference: I 

[3) G. Perrotta, G. Cirri, G. Matticari " 

Eloctric propulsion for liqhtsats: a 

review oP applications and advantages": 

this Conference: 

[4) D. Caeey, J. Way Orbit selection for 

the EOS mission and its synergism 

implications": IEEE Tranoacticns on 

Geoscience $and Remote Sensing: Vol 29 n' 

6, NOV. '91.*i 

' I 

[5] H.J.Schodol,T.Kutscheid I' The X-band 

CFRP WaVeqUidQ antenna for the Spaco Radar 

Lab.81: ESA Workshop on Antenna Technoloqy, 

Nov. 1830. ,, 

. .. 

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008e~Ensrr witfa ~ bde~ec~ion s of ground 

rmaaIWim~: llmgeas hm b n demonaJQated to 

afford QJILP ercrmeaaely valuable Military 

caopabili~. & I consequence there is 

mnhueal devenogment the* system 

~o~etber wi~h refinements in tbeir 

o eraaiondl deployment and usage. 

J weveu, a number of resopictions exist in 

the deployment of these systems 

mwhued wialto their xlnm.imPlm oprating 

range. "Erie &mum Q erating range is 

G.E. Mefie and L.M. MMU-~Q governed by the heig I! t at which the 

D W-Farnborough 

platform can fly, so for example a radar 

Farnborough 

a i an aircraft with a ceiling height of 

30,MO 

Hampshire GU 14 6TD 

feet will ordv be able to operate 

QUO to about 250 Km before grazing 


inddence is reached. This limitation can 

be removed by p9cocilmg the sensor in a 

AIPsOmeU 

space-based platform. In order to 

maximise the military utility of the 

The gayload concept covered; by this information produced by the instrument 

paper PS that of a low CO&, hieh and 00 allow recognition of targets, a 

performance radar sensor capable of desipn goal of 1m has been assumed for 

detectinn8 and rceognising suak objects spatla9 rewllu~on. 

within &IW imaged scene of be' IEm-th's 

surface usiw the Synthetic A~CROUR~ The poaenaiaP advantages of extensive, 

Radar (SARf technique ~ ~ a noverail 3 

U~RSUR~CR~ fields of view afforded by 

system is integrated with (a TACSAT space baed sensors makes then extremely 

platform in Low Earth Orbit ($!JdCD) ad, attrasaive for wide area Military 

although ~ nly prnssing reference is made surveillance md hence worthy of further 

to this feature in the 

attention, particularPy with a view to 

could anso bavc a 

replacing atrborne systems (although it 

detection of 

should be recognised that there are a 

(GMPP). 

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number of inherent technical difficulties 

in designing a spaccbrne system that has 

me paper provides a parametria Aview similar sensor capabilities). 

of sucb a scwx in the light of ah.: target 

and backpound features to bc ob%~wed. hge acas of the Emroh's surtace can be 

c~ncept is included showing the observed on a periodic basis and more 

hardware realisation of a detailad infomation may be obtained by 

cmdidsarc system, as well as budpas for dwelling on seleaed areas. Radar also has 

the mass, sizc, power and pointing the added advantage of a!l weather 

requirements of the instrumknt. daylnigho operation. Recently imaging 

Additional design features csmEidescd are radars ($AIR) have begun to demonstrate 

the inhencc that short duration missions the capability achievable from 

may have on hardware rcdundawcy and space-based systems but use relative1 

the effect of short, low dunby-cycle hea platf~r~~ns (eg EM-1 weighs 127 4 

observation periods on solar amay and 

C C ~ io contains 4 other sensors as 

battery sizing. 

well ios the SA83 and hence require large 

and costly 1 aunch systems and 

The gaper concludes by pointing the way infra-structures. Further the 

towards a low cost Pi and D dlemowmmr relatively poor resolutions (e6 E k S-1 have is 

system allowing a practical investipauion approxijnjitely 30m) makinp them 

of the key t@c.iniques and technolcPBes. unsuitabli fiw most Military applications 

I and have no inherent capability for the 

1 Iatda8d0Eo.s 

As a result of the recent UK ASTBW 

programme and the deploymenu of US 

system such as JSTARS and ASNRS, the 

ability to combine information derived 

from high resolution imaging radars 

detection of ground moving targets. ' 

27-1 

Bg is, Pa~ever, passible to conceive SAR 

sensors for integration with various forms 

of s d saaelllite glaaoP~m and depending 

on the type of platform used to carry the 

sensor, different options exist for its

The small size aaad low mts of the 

FGlkUb2 tXUd SCWf S bITI%ideRed hl 

this papea win1 resu ? t in sipificm~ cost 

savings waking the dcplsymeno cf 

constdlmiolms of satellites vcuy much 

more attractive. Tbis has the ffurther 

sdvaamuqge of redusing revisit atimcs and 

conseqancw~Py providing information not 

otherwise available from amy I other 

source, and of improprimg iystem 

sumivmbility. In the next scc~ion some of 

the options for a sensor CQDCX~P ape 

descrnbed. This is followed by a 

considcraaion QP system aspects md cost 

and schedule drivers. 

2 Ilmpac~ OP a PodsaeQixnO TACSAT' Slhw 

Missrim om S~RQMO~~ Desdgm 

2.1 A PotermUdaP TACSAT Mhdanop 

The TACSAT mission is onc w&b is 

associated with a Theatre conflict wheee 

the Theatre is defined as being a region 

measuriq some 2WOh by 20WEm aund 

the duraunon of the conflict is mtid ated 

as being relativcly short, typicin8 P y of 

months, rather than weeks or years. 

Although areas of political and mniimy 

risk can Pic at my lati.ude, the emding of 

the Cold Wx suggests that if there were 

to be ~mch a Theatre conflict, then its 

occurrence in the lower latitude regions, 

rather than the more Northerly latitudes, 

seem more likely. 

The mission envisaged for a TACSAT 

SIIR is to provide the Theatre 

Commander with a dedicated saxvice 

yielding surveillance data only mer the 

crisis ~PCZB. In this a er, the dedicated 

nature of the TA U2.g. A mission Brim beam 

taken to mean that the Theatre 

Findip, the dedicated nature of the 

~trvici propsed for thc TACSAT S M 

facilitates some interesting departures 

from the system thinking associated with 

global space suweillmce concepts: these 

departures influence the choice of orbit, 

the spacecraft bus design, and the basic 

sensor design. 

The expectation of a Theatre location 

away from tbe NQP~~w~ latitudes invites 

consideration of orbits of a smaller 

inclination than the golae sunspcbroncpus 

orbit which is characteristic 

of civil remote sensing missions. In 

particular, if the chosen opercting 

philosophy for the TACSAT SAR is one 

of launch-on-demand in time of crisis, 

then the orbit inclination can be chosen to 

maximise viewing opportunities over the 

crisis area. if9 how eve^, the philosoph is 

one of in-orbit storage then an ear I ier 

decision must be made about inclination 

because of the large fuel overhead 

involved in effecting chamEes in orbit 

inclination. Wowever, even in this latter 

case, it may well be appropriate to set the 

inclination oh the storage orbit so that 

covera e is optirnised for the smaller 

latitu t e repions. The absence of 

sun-synshromwn, come 

orbit inclination, 

particular problem 

which is ca able of operating as well by 

nightasby B ay. 

In addition, the relatively short duration 

envisaged for a Theatre conflict allows 

serious camideration to be given to orbits 

significantly lower than those used for 

long duration remote sensing missions: 

these lower orbits, perhaps as low as 

Z4bk.m. would be suited to a ghiloso hy of 

launch-om-demanwd. However, a1 t R ough 

miculwly low orbits we less attractive 

For the case of in-orbit storage because of 

the short life time which results from

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The dediated nature of the sumeiUUance 

required horn the satellite mea th;n~ the 

periods dnardwg which service is required 

are of short duraaion. T idly* a ~tellite 

in the b w UP^ orbitTU0) wccsesmy 

for SAR sprations takes only 5 minutes 

to traverse a "heatre meEasursw6 2QntQkm 

on the SidG! ad with only 2 such passes 

likely day, payload power demands 

can readily be mct from battcmies. "be 

advantqy of this to the platform desip is 

that relativdy smdl solar arrays cm then 

be used to collect electrical pwer and 

trickle-charge the batteries durisna the 

prolonged periods of payload inrachty. 

2.4 Ssmm Dosdgm Gads 

The desien oals for the icnsor concept 

are show in $. able 1. A major diffiwlty in 

realising a radar desien off this 

sophistication is the achievement of such 

high resolutions and in the 

im lementation of a phascd array antenna 

ab P e to operate over isuch wide 

inwmmxmsi bandwidths. / 

Synthetic Aperture Radar '(SAR) is a 

sideways looking coherent irritn~gimg 

technique an able of produein8 rnq14k.e 

imagery. {AIR employs difftlmttnt 

principlles foi achievin rcsoludon in oQle 

two dimensions of the imaBery. 

Convewaisnal high resolutiooa radar 

techniques such as transwniutian~ a 

wideband, lowe duration pu8m caad 

correcolg anmatch~n? to it on reer+' bUWri! we 

employed in Ppnc dunension pqwmdidm 

27-3 

to tRK2 m?!eMiu@ 8rn& Tcbk a iflmu. .a 

the GpplrndWidOBls; commeun5ura8e \%;am 

rmlenaiiom BOP 8 dcty of 

me G~U8~0rn 00 a&mal$Be bm&duI$ 

me due 00 U$@ capabili0ies of vavefom 

d pew era to as mud digititseas and the 

dispersion Ullnl.aParegPg uhe U 

HeceiVg Chai!?I§. '&aPeDt 

impose$ $I redlo~c limit of 

Unless cbmps can be aopceed, a huPaher 

limitirolg fac~au will be the current 

o rating band Jlmdom defined by the 

Gdd AdViSQV %tdk COUlndl (wmc) 

which im se restriaionas of 300 MWZ at 

X-band (GGpB9) and WO MWZ at J-band 

(13.7CIHIa). Dispersion in the atmosphere 

md ionos here is not thought to present a 

majjou pm $, Bern and, if present, the effects 

could be removed using techniques 

equivalent to S~U~Q~OSUS. Ovtr31 it is felt 

that a resolution of Irn at baqd is 

feasible at a 30' gnhg angle. 

The synthetic aperture technique is 

employed in the damemion parallel to the 

satellite track This involves the coherent 

addition of many pulses to synthesize an 

ogertuue sufficienoly Pong to provide the 

desired resolution on the ground. "his 

synthesis is only passible if the variation in 

phase pasah from uhe sews& to the tar et 

and back is k n ~ to ~ 8 n fraction of t fl e 

radar wavekngoh along the synthetic 

aperture. This implies that very accurate 

knowledge of the orbital path of the 

satellite is required. Hobper,, for 

resolutions of the order.;i';@€., Im no 

measurement method of &@t;bkbit gives 

sufficient acmacy in realistic timescales. 

To sumournt this problem it is expected 

that autofocus techniques will have to be 

employed. These have the added benefit 

that they will also automatically correct 

for other effects which can alter the phase 

path length, such as atmospheric, 

ionospheric and gravity perturbations. 

3 TACSAT SAR Sjettellite Concept

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274 

The outhe cdmcept of a SAR mounted 

on such a9 toroidal platform is presented in 

Figure B. B~d~ets showing the mass and 

power demands likely to be associated 

with such a satellite are presented in 

Table 3. 

nee ckthet options 0f S M design can 

be envisa ed QS provide a tactical 

apabdity. i7 n order of rising complexi 

these options include, rnsshanica$ 

steered system usin a single centrzl hi 

power amplifier ( h PA), electronica 

steered systems Pike RADARSAT whic 

iiie a single cenurd HPA and ferrite phase 

shifters for beam deflection, and 

c.lectrslQicalP steered systems like the 

Eu~ogeim A AI2 which use fully active 

hased array technology to provide 

ad Spotlight operating modes. 

Of these fundamental design options, two 

were considered as candidates for 

dli~~~ssic~n in this paper, a partial phased 

array grddin electronic steerin only in 

the azimuth cf iaection and a ful P y\active 

phased may providing both azimuth and 

elevation steering. 

"he case of the potential1 simpler, partial 

evauon steering 

is provided only by mechanical pointing 

was considered, but it was concluded that 

because the Pime taken to mechanically 

int the s tern would be on the order 

'"p" o minute& P F Q number of useful Spotlight 

ima@wg opporaannMes available to the 

Theartae Co.wder would be limited to 

a rather smdi inumber. When this number 

is corn area0 wiahtn uhe much larger number 

of SMC YI ogpo~a~noitia potentially made 

aslilabk f~om a PUUy active phased may, 

@.sed may where the e r 

there appeared to be 8 strong case in

274 

from soia may. For this mission, 

where mamy roRl manoeuvres are 

envisaged and speed is likely to 

x 

be 

~~~OPBZIIIII~U, the approach corn ares 

BWDUJIR~D~~~ wi~b the use of col gas 

@hmtets whkb provide a finite life to the 

told &isW. 

The mP~anua e of this operational 

pMw by is 8 at a$e manoeuvre enables 

! 

re 'QEU on eitber side of 

the S AE US viw~ 

he nadir taaack. U& an o erational 

philosophy requires that t E e wplolc 

satellite indudinmg latforw, solar arrays, 

md SAR muenma, L designed to form a 

robust structure with no flimsy 

pro~ism. 

on the 

oprauing duitpade, carrier frequency, 

spatid ~esoi~uia~n, and possible antema 

stmmres. Wwever, in OPdQP to linlit the 

scope of he pap9 dl options Rave been 

based on an asumed antenna area of 

ha. This area is derived from 

co~~ide~atic~~~i of viable payloads for 

hglcmew~a~on onto a toroidal platform 

within the TACSAT mass goal of < 

7043. 

The deadled domce of a SAR is 

described in t 's section, specifically for 

the single-lobk ca abilities whicb will 

chauracuerise ins; pc 3 ommce in Spotlight 

mode, by parameters which include; 

sensitivity expressed in terms of noise 

equivalent OQ) (PIIEOQ) and presented 

foe the worst cases situation which is 

&aased whh oh6 furthest edge of the 

available ccvemge width 

access croveqe width as that distance 

from nadir beyond wEch ambiguities 

rise to MI unacceptable level 

available swath width for various 

operauixlg mdep : 

Jt 

,,%? ';, 

s atial re$&'hon' in azimuth and 

evation fot$arious operating modes 

e P

In order to erform a useful 

recoanwJssaPnm PO P e, the SAR must be 

capable of grovidina imnBcs of s 

target zones such as airPdeMs, ~nnn ours, 

choke pints aand railwa iwsnaa@rttism at 

the finesa possible reso I ctiow. This task 

calls PCDB Sptiigha operation ian order :o 

provide adequate resolution in the 

alon~-trrmch (azimuth) direction and the 

provnsiorm of this ca ability tis major 

the moer~p~a. 

driver in ohe design o P 

Pfic 

in prirnciple, the azimuth ssmning 

associated with Spotli8ht ogerauiow can be 

provided by rwssh6ulical steeuiun of the 

antenna. However the diff P acnalties 

assxiaaed wiah repeating such mcchdd steerin several times during t ab@c pm 

over t P 

ce theatre are believed 80 be so 

great ahat electronic steering in the 

azimuth direction is considered to be 

essential. 

In addidion, it is envisaged that a 

TACS4T $Ail% my also be required to 

rovide s~m~illmce over a larger re@n. 

!uch cmer cm readily be grmdm!l in the 

form sP 8 continuous strip-map m5in.e~ the 

convenan'aswal Steered SAR mat& which 

has been characterised by SEASAT, 

ERS-1 and the SIR missions. 

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In this mode, which may bc sombiuned 

with Scmsm, interferometric tcs8ndques 

, I 

Access coverange width is fundamentdl 

limited by system parameters whic 

include; antenna areq.slant range to 

ground, RIF carrier fre'quency, and 

satellite ve8scity - although there is no 

si miificzm~ impast from satellite veiocity 

w il 'ch cbmges but little with altitude. FOP 

thio w e in whish antenna area has been 

constrained to 6m2, the dominant 

armeters are slant range and RF carrier 

aequenq. 

P 

The effect of changes in altitude ou access 

mQ sensitivity is show in Figures 3 and 4. 

The data are presented for the case of 

operation inn Spotpi ht mode with an 

a.sumed brandGdah o P 3WIwIM[z. Althou 

this bandwidth is characteristic of t i? e 

WAR@ Umio at X-band md is in excess of 

tile ddB~~tiom at S and C, it is nontheless 

&an 4w. 

It can be seen that at the lower 

frequencies, iwsrreaine altitude provides 

relatively small iw tovements in access 

ca ability while 10 t E e higher frequencies, 

su 1 s ~ improvements ~ d cm be realised. 

Wowever, in both cases, increasing 

dhde sipificmtly de~iades sensitivity. 

The seelmsi@vity data ~ P W E Q R in ~ Figure ~ 4 

shw ahe worn case sensitivity; i.e. at the 

PMnBseso dlistamse from nadir for which 

ampmble owbigunity pdomance cihn be 

achieved Dam shwng the variation of 

h

=mitrioa~ ~ ~ h i frown ~ ~ e alleimdk f off 

5wEraw ffm bth c and x bmd Hs gmE:waed 

in Fipw 5. 

A iuruhea impact of increminn antitudc 

can be wen in Figure 6 where 8 CI iumgact 

on the amms track component of s&d 

resolm8ioaa, rm e resol~~io~ IS been 

presented as a B unction of dista~~ce Iuom 

nadir md ~geri~ing altitude for 8 sh@e 

RF chirp hd~c8tI.J - 3WMk In sele&une an WF carrier frieqancnacy for a 

spacc2-bwe high resolution rnnli8m-y SAR, 

several faactors must be taken into 

accomu. First, is must be noted that, in 

rincigle, my grscpunmd raqe rewinntiorn cm 

[e- rnsixievcd by provision of 8 radar 

emission puke of adequate bmdcdd~h - 

id cxtmmples axe shown in Fipm 6 for 

% w e of 3mMm bm~dtltn deration, 

but inuemational agreements constrain 

the bsaw&d& rm8Umaed to space hdm as 

indicated in Table 2b. Howevcn; althou@ 

such apxmms might be brcalrfhcd in 

times oh crisis, the TACSAT mission 

concept also indudes peacetime uw and 

for this, udhercnce to ,barndwidth 

allocations is essential. f 

The fipcs presented in Tables 2!a nmd 2b 

indicaec uhao only an X or 4 bamil sysuem 

would be capable of provichg a pound 

resolution close to lm, whilst the uvs of E, 

C or band wouid fail to provide a 

ground resolution better thaw 3wq over 

most OP the pazing angles of inuermo. 

In addition to the internaaioamal 

regulations, other factors affesaiwg the 

choice of WF carrier frequency are as 

follows; 

- the need for the SAR wavelcaagth to be 

significant1 less than the ima e 

resolution. #his is likely to exclude t 1 e 

use of Lband (0.23m waveleaguh) for a 

system aiming to achieve around ,lm 

resolution. 

- ionospheric dispersion. This is a 

frequency dependent phenomenon 

which can cause a signifficant 

degradation in ima e qualiay for 

frequencies around or %e low Lbmd. , 

27-7 

atmosphwrie driop~~nion. This is 

8er4eaanny, IUDQ Q ~001em for 

irequewcna below X- B and, but may 

degurmde image quality at bighcr 

frequencies, s.8. around the water 

vqxu~ rmmm frequency of 2ZGBHZ 

atmosphsric attenuation. "his varies 

wib ffreqnnemq, Preconmhg more acute 

POP frequcndes abe: X-bm$ possibly 

din onat J-hd and probably ruling 

out & -band. Wowwer, the attraction 

of the very wide bandwidth allocation 

at I-bmd ad the assodated potential 

for very fine spatial resolution may 

mitigate in its favour. 

~OQPQP efficiency of solid state power 

a IP, p B i f i e r s at hi 8 he r ope rat i ng 

frequencies These factors inchcite that 

X-band is likely to be an optimum 

frequency for very high resolution 

(around h@nilit surveillance SAR, 

with C QP possibly Y band representing 

a viable alternative providing 

somewhat p rer resolution. 

4.3 Ima@mB CapabLPPQBos 

For the TACSAT SAR mission 

considered in his apr, target imaginq 

requirements may e considered to fall 

into the foilowing two m+in categories; 

(i) deaecction and classification of hard 

targets, e.g. military vehicles, tanks, 

pounded &craft, ships, etc. 

(ii) monitoring md change detection for 

distributed targets, e.g. airfields, 

military camps and instaliations, 

~IP~QUBS, railway yards, choke 

points, etc. 

! In the fomcr cases, the targets of interest 

generally have large radar cross sections 

relative to the background scene. As a 

result, the ability to detect and 

subsequently claify such tar ets depends 

primarily on the spatid reso f ution of the 

ima ery, the s stem radiometric 

per P ormance Ling relatively 

unimportant. A spatial resolution of at 

least 3w, and ideally less than lm, is 

.< ' 

4' *,. 

considered necesury. (#' . 0 , : . : 

.. . . 

In the latter case, howrcvef,~t~~~features of 

interest anre general1 no brighter than 

other features in t i! c scene; the key

I 

I

e 

The SAW must possess a raa)is$wetric When ~p~athg in this mode there is a 

' resolution adequate to1 hilow need foe the emissiasm cif a parpicularly 

disc ri mi no t i o n bet we en odj ace n t higb levd of mean WH: pwcr io order to 

distributed features. A sedfivilty restore the Bids budget whish is a&erdy 

charrarcaerixed by a noise e$uivdem sigma affes~ed b the increased noise level 

zero (Nk,) of -23dB is considered which raun T ts from the wide bandwidth 

ne.ce-. needed to achieve fine range resolution. 

4.4 AQ~QQR~ S~~oonnrs 

; 

discussion, that the TACSA P' 

It can $e seen from B~ac receding 

i~\rmtenwa 

requires IMP el~t~wd~ steering in mimnnth 

in order to provide the Spotllight mode 

and thaa a similar capability3 in the 

elevation diredon is highly desirnablc in 

order to facilitate the imaging, a~blrin I 

sin e pw, of different tongss iiarcntctao 

dif P emwo elmation bearings relauivc PO the 

satellite. 

Thus, obe case for electronic soeerinp in , 

both mimuoh and elevation direcusons 

appears to be stron and ha Dcd ohis 

paper eo propose a f ully acuivc phased 

array mPuoi0n for the enwsged - TACSAT 

mission. 

The partimllar aspect ratio ZSSM~G~ for 

the antema is based on the mccd to 

accomsda~c around the toroidd &"&, the 

6m2 ovcrdl 

r 

area required to providc,the 

unarnbi OMS access demonnsomWl in the 

earlier kcusion. '!bo distinct CS,?JC$ ~ ~ I W Q 

been emmined one at C-band, O ~ I C other 

at X-band. Bn bth cases, the an~cmna is 

built from 11 panels which are wenanbled 

onto the bus as indicated in Fipc 8. lin 

the C-bmd -e, each panel is pgulated 

with 32 TP. modules and meaurax .some 

1300x418mm2 whereas in the X-band 

case, each panel is populated with 64 T/R 

modules and measurcs 

1400#388pnm2. Thus, the aspcct mi9 ~f 

the antema is similar in both cams being 

4.6m(az b 1.3m(cl) in the C-brmord cw, 

and 4.*k&z) by 1.4m(el) in the X-band 

I 

I 

&caw aha uegiow being imaged is only I 

smarD1 rasp~ow of the mhuw, rangewarn 

B ipous swath, it is possible eo 

iricrew the trrmsmittea duty cycle and 

rovide a several-fold increase in wem 

IF power output during sgotli ~na 

~lb~ewiati~ws. T icdly, increases o F a 

factor of 5 cm T e achieved over that 

no~mdly associated with civil remote 

semiw rmaissiom W ~ R ~ R C ob& duty cycle is 

Pimite d eo around 9%. The advantage of 

this O ~~ROZ~IE is thane these increases an be achieved W ~ O ~ Qresortin U ~ to an 

increase of r z the ab RIF power andling 

capability of t e T/R module output 

stages. 

PO is interesting to mw are this TACSAT 

mission with ar civi P remote sensing 

rpaiuiow. Pw a i d C-band civil &ion, 

320 T/R modu T es operate at up to 8 W 

ak RIF p~~er in order 90 provrde < 150 

mean RlF ower, whereas in the 

E 

Spotli ht TAC ! AT mission considered 

here, 4 52 T/R rw&ula operating at 6 W 

F power. In the 

2 -$ad case considered in this paper, 704 

peak power cmn are o rated to provide 

U to 750 W mean wt" 

T/R ~ ~ M I ~ are Q s operated at less than 3 

W peak power in order to provide the 

same mean RF power (750 W). 

However, the technique is od applicable 

tc achieving short tern gains i 

r 

ecause the 

increased trwnwinaer cr requires that 

the system be copanb e of handling the 

asmsnated inaee in waste per. In this 

concept 08n~ uhed paobRem is re arded 

as a thermal impulse and Raaded 

f by

-.- 

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27-9 

Different data rate: can be associated 

with the SAR depending on whether 

range ccpmwpreskm IS conducted on-bonrd 

or on the Pround. With the long duty 

cycles envisaBed for use in Spotlight 

mode, there is a need to receive radar 

returns, not ody for the duration of the 

time delay from near to far sides of the 

image regon, but also for the duration of 

the transmit puk. 

The classical technique for reducing SAR 

down linEc rates is to accept dl the returns 

from a given single puke emission into a 

register (during a receive 'window period 

which is mucpI longer than the transmit 

, and then to transmit the 

data pulse scam pepio3 ated in that register during 

the longer period associated with one 

pulse repetition interval. However, when 

the receive window is shorter tban the 

transmit pulse, there is less opportunity 

for data rote compression. if, on the other 

hand, pulse compression is conducted 

on-had, then the duration of the receive 

window - post range aom ression - is 

identical with the time delay i etween near 

and far sides OP the image region. This 

time difference can be significantly 

smaller ohan the interpulse period and 

appreciable reductions made to the data 

rate. 

Using such techniques, it is possible to 

limit the data rate t0 values ips small as 

13Q MWs for operations at C-band 

where he $Mi chirp bandwidth is limited 

to lOOM.Wz, and to BQQMbit/s for 

operotions a~ X-band where the chirp 

bandwidth is lidacd to 34#)MWz. Data 

links with these $r;sradwidohs exist but the 

problem of Rmdin these quantities and 

rates of data WI 7 I require further 

examimaioa

27-10 

Currcunaly available ground 

algoria8nm will puscess 'ITA@$ 'IT &ta in 

its Saeeucd Beam and Scanmar modes. 

Funhear development could be required 

for the &gh ~csdution Spatlight miode ty 

cope with the rapidly varying Do pler, 

aliasinmg aut Bm resolution, e5p~a B" Uy at 

X-band, sand ouoofocusaing will be 

iequired to maintain focus over varying 

terraria height. Existing airborne 

techniques are not applicable. 

/ 

I 

TkiQg 

Data is received at 108 samples per 

second: Spotlight processincfg with - 

autofocus W~PI re uire some I@ ~ O P 

per resaPBution ce 7 1, and therefore, real 

h e processing could re uire a mmptcr 

power of met 1QOG F& 

d 

B. Cumeantl 

this wodd require an a m of mm 5 

vector prctasmrs and co J d be idl smte of 

the in6 machine, osing major data 

handling problem. I!$ owever, maomin a 

deploymcamt date at least 5 ymn in t 8h e 

future, bprorremcnts in processasor speed 

of at leet 4 times can be anticipated. 

If 40 minutes, rather than red time, is d 

dl~wed to roccss the rnax.inwunrra data 

anticipated P rom a single gam, then the 

number sf vector processoriuna modes 

required cm be reduced to 125. Such a 

processor couPd be Roused in a sin le 

19inch equipment rack and wopd %J e 

equivdenmo to top-of-thetrange 

commercial equipment. 

I , 

I 

*& 

. .: * 

. ., . 

, 

5.1 Eapnnnca ca3as / UhrasOe~Qioer S h 

There is much discussion about the 

skible &the of a TACSAT mission. 

Epewding on the mission concept, the 

intended Pnfehes cm vary from several 

weeks - associated with launch on 

demaund, e$nou@ months - associated with 

+ , launch in mtia don of a crisis, to years 

+ - 

" 1 .g. 

sswiaoed wit Til prc-deployment of the 

satellite(s) and storage in space. 

ma: case in P ~VOU~ of launches using the 

residual mm apabili r often assmatcd 

with luge launch vehic es has been made 

in section 3 of this paper. Here, we discuss 

the possible im act of that launch 

Bi1oaup;lbgr on re P iability required of a 

ACSATSAPL 

The particular needs which might be 

envisaged for a TACSAT SAR are that it 

: be capable of viewin the designated 

* Theatre at very rep P ar intervals. For 

'1 

. ., 1' 

', instance. ip full mtem mav be reauired to 

g provide 

hesving*oppodties at 8-hourly 

mtexvals: such a revisit rate would call for 

the service of a constellation of 3 

satellites. 

The toroidal bus design discussed earlier 

. facilitates the launch of a 

miui-ccBmteElaaion of 4 or 5 satellites from 

a sin e, dedicated launch using Ariane4 

or T@ itan. System reliability can in this 

case, be improved by the 3 from 4 (or 5) 

. redundancy which results from using the 

multiple Barunch. 

I

In resent ears, industry made 

gr0fpS b?lU.& S B d g Of QlR-EJfOUd 

testrq in order to op~rmnise mission 

reliabality vcnus programme COSR and 

schedule. Wowever, indust ri~a~froaasly 

retains tbtc service of flie T t qualified 

compcPnentsfordIprogrammes. ' I 

I 

It is iaIUeH49SRiQg to recall that Wight 

campomems are in genera! &mm Porn 

&e same gmdsrdon lincs w8nm'dn debver 

Mil Sodl mmpnaenn&. The premium chge 

made OR &@t components read& from 

the additional tests and ri~orous 

traceability wbi& is impolsed on rtlima bmic 

Mil Sod corn onents to rovide the 

greater lewd Q P anfidence 2 emded for 

their use in space. 

TWO pania~lao features of i d space 

programmes favour the hig 9 level of 

caution inn licit in the dedicated use of 

fully udi P ied components. One is the 

long I' 3 e usually demanded of the 

z 

the other is ~e one-off nature ca mod 

large) satellite systems. The fit of these 

eatures demands the reater level of 

cod~dem d t e d wit ?I fi@t qded corn ORR~QPS in order to gumamtee 

relia iiity cver the (long) life time; the 

other dlemmds hi& intrinsic reliability 

because wiuh a one-off system, taaeae can 

be no resort to the N from M option for 

reduciafJ OB& overall risk of failure. 

Notwithstanding these cautions, in the 

case of launch on demand, the iife time 

expected of the satellite can $a, quite short 

- typically around 6 montbs - "pnd he 

poteatid a-mes of using less1 higM 

qualified components is wort 

coasidemtion. 

T"&"' 

h 

I 

I 

' 27-1 1 

The mpabilhks of a TACSAT SAW have 

kcn reviewed in he context of notiod 

Theatre sweiUmce hion. Of various 

cpgti~m~, io Pas been argued ohao only a 

SAR based on active ghbsed array 

technolorn will provide the flexibility of 

performance needed to satisfy the 

notional mission. 

It has ben shm that a SAR operatingl at 

X-bmd would be capable of providin 

single-look imagery at Am spatia 

resolution md a noise floor of better than 

-2WB when flown in a circular orbit at 

SOOkm altitude. The total mass of a 

satellite carrying this SAW has been 

estimated at around 600 to 7Wkg. 

While it is quite within the bounds of 

to conceive integration of 

§AJfb &cussed in the paper 

on a gliuform suited to individual launch, 

it is specifid1 the absence of dedicated 

launch vehic r es optimised for single 

launch of such a satellite mass which has 

ken t&en as io driver towards a toroidal 

bw structure suited to a multiple launch 

making use of the residual mass often 

associated with launches on larger 

vehicles. 

The adoption of such a philosophy has 

ken shm to provide the opportunity of 

getting single satellites into orbit 

economicall but not with a ra id 

turn-round. I n addlition, the toroidal us 

structure provides the possibility of 

dep80pe~t of a complete constellation, 

wua a single launch from a large vehicle. 

In t&s wa it is possible to amortise the 

cost of t l e larpr launch against the 

corresponding cost of several individual 

hunches using smaller vehicles. 

IQ order to M y understand the operation 

of, and iwRePphy between, the various 

cornpnem~ whicb mmpriqe a TACSAT 

system md RO o aidsa tbe design of a 

military comael P mion, I demonstrator 

system is chdy required In particular, 

f

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27- 12 

7.0 STA'lilIUMmT OF ~ ~ N ~ ~ ~ ~ L ' H ' 0.3 Y 

Any views expressed are tho& of the 

author(s md do not n e d y represeat 

those of g, A4 Government. 

Table 1 

I i 

1' 

I 

I 

I 

I 

r 

10 J 

A 

0.1 

Table 2a 

as Sa 48 

e7 110 

a60 sa0 

C a 9-25 - 5.J5 ~ 

Table28 

150 

450 

070 1100 1500 

aooo moo 4500 

100 

aoo 

300 

600 

- 

a0 4

Figure 1 

Figure 2 

\ 

'. 

0 

# 

--e- 

I 

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Fipre 3 

27-13

27-14 

, 

I I

SliMMARY 

Cost and ycrformancc technology hrcakthroughc it1 rcccnt 

ycarc havr niadc po\cihlc thc ncar icrm dcvclopnicnl and 

clcployincnt of a low cmt TACSAl \uncillaiicc \y\tt*in. Thc 

prtciitial rtrr hoth ihc \pacecraft and wnuir IO hc lauiwhcil cm 

loucr coi\t I:iuiicli \y\tcni\ I\ ihc funtlainsntal for rctlucccl 

\y\tcni ci~t. Acltlitionally. thc spiicccraft and scn\or iiiN hc 

anirnahlc III IOU' co\i maw protlucticin. Virr all weather. 

d;ry/night survcillancc. an activc synthetic :ipcrturc radar 

I$:\RI it thc ideal in\trumcnt. ancl thc obilily 1st masinanufacwc 

thour;ld% of vcry low ccnt iran\niii/rcccivc tT/R) 

IIIIJUIC\ ha% kcn dcvclopccl at H~phc*. Sincc ihc si/r of a 

SAR incrcasc.; ac thc orhital aliitudc is incrcarccl. b final 

clmcnt of thc cconcmicrl hviq for a low ciht 'I'A

, ._ 

.'< . , 

'\ '

. 

FIQURE 2. REPRESENTATIVE OPERATIONAL SAR SYSTEM 

3.l PFXCFIIME SPACB CONST,TEI.I.ATION 

SCENARIO 

Cmtraq b thc launch-on-demand ucnario. ihr rracctinn 

spscchmc radar ucnario mah uw of a -mall l.EO rHIar 

c~mr~ainn that pmvk horl ma IhcNcr wmh. a* wcll m 

high mnlulim imaginp upm thc dclcclin or cueing nl a 

tar:ct'* C'cwncc. Thiq sccnarin dncr niii prrcludc ihc 

capahilily to c~ecut~ a wgc launch In *uppkmnla p-acclim 

cnnsicllalinn or to rccnnhlulc thc *ywm aq ~~ICIIIICI arc 

dewmycd dump majw mnflici.. Thr cimlml nl this siiunkm 

. wnuld rc%idc in Ihc Ihcatcr cnmmmdcr who a1.o ha% ihc 

rcqwnsihilily and capahilily 10, rral :imr tarkin: 111 thc 

.pacchmm radar and ~pacrcrafl. In Firure 2. lhrrc radan 

npntm: in lhc SAR modc am dcpicicd. mr pwidinp .!rip 

map imaging in I wide arc8 urpi I*mcion mdc and the 

nkr tw pmviding thc hi#hcr mu,lutinn *lightme In nJri 

in chimlniring rmy iarylr that harc hrcn dcitxtrd. Mi* 

chmy tn*truinnr to Ionb. in diflrmni urn. lor cxamp~c. are 

cnmmandcd in real time hy IIK field cmnniantdr mnhilc 

cimtml uarim. n huh can alw xccp~ mhovrd pwc\utl m 

paniallr prnccwd imaging data fmm ihc orhilirp rrdan. 

kpcnding m Ihc lime lram el Ihc lint launch. lhcre iq an 

impurtani iradcnll hclwccn accnmpliqhinp a11 imapins 

pcwng mhurd thc rpcccrali. lhclulinp rnmprium nf 

input data to .lomi imap nf ptrniid iaryir. vcnuq thc 

dnwnlinkin: nl rmkr widchnd imapin: data fnr war real 

tim pmcrwin: in thc cnmmadrr's m wd rrmtml cnnudc. 

Thc Iallcr is mnsl likcly to be prrfcmd. until cnmplcaly 

reliahk autnpmn-in: d inulin: &a hn hn urmdully 

vrlidalcd. The implcmcntalinn nf an cfficicni widchand 

dnmlink is very rmightlmad and cm nm M thc mhrrrd 

ndar M y 10 pide the canrmnicalhr &nunlink apmum 

10 lhsl anhcr tnnuniturlmcnru nuld m k -q. 

The pwirinn nl a commander'* cm:mad cwwol c#mu*lc 

ur( d statim to usk ud crmd the nd wmw. 

pl"S mlkled data. n*l pmidc J.U 1u.m at quid i. 

an c.unlial pan dah mal qrnlMl ryum. ah# with t k 

Uidehnd mal time damlink imn ~hce uakm. 

unall aimnna lranuni18 a canmand la Ihc SAR In 'spotlight" 

a pnr(inn 01 Smn Charlie where unmnpnizcd cnmy arwir 

may hc hidden in a wmdcd area. AI lime 1.1. Ihc SAR 

SpuliQhlr k tm Charlie a1 high reudulicm. using I uinninp 

km. a d wcnmplirk mpcal Id- a nrrwry in inreme 

rrwlulnm. AI lim 14. a SAR plrrsud nr panialiy pmccrd 

imapc ir dnwnlinkcd I o Ihc mnhilc grnund rtalinn. which 

mvcaI\ a clu

LOW.oIlN 

ANTENNA 

b ClsLEWRIP 

4 SOWRPANEL 

FWURE 4. MAQELUN SPACECRAFl 

FIGURE 5, RMAR ARCHITECTURE COMPARISON - 

Anothn fwr.saiellite mnriellaiion would hc placed a1 half 

Ihc allilude of lk one juu dernikcd iue Figurn HI. In thir caw. 

the allilude for 111 rpacecrafl wnuld be 300 n.mi.. and 

lhc irrlinalimr far ihc rp~ecrafi would br 0.. YIP. 51'. and 

W. respectively. The orhil period for each would be 

W miwlcr. and the avmw wkil gap glohrlly would nnp 

rmn 2 m 4 houn. Fi8u1-e R shnws lhc gmund I ~ ovo I lhm 

mdutimx (4.8 huun) tw lhnc four Wim. 

6. REPRESENTATIVE LOW COST SPACE SYSTEM 

DESIGN 

Hugh hn devc)opd I low eosi sp.rrmll nd SAR pyld Ib.( v s one lam O r b ai. kq Ilk s m h In Ihe

mr a 

n 

problem. The pal was to Jcwgn ailightwei~ht. low colt. 

manufacturable pacec craft ihlt could wpporl a fairly 

lulmutuial (W ultra-li~htweighll *AR and bc cmpniMc with 

the Delu II launch ryrtm. Tbc debign ii for an a f t e m sun 

synchnmur ahil with M allilvdc Of appmrimalcly 370 %mi. 

Ihe pi- dv pwr spin is appmninnvly 5 kW. and 

Ihc SAR amy ir appuainutcly 12 x 4 nte~R. for 8 to%t c m 

d 4 d. In thim pniculn dcripn. il is dcrinhk io include a 

luge (6 faa, diameter). dud limb1 pointing pahnlic ~tenna 

to rclny wideband SAR data to a gen(yn.Vronour 

communications relay satellite. Furthennore. an X-hand 

downlink is provided to enable real lime SAR data to he 

Iranrmilled to operitional userr directly below Ihc 

Ip8cecnfUSAb at any time. The entire Ipwccrafl. power 

rysHm radar. p~pulrim syum. d dI arbmd ekrtmnics 

me desiyrd fa an abiial lifctimc d 4 ye=. 

’The very liihrweighl spacecraft fvr this appli&alion ir a 

simp* lri~&~ wss amngenmtn. whcm5y thc SAR uny 

ir lfftncd 10 OM of lhm rider of thc bus. md each d ihe 

rolu wing 11 a~irhcd toone or the IWO Rnuininl rides. U is 

lhmrn in Fipm 9. Note that in this filum. the hiring abow 

the Delu I1 s e d u8;e has s I IO inch envelop for the 

pylad ud ihe large reflccta utlcnlu is ab0 rmnmodd 

within Ihc fairing. 

Ague IO depicts this apaccnfVSAR pylod in the spndeployed 

configuration. The SAR antenna 11 canted 

rppahn~~ly 30’ OR thc horimtal, to pmnh s&-lonkitt; 

1 STELLITES 

2ORBilPLAMSATWI 

MU mN ALTRUOE 

FIGURE 7. HIGH ORBITAL ALTITUDE 

~TELUTION 

only. In this puikulu &sign. ~hc quimmtn am fa fwT 

scat c.pMlily in Ihc ckvation uii md ran capbli~~ in 

thc uimulh axis. Similu destplr haw alkd lor the amy to 

bc dcploycd nunul b ihc euh’s ndiw wcmr to mac mdtly 

um~ 0 thc right nd kft U the tywrcnll mua aIm8 the 

abilal plh. In chr bar CDU. hc desim bve :ypkdly dkd 

form d SCM in bah LICL

NOI-1-0' 

MZ-1-90 

NO 3- I I 57 

NO1-1-57 

110 n 

DIaMETEI) 

mnom i' 

ENVELOPE 

t 

win 

1.0. RI. 57 57, PED --mk 

TOP VIEW 

I 

FIGUAE e SATELLITE GROUND TRACES 

I 

t. 

FIGURE 9. SPACECRAFT LAUNCH CONFIGURATION 

DATA LINK WTEEWNA e , lwlL OlMBIL POINTMOI 

m' SFUECIUFT BUS 

FIGURE 10. SPACECRAFT DEPLOYED CONFDURATloN

w 

4 

I 

Discussion 

Question: May you give (rough order of magnitude) 

how many PEGASUS launched small satellites you plan 

to build to have an economically efficient approach 

in terms of manufacturing facilities and effective 

service? 

Reply: That one concept was based on . -omer long- 

term need for hundreds of spacccrac very low cost 

to be deployed in the field for , periods. The 

PEGASUS solution was a design cmstraint, but is high 

in $s /lb to orbit. Multiple spacecraft launchers 

for peacetime constellations and short (approximately 

1 year) orbit life may make more sense. However, the 

very large, high performance radar (on Delta 11) is 

Close in cost to :he TACSAT goals discussed by Charlie 

Heimach, et al. 

! 

. .:.

Cost Efl'ectivc TacSats for Military Support 

By h.T. Crodsky, M.D. Benz & J.T. Neer 

Lockheecl RPissilcs & Space Company, Inc. 

0q:mhtIm 6F-01, Buildin& 590 

11 I1 Lurkbred Way 

SuonJnle, CalUolrb 94089.350) USA. 

This pper diseuses the key spxc system fcWrcs 

rrquind U) provide ~Ncctivc suppwc to military fcld 

uniu anti discusses Lockhcad's Conccp to fill crihl 

nkhw in military survcillancc and remote sensing. 

Thc military is aware of kncfiU availahlc from m n 

effective usc of ~poce. To provide lhose bcnefiu, spacc 

systcmq must be dependable. casy U, use. flc cibk. 

msponsive Md aNordablc. This paper describes itou a 

programmable, multi-specml 0-0 scnsor wm ?ined 

with a new small satellice bus. nnd suppming msnd 

and conml and dau processing tools can providc 

cnvimnmenlol and surveillance suppon lo users in 

pemlime, crisis and combat. Also discussed arc how 

such a system mccu csscnlial military utility criteria 

and an llppasch for rapid TacSat systcm dcvelopmcnl. 

evaluation nd deployment. 

In M m wha burinascs arc learning Ihc imporonec 

of 10181 Customer sslisfrtion. devcbpn of new space 

systems have opportunities to achieve similnr gmoal~. 

lust as pmducu emphasizing user crmvenknce. hank- 

froc service and high quality at an affordPblc price am 

essential in ay's economy. spa system I;;velopcn 

must usc emerging tcchm~ks to niccl similar nee& 

for civil nd mililary sytms. In Ihc cunmcrc*l m. 

a system designed fw talal customer satisfaction. 

Motorola's IRIDIUMTM'sM global pcrsonal 

communications systcm is in dcvelopmcnt. Ihc s~mc 

philosophies can k reflected in a octid surveillance 

system and Ihc pjcctcd commercial infnrvuciurc un 

aidU~~ocmcwnicfcuibd~tyofsluhrlynan. 

The IRIDIUM system providcs ~lob~l penonal 

comrnmbations using a constellation d small LEO 

salellius. supponing ground facilitiei and a user 

cquipmcnl family including a small. hand-held 

tekphane and a vuiay of dam terminals. Thc system 

lhnra ir Y) provide cellular telephone-like convenience 

and quality with U hour dependability mywhen on UIC 

fUe Of ule Ennh. The IRIDIUM sysm will provide 

Itigh quality telephone connections anywhere with he 

sunc c h i normally required IO call ktwan onicw in 

a hgc city. In shac. the IaIDlUM sylta applies 

qnu-ol-lhc-811 whnobgies IO make things simple and 

um~aiat fa cuaomus. Wih modem crypollrqhi 

III(DlUM la mTrdanut nd Swim M lLd Mopmblrp. 

31-1 

devices and GPS rccciven. an IRIDNM subscrihr unit 

could k id4 for scvcral voicc and pncision location 

functions in pcacctimc and limilcd wiufm situations. 

AnMhcr mililsy bencfil fiom the IRIDIUM systcm 

may be UIC user satisfaction modcl it pmvidcs. A like 

philosophy. applied to Ihe dcvclopmcnl of milimy 

arrvcillnnce sysums. could pmduee huge bcncfils. 

Any discussion of a ncw military capability must 

ddresJ new world replitics. The wckome rcduction in 

superpower tensions has come with unpleawnl sidc- 

cllecls including gmcr political instability. local "hot 

spas." and Ihc danger ora low1 conflict spinling OUI of 

eonvol. Thc political reality of reduced western 

military spncing and constrained forward basing 

accompanies lhcsc threats. The iacton combine to 

demand greatcr flexibility and msponsivcncn of Ihc 

remaining lows. The Persian Gulf showed that timcly 

warning and inlclligcncc information in thc honds of 

commandcn can pmducc forcc multipliers that allow 

thc pmrocution of conflict with low casdty Icwls. 

Onc consqucncc of this cnvironment is an emerging 

need for wer controlled. cost cffcctivc, tactical space 

syacm IO provide timely information to commandcn. 

The systems could give indications and warnings of 

forcc build-ups, allow wty compliance moniloring. 

and suppon nc.~olurl and allied form in pcocctimc. 

crisis and combat. Thcy could opt.qtc in modes to 

&fy Ihc dillcrent ncedc ofscml usen. 

5hc Keded capability qn* cffcctivcly provided by a 

small LEO sptcllitc with .e programmahlc. multi- 

rpecvll scrim combinc$rtlrUi a "Tadat' spacc syslem 

shown in Figure 1. && tr:iac syrum fcatumx would 

include a disvibutcd architccturc with direct user 

asking and dau reudout. Tcchnologics central U) this 

TrSat systun wncep arc multi-band. CCD focal- 

planc arrays. satellite on-bonrd computing and 

dvPnad vat station gmund dm pmcessing. 

lkLwkmu 

At Ihc mosc bp*c level. Ihc fundamcnlal requiruncnl Of 

MY system is that it satisfy user meds. In a military 

surveillance system. that vanslaws inlo a nced IO 

povide timely infamation on foccc dimition. local 

envimmenul. infraanrtun ud olhu conditions U, 

ammudw 11 is technically l dble U) build a m e

- SURVEILLANCE 

- ENVIRONMENTAL 

FLEXIBLE, nww, 

RESPONSIVE APtU ' 

sysum with lhc spatial and spectral ~ lutim IO Jo the 

job. 11 U huder IO nuin adequate nsolulim while 

satisfyinn rqUCfl1 covcmge. large ma mumillance. 

tLnely recu IO inlamakm poducu. rase of W. and 

dcpndrbilily needs, dl with bw s y W rosa Many 

lhink IIU Jr simuluvau satisfrh dlhcr nccdr is 

.01 pdd. I1 is pncciul. however. IO build a syslan 

1 SYSTEM OPERATOR 

-A?%€- 

Alx?mlw 

IJUI meeu lhcr varied wr nocdn at sclccccd timw. 

Using low cm systems and Ibchnolcgm, il is possibk 

IO achieve high user salisfaction wtth I mbusi and 

rcsponsi~ ryscan mhilccuuc. Dc-mnvnli7Plion does 

IKU rwlt in higher cosu than rmnt capabilities. This 

rchilcclun. shown in Figw 2. momgcs ~~SOU~OCS IO 

Ill I situation and is Ihc lhrupl of our TaeSel coneep~ 

ClNC X

' Figure 3. Usa Driven Dwign Future Muria 

- 

Figure 3 shows UIC key uscr necds utisficd by an 

clocuuopical T=Sat sysccm. and how lhose n& 

map into desired design fcatuns. The Snt syslcm 

&sign slcp is lhc dcrinition of kcy mission driven 

sRIol ctlaralcristiu. Thcsc cheractuislicr combined 

with orbit slechn. define Ihe syrm's 'capability to 

rurvcy and collect". 

Tdat ryncm pcrfrrmpncc is ~ unklally dcfincd 

by the combination of scrim chmcieristics and 

mission orbit. As shown in Figurc 4. Ihe pmccss of 

slccting lhesc pmacn s m with he delinilion of 

mission rcquircmcna: i.e. what. specific mles will UIC 

system be dcsigncd IO satisfy dnd what performance 

levcls will be required for the.* mlcs. h eanmple. 

onc mlc might bc daylight surveillance of a botcle am 

IO decst mw. Mocha might bo suneillnncc of n pm 

area IO detect shipping activity. Ewh of there 

missions rcquircn some spccific qunntifishlc threshold 

perfonnnnee and a range of characteristic goals thot 

affcct basking. The key IO Sensor and orbit design is 

brlnncing ily many lasking thresholds U pnclicpl while 

maintaining pufomunce againv UIC varisbk gds. rll 

at M affodable cost. 

The multiple areas of prlonnanco nquind for TrSu 

missions uc achievable in sevcnl ways. Ths 

mvaltiooll.pporhisloum Iw0~msat)ps. 

me emphasizing wide ficld-of-vicw. be olher iigh 

nsoludoo. Tbe key to wc concept b Ihe c*pabllky to 

nully lbe key TrS.1 mldocll ritb a s h k -. 

31-3 

bpmn'blethmgh tholns of two diffmt foal 

plmra md che flexibility m e In either 'amingm 

or 'running' modor Ths "nuing" mode capons 

high n.~lulioo dam d a relatively small geographic 

M. In this mode. a sensor continuously wka, 01 

%arcs" at a putieular urga and the image site is 

limited to Ihe kkl of view 0. 

The mm UD scan in eilher Ihe 'push-broom' or 

"whisk-bmom" modu When scanning in the "push- 

bram' &. I seasor imagrs a nrip determined by its 

FOV. A wider area. with reduced dim targct 

pcrfonnrre. M be imaged using the "whisk-braom" 

lcll mode. This dual-nmdc upbiliy. discuJsed later, 

provides a surveillance option 'menu" to the uaer 

ranging Ifom small arca. higha nsolution IO large area. 

mcdium rcdution. In addition. UIC pointing capability 

required foc scanning and staring also allows mget 

area sleclim wilhin a field of regard (FOR) of about 

MY to crsh rirle of nadir dong Ihe flight pth. 

In addition to wr-programmable pointing, che sensor 

should feature multi-spccvP1 capability. The scan 

modes might be suppaned by a series of multi-element 

linor focal-plpne arrays. each covcscd by narrow bend 

oplical film. The high resolulioo Waring modc wulJ 

uw a rgu~ panchromatic array oprating in the visible 

band. This combinnlion makes it possible to suppon 

lhe many spccual bnnds Md differing rcsotutions 

ncuM IO putam TrSpl missiau. 

CClVCrppC 

TacSnt system flexibility and timeliness arc. to e luge 

cxlcnt. orbit dependent. Of cows?. orbit selection 

ofm invdva adcs agairut nsolution. Orbit xlcction 

requires consideration of options for altitude. 

inclination and. in some cow. ecccnuicily. Figurc S 

shows some d che fecws effecting altilude selection. 

Environmcntnl facton bound the range of available 

optiau. Below aboul4SO KM. wnosphetic dng staris 

IO became a factor by increasing propellant for orbit 

mainlc- and beginning IO pmduce ntutude conlrol 

design issues. At be ocher cxuemc. alitudu abovc 

about 1400 KM rcrult in incruccd rcquircmcnU fOr 

componcnt hardening against the radiation 

envinmmcnt. (Orbiu above he dintion bclu would 

rnn rred .ss much hsrdening. but would quire sN0n 

dadinirrniclarihmlhosediacmdherc.)

31-4 

spciri dtilrdo * beMsa 450 rd 1400 KM 

in- rninimizka the lool COOI fa a dcdd 

~lU(i0n kvcl. k altiode inaenC:. rrmw~ focd 

length must also increase to maintain cm-nt 

rrroluion on cha wnd. ~neruping he rarl length 

wdy iocrcaw boch the WIWX and %Wite weight. 

This combination d hnucd weight and dtiludc 

incmscs satellite cost and. gemlly, huxh cosU. 

However. UIC higher altiwdes have rved ngnifiunt 

dvmuger. Fa even at CQumnt redulim kvelr. it 

is possible to gain a widcrreess araona single pur 

by taking ad~muge or gmtu off-& pcrfamsnce. 

Second. if reduced resolution is allowed. higher 

dtiuda allow imaging muhs on a single pur 

even with a conomt Qwn-link dam rate. Ihcrrforc. a 

sensible duip stMegy i? to oplimizs for the highesl 

pncciul OM @Clw 1400 KM) availabk with the 

reketed launch vehicle. Sizing lhe sensor to povide 

lhs rrgllircd nr0tul;Xl would then give the best 

ba1ance ktwecn rrrolution, single Wlite covcrage 

and COBL This p~pa llsumcs lhnt boosler umsminu 

would rrsult in a ryswn at the low end of lhe mnge 

(450 KM). but no lid Mi is implii 

Other impormi puuneufs nn whok eyth venuc 

mid-tcipnk mvcnge. revisit times and he numbs of 

sntellitcs quid 10 Wive Ihun. orbit inclidon is 

elected based on Ihe desired range of urge1 ma latitude8 and the pvticd consminintr d available 

launch dm. though l~mc mobih launch ryaanr could 

eliminate lbose consminu given suflicient payload 

apability. The ode ir usually bavcn a polar orbit 

and m inclined dit. either ciaular or elliptical. Ths 

polar diu have the ndvantage d cowing lhe cntire 

unh wilh paentially rcpoting ground WU Their 

disadodvmtage is hat the satellite spends a significant 

ponion of iu orbit over lhc polar regions. Inclined 

orbiu M wcr Ihe PEmpUare zones or hir3ha lpciwda 

as required. Hawcwr. .* is diicuh if not impassible to 

design an inclid abil when a WfiU il available at 

the same time each day with only a few satellitcr 

wilh the fadIider rd cxpmhn 1O manage and mad 

adnphT~oralDultipkucllinonpelLcia 

Tbe opcmtltloaal prl.rlpk In bad on the idea ol 

lkld cummnnden udq I pndetemined scbeduk 

d n r ~ ~~llrblllty 

o ~ to inili.tr targeting. They 

would know in advnce of sa~~llite orbid paaa over 

their ueu of inlensL The n~p echelon activity would 

op~lc he spaufmfc and perform housekeeping 

functions. Uscm would lolow hat, between qwifmi 

timer lhey covld point the sensor, select SpEElnl bands 

to aquirc necded data and direct it to he nppmpdm 

user gmund station. would not have to conml 

satellite. auilude or provide pointing angles. InsW. 

lhey would pmvide mget coadinnca. Sysm design 

faturcs and UST mk phning l~dr would ensure w 

the UIU canmands were wilhin system capabilities. 

ud M POMIiJly damaging IO the satellite. 

The suategy allows regional commands to use a 

satellile U a- organlc aset when it is overhad, even 

lhough LEC mtcllilcs arc inherently inorganic global 

prreu. Usn would conml lhe sascu bascd on local 

priorities. It would k possiblc for a command to make 

a decision on the bes~ ktiking use just prior IO a pass. 

send commands to he TacSar. have it image the targa. 

and renun the dala for processing and analysis. This 

high degrcc of WQ auVmomy requires tha~ the satcllite 

and suppon system be designed fmm the sIan to 

separate hauclreeping md payload operations. This 

fcolurc raquim a mar echelon ruppon capability thaI 

opcmtes Ihe satellites and pmvidcs uscr suppon. 

Satellite operations include such traditional functions 

U: launch conlrol, injection. check-out. navigation. 

orbit adjusu &ad mainlenance. User suppon includes 

Ihc dislribulion anl prioritialiM) of tasking allocntions. 

and the rwalution ofopuolio~i poblans. 

Figurc 6 shows a typicid TacSar pass. With thc 3' 

POV multi-pwpose snsor, a single pass swath width is 

limiccd by thc allowable scrim obliquity. At 45". the 

walh iC about loo0 KM by 1930 KM at IO' elevation 

angle.. The u9u secess arca is limited by linc-of-sight 

fmn the satcllitc to he mobilc exploitation siles that 

rcrcive Ihc dam, Reseha of 780 KM arc co~Irrvative 

and could be incrcascd by reducing allowcd elcvation 

Per satellite coveragc is a kcy musun of cost 

tfTcctimwJs and is. in nun, driven heavily by LMcha 

bpcionr in two ways. Fira. use of mimum launcher 

rfomunce incrrr+r orbiul altitude and coveragc. 

!? ofond. launcher Ilexibility dlows varying, situation angks a swplh lcnglhr. The linkup is made bclween 

tpocific diu when ' .Anahaappmachh 3' and 5' elevation and commands and o h data up 

r~omlpVpopG~~.c~lm,llCOPOk W d betcvecn So and 10" elevation. 

kbit Ihr pwida a global. h g lcrm upbility. 

TacSat operational objectives to maximize user 

benefits and flexlbilIly and rninimizc user 

An effective command and control archilaturc is lhe perrurmed satellite operations drive the C3 

key to kSat rysUm useability. U shown in Figure 2. mrcbitccture. Dirvibulcd paylod larking h a key IO 

I~IC FhUV uchilc*ural smgy divides umtd into the TSCSa anvcpl Uwrs rcquirc a system that simply 

two functions. mission suppon and wrllitc ruppa~ and responsively rupplics support without being 

Tbe char uparatiom of these hm fulrctiooa h hampered by insufficient salcllite knowledge or the 

crltkal lo our utLshcI100 since It rtlm cambat burdcn of additional infrastructure. Figwc 7 shows the 

comma& to obtalm u(cllltc survelllarm bewnla C3 capabilities divided into categorics. hylond 

allhut CLe burden ol satelllle mma#enent Thi usking COMW of simple. user wmmandr on a prc- 

~lp~an r-rion, ~pieteiy -t to the fieid 

eanllpndr. is warnplihed by &h etivitiu 

Jlocpcrd. rime shnrc W. Allowing users to lark he 

mJor payload in m nd coadinales. eliminates Ihe 

nmJ for lgo ephemerides and pointing undcnlanding.

L 

Figure 6. Tu&oprrpliom Rovi Usus with a Sumilbnce Reach or 100‘s of Kilometers 

- 

31-5 

dk.etive aplks IO maintain M YT~IC rurlacc figure. 

Aminahrgd cnwgh for lhedcsircd apenure and FOR 

mw be stiff and lhennally conmlled IO mainmin its 

flgm. lhir nukes Ihc girnhlal smsm a lighter wight 

duip OVerrJd, though 11 rcquker I huge# moving mrss 

llis is just one example of Ihe many &la and criteria 

nquircd to propcrly evaluate and rolecl TacSal systcm 

design fames. Thc mmr achieves Ihe prlmsncc 

rcquircd wilh I singk opcid system serving two focal 

plmcs. It h cmicr IO mantafacture and mae vmtik 

hu UIC allenrmivcs. which ladr IO rcdffid costs. 

Figure 9 rhowr a modular, multimode ekctmoprical 

TICSpl g’w(~ paylcd. Thc design has a wide fWd of 

vicw and twmxis gimbals for scanning Operations in 

lnnh push and whisk bmm modeJ and/or staring, a9 

dunvn in Rgun 10. Multi-mode operalion is ccnval to 

supporung diffcrcnc. time varying missians. With a 

multi-rpcctrPI rout planc. it pmvidcs IR mapping, 

topographic and occpnographic sensing dau. and 

depcnding on objoftivcs. could provide the bands 

rhdwn in Figurc 11. Fa Mghw ctsolution , a squsn. 

ll~mu FOV, visible f d plMc h ukkd.

*APERTURE 

*FOCALLENmn 

OAS U 

STARINO ARRAY 6.78 U 

STRIP ARRAY 3.16 U 

OpTlCS FIELD OF VIEW 

STARINQ ARRAY .e* 

~~ 

x Ar 

STRIP ARRAY 3.00 X.1. 

*POINTING CAPABILITY f 45- 

24x1s GIMBALUNQ WITH MOUEIZUM 

COMPENSATION 

SPUTSTrRUNQ CYCLE FPA REFRIGERATOR 

- Figurc 9. TrSU Multi-PurpoJc MSI Sensor Concept 

m y 

The unh'r atmosphere hac many highly absorbing 

molecular specie. I5cu influences esWblish spcelnl 

windows for satellite stlsm to dcmt surface or near- 

surface phenomena. Waveband opions must bc chosen 

midwing wet phmomnology and Uusc windows. 

." .- 

- U-.,- 

.U 

D("1lm- 

." .- oDy.ou WIIIIICIO) 

." .- .I-- 

".. ..- U-. --.I- 

a .- 1.- 

Y l l l C l P 

1. I.- UD.. 

m. .4 *A sa". 

Figwe It. MSI Sensor Bads & Uses 

Mulllapertral information U highly useful for many 

TacSat missions. When used to supplement 

panchromatic data, the non-visible bands add 

dclcctrbility. Camouflage can bc delcelcd ac can warm 

&&U against a cooler background. Multiple band 

mesurmenu can bc uscd IO compcnwc data lor 

environmental conditions such ac water vapor eNsu. 

The bands listed in Figure I1 represent an initial 

selslion based on eapcted targets and backgrounds of 

grrrcal inkrest and likelihood. llw system and 

scnsofs programmable fcaturcs allow rpeik uses ol 

band umbdms for each mission with dur famolted 

for vuumillll IO he gmund. 

All-rellecling opllrs designs are nuperlor for 

rimul(rneoul uae of dillcrenl apcclral bands. 

Refkctin# optical sysans also offu f&bk veighu in 

this apcnure range. Except lor small refractive 

ekmenu providing image correction in he hi#h- 

resolution visual band. thc design u.sa all reflecting 

@S. DccSton for h e high remlulucion pnchmnulie 

arc locatcd with che central lo or the line FOV 

when gcomclric abcnations arc small. This has chc 

disadvantage of reducing available visual coverage 

rates. but is necessary to balance distortion and 

rcsolution. Using two focal planes with diflercnt focnl 

dos maaimims he combined FDV and msolulion. 

Physical law diclatcs ihat rcsolution IS proponional U) 

the ratio of apriun diameter and specvol wavelength. 

For apncres feasible on a small satcllitc. high 

resolulion is atwinable only in lhe visual and ncar-lo- 

mid-IR bands, fmm lower orbiu. The 45 cm apnure 

compromise provides good performance (SNR and 

resolution) for most missions. and construction with 

reasonable size and weight. For mapping, SNR 

gcnedly docrears and resolution increases with I/#. 

The 117 Icmnlngmode optkal path U a compromise 

betwcen SNR and resolution performance. In 

slnring. high resolution-mode. a higher I/# is desired. 

With a large square silicon CCD delcclor, am f/lS 

system mnU resolution requirements with good 

FOV and SNR perfornunre. 

For given ap9lurC and resolution. wide-field-of-view 

sensors knd IO bc large. The design has a slightly ON 

axis optical path providing a wide. one dimcnsion FOV. 

with resolution only pulially degraded by gmevic 

aberrations. This approsch is kcceptabic for IR hands. 

when dillnaion blur cac& h goomevie blur. An 

additid square high-resolution local plane uses the 

on-axis opliwl path md operalu only in the visual 

band. providing maximum resolulion for designated 

areas of intutst. Operating the highest nsolution 

missions solely in he sham wavclcngth visual band 

keeps he apcnure size small. When sunlit. most 

gmund and wcachu lcatwcs of intnul show visual- 

budmnvra8df!quUcfmOh 

'Ihc quam visiblc'ruring m y receives the on-axis 

oumv-pOV beam thrwgh a muat hole in he pimay 

mina. The multi-lpreml opial F+III lia just U) he 

side of he nuing rynunr lens ekmenu. Fiqun 12

Vlrtbl~ D~tect~n 

b Rows of 18um quam dmtocton, doubb oWu( mwr, -0gaO bna 

1 Row of 10um quam delacton, dwbh oHW( row, 6m( 

IR D.hclom *' 1 

2 Row 01 Wum quam oatulon, doubb 0ffl.C row& -3OOO lo&' ' 

3 Row of 1Wum qwn G Mulon, doubh off.* row. -1- long 

Each row cowmd by.pproprf.1. fllhn 

FigllrC I2 M~lri-Sp~~ml Focrl Plphe 

shows he mulii-spcvrl Focal Plane Array (FPA) 

layouL A lhcrd irolacor divides Ihc FPA into an 

unroolcd visual and cooled (EO OK) IR waveband 

scctiau. Film IO define the dcmwd wnvcband cowl 

$4 ~rcd-atignment 

the dclccm in aEh p r 

rows, 

with multiabr dam miva! lutomlticrlly as he rows 

svcep rmn the sccnc. l'hc FPA kngth will lil ely 

nquh lllc ad Jignmat of scparatc mJk line umy 

rcctions combined lo lorn the FPA. Signal-hnoise 

rnlio lnalyris of a MIM IO bc imaged a mappcd must 

account fa Ihs obsrrvcr's desired COIVISI level. 

Backgmund noise nlhcr than internal sensor noise 

limiu TWSU mapping observations. This is bcuue 

Ihc unh is bright in most wavebands, upcially Ihe 

sunlit hall. The result is thc panbolif relation of 

contra to photon count. Since detectable convast 

depends on photon count. for background-limird 

dc~tion Ihe relation btwcen CO~IUSI level. required 

SNR. M me, rd rpean( bandwidth, is 

1 PAYLOAD I 

ON-GIMBAL I GIMBAL OFF-GIMBAL 

Vlslble 

Thermal 

Isolator 

IR 

31-7 

Conwan 9 SNR8(Scan Raier5l(Sp. Bandwidthp.'. 

lhin hclps IO ehoosc bo acari nu, once be expeeccd 

lsrgct Md background rignnlurrs. Wnr search amas 

IIE Wi. A MmmMdnbk sensor allows operaions 

lpilaed U) iMnediu missicm rcquimnmu. 

SenJoc operalions could involve bi-directional whisk- 

kmm scans cwcring about a 14O-wide swath parallel 

U) he flight path at up to 45' lrom nadir. Desired 

gmund raolutions am challenging IO achieve ovcr he 

full FoV with a modaalc apcrIun, cspccially in be IR 

bands. and a widc field-of-view wih r-able and 

wcighl is noeded for lhuc mi.sions. Data downlink 

mm ~IC high lor mapping and suweilla~c missions. 

This molru it dillicult 10 pmasr ad reuirn data withii 

time unmrpinu. 'Ihesc reflect Ihe combination of widc 

covetage and modium resolution. If aucntion is limited 

0 a fm uepr. slower scan and d;lu mes am possible. 

Fiyn I3 shows the rensa block dipgram.

Tb lSB in &a "heat" of ha TacSet spacecdk. It is a 

hat ~ ~ U tIs rcnvcntiol. n oparlh of Imfmd smcam ~ln~la e k m h pbgo with a mudular dm bus. A 

quires cooling of detecton and 0th Docn! hemal safis of mhbn d applica i .i specific cards attach to 

phom mise sawces (optics and SoIPctU"~). ~E~tOOs. the data bus These cads connect the bus systems, and 

if MgCdl%e, opwa~c with 3uPficicndy bw CaarBr turrcnt pmylmd if desired, @ the data bus. A high speed CPU 

whcn ai 8O0K To cchicve such Rna~mKums ailhout is also on the data bus, ai shown in Figure 16. Locally 

Ixgc dintors, mcchnnical coolcrs ~ rn saccdcd. Two generated +tar and ground commands move to the 

small radbrors m usdd. one fm the mtlxhaniccpl COoEer pmcessor. Once in mcmory, this data is used to 

and on-Bimbn9 electronics, and the mhcr to kccp the generate spacecraft or lrsrnsmission commands. 

optics and slructurrs cool. A 9i@~lwei8hl, rapidreadincss, 

cooler with long slomgo life codld bc I 

-- 

01IYju%3 manu DItl WO 

q u i d for TxSe6 missions. In U!! &ired size range, 

-U- 

a mmbnicid Stcrling cyclc coolcr is 8 pod choke. It 

opcratcs at (I coefficieot of operating paver of 

approximatcly 1W Wax consumed per Watt of 

cryocaoling dissipath. 

Sincc the scnsor is dcsigncd to opernte in the "push 

broom" or "whisk broom" mode. it is urllikely that a 

radiator would bc continuously shradcd. Some 

altcrniivcs are: periodically movin8 'the primary 

spacccdt nadir-pointing axis off diu, fitting a sun 

shicld, or using a sun-synchronous abit and "whisk 

broom" mode cxclusivcly. It might also be possible to 

change qrmtional modcs so that mdintm sun capsure 

is less than 35 minutcs per orbit. However, the 

combination of a sun shicld and nlternating modes 

could allow shad4 oprntions with minimal made use 

interference and allowing inclination choice frccdom. 

I 

Figure 14 shows U possible TacSat configuration. The 

TacSat bus houscs 8111 cquipmcnt to support thc scnsor 

payload and communications cquipmcnt. 'fhc kcy to 

TncSat flcxibility and utility is a bus that uscs a singlc 

Intcgmtcd Spacccraft Elccmnics !ISE). Figurc IS, the 

spacecraft block diagram, shbws major vehicle 

components and intcrfaccs and hJw ahr ISE conmls 

and cmdinatcs functions. Thr ISE pmccsws attitude 

scnsor data and controls or5it and ataituffe through the 

rcaction whecls and the propulsion spuem. Thc ISE 

also collccls and formats spacmaft ksdiccping data 

for storage and/or transmission. i 

I =lr 

I 

Figure 16. ISE Block Diagram 

The electricrsl power system (EPS) design should be 

simplc and flexiblc. Thc system uses cithcr gallium- 

arsenide-on-gmanium or silicon solar cells and nickcl- 

hydrogen battcrics. Gallium-arscnide solar pancls, 

while more expnsivc. offcr improved packaging, loww 

wcighl and rcduce orbital disturbance torqucs and 

momcnls of inda comparcd to silicoQ ccll pancls. A 

singlc prcssurc vcsxl (SPV) nickcl-hydrogen battery 

can lowcr both wcighl and cost comparcd to an 

cquivrllcnt individual pressure vcsscl (IPV) system. 

Tolcse factors combine to rcducc propcllant mass. 

TRrcc-axis stabilized TacSat attitude contro! and 

propusion subsystcm functions providc a swblc Sensor 

platform and include: dclermination of attitude and 

'

I 

I 

I 

. . 

/ 

0 

- 0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

4 

0 

0 

4 

0 

0 

4 

b 

0 

0 

4 

0 

0 

0 

0 

0 

0 

44 

psi lion, attitudc control arid pointing agility. orbit 

adjust control and actuation. prayloml torque anJ 

mcmcntum compcnsation. safcmodc conlr~l and dcorb^, 

;I q u i d . TRc subsystem hardwssrc consists of 

x,xm. txtu;~~ors and propellant storage and &livery 

systcm. All control law. safemode and oihcr software 

rcsidc in thc ISE. Thrce faction whecls pvidc torquc 

actuation, with agility rcquircmcnts and residual 

payload toqucs aftcr momentum compensation driving 

their six and magnctic torquers for desntlaration. Low 

cost staf camcra scnsors providc thc kind of knowlcdgc 

nceded. with a sun scrim for cwfsc pointing. 1 

?he propulsion systcm consisls of 3 conventional 

hydrazine mono-propcllant unk wiah proprllanl 

Aanagcment systcm. lines. filler. valves, 

ihstrumcnution and Lhrustcrs. Syslcm p~essuri?ation 

could use cithcr a b!ow-down or a rc-pressurization 

systcm. The propulsion systcm is uscd to correct 

launch vehicle injection errors. perform orbit trim 

haneuvers and dc-boost if rcquircd. 

Major bus structurc components me: thc frame. 

equipment pai!cls. propulsion module, and interfacc 

ring. Thc modular design allows subsystem mounting 

while mainiaining alignments during test, 

mwcmion, and storage. Thc modulstr agproach also 

reduces pm count and assembly spans. The interface 

ring provide3 Ihe suuctural load path brKwam the bus 

slructure and launch vehicle. Omghite-epoxy 

composilc (Gr/E) was selected ova a meanllic malcrial. 

for both primary and secondary structure. after 

conducting Yadc studies. GrE providrs LI stslble (near 

zero CTE! stru-ture to meet and maintain attitude 

Figure 19. T} pical TacSat Block Diagram 

31-9 

control scnsor pointing accuracy. Thc Gr/E suucturc 

saves 4.9 kilograms ovcr AVLi and 7.9 kilograms ovcr 

Al. Thc primary structurc providcs continuity. strcngth 

and rigidity between IRc payload and thc intcrfacc ring. 

- 

Spa-Ground Link Systcm (SGLS) and high data-ntc 

anwnnm stow against thc vchiclc and dcploy on hingcs. 

Spring driven mechanisms dcploy both antcnnas and 

Ihc solar mays. Each solar array gimbal is drivcn by 

small motors and rc8ucers. Rcx harness and slip rings 

cany clccrrical power and lelcmctry across thc joints. 

Temperature. exhfemcs allowed in olhcr subsystems 

drivc the salcllite thcnnal subsyslcm. Assuming the 

general case using a non-sun synchronous orbit. 

TacSau would not have "hot" and "cold" sidcs, as the 

thermal cnvironmcnt varics on thc satcllitc sidcs 

depending cm inclination and timc of ycar. A TscSat is 

subject to many cclipse cyclcs and must bc dcsigncd to 

accommodate them. For example. componcnts that 

operatc during sunlit portion of thc orbit would have 

a significant thcrmal radiation arca to rcjcct both 

intcmal and incident hat. Ilnfonunately, whcn this 

surface is in cclipsc, heater power must now mainlain 

the item with the larger radiator sizcd for the full-sun 

operation case. Albedo and earthshine (planet IR 

hearing) also influence LEO vehicle environments. 

RE& 

Fi$urc 17 shows thc two major communication system 

hrdware groups. User support is provided by an 

encryped two-way common dam link (CDL) at X- 

Band. A small stecrablc downlink dish can provide 

about 274 megsbit/scc in LEO orbits. The up-link

: 

0' 

31-10 

plovadm mglc apecity into an md mzmm a 16 or 

200 km. "lis is LBkt primary raser p ytd mml Oink 

but could support housekeeping. as nm SOLS altchate. 

Figure 17. Typical TacSat Comm & Data Links 

P m I 

Figure 18 shows a summary lcvcl weinh, and power 

budgct of a typical TacSat in thc small satcllitc (450 

kilogram) class. With the use of advmd compmics, 

high efficiency electric powcr gcncmtlon and stbmgc 

devices. nnd advanced digital techno!o$y, a TncSat 

could xhicvc a high payload to total chylmmss uatio. 

Thc spacecnft dry wcight is about 45% payload, 

(scnsor and data link) and thc rcst is llic bus. Tlic 

clccuicml pwcr rcquircmcnt cairnate is shout 480 

... *at& avcmgc. The powcr systcm is driven by thc 

sensor duty cycle, cclipu: operations ,and cooling 

bwcr. erc. Thc 68 kilograms of propesllani suppru, 

in,ection and dng-makcup for 1 - 2 years. 

syotom I SaIYboyotoon 

OVQ 

PAY LOA0 

h I 

Figure 18. Typical 'TacSat Weight & Power Budget 

TacSat conccyls have been discussed fm many years. 

Changes in Lhc international climate now make 

surveillance 'I'acSats the right capability nt he right 

lime. Potential users now havc a bcuer untkmding. 

gaincd in thc Persian Gulf. of the value of spe basal 

surv6illancc dam. Syslcm dcvclopen hve !car+ to 

. Ibhk . 0,t apace surveillance from chc fzld m W s 

.?. ., 

Finally, many TacSal sysm elmernu err 

tieing &ir'opul for ohcz purpscs. Fa &e.= reasons, 

. pc&p&$,v. 

1 

andl hdgetzary dides, the time is right to begin a 

phased T a t deZve3ctpmnt and acquisition program. 

Simx the T&mp concept centers on directly satisfying 

Centralized conml nnd maintenance redwe the ~wr's user needs, implemenodon efforts must include 

workload. Because the spxccmh would pratonn continuous user invohemnt. This involvement could 

normal systems manmgement, Rousekpiss~ corsld %c smrl with two sinauhtiorns. The first would provide 

done from m small ground station, CO!OCRif!g tclqoletry, asea with ample sensor dam of various Scene types to 

corntin8 momdies, etc. Continued bu.z-Ccoeping for BISSCSS their utility an8 value. ThC second simulation 

a large constcllation quires a larger mission convol would educate potential users about TacSat command 

ccnlcr. Existing bunch command and onnW rewu~ces and conml smlegy. planned sensor tasking and how 

an a ctmicc For launch and early orbit functions. they would receive. process and exploit the data 

--wc?ciicwm 

W A U W mac While both simulations could be done in a laboratory 

. ComwAnaM 

environment, a porlion of the process should be foldcd 

into military exenis. The uscr feedback will establish 

quantitative criteria for the TacSat system dcsign based 

on user nccds. Simulated sensor data for such an 

evaluation pmpm could bc gencrated bcforc the event 

using pmesscd airborne imagery. Imagery of typical 

bttlcfield objccts and subscqucnt computcr processing 

to vary imagc quality would allow thc uscrs to fully 

assess thc utility of various data typcs and qualities. 

Once dcsign criteria arc cstablishcd. thc TacSat 

dcrnonstration and validation program would begin. 

Thc program would be initiatcd with the first TacSat 

and a fcw user ground terminals. Activitics planned, or 

now undcrway. indicatc that most of thc systems 

rcquircd for a dcmonsmtion will bc availablc "off-the- 

shclf." The major cxccption is thc multi-spccwal 

scnsor. Howcvcr. i& ckvclopmcni risks arc nomind DS 

most of the componcnts arc cithcr commcrcially 

availablc or of stmightlorward dcsign and fabrication. 

It is likcly that UIC spcccnft bus will bc availablc as a 

dcrivativc of thc U.S. Air Forcc's Advonccd 

Technology Standard Satcllitc Bus (ATSSB) or othcr 

grogram. Thcrc should bc at lcast onc viablc candidate 

launch vchiclc for this Dcm-Val phasc. Thc Taurus 

bstcr should k availablc and it is likcly that anothcr 

launct system will cmcrgc to support IRIDIUM 

program operations and mainicnance launchcs. 

Satellile conuol for TacSat Dcm-Val phasc codd bc 

done cffcctivcly n.9 a factory effort by thc dcvclopcr. 

Comntcrcially availablc hardwarc would be cmploycd 

for uscr ground stations. Softwarc would be a 

combination of existing program and uniquc codc. 

A Dcm-Val proam would allow dcmonsmtion of: 

Disoibutcd C3 Archimturc Roof of Concept 

k ~ Cast w Satellite Control 

Multipk User Suggon 

Us( 7 ,',.ing Effcctivencss 

. I . L? hcs%ing & Exploimtion 

-.- ;cnonsmwaion grogram would providc an initial 

s;ctariond apbility hat could expand. ns shown in 

Ftpm 19. TRe infmstruciurc, once establishcd. could 

support other pyhds lo form a mixed. highly capable 

tactid weillancc system. 

A phttd. "Dzm-Val" TacSat implcmcnlalion slralc~y 

would provide B tea-bed lo evaluate TacSat system 

utility. provide multi-spectral imagery in many bands

covering a variety of scenes, asses 1:~ kncfits of 

ljmcly, mctsium resoltition MSI, pmvid.: an interim 

uaty monitoring capability, and Imrniliiarizc military 

USCIS wih tasking , dircct conml and dcS c !QlOilauOn. 

. vAcIc(usI M 

An opcrational TacSat systcm must grovidr h high lcvcl 

of dcprndability and timcly acccSs lo &la. The numkr 

of satclliacs availablc dircctly dribcs IRc system's ability 

to satisfy thcsc nccds. A singlc salcllitc can only 

providc a fcw opportunitics pcr day to imagc a givcn 

mgct arm. If thcrc nrc: conflicting drnler Pcquircmcnls 

from multiplc largcts in a givcn gcognpnic arca, or if 

thcrc mc sgccific timc windows or other constraints, a 

singlc atcllitc may not pmvidc timcly sopport. Ih 

addition. Ihc dcpcndability of a singlc satcllitc will 

always be at risk. Thcrcforc:. it is vcry likcly that an 

opcrational TacSat systcm will rcquirc, in somc way, 

multiplc sotcllitcq. This nccd can bc satisfied in (r c of 

two ways, and sclcction will bc hcuvily offcctcd by thc 

launch copbilitics that cmcrgc in thc ncxt fcW yars. 

If a quick rcaction launch systcm bccomes availablc, a 

flcxiblc approach to a TacSat capability, whcn and 

whcrc it is nccdcd, would bc practical. Salcllitcs and 

launch vchiclcs could bc storcd for call-up and launch 

in days whcn a sccurity cmcrgcncy rcquircs support. 

To mintdin rcadincss, a satcllitc would masiwally bc 

launchcd undcr cxcrcisc conditions. Thcsc would 

providc a lcvcl of continuous capability for non-crisis 

activitics, such as training and m ty monitoring. With 

this capability. satcllitcs could bc launchcd into 

situation-specific orbits to incrcasc thc availablc 

covcngc for a givcn cmcrgcncy. 

T'ie abscncc of a quick rcaction launch systcm would 

lad to a diffcrcnt stntcgy. This scenario would bc 

xrvcd by in-place TacSats, forming a pcrmancnt 

constcllation. Hcrc, thc sarcllitcs would &: in gcncral 

purpose orbils covcring thc cuth. A set of near-polar 

sun-synchronous orbits would ttc likely. For covcragc 

and dcpcndability, the constcllation would consi!.l of 

two of lhrcc satcllilcs. Thcir phasing would bc diffc rcnl 

but altitudc and inclination would bc similar. Assunling 

current boostcrs. the conccpt is to launch the cntirc 

constcllation on a singlc mcdium boostcr. A similar 

launch every fcw ycars allows for planncd rcglaccmcnt, 

cmstcllation cnhanccmcnt or capability upgdcs. 

Initiating a Dcm-Val proccss for TacSots dws not 

rcquirc an early answcr to thc qucstim of how an 

opention?! :system will be dcployd md launchcd. 

Then is a good chance bat Lhc IRIDIUM program's 

i 

0 

31-11 

O&M rqui&men(s will provide the foundation for h 

quick mtion launch system with sdcqualc capability 

for TncSlat use. If this docs not occur, thc permanent 

consellation of multiply launchcd mtcllitcs can satisfy 

operational needs with existing launch vchiclcs. 

Wc now have thc opportunity to providc our military 

Corccs with 8 cost cffcctivc forcc multiplicr. This 

opportunity exisls because: 

1) Military organiiations arc laming how dala from 

spacc can be used to cnhancc thc cffcctivcncss of 

cxisting and planncd forcc svuclurcs. 

2) Thc tcchnologics nccdcd for smallcr. vcry capable 

survcillancc satcllitcs cxist, gcncrally off-thc-shclf. 

3) Commcrcidl spxc programs and various govcmmcnt 

dcvclopmcnts arc providing thc cconomic 

foundation that will makc most kcy TacSat systcm 

clcmcnts available at affordable costs. 

Thc singlc major unfundcd dcvclopmcnt rcquircd 

kforc iaunch of thc first TacSat is for thc scnsor. 

Undcrtaking that dcvclopmcnt would allow 

dcmonsmtioa of thc tactical bcncfits of multi-spccual 

imagcry and lcad to the introduction of growing 

apabilitics To? military suppon from spxc. 

In an unstablc global sccurity transition cra, flcxiblc, 

multi-purposc spncc assct~ arc csscntinl. Multi-spccual 

imaging offcrs lactical uscrs cnhsnccd capabilitics not 

currcntly availablc. A uscr taskcd, multi-rolc MSI 

Scnsor and spacccraft can form a practical TacSat 

systcm. Thc prcmisc for and thc validity of TacSats 

havr bccn subslantiatcd barcd on thc tcchnical analysis 

ptescned. It is thc aulhors' opinion that TacSats should 

bc implcmcntcd with a scnsc of national and allicd 

wgcncy and ncccssity. 

LMSC & BA&H undcr AFSSD Conuact #M4701-89- 

C-0088, ' Octobcr 1990. 

S. & V.M. Kilston & Capt. T.F. Utch. USAF. Small 

First Intcmational Symposium on Small Satcllitcs 

Systcms and Scrviccs, Arachon. Francc. Junc 1992. 

T.C. Lcisgang & M.D. Bcnz. U w - 

v, 

. . AIAA-92-1952, 14th 

AIAA Intcmational Communications Satcllitc Systcms 

Confcrcncc. April. 1992. 

Significant portions of thc tcchnical content of this 

paper originated from work donc for thc USAF Spacc 

Systcms Division's RESERVES study. Thc authors 

spprocia~c 

the contributions IO hat cffon by: 

Capt. T. Utsch USAF 

W. S. Kilslon LMSC 

Ms. V.M. Kilston LMSC 

Mr. J. KcRm LMSC 

Mr. M. Rhynard Bm.. Allen Rr Hnmilton Ins.

31-12 

_. 

’ Discussion 

Question: Would a reduction in altitude allow the 

0 size, mass, and cost of the optical system be reduced? 

Reply: Yes, a lower altitude would reduce the optical 

system weight. but at the expense of reduced coverage. 

Also, the increased drag would increase fuel 

requirements; thereby, ofEsetting the optics weight 

reduction. The likely affect is J push on weight and 

reducej. coverage. . 

Question: What is approximately the total mass of 

the space segment under discussion or in your paper? 

Reply: The approximate.mass of the concept is 45Bkg 

including fuel and a contingency of 20%.

AbsltmsU 

'E'AC.WT MEmOROWflCU 

PAYLOADS 

by 

ID. Nickman 

Matra-Marconi Space 

Anchorage Road 

Portsmouth PO3 5BU 

Hampshi rc 


Information derivable from 

Meteoroio@cd satellites are revkwed in 

tern of their ag , liability to rnillitary use. 

Potential TA 8 SAT meteordo ical 

system are discussed in term of &EO 

and EO payloads currently in operation. 

1. InthosilnoccUiOna 

Knowledge of changes in weather 

conditions could provide essential 

information in numerous militaky 

scenarios. Such information has becn 

obtained for many years from both ciril 

aiid militauy satellite systems and is now a 

well established technology with ti ,e 

accuracy of information retrieval arld 

processing cor,;inually improving. 

Meteorological data can relate PO either 

actual regional variations or to predictions 

of cpli~gcs for a Liven area. bOBp 

infomaion could be of consider 

to a ground commander. For military 

operations involving the movement or 

deployment of men 

frequent and accurate 

maps and forecasts 

assistance with operational g8anranio . 

Furthermore, meteorolo icd da@ wou P d 

also play a significant ro f: e in ~hc tactical 

and strategic de loyment of foums in both 

defensive and o H" Pensive 0pemtiom.l 

The present papet aims to crspnoue the 

a p p 1 I cab i 1 i t y of me t eo u d og i CP 1, 

measurements from dedicated mtelli$tf 

systems to support 

military operataons. 

atmospheric physics 

meteorolo&ical data p~oscsohg are 

outside the swpe of this paper sa~d awe not 

considered here. Of more irnpmi-tance is 

I 

33-1 

tbri! rel~vmss of atmagheriic parameters 

trhich could be measured through a 

dedicated tacoid meteorological system. 

These requirements are reviewed in 

wdon 2. 

To ascertain what information could be 

retrieved from such a TACSAT payload, 

section 3 discusses the capabilities of a 

nunbet of current civil and military 

meteorological payloads which, it is felt, 

demonstrate how the requirements of a 

ground commander can be met. The 

central discussion will be based on the 

METEOSAT series of satellites together 

with its companion satellites which form 

part of a lobal monitoring s stem. 

Although a P 

r ull review of meteor0 ogical 

payloads cannot be given here, the 

payloads which are discussed are 

considered to be relevant to TACSAT 

applications and indicate what 

measurements can be performed. 

Satellite system can take the form of 

either 6eostationary Earth Orbit (GEO) 

or Low Earth Orbit (LEO), the choice of 

orbit being dependent on the resolution, 

ground coverage and data rates as well as 

the scan characteristics of the satellite 

pa load. A further distinction between 

G6O and LEO satellites is that the 

former employs assive sensors whereas 

the latter can a P so 

developments in 

ere. Active 

are not considered in any detail 

in phis ager. However, it should be noted 

that t R ey are becoming increasingly 

important and do represent important 

advances in meteorological systems. 

In section 4, the features identified in 

section 2 and the systems presented in 

section 3 are brought together and 

disclased in the context of meteorolo.ica1 

TACSAT payloads. Additional nee& of 

TACSAT system which are not currently 

met by meteorological payloads are 

reviewed in term of extensions to present 

satellite system. Finally, an assessment is 

offered on the usefulness of 

meteorological payloads in a TACSAT 

role. 

2. RqWrnemU Revim 

Atmospheric cswditiom clearly play a 

m'or role in d itay operations and must 

in d uence decisions mode by a local

33-2 

commander. Parameters sP iwtereiit 

I 

include: 

i) cloud Bssaaaion; 

11) dkaison md speed of clonad 

rn~eanacemss; 

iii) dqpe of cloud cover; 

iv) cloud a! titude; i 

V) wind spreds and direction; I 

VI) rain snow conditions; 

vil) flood waming5; 

viii) fog conditions. 

Cloud location, cover and allaiaaade ar3 

important measurements reqanised f ~ r 

both day anad night o 

limit aarborne visi 

illumination. 

controls ground temperature which in 

turn iwBps,m on penomel and ment. 

Cou led OS this 1s the direction m bsD speed 

of c P oud movement which can ke Lased to 

provide forecasts of cloud cover. 

Wind speeds a d diiectioos wne also 

important aoticdwrrly at a 

the deglopcnt 

r 

8ircaiou-s of 

wea xu me dependent on uind vduxity. 

In esen terrains, wind conditions will 

govern sand-stnrms. 

Wain and snow not only affect visibility 

but are dm be very restrictive for pound 

operations. 'Warnings of oiential 

floodin8 and fog condition WO 3 d &Q be 

of abvious use to a ground commwder. 

Meteorobgical measurements of the 

above parameters are required during 

both day and night. 

In addition to the measurements of the 

conditions present in a given region, other 

aspects of meteorolo y must be 

considered. These inch c$ c the rate at 

which weather information is updated as 

well as the forecasting period. In srder to 

provide a major advantage, the 

meteoroiogid data should be updated on 

a timescals of minutes rather thm houn. 

Another important factor is ohat thc 

meteorological measuremcum and 

forecasting are already both accurate and 

reliable. 

Finally, the format of the data resented 

s ccw~czful 

consideranuion to ensure that the eswnrid 

information is readily accessible and 

to the local commander nee B 

3. PPessnaQ Meteorological 

PayOQeado 

3.1 MsacxDGuDn~ 

- GzpOBaR MsamiOo~Plg 

The World Meteorology Organisation 

(WMO) is responsible for providing 

Goverage of meteorological data. 

e network is illustrated in Figure 1. 

Currently, there are five GIE0 satellites 

positioned at VX~OUS points around the 

e U~OOP at an altitude of approximately 

3 i! ,W&mps. 

Inn additionto these, there are a 

numbei of polar satellites (in a LEO) 

which operate at an altitude of 

approximately 85Okm. Table 1 provides a 

summary of some of the key features of 

these meteorology satellites. 

The primary role of the. geostationary 

satellites is to provide cloud imagery at 

replar intervals of ap roximately 30 

rmnutcs. Meteosat, whic R forms part af 

the GEO ring is discussed in more detail 

in the next section. 

Apart from their imaging role, the ring of 

satellites also serve a number of other 

functions including the transmission and 

relay of meteorological data from both 

ground stations and other satellites. They 

also can be used to relay 

meteorological data between t 

processing centre and the users 

The polar satellites are sun-synchronous 

and each arbit is stepped with respect to 

the previous such that a full earth 

coverage is achieved twice per day from 

each satellite. The mdn purpose of these 

hl satellites is LO monitor clouds, surface 

tit'', temperatures and vegetation cover. 

.L .*.,. 

'c.3.2 Metmart Oprmtionni Prqpmme 

The basic design Meteosot Operational 

§ystern ;brad iss main instrument, the 

Imaging Wadhrneter, is over Z years old. 

However, because of the success of the 

Meteosart Operational. Programme 

(MOP , a huber modcl (with possibly a 

semn d 80 follow next year) is currently 

being built. This is the Meteosat

I 

I 

I 

I 

Trtarasiaiaand Pnogramme (MTP) mud 

bridges to &I to the l,Meacoz~: !bcond 

(~CXI~RIM~~IE td SG) as disc'wed ian section 

3.3. A historicad review of elm Mefiemat 

Frog~me clppl $e found i$ rcfepewce 1. 

Meteosmt is a spin-stabilised aaaellite 

whose axis of rotation is ali ncd with the 

Mh's NJOhPh-kUrPR PoleS. h e est west 

san is achieved through ,the romaion of 

the satellite and the north soanUh scan is 

accomplished by a scanning mirror. 

The key parameters of Metecosat are 

summmxd in table 2. 

Meteosat has three ke roles. Fi~s~ly, it 

~ovides images of the 

b 

k arth at Qowgitude 

which are then transmitted 00 t pound 

processing station. Its second rsne is to 

distribute the processed dlda~ag ~o user 

stqtions ix?. thirdly, it provides P point of 

data coliecoion and distribution from 

other meteorological stations. 

The raw data is processed au a ground 

station and the following information is 

derived: 

! 

- cloudmotion and winds i 

- sea-surface temperatures 

- cloud top height maps 

- cloud coverage data /' 

- prccipieation indices 

The rmwd images are trw&ttcd, via 

the R etcosat down-link cPamnne8, il 

transmission rate of 2400 b/o. Thc 

resolution of the processed irn~~c~s is 

lower than that of the radiometer. 

TypicdB , he cloud top hei ha ~TIB are 

resolve d on a site of 20Em whiba the 

grid for be other parameters is 2fTQkrn. 

Meteorno mm rises three srv;cwd bands, 

one visible m 6! tw~ iIW bands. visible 

channel is wed IC' pitwide high wsIPUaneion 

cloud imasgss during daylight. Thc ahemal 

PW w band prrovides ima es com~iun~orasly 

since io relies on the t emaR rpediinnce 

from the clouds. The IR WV shsmocl 

rovides on atmospheric distribaoalisn of 

Rumidity in cloud free regions glund also 

provides images of cloud tops. 

Two detector units are used, orme for the 

visible chmel and one which mmbinces 

the PR wv md IR. The deteaom m SMCR 

are singk e!ernent devices wish V G hi ~ 

(quantum-limited) erforninamce, t I? e 

layout being illustrate B in Figwe 2 

33-3 

MSG is the replbnwment qstem for the 

payload desip~ in the operational and 

trmltritiound pro rmmes. It cow rises 

WBQP~ 

wavebmd c f amels in the & and 

and has mddphe mow spectral bmds 

in the visible s ectpum. Like MOP and 

MTP, the MS 8 satellite system will be 

s in stabilised, with a spin-rate of lUUrpm. 

8round resolution is improved 

co~~espndh to 1.4b in the visible and 

4.8b in the %W and IPB. 

A notable fcamre of the ro osed system 

is that it produces a fulp &! imay in 12 

minutes. The calibration and stab1 isation 

time is 3 minutes and the subsequent 

repeat cycle is 15 minutes. 

3.4 DMSP 

The DMSP (Defense Meteorological 

Satellite Programme) is a US military 

pro ramme comprising two orbitin 

sate P lites. The pli ht histor), of the DMS 

t! 

began in 1965 ut remained classified 

until the inid-70's. The satellite operates 

in a heliosynchronous orbit of altitude of 

ap roxirnaoel 800 km and is a 3-axis 

orm. 

sta e ilised plat I 

The DMSP satellites contain three 

B ayloa&. The fino of these is the OLS 

Operational Einescan S 

rcovides visible and IX 

F he second inastmme~t 

(Specid SQWJOP Microwave / Imager) 

wRic$ gives idomfion on 

water vapour, SODOW mer an 

ice. The thkd insummcnt 

Sensor Microwave / \:r$:km) and this provides surface 

temperatures, vertical moisture and 

temperature profiles. 

From the few examples described in 

section 3, it can be stated that present 

meteordogid system arc capable of 

measuring many of the parameters 

indicated in the requirements review of 

section 2 

The concept of the five GEO satellites 

which provide global coverage is 

appdhng POP potential TACSAT systems 

sincc continuous monitoring of a ground 

&f

, 

I 

I 

I 

: 

I 

I 

33-4 

. I. 

psitiom am t!&ui~&. FN~~%~~zuc, EC~ZUB U&. WD~GV~P, &is is generally a 

&e &iiIity DO ITC~OS~~~OXI ~tditc kTd ifif~~wps *fhed vdue md CAUUUQ~ be ogti&d for a 

in orbit inn OR&H to m~lrimf5.c ~prtem @vel73 pnimtion. A three-* smbipised 

&~&hduy a00 an @mn lon@tv~dz mmures sy~aenrra % iag lo@ean& anxi latitude SXUIS 

iht &!Q S'jD8~io) PCWhl~Oll k3 VWWXd. genenatcd tBusu@~ a scan mirror 

~WW?XD~XTIU. 'hh then provides a more 

T$e dam p b m and redh~bpwrSiOaa of fle~.~~~ spRem. Additionally, the dwell 

xnetscorollo&ical 3 i omation ~ f current 

f 

time for signal integration can be 

$stern dm lends itself tb &e TACSAT selectively mntrolled to optimise signal to 

Qoncept. However, the format df data noise patio, image repetition frequency 

presentation may need fbrther and image size. 

development to ensure that the 

information presented is in ~Poe most The detector configuration is also an 

Eseful form. There may ~ P S O be, a o tion which needs further consideration. 

requirement for 'real-time' interrogation &r MOP, single element detectors were 

of the TACSAT system. 

used md this provided a relatively simple 

imaging system. Alternatively, a staring 

Throun Pn the appropriate seQection of array could be used. In this case a 

s y d l charneb, rneteorolo 0ca.1 data is boresight pointing system would be 

o tained on a 24 hour bask. f$y sclesoing required. Although this ma be an 

the iappro riaoe spectral ban& md their attractive option since t z e scan 

associate $ spectral widths, the most mecPnmisws are simplified, ir ma be 

approprhte information cm obtahed. difficult to obtain an IR ;imy or the 

AlPPl~ugh present metcorolo 'd system required d' ensions. For example an area 

provide much of the data a0 i&cly tO be of 1000 km ? with a resolutim of 1 km 

would require a 1024 x 1024 array. 

required by the theatre commder, the 

emphasis ow spectral bands for a 

TACSAT ma be different awd a full 

analysis woul B be required. lmdee& the 

system demands may be such that a 

variable band-pass should be employed 

thou the use of diffraction mung or 

tunab !@ e interference filters. 

For a TACSAT system operatlirmg in GEO, 

it is un.kc8 that full Earth mmee wiil 

be reqaedA Wibk conaepa wuld be 

zones of meteorological data amtred on 

the loation of interest. The obs2mtion 

or dwell times on a given region would 

then be controlled through a preset 

weighting scale Or by request from a 

ground commander. 

A possible need from a GEO TACSAT 

system is to produce hi er resolution 

images tban are currenty P available. Ef 

such a need is io be satisffisd, the 

fallowing points will need to be 

considered: 

i) scan mechanism / beam c+fldon 

ii) si@ KO nok ratio . 

iu de~~amr mnfi~tion 

iv I achimablc resolution 

v) saoelfite platform 

Firstly, the satellite platform cam k either 

spin or tbrec-axis ssabiliscd. For the 

former case, the satellite spin give one 

A different 

iic to use a 

before adopting such an approach. These 

include si@ to noise ratios, multiple 

rvaveband channels and detector cooling. 

The telescope system must be capable of 

providing the resolution within its 

diffraction limit. This then sets a 

re airement on the telescope aperture 

an 1 

angula- mgmfication. For the case of 

1 lan resolution, an aperture diameter of 

approximately 500 mm would bc required 

with a magnification of t pically 10. 

Current telescope system cr esigns have 

sloown that these paramcters can be 

readily met. 

A major benefit from a TACSAT 

meteorological capability will be 

indepaadlena from avilian :-: mms and 

mdod forecasting senrim so that in the 

event 00 10, mjor crisis during which the 

civil we@ may be switched off for 

reasons sf security, me tcorological 

forecasting is not lost to the Theatre 

c o w r .

several chys. 

If S~CDPO term forecastin od was 

CSA with 

an HWoptical imager and 81 Plimiaed 

SOUI~C~F. capability would probably 

suffice nB used in conjunction with a 

skilled Id forecaster. 

required, a gcosaationiuy T 1 % 

. i 

I 

, 

I 

I 

h i 

The concept of a meteorrsloaical 

TACSAT system has been lmddaessed 

through P review of current payUa~a& aund 

military requirements. The use of the 

GEO systsm is wen as being pmisleiar1rly 

attractive since these can provide 

continual observation as well as a data 

transmission link. LEO payloads me seen 

as a complement to those in GIEO md can 

offer a number of additional benefits. 

Indeed, for complete atmm Daeric 

monitoring and data extraction, b 5 LEO 

and GEO satellites are necessary. 

From review of the possibla: military 

requirements, it is considered that present 

meteorolo ical payloads can provide 

P useful information. 

current technmc~la~~ can 

offer improvements which auld lead to a 

viable TACSAT system. 

The oaential value of a dedicated 

’ TAC sp AT meteorological system cappears 

I 

2 

to hh@ on the possible need to replace 

~et~a~~dogid data derived €rom civil 

mums whch my be switched off in time 

of CI%~S, ad o$e tactid need for the 

timely delilev of processed data. 

system based an 

iting satellites co\L;a 

provide data adequate for forecasting up 

to several days &ea& and compensate for 

the loss of cid data sources, should those 

be switched off durin a crisis. If such 

assets are not switche df off then current 

GEO system provide full Earth cloud 

maps at a refresh rate of 

minutes which is adequate Tically or global 3Q 

monitoring. However, there may be a 

requirement for ditay operations in 

which the provision o a more ra id 

update over an area much smaller t K an 

the globd image would be of value. Such 

ill system could be obtained through only a 

minimal development of current 

techology and in con’unction with global 

imsa e?, would provi d e sufficient data to 

A m d d me0eoro)lo ‘d 

2 or 3 Low Earth Or % 

em % le short tern forecasting. 

The ultimate assessment of the need for a 

rne~eo~olo@d system and its subsequent 

performance charaaeristics falls to the 

various Ministries and De artments of 

Defense. However, it is P elt that the 

tecPlPlical capability to rovide a variety of 

tactical meoeorologi cap systems has been 

demonstrated. 

An views ex ressed are those of the 

aut 1 or(s) and f o not necessarily represent 

those of HM Government. 

REFERENCES 

[ 11 RTessier ‘The Metcosat Programme’ 

ESA Bulletin 58, May 1989, pp45-47

Figure1 World Met roroloKy 

-h 

Visiblm Wtmetor Ilsamntm 

In D8tector Llennts 

1. . 

3 6.: 

111 

I 0o.y 1.l.I 1. .U. H... -1.c.l w -111 lllpyn I 

I ."l. 

Table 1 Summary of Global 

Mod- Sstditcr 

Irc m e l d [ as .I" 

[ s b I.* 4 111

e: 

l 

, 

/ 

I 

Discussion 

Question: You put great emphasis on GEO meteorological 

satellites, bllt these cannot give full polar coverage. 

Could you comment on the significance of this incomplete 

coverage. 

Reply: There is an anticipation that if a crisis/theater 

operation were to wcur, then that operation is more 

likely in lattitudes remote from the poles. The objection 

voiced to LEO sensors was based on the relatively 

Long revisit times associated with polar LEO satellites. 

However, near the poles, ,revisit times are much more 

frequent and will probably provide short term data. 

33-7

, 

Comment: TACSATS, 1 

only as "trucks" bpb 

c all sakellltes, are useful 

'I provide data to supported 

commanders. Whcrc I 

strategic/operat.I' 

Ioyment distances and 

b l depths are large, as in Desert 

Storm, spacecraft :e useful. In other situations, 

such as the \IS If. ."rvention in Grenada, spacecraft 

are useless because of dwell and ... limitations. 

What we should do IS to examine the functions performed 

(comms, nav, etc.;; remember that these functions 

are as old as warfare and - not unique to space: and 

then find a means to determine when other means of 

support are more appropriate from spacecraft. 

Question: This is a conference about tactical, low 

cost, lightsat concepts. 

Reply: Possibly yes, but the confusion comes from 

the mere existence of systems providing support to 

the theater and that dedicated systems can only be 

deployed if they are low cost, hence lightsat. 

Question: There may be problems of jamming TACSATS. 

Reply: Yes. Probably mare for SAR than optical systems. 

Nevertheless, means exist to reduce such damaging 

effects to a radar, in general. It may be worthwhile 

to develop some tests t.o better assess how to cope 

with the jammer threat. 

.'

7 

t!lETTl?3T iDOCWMEWAmOT'd PAGE 

AGARD-CP-5 22 ISBN 92-835-0700-2 UNCLASSIFIED/ 

5. Oddnotor Advisory Group for Acroipacc Research and Development 

North Atlantic Treaty Qrfpization 

7 RUC Anccllc. 82200 Ncriilly sur Seine, France 

6. I ltk 

--- 

TACSATS FOR St.kVElLLANCE, VERIFICATION AND C31 

-- -- 

7. I'n~nted at thc Avionics Panel Symposium held in 

Brusscls, bclgium from 19th-22nd October 1992. 

--- 

8. AulRoo(s)/Editor(s) 9. Date 

Various February 1993 

IO. AutMdEditor's Address 11. Pages 

Various 26 2 

I_ I 

fihtr%don . Thcre arc no rcstrictions on the distribution of this documcnt. 

lnfonnation about the availability of this and other AGARD 

unclassified publications is givcn on thc back cover. 

13. #a~Qds/Dt'SCdptW 

TacSats Satcllitc communications 

Small satcllitcs Satcllitc navigation 

Launch vchiclcs Satcllitc survcillancc 

Satcllitc payloads 1 Spacccraft bus 

This Symposium dealt with smdl satcllitcs uscd for tactical (as opposcd to strategic) zpplications 

that might bc of value to NATO. 3 %~ 1 1 Scssions covcrcd TacSat concepts and needs, aspccts of 

TacSat applications, TacSat systcm applications, communication concepts, launch systcms, 

spacccraft bus. advanccd tcchnology, radar concepts, clectro-optics concepts and two pancl 

discussions. The information gencratcd by thc Symposium will bc used by Working Group 16 to 

rcpn on thc utility of such salcllitcs and applications to mcct futurc NATO needs.

. 1.

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