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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.