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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