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*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.
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Y l l l C l P
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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