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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.
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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.
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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.
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