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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 .