Firat Barlas posted:
>I think Geosats enter eclipse season near equinox. Are they visible at local
>midnight during these peak days?
Geosats with inclinations reasonably close to zero will go into eclipse
for about one hour. Here is a prediction for one object on March 8:
Lat 30.313N Long 97.866W Bee Caves Rsrch Ctr
*** 2003 Mar 8 Sat evening *** Times are CST ***
23764 PAS 3R 96 2A
HGT ALT AZI HRS MIN R A DEC
22247 22 110 8 20 10 58.5 -4.7
22247 22 110 8 25 11 3.5 -4.7
22247 22 110 8 30 11 8.5 -4.7
... eclipse ...
22247 22 110 9 35 12 13.6 -4.7
22247 22 110 9 40 12 18.7 -4.7
22247 22 110 9 45 12 23.7 -4.7
This geosync has typically been seen about magnitude 5.5 just before
it enters the Earth's shadow. The observing plan in the past has been
to watch the part of the sky just a little to the west of the eclipse
entry point. The assumption is that solay arrays that are tracking the
RA of the sun will reflect best just before/after the satellite enters/
leaves the Earth's shadow. Since the observer is nearer to the limb of
the Earth (as seen from the satellite) in the early evening and moves
gradually farther from the limb of the Earth as the night goes on, the
assumption is that evening objects will be brighter than midnight objects
(that have the same solar panel area). Similarly, early morning objects
exiting the Earth's shadow should also be brighter, but we have never
tried to observe them.
But some geosyncs have been observed to be unusually bright many hours
before their shadow entry. The assumption is that this is caused by
reflections from solar panel concentrators.
Mike McCants
Austin, Tx
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