[aprssig] Digital APRS sats you can work, where?
bruninga at usna.edu
Fri Nov 25 10:22:02 CST 2005
Part 2, PCsat and PCSAT2 oribts:
A lesson in orbits is easy to see with PCsat and
PCSAT2. PCsat has come back to life and PCSAT2
has shut down, both due to sun angle. Their
orbits both are flying more or less above the
day/night terminator line. This is obvious as
you notice that passes are occruing at mid latitudes
within a few hours of sunrise/sunset.
For PCsat, this means it is now in full sun the
entire orbit with the sun coming from the side.
Without the normal 35 minute eclipse every
orbit, this lets it stay alive long enough for us
to command OFF its two backup receivers,
and once we get them off, then there is enough
solar power for a full receovery.
PCSAT2, attached to the ISS is facing UP. But
in this case, just like PCsat, the sun is coming
from the side and so we are nice and warm, but
insufficent sunlight is getting to the upward
facing solar panels. So it is presently shut down.
Both spacecraft enter these full sun periods
periodically as their orbits precess a few degrees
westward every day. For PCsat, we have
found that we can always recover her when
these alignments occur in the winter but not the
summer. Reasons are:
1) Best PCsat solar panel is on +Z axis but that
is the SOUTH seeking pole. Since sun is 46 deg
further south in WInter, this gives us an added
2) When we attempt to command, in the Northern
hemisphere, the higher reflection off of winter
snow gives a slight boost to all solar panels too.
And Antarctica which always faces our +Z axis
is in nearly full sun giving also good reflection.
We thought about trying summer recoveries from
Antarctica since the best panel faces the snow.....
but in our summers, its 24hrs dark at the south pole.
Its easy to visualize.
de Wb4APR, Bob
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