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Re: OSCAR-E question



On Fri, 14 Jun 2002, William Leijenaar wrote:

> I was also wondering if it will not have overheating problems. In an GTO it
> can be long times into sunlight. I don't know if this can give
> problems....

For what it is worth,
PCsat is currently in 24 hour full sun this month and is very comfortable
throughout and stays within a few degrees of these room termeratures:

Sides are around  70 degF  (21 C)
Top is around     57 degF  (14 C)  (it is not facing the sun)
XMTR is           73 degF  (23 C)

When it is in maximum eclipse (35%) it averages 38 degF (3 C) but the
fluctuation per orbit then is +/- about 15 degF (5 C).  We would have
liked to have it about 15 deg warmer, and I wanted to add some low-E tape
to warm it up, but given that we had little confidence in our pre-launch
termperature calculations, we decided the risk of overheating was worse
then being too cool, so did not put on the tape..

PCsat maintains its relatively low temeprature fluctuations by being
relatively heavily made out of thicker aluminum than structurally needed,
and by a 1/2 RPM spin about the Z axis (white/black antennas) and a twice
per orbit tumble of the Z axis due to a bar magnet..  Further, all the
internals are only mounted to a central aluminum plate that conducts to
all 4 sides of the spacecraft.  THus any one hot (or cold) side is
averaged out by the others..

de WB4APR, Bob


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