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PCSAT2 high-beta-angle shut-down.



PCSAT2 shut down due to low voltage sometime
after 1855z on 23 Nov due to high beta angle.
Nothing was heard on the 2032z pass.
PCSAT2 is attached to the outside of ISS and
only gets sun when ISS is maintaining an attitude
with good sun angle on our location.  The worst
angle is still to come on Saturday.  We do not
expect to recover until later next week when
sun angles begin to improve for us.  Then we hope
to do joint ops with PCsat (NO44).

Last telemetry was showing the 16 volt Lithimu-Ion
Battery down to 11.6 volts and these cell readings:
Cell 4 = 3.48
Cell 3 = 1.52
Cell 2 = 3.46
Cell 1 = 3.12 
Load current was the usual 313 mA
Solar current was 377 mA but that was just
about at local noon.   I'll post a plot on the
PCSAT2 web page in a few minutes that captures
the sudden loss of voltage, though you can see
it on the plots of the Side A telemetry on FINDU.

http://www.ew.usna.edu/~bruninga/pec/pc2ops.html 

Even with load sheding, and re-charge, the PC2 
receivers will be on and the only power savings
due to the shut-down will be the 60 mA of the
TNC's.  This is only 20% of the nominal load current
and is insufficient to gain much ground until the entire
system returns to better sun angles sometime
after 1 Dec.

Bob Bruninga, WB4APR
USNA Satellite lab

>>> Robert Bruninga 11/21/05 1:42 PM >>>
PCSAT2 is entering a phase of low voltage
due to high beta angle.  From the attached
plot, we can see that by tomorrow, we will be
below the 14 volt point which is the lowest
we have seen on orbit.

PCSAT2 should work down to 12 volts, though.
but Phil (GRC) has tested his ability to get
FTSCE data on demand, so he is comfortable
with turning off the FTSCE beacon.

This will save us 30 mA out of our nominal load
of 330 mA or about 10%.  Everything else is 
minimized only a 1 minute telemetry packet will
remain.

Bob
USNA Sat Lab
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