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Re: Re: Re: AO-40: why did they have to rotate it?

on 2/19/02 1:58 PM, Stacey E. Mills at w4sm@cstone.net wrote:

>> Now how does this situation affect the eventual (?) move to 3 axis
>> stabilization using the momentum wheels?  If I understand things correctly,
>> even under momentum wheel control, the bird will still experience periods of
>> non-optimum squint angle in order for the solar panels to catch the sun.
> True, though in theory we should be able to tolerate a few hours of bad
> solar angle to give optimal squints, then swing back to recharge the
> batteries.

OK, but perhaps I'll put it differently.  Under 3 axis stabilization, will
we still have extended periods of bad sun angle where the transponder will
be unusable?

>> Now will the additional, unfolded panels help to decrease periods of bad sun
>> angle since you have more panels out there and so thereby we have a better
>> point to earth?
> I'm not quite sure if I understand your point, but I think the answer is
> no.  In part we have to try to stay within solar sensor ranges.

The unfolded panels give us greater area for the sun to hit.  Will they help
reduce the amount of time that we are at bad solar angles or does it make no
difference?  Is that clearer?  I don't know how else to put it....

>> Finally, what is the status and plan of moving to spin up the momentum
>> wheels and open the panels?  Is it ever going to happen or are we just too
>> unsure of the condition of the bird to risk it?
> As soon as we have a final timetable, I'll sure pass it along.  It's not a
> matter of uncertainty about the spacecraft.  It's a matter of testing a lot
> of software, making sure all the contingencies like the mystery effect and
> protracted eclipses are covered, and that we can get back to spin mode if
> we need to. The original plans for 3-axis mode were based on a much higher
> inclination....  Some of the software routines will need to be loaded in
> the spacecraft and tested in bits and pieces.  Others can be tested in
> ground simulations.  This is all under active development, but we do not
> want to rush it or back ourselves into a corner from which we cannot retreat.

A very good point.  The protracted eclipse part that you mention is what I
am asking about in particular in my whole response.  But you're right in
that having changed the inclination from what was planned, I guess there is
a lot to consider.



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