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



on 2/18/02 1:19 PM, Stacey E. Mills at w4sm@cstone.net wrote:

> Since the solar panels are on the
> sides, as the sun moves towards the front or back, illumination on the
> solar panels decreases to unacceptable levels and the satellite must be
> rotated.  We can generally tolerate solar angles to +/- 45 degs (90 deg
> total range) on the solar panels.  Therefore, during a year, there are
> roughly six months of good orientation (the two "good" 90 deg ranges), and
> six months of compromise (the two "bad" 90 deg. ranges).  If the
> inclination of the satellite is substantially out of the earth's orbital
> plane, which is not the case for AO-40, then the illumination situation
> becomes considerably better.  If the orbit did not precess, then the times
> of bad illumination, would be exactly the same each year.  However, because
> the orbit slowly changes over time, the times of good/bad illumination will
> vary as well.

Stacy,

Good explanation and I guess this is one of the problems with a satellite
that does not have a high degree of orbital inclination.

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.

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?

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?

73,

Jon
NA9D

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