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Mystery Effect reply




>Wayne replies:
>
>If the mystery force doesn't go away, how would it affect long-term
>operation of AO40?  My guess:
>
>1. Less sleep for the controllers because they have to frequently check the
>ALON/ALAT and adjust the magnetorquing parameters.

As long as the ME is constant, we correct for it in our calculations, 
torques, software, etc.

>2. Assuming AO40 stays spin-stabilized, the ALON/ALAT at apogee would
>occasionally vary by a few degrees, making S1 downlink performance more
>variable.

As above, we can easily correct for it.  By spinning faster we can reduce 
its effect.  We can even put the magnetorquers into "station keeping" 
mode.  The S/C already has an ME correction that we have added to its code.

>3. Major complication to 3-axis stabilization?

The momentum wheels will have to be "unloaded" more often through the 
magnetorquers.

>4. Impact on power budget due to frequent magnetorquing?

Not a problem!  The magnetorquers are very low power.


>If the mystery force only acts near perigee, does that rule out propellant
>leak as a possible cause?

Probably.

BTW:  There is a one word error in my prior post.  I said:

"Remember, to change ALON in the observed direction on a spinning 
spacecraft requires a net "upward" torque (trying to raise
ALAT)."  To be more precise, it requires an "upward" FORCE (on the +Z side, 
trying to push the 400N motor upward and raise ALAT).  The torque vector 
for this force would be 90 degs to that.




-- 
  ________________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
    Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  ________________________________________________________________________

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