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AO-40 Update 2001-07-24




ALON/ALAT
----------
As Paul Willmott reported, the latest set of images, set up and downloaded 
by Graham Ratcliff, show that we have drifted backwards somewhat to 
ALON/ALAT = 309.8 / 7.4  (+/- 0.2) degs.

Mystery Efect
--------------
The above indicates that the mystery effect (ME) is still very much 
active.  Initial analysis by G3RUH shows that the effect is only slightly 
reduced when compared to measurements before the arcjet outgassing, even 
though perigee height has increased from about 220 km to about 900 
km.  More measurements will allow us to further refine the magnitude of the 
ME.  However, current data would appear to eliminate atmospheric drag as 
the source of the ME, and seem to make magnetic effects unlikely as well. 
Yet, the ME clearly exerts the bulk of its effect around perigee as 
observed in the solar angle values pre- and post- perigee.   Here is a 
substantial mystery waiting for you to solve it.  The data are all there in 
the telemetry archives.  Remember, to change ALON in the observed direction 
on a spinning spacecraft requires a net "upward" torque (trying to raise 
ALAT).  However, to produce a net "upward" torque requires a "despun" 
force, as any spun force would sum to zero.  So, any viable theory must 
produce a despun upward torque.

Magnetorquing
--------------
To prevent the squint angles from deteriorating further, we have initiated 
a 3-orbit magnetorque to take us back to the solar sensor edge at approx. 
ALON/ALAT = 336/3.  Once there we will spin up somewhat to decrease the 
rate of back-drift.

Orbit 339
----------
As mentioned previously, the U/L1 -> S2 passbands are currently scheduled 
to be off on orbit 339 for RUDAK testing and software loading.  The middle 
beacon may be off for extended periods of time during this orbit as 
well.  Do not despair if you can't hear the beacon!

KEPS
----
The latest NORAD keps, day 203 are in reasonable agreement with 
ranging-derived keps for AO-40.  However, note that the orbit number 
remains incorrect in these.  These keps set the orbit number one lower than 
it should be.




--
  _______________________________________________________________________
  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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