[amsat-bb] AO-40 Update 2001-07-18

["Stacey E. Mills" <w4sm@xxxxxxxxxx>]

On Orbit 328/329, the magnetorquer took us, as expected, to the limits of 
the solar sensors, with a solar angle of about 48 degs.  As soon as lock 
was lost, effective torquing stopped.  Subsequently, we turned off the 
torquer and sensor lock came back at the extreme limit of its range.

This was followed by a long and busy night last night stretching to 04:00 
this morning.  During this time, the IHU-2 was quickly set up for picture 
taking, 14 images were taken at 9 minute intervals, and almost 300 D-blocks 
of compressed image data were downloaded.  We now have an extremely good 
fix on AO-40's alon/alat.

(Orbit 329) ALON / ALAT   = 325.5 / 6.2   (+/- 0.2 degs)

This is in very good agreement with our computer simulations, as well as 
other sensor data, indicating that we have the S/C reasonably well 
calibrated for these manuevers.

The 14 images and a graphic plot of our attitude will be available later 
tonight in Paul Willmott's telemetry archives, as soon as we finalize things.

Please read the Note accompanying the images when they are posted.  Be 
warned that the full zip file of spun and despun images is >500K bytes in 
size.   There is a phenomenon in the images which has been seen before, but 
is brought into greater visibility by the solar angle across the face of 
the camera.

****************

Now that we have a very good fix we will do nothing to the attitude for 
several weeks to see if we can re-calculate the "mystery effect".  During 
this time the solar angle will progressively decrease.

****************
The transponders should be back on very soon.
Watch this space, AO-40 message blocks, and the telemetry matrix settings.

As noted previously, transponder and beacon activity may be interrupted for 
RUDAK testing.




-- 
  ________________________________________________________________________
  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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