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AO-40: camera pictures OK



Dear All,

We have all the data now, and normal tlm is back on again.
  
James Miller G3RUH provided the following information:


Camera Pictures Orbit 207 MA 250
--------------------------------
Four pictures were taken. The JPEG quality was Q=20 in order to keep the
file size small. The JPEGs are 256 greyscale. 

The IHU-2 clock was checked and found to be correct within a few
seconds. 

Based on the latest keplerian elements, conditions were:

                         2001 Apr 13   Rev 207
  Image     Filename        utc          MA
  --------------------------------------------------------- 
    P1     133206.JPG      1332:06     250.17
    P2     133504.JPG      1335:06     250.84
    P3     133803.JPG      1338:06     251.53                  
    P4     134101.JPG      1341:06     252.20                 
  ---------------------------------------------------------


Spin rate is 2.047 rpm

At the time, AO-40's camera view of the Earth was The Gulf of Mexico. 

Comments
--------
1. The spacecraft spins some 14 deg during the exposure; distortion is
   minimal.
   
2. Circular aberrations (like a crater) are observed at top and bottom.
   However they are /not/ in the same place as the pictures taken on orbit
   152.

3. The Earth's edge is in three of these images, and the angular distance
   from the bore-sight indicates an attitude of alon/alat = 128/14 with
   pin-point convergence. 

4. This estimate agrees with the Earth sensors' last triggers at  1232:08
   (lower) and 1307:10 (upper), as was the case before the incident.
   
5. Assuming the attitude 128/14 is correct, the Sun angle for these images
   is -55°;  that is, the Sun is 35° from the -Z (spin) axis;  the camera
   view is +Z.
   

Conclusion
----------
1. The camera and much of the IHU-2 is working.

2. ES and camera mountings are unchanged.

3. We now have a firm idea on the attitude direction.



73s Peter DB2OS
for the AO-40 command team


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