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Special Bulletin: January 8, 2001

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Phase 3D/AO-40 Update

AMSAT-DL President AMSAT-DL President Karl Meinzer, DJ4ZC, provided ANS with the latest information about AMSAT OSCAR 40:

Greetings,

Since my report from late December, command stations have implemented the strategy which I had outlined. The first priority was to determine which command-uplink channels were available. This work was difficult, very time consuming (and for the satellite) somewhat dangerous due to the unknowns. The command stations did a magnificent job! Due to their combined efforts I can report the following findings:

1. After some blind transmissions to test the omni-antennas around apogee (that failed to produce a response), the scheduler was activated and programmed in such a way as to prevent lock-out. This strategy turned out to be very prudent and the scheduler-operation went smoothly and resulted in no additional anomalies.

2. The scheduler then took AO-40 through a number of modes, which allowed the P3D team to determine the following:

a. V, U and L-1 receivers work
b. V, U and L high-gain antennas work
c. U and L low-gain antennas do not work
d. the status of the V-band low-gain antenna has not been finally determined. Apogee blinds tests are in progress as I write this to accurately determine the status of this antenna

3. The V-band transmitter was operated for one MA-unit. It demonstrated a marked temperature increase, but no signal was heard. This was a quick-look test and this result should not be considered final. Further tests will be necessary (including the need to determine if the matrix was set properly). These tests will have to wait until the spin rate is reduced to ensure that the satellites heat-pipes will be able to handle the dissipation for extended periods.

4. Magnetorquing was started to reduce spin and the first indications are a loss of around 0.5 rpm - roughly consistent with theoretical predictions. We can conclude that the system works. In order to use Earth-sensing data, a small additional program needs to be installed which stores data at apogee for later recovery when telemetry reception becomes available.

What's next?

During the next days the attitude control system should be returned to full functionality. It will be used to reduce the spin to a value consistent with heat-pipe operation and also with the requirements to change attitude. These changes are necessary for sun-angle constraints, communication access and also to reduce the effect of our ongoing mass-loss on perigee altitude. Newer model calculations show that the mass loss could be larger than my previous estimates; thus it would be prudent to use the resulting thrust to increase perigee altitude (right now it is decreasing it).

Once the spin/attitude situation is under control, we will continue the check-out of other systems (such as):

1. Determine the status of the V-band transmitter (controlled experiments)

2. Determine the status of the U-band transmitter

3. Determine the serviceability of the ATOS (arcjet) to determine if it can be planned on for a strategy toward an improved orbit

4. Test the momentum wheels to determine if AO-40 can be put into a three-axis mode which would greatly reduce the impact of the loss of the omni-antennas

Present data so far indicates that although we have lost some systems in AO-40, there has been no further deterioration after the second incident. In particular, if ATOS and three-axis stabilization are still serviceable, AO-40 will still be able to produce a large fraction of the amateur radio service expected from it.

Personally, I am optimistic and I believe that the command-and engineering team stand a good chance of turning AO-40 into an extremely useful amateur radio satellite.

73, Dr. Karl Meinzer, DJ4ZC

Stay tuned to ANS, the official source of information on AMSAT OSCAR 40.

[ANS thanks AMSAT-DL and AMSAT-NA for this information]


This AMSAT News Service special bulletin was edited by AMSAT  News Service editor Dan James, NN0DJ.

Please send any amateur satellite news or reports to the ANS Editors at ans-editor@amsat.org, or to ANS Editor Dan James, NN0DJ, at nn0dj@amsat.org.

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