AMSAT-DL Vice President Peter Guelzow, DB2OS, provided ANS with the latest information about AMSAT OSCAR 40:
Dear All,
I know that many people are looking for more information and I can understand this, but please keep in mind that the recovery efforts are not easy and take a lot of time. Everyone involved in the recovery is indeed very busy and we all have our full time jobs and our families to consider in addition to the recovery efforts.
Due to the currently limited downlink capabilities, uploading of new commands and analyzing the results takes some time. So far, it has been determined that the L-band uplink receiver (on a high-gain antenna) is OK. Also, the VHF and UHF uplink receivers are OK and they seem to be working nominally. Since we know that the high-gain antennas are working, the V-band transmitter was switched 'on' for 1 MA count recently during a perigee pass over Australia (by command-station Graham Ratcliff, VK5AGR). Telemetry indicated a temperature rise but Graham could not detect any AO-40 telemetry signal on 2 meters. Unfortunately, the telemetry Gram was receiving on S-band at the time of this test was not error free and therefore some telemetry might be missing. The V-TX clearly needs to be tested again in the next few orbits.
Magnetorquing did commence and the results will be analyzed. Because of this action some additional FM wobbling may be noted on the S-band downlink when the magnetorquers are in action. If successful, the magnetorquing attitude control system will allow us to spin 'down' the spacecraft and adjust the attitude for a better sun and squint angle. Following this, it will take some time to evaluate the status of the various other systems and experiments, including the arcjet and momentum wheels.
However, there is a sign of a small leak, which we believe is also the reason for the higher spin rate we are seeing. The internal pressures of the propellant tanks are measured by discrete pressure transducers which are part of the PFA module. While the transducers could be damaged, it seems to be very unlikely. So for now the reason for the leak and the possible effects are under investigation and results will be reported when a final conclusion is made.
At the moment we clearly have priorities and the most important one is to bring AO-40 back into 'normal' mode as soon as possible. Depending on the outcome of these tests we can devise a new schedule that best exploits our currently known communications capability.
73, Peter, DB2OS
Following Peter's report, AMSAT-DL President Karl Meinzer, DJ4ZC, provided the following:
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. As Peter noted 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
AO-40 command-station operator Stacey Mills, W4SM, has done a long-term calculation of AO-40's current orbit in the unlikely event that a malfunction within AO-40's propulsion system means that no further orbital maneuvers could take place. W4SM calculates the current orbit will be stable for a very long period.
Both the W4SM orbit calculation and the measured AO-40 beacon frequencies (during RF testing in Kourou) have been posted to the AMSAT-DL web site. See http://www.amsat-dl.org/journal/adlj-p3d.htm
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.