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 Previous: Surfin': Web Resources for the Yaesu FT-1000MP |  Next: Amateur Antenna Bill Introduced in Arkansas |
NEWINGTON, CT, Mar 19, 2001--AMSAT-NA President Robin Haighton, VE3FRH, has issued a likely explanation of why AO-40 suddenly went silent in mid-December. Haighton's approximately 1200-word statement, released March 16, outlines a three-part failure scenario theorizing that AO-40's problems began with a fault in a helium valve.
"Initial thoughts were that the spacecraft was completely dead and that chances of recovery were remote, with the possibility that AO-40 was in multiple pieces," Haighton said. The satellite's 2-meter beacon quit while ground controllers were attempting to test the onboard 400-newton motor system after anomalies with an orbit-shifting burn that lasted several minutes longer than it should have. It was almost two weeks before ground controllers were able to reset the onboard computers and restart a beacon on 2.4 GHz.
Ground controllers have been somewhat successful in regaining control of the next-generation amateur satellite since telemetry transmissions resumed Christmas Day, but Haighton concedes some onboard systems may not be recoverable.
Haighton said that while the Phase 3D team may never know exactly what happened, the likely scenario includes what Haighton--in an interview with ARRL--called "a minor explosion" aboard AO-40 that apparently damaged or destroyed some systems. Haighton said in his statement that the motor could have "burped" or "popped' as out-of-place fuel mixed and then ignited as a result of a blocked exhaust port on a helium valve.
"We think it was a human error thing," Haighton conceded in an interview with the ARRL. He did not elaborate. Before reaching any firm conclusions, Haighton said, the AO-40 team would have to talk out the issues and come up with an answer. The most important goal, he said, would be to avoid a similar occurrence in future AMSAT projects.
Ground controllers have used AO-40's magnetorquing system to reduce the satellite's spin rate to around 5 RPM and are optimistic that they'll be able to re-orient the satellite for communication with Earth. The satellite's omnidirectional antennas appear to be lost, but ground controllers hope the high-gain directional antennas still work and that reorienting the spacecraft will bring about a resumption of signals from other transmitters.
AO-40's heat pipe system--which could not work at the higher spin rates--has begun operating again too, considerably reducing internal temperatures. But ground controllers are pessimistic about being able to restore AO-40's 2-meter and 70 cm transmitters.
"The 2-meter and 70-cm transmitters still are in doubt," Haighton said. "We think we've got a problem with both of those." The 70-cm transmitter was not working properly from the time AO-40 was launched in mid-November. Haighton said the 2-meter and 70-cm receivers appear to be working, however. Yet to be tested is the onboard arc-jet motor, which ground controllers hope to use to adjust the satellite's orbit for future use.
Haighton said one of the things ground controllers determined that the satellite had lost quite a lot of its 400-newton motor fuel--and thus a substantial amount of weight. "We're fairly sure there was a leak," he said. The lighter satellite is responding better to ground controllers. Through additional magnetorquing, ground controllers will reorient the satellite so that the high-gain antennas will face the Earth.
"Following the reorientation it will be possible to test the remaining systems on board the spacecraft and to determine which systems and bands will be available for future operations and under what conditions," Haighton said.
| Previous: Surfin': Web Resources for the Yaesu FT-1000MP | Next: Amateur Antenna Bill Introduced in Arkansas |
