AMSAT-OSCAR 40 mission patch. Photo: AMSAT

The amateur radio community received a welcome Christmas present Monday when workers were able to restore contact with a satellite that had been silent for nearly two weeks.

Commands uplinked to an L-band receiver on the AMSAT-OSCAR 40 (AO-40) spacecraft at 4:45 pm EST (2145 GMT) Monday succeeded in resetting one of the S-band transmitters on the six-week old satellite, and amateur radio operators worldwide soon reported detecting a signal from the spacecraft, which had been silent since December 13.

"The excellent news of contact with AO-40 through the L-band uplink and S-band downlink has been received with joy and relief by AMSAT members around the world," Robin Haighton, president of AMSAT-NA, the Radio Amateur Satellite Corporation of North America, said Tuesday. The news, Haighton added, was "a fantastic gift to the Amateur Radio community."

Later Tuesday project engineers received the first telemetry from the spacecraft since it went silent, allowing them to assess the spacecraft's overall health. "A first quick look has revealed that some temperature sensors and possibly some current sensors have been lost by whatever incident caused the telemetry transmissions to stop," said Karl Meinzer, AO-40 project leader and president of AMSAT-DL, the German counterpart of AMSAT-NA. "However, the power situation, in particular the battery voltages, look nominal."

The AO-40 team now plans to spend the next several days slowing bringing up other spacecraft systems, including uploading software that will allow them to take full control over the spacecraft's power control system. "The command stations will continue to follow a conservative philosophy with the primary target of not causing any additional damage along with retaining as much evidence as possible for the analysis of the incident," said Meinzer. "During the next few days we hope to learn to what extent the satellite was damaged and to what extent this will impact mission targets."

While communications with the spacecraft have been restored, project officials do not yet know why contact with the spacecraft was lost on December 13. The loss may be linked to the spacecraft's 400-newton maneuvering thruster: the thruster had experienced problems in the days leading up to the loss of signal, and work on the thruster was in progress when communications with AO-40 were lost. Fears that the engine may have caused a catastrophic failure, though, were laid to rest last week when radar scans conducted by NORAD showed no evidence of any debris that would have been created by an explosion.

On Saturday Haighton announced plans to form an inquiry committee to determine the cause of the problem and any steps that can be taken to prevent it from happening in the future. "AMSAT believes that it is in the best interests of our organization to determine all the facts surrounding this incident and to make sure that a similar situation cannot happen again either on AO-40 or on a future satellite," Haighton said in a statement.

AO-40, originally known as Phase 3D, is a project of AMSAT-NA and AMSAT-DL to build the largest and most powerful amateur radio satellite ever. The spacecraft carries a number of receivers and transmitters designed to facilitate communications by amateur radio operators worldwide, as well as a cosmic ray experiment, a pair of cameras, and a GPS receiver. The spacecraft was built by an international team of volunteers and paid for with several million dollars in donations.

After years of work, as well as several years of launch delays, AO-40 made it into orbit last month as a secondary payload on the Ariane 5 booster that launched the PAS-1R communications satellite and the STRV-1C and STRV-1D British military research spacecraft. Initially placed in a geosynchronous transfer orbit, AO-40 will maneuver into a Molniya-like elliptical, inclined orbit ranging between 4,000 and 47,000 km, phased to maximize coverage over North America, Western Europe, and Japan. Those maneuvers require the use of the spacecraft's 400-N thruster as well as a separate electric propulsion system