The AMSAT Oscar 7 satellite was launched in November 1974 as a piggyback payload with a NOAA weather satellite. The AMAteur SATellite organization has been constructing satellites since the nineteen sixties, serving the needs of amateur radio enthusiasts around the world.

The satellites typically carry the designation "Oscar", an acronym for Orbiting Satellite Carrying Amateur Radio. In a typical lifespan for a small satellite, the octahedral Oscar 7 functioned normally for six and a half years before it experienced battery failure in 1981, bringing its normal operations to an end.

With a steady stream of more advanced AMSAT satellites reaching orbit in the years that followed, Oscar 7 was essentially forgotten for more than a decade, apparently a lifeless "rock" that could not be used for radio communications.

Circumstances changed on June 21 of this year, when AMSAT member Pat Gowen encountered an unexpected transmission, which was soon discovered to be a signal from the satellite.

Oscar 7 is not a fully operational spacecraft. Its batteries remain useless, and the satellite draws its power directly from its solar arrays. Oscar 7 project manager Jan King dubs it a "daylight-only satellite" in an AMSAT bulletin.

The spacecraft essentially wakes up for a short period on each orbit when its solar arrays generate enough power, turning on subsystems on board the satellite. The limited operations of Oscar 7 would still make it difficult to use for amateur radio communications, but simply receiving a cheerio call from the satellite would please most enthusiasts.

AMSAT president Robin Haighton told SpaceDaily that the recent activity from the satellite is apparently due to a change in the physical properties of the battery. Haighton stated that the battery is serving as an open circuit "or at least high resistance", making it possible for current to flow from the solar panels through the battery and into the satellite's components.

Haighton stated that tests are still being conducted, but "as far as we know, transmitters in the 10 metre band are working fine." A 70 cm wavelength beacon has an intermittent problem. Receivers in the 2 metre and 70 centimetre bands also seem to be functioning. Haighton added that the majority of the electronic control circuits on Oscar 7 seem to be functional.

Spacecraft engineers are normally proud if a multimillion-dollar satellite can survive in space for more than a decade, but such a long lifespan for an amateur spacecraft is even more remarkable. Oscar 7 was constructed on a low budget with voluntary labour and the use of components that commercial engineers would shun as unspaceworthy. The event provides an interesting lesson in the potential merits of innovative spacecraft engineering.

"It demonstrates the value of robust engineering versus throwing money at parts," said Rick Fleeter, president of AeroAstro, a company specialising in the design of small satellites. Fleeter noted that the ALEXIS small satellite, built by his company with a six-month design lifetime, has been in continuous operation since 1993. But he added that the Oscar 7 incident was also one in a series of successes for AMSAT itself. "Most of (their satellites) exceed their design lifetimes."

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