A COMMUNICATIONS satellite has come back from the dead after vanishing without trace 20 years ago, and has presented its owners with some tricky technical and legal problems.
Last week satellite sleuth Pat Gowen was scanning the airwaves when he picked up a brief signal from the satellite, dubbed Oscar 7. The probe disappeared six years after it was launched in 1974, when it developed a leak in its battery that short-circuited its solar cell. It was originally sent up to serve as a communications satellite for ham radio enthusiasts, tirelessly bouncing Morse and voice signals across the planet.
But no sooner had the satellite burst back into life than it faded away again. The ghostly spacecraft now appears to be sending signals only intermittently.
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鈥淚鈥檓 blown away,鈥� says Jan King, original project manager for Oscar 7, after he had dusted off a 27-year-old copy of the Morse Code Telemetry Encoder to confirm its identity. 鈥淭his old warhorse of a spacecraft seems to have come back from the dead, if only for a few moments.鈥�
Gowen is a member of the international amateur satellite community AMSAT, and fellow members have since confirmed his discovery. The batteries have probably dried out, AMSAT president Robin Haighton told New 杏吧原创. 鈥淭he solar cells are now directly feeding the electronics.鈥� This would explain why it appears to be operating only sporadically, when its orbit 1460 kilometres above the Earth takes it in view of the Sun.
Surprisingly, during its brief spells of activity Oscar 7 is still functioning as well as ever. 鈥淚t鈥檚 doing exactly what it was originally designed for except that it won鈥檛 work in the dark,鈥� says Haighton. The satellite was not designed to withstand the radiation it would have endured over the past 27 years, and had an expected lifespan of about seven years.
Oscar 7 was the seventh amateur satellite to be launched in North America and cost just $38,000. 鈥淚 wish we built them for that these days,鈥� says Haighton.
Since the satellite鈥檚 launch, some countries have changed the frequencies that amateurs are allowed to use for satellite communication. Half of those used by Oscar 7 are now illegal, so the satellite鈥檚 AMSAT owners are trying to reprogram it to only broadcast at legal frequencies.