The April 1974 cover of QST bore this artist's conception of the AO-7 satellite, which was still under construction at the time.
NEWINGTON, CT, Jun 24, 2002--The Amateur Radio satellite world is abuzz with news that the nearly three-decades-old OSCAR 7 satellite suddenly has come back to life. First heard June 21 by Pat Gowan, G3IOR--who copied and downloaded CW telemetry on 145.9738 from the bird--AO-7 subsequently was monitored by several other AMSAT members. AO-7 was launched November 15, 1974, and it remained operational for more than six years.
"I'm blown away," was the reaction of AO-7 Project Manager Jan King, W3GEY. "So, this old war horse of a spacecraft seems to have come back from the dead if only for a few moments." King says the bottom line is that even "a cheap spacecraft built by a bunch of hams, without very many high reliability parts and without designing for a radiation dose like this, can last for 27+ years in space as far as a majority of its electronics is concerned." AO-7 is in a 1460 km orbit.
Exclaimed satellite enthusiast and AMSAT Vice President for User Services Bruce Paige, KK5DO, "This is really awesome!" Paige said the latest turn of events makes AO-7 the oldest amateur satellite that's still working, although it was dormant for some 21 years. Following commissioning in 1974, AO-7 stopped transmitting in 1981 after a battery failure.
Gowan reports he came across the slow-speed CW beacon as he was checking out some interlopers in the 2-meter satellite segment while using a new vertical antenna he'd installed. "It sounded very familiar," he said, but he wasn't sure at first which of the early OSCAR satellites he was hearing. Gowan said the beacon peaked at S9 and, at times, "took on a rough quality, wobbling in frequency, then coming back strong and quite stable again."
AMSAT says it seems certain the satellite is running only off its solar panels, not from the onboard batteries, so it will only remain operational while it's in sunlight. King noted that the satellite had a very sensitive receiver and a good uplink antenna and that just 5 W EIRP should provide a good downlink.
King speculates that the batteries, which shorted as they failed two decades ago, now are "un-shorting" and causing the satellite to come back to life as long as it's in the sun. "Now you have a daytime only satellite but, each time the sun rises at the spacecraft you have a random generator that either turns on Mode A or Mode B or whatever it wants," King said. "So, occasionally that 70 cm/2 meter transponder transmitter and beacon must at least work."
Now, some 27 years later, Mode A (2 meters up/10 meters down) is not a problem, but Mode B (70 cm up/2 meters down) is. Because of changes in the international Radio Regulations that went into effect in the 1970s as AO-7 was under construction, the 432.1 MHz uplink frequency is no longer authorized for space communications.
"Potential users should realize that when they are uplinking to a satellite, they are no longer operating in the Amateur Service but instead operating in the Amateur-Satellite Service," AMSAT-NA advises on its Web site. AMSAT says uplinking to AO-7 "is possibly illegal since the Amateur Satellite Service is not permitted at 432.1 MHz." AMSAT also notes that the current band plan earmarks the 432.1 MHz range for weak signal work.
ARRL Regulatory Information Specialist John Hennessee, N1KB, notes that §97.207(c) of the FCC's rules authorizes space station operation only in the 435-438 MHz segment. It's also not clear at this point if the satellite still can be controlled from Earth--a requirement for a space station. Given the current situation, plans are reportedly under way to set up an AO-7 Earth station.
Regardless of the legalities involved, several stations reported making contacts through AO-7 over the weekend.
Built by a multinational team under the direction of AMSAT-NA, AO-7 carries Mode A (145.850-950 MHz uplink; 29.400-500 MHz downlink) and Mode B (432.180-120 MHz uplink; 145.920-980 MHz downlink) linear transponders plus beacons on 29.502 and 145.972 MHz. A 2304.1 MHz beacon was never turned on because of international treaty constraints.
AMSAT has additional information on AO-7 on its Web site.
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