Tuesday, July 24, 2012

OSCAR-7: 10 Years Back on the Air

A QSL card from 2004, commemorating the 30th anniversary
of the launch of OSCAR-7. (Courtesy AMSAT)
It's an amazing story that just keeps getting more amazing. OSCAR-7, part of the first generation of amateur radio satellites, was launched in 1974 and operated until its batteries short-circuited in 1981. Twenty-one years later, in 2002, the satellite incredibly came back to life. AMSAT officials speculate that the batteries somehow went from a short-circuit condition to open-circuit, allowing the satellite's solar panels to power its radios when in sunlight. 

Ten years after returning to the air, AO-7 is still going strong, with uplinks on 2 meters and 70 centimeters and downlinks on 10 meters and 2 meters, respectively. It switches between bands randomly each time it starts up on re-entering sunlight, and is currently the only amateur satellite providing really long-range communications. In fact, the AMSAT News Service reports that two new distance records were recently set via AO-7, with contacts 7849 kilometers (4877 miles) and then 7903.55 km (4911 mi), just short of the satellite's theoretical maximum range of 7907 km (4913 mi).