description AO-7 (OSCAR-7) Overview
AO-7 (OSCAR-7) is an amateur radio satellite constructed by volunteers and launched into low Earth orbit by the Radio Amateur Satellite Corporation (AMSAT) in 1974. After its batteries failed in 1981, the satellite ceased transmissions and was presumed permanently lost. However, it unexpectedly resumed operation in 2002 when the shorted batteries finally became open circuits, allowing the solar panels to directly power the spacecraft when illuminated. It remains the oldest operational satellite in orbit, actively used by the global ham radio community.
help AO-7 (OSCAR-7) FAQ
How did AO-7 come back to life after more than 20 years of silence?
AO-7 (OSCAR-7), which went silent in 1981 due to a battery failure, unexpectedly resumed transmitting in 2002 when the dead batteries degraded into a short circuit. This short inadvertently reconnected the solar panels directly to the satellite's transmitter systems, so whenever sunlight hits the panels, the transponder powers on.
What ham radio transponders does AO-7 carry and which ones still work?
AO-7 carries two linear transponders: Mode A (2-meter uplink / 10-meter downlink) and Mode B (70-centimeter uplink / 2-meter downlink). Since its 2002 revival, Mode B has been the primary operational mode, while Mode A is heard less frequently due to changing conditions in the aging satellite.
Who built and launched OSCAR-7?
OSCAR-7 was built by volunteers associated with the Radio Amateur Satellite Corporation (AMSAT) and was launched on November 15, 1974, from Vandenberg Air Force Base alongside several other payloads. It was part of AMSAT's Phase 2 series of amateur radio satellites designed and constructed primarily by a dedicated volunteer engineering team.
Is AO-7 still usable by amateur radio operators today?
Yes, as of the 2020s, AO-7 remains one of the oldest operational satellites in orbit and is actively used by ham operators worldwide. However, it only functions during sunlight because there are no working batteries to sustain it during eclipse periods, and operators must also contend with interference from terrestrial FM repeaters on its 2-meter downlink frequency.
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