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AMSAT-OSCAR 7
AO-7 (aka AMSAT-OSCAR 7) is the second Phase 2 amateur radio satellite constructed by AMSAT-NA, and it was launched into Low Earth Orbit on November 15, 1974. It remained operational until a battery failure in 1981. Then after 21 years of silence, the satellite was heard again on June 21, 2002 — 27 years after launch.
AO-7 is the oldest amateur satellite still in use, and is one of the oldest operational communications satellites. It carries two amateur radio transponders. Its "Mode A" transponder has an uplink on the 2-meter band and a downlink on the 10-meter band. The "Mode B" transponder has an uplink on the 70-centimeter band and a downlink on the 2-meter band. AMSAT-OSCAR 7 also carries four beacons which are designed to operate on the 10 meter, 2 meter, 70 centimeter and 13-centimeter bands. The 13 cm beacon was never activated due to a change in international treaties.
AMSAT reported AO-7 still operational on June 25, 2015, with reliable power only from its solar panels; the report stated the cause of the 21-year outage was a short circuit in the battery and the restoration of service was due to its becoming an open circuit. The satellite eclipses on every orbit during the northern summer and autumn; the rest of the year it is in continuous sunlight and alternates between transmission modes A and B. All transponders and beacons are operational.
==Build==
AO-7 was the second Phase 2 satellite (Phase II-B). It weighs 28.6 kg (63 Pounds). AO-7's is in a 1444 x 1459 km high orbit. It is Octahedrally shaped 360 mm high and 424 mm in diameter. AO-7 has a Circularly polarized canted turnstile VHF/UHF antenna system and HF dipole. Four radio masts mounted at 90 degree intervals on the base of the satellite and two experimental repeater systems provided store-and-forward for morse and teletype messages (Codestore) as it orbited around the world. The Mode-B transponder was designed and build by Karl Meinzer, DJ4ZC and Werner Haas, DJ5KQ. The Mode-B transponder was the first using “HELAPS” (High Efficient Linear Amplification by Parametric Synthesis) technology was developed by Dr. Karl Meinzer as part of his Ph.D. AO-7 has Redundant command decoders of a design similar to the unit proven highly successful in OSCAR 6 were flown. The decoder has provisions for 35 separate functions, and is designed to provide a reliable means of controlling the emissions of the repeaters, beacons and other experiments aboard the spacecraft.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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