AMSAT-OSCAR 7

Build

AO-7 was the second Phase 2 satellite (Phase II-B). At launch, the satellite had a mass of 28.6 kg and it was placed into a 1,444×1,459 km orbit. It is shaped as an octagonal prism 360 mm high and 424 mm in diameter. It 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 code and teletype messages ("codestore") as it orbited around the world. The Mode-B transponder was designed and built 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 and was developed by Dr. Karl Meinzer as part of his Ph.D. research. AO-7 has redundant command decoders of a design similar to the unit proven highly successful in AMSAT-OSCAR 6. 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.

Firsts

AO-7 demonstrated several uses of new technologies and operations

• First satellite-to-satellite relay, through AO-6.
• Early demonstrations of low-budget medical data relay and Doppler location of ground transmitters for search-and-rescue operations were carried out using this satellite.
• The Mode-B transponder was the first using "HELAPS" (High Efficient Linear Amplification by Parametric Synthesis) technology developed by Dr. Karl Meinzer as part of his Ph.D.
• First to fly a battery charge regulator.

Legal issues

The uplink frequency predates the WARC 1979 allocation of 435-438 MHz by the ITU for the Amateur Satellite Service which places the uplink in the 70cm weak signal segment. Additionally, the IARU bandplan has the 432.1 MHz range (which is used for mode B uplink) marked for "weak signal" in all three Regions. Accessing the Mode B uplink is permitted in the United States under a waiver from the FCC.

Use by Polish anticommunist opposition

In the summer of 1982 the Fighting Solidarity in Wrocław learned that AO-7 became periodically functional, when its solar panels got enough sunlight to power up the satellite. It was then used to communicate with Solidarity activists in other Polish cities and to send messages to the West. Satellite communication was invaluable at that time, as the regular telephone network was tapped by the government and shut down when martial law was imposed in December 1981. Ham radios were not of much use as they were easy to track. On the other hand, a satellite link required highly directional antennas which were impossible to track by the regime. In 2002 Pat Gowen (G3IOR), inspired by the history of Fighting Solidarity, attempted to communicate with AO-7 and confirmed it to be operational.

Current status

, contacts with AO-7 are reported daily.{{cite web |archive-date=2017-10-19 |archive-url=https://web.archive.org/web/20171019183529/http://www.amsat.org/status/ |url-status=live

References

References

1. Gowen, Pat. (2002-06-21). ""Lazarus?"". self-published.
2. Kołodziej, Andrzej. (2015-05-15). "Jak Solidarność Walcząca wykorzystała satelitę do zbudowania systemu łączności".
3. (November 15, 2024). "AMSAT AO-7…A Fifty Year Anniversary!". Radio Amateur Satellite Corporation.
4. ARRL staff. (24 June 2006). "ARRLWeb: It's Aliiiiive! AMSAT-OSCAR 7 Satellite Returns from the Dead". [[American Radio Relay League]].
5. (6 April 2006). "AMSAT - Satellite Detail - AMSAT-OSCAR 7". AMSAT.
6. (31 May 2003). "AMSAT-OSCAR 7 Satellite Summary". AMSAT.
7. Klein, Perry. (October 1975). "Intersatellite communication using the AMSAT-OSCAR 6 and AMSAT-OSCAR 7 radio amateur satellites". [[IEEE]].
8. FCC Safety and Special Action. (19 April 1974). "FCC waiver for AMSAT AO-7, Oscar 7".