AMSAT-VK History

  

History

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Australis OSCAR-5

The following material was reproduced from The Satellite Experimenter's Handbook written by Martin Davidoff K2UBC (by permission).

The OSCAR 5 story begins in Australia. Late in 1965, several students at the University of Melbourne, mostly undergraduate members of the Astronautical Society and Radio Club, seriously began to consider building a satellite. Though none of them had any spacecraft construction experience, they were competent in electronics and mechanical design. When the California-based Project OSCAR agreed to take care of final environmental testing, locating a launch, and launch operations for Australis OSCAR 5 (AO-5), the "down under" crew began the project in earnest. (Note: With the fifth amateur satellite being readied for flight, amateurs decided to acknowledge the advantage of Arabic numerals over their Roman counterparts-hence OSCAR 5, not OSCAR V.)

Australis-OSCAR 5 shown with its antennas deployed. Note that this satellite carried no solar cells and that actual steel carpenter rule was used for the antenna elements.

     Members of the Melbourne group wanted to make a unique and significant contribution to the amateur space program, but they recognized that their isolation and lack of experience dictated a relatively simple spacecraft. The design, finalized in March 1966, showed that their desire and the constraints they were working under could be reconciled.

     AO-5 would attempt to: (1) evaluate the suitability of the 10-meter band for a downlink on future transponders; (2) test a passive magnetic attitude stabilization scheme; and (3) demonstrate the feasibility of controlling an amateur spacecraft via uplink commands. The flight hardware to accomplish these goals included telemetry beacons at 144.050 Mhz (50 mW) and 29.450 Mhz (250 mW at launch), a command receiver and decoder, a seven-channel analog telemetry system and a simple manganese-alkaline battery power supply. The spacecraft did not contain a transponder or use solar cells.

     Though technical aspects of the AO-5 project went smoothly, they turned out to be just the tip of the project's iceberg; administrative concerns were a constant frustation. Air-posting a special 50-cent part from the US to Australia might cost $10, and clearing the part through customs often required pages of paperwork and several trips to government offices. You probably get the picture: Technical competence isn't enough. People who build satellites also need great perseverance. Step-by-step, Australian dollar by Australian dollar, AO-5 took shape. On June 1, 1967, 15 months after final plans were okayed, the completed spacecraft was delivered to Project OSCAR in California. A launch opportunity was targeted for early 1968. Delay followed delay, however, until the host mission was indefinitely postponed. No other suitable launch was immediately available.

     So stood the situation in January 1969 when George Jacobs (W3ASK) spoke to the COMSAT Amateur Radio Club in downtown Washington, DC. Jacobs suggested that, with the space-related expertise and facilities in the area, the amateur space program might benefit from an East Coast analog of Project OSCAR. As a result, AMSAT (the Radio Amateur Satellite Corporation) was founded. Formal incorporation took place on March 3, 1969, in Washington, DC, and the first task of the new organization was arranging for an Australis-OSCAR 5 launch.

     Environmental and vibration tests of AO-5 showed that some minor changes were needed. AMSAT performed the modifications and identified a suitble host mission. Finally, on January 23, 1970, AO-5 was launched on a National Aeronautics and Space Administration (NASA) rocket (previous OSCARs had all flown with the US Air Force). Electronically, the satellite performed almost flawlessly. One small glitch prevented telemetry data from being sent over the 29-Mhz beacon. Since the same telemetry information was available on 144 Mhz, the problem had little impact on the overall success of the mission. The magnetic attitude stabilization system worked beautifully.

     The spacecraft's spin rate decreased by a factor of 40 from 4 revolutions per minute to 0.1 revolution per minute over the first two weeks. A network of ground stations periodically transmitted commands to the satellite , turning the 29-Mhz beacon on and off. Allowing the beacon to operate only on weekends helped to conserve the limited battery power. The first successful command of an amateur satellite took place on orbit 61, on January 28, 1970, when the 29-Mhz beacon was turned off. The demonstration of command capabilities was to prove very important in obtaining FCC licences for future missions.

 

 In this view of Australis-OSCAR 5, the flexible antennas have been tied back, where they will remain during launch. At the proper time , as the satellite is separated from its launch vehicle, these elements will spring out to their full pre-cut length.

     Performance measurements of the 29-Mhz beacon confirmed hopes that this band would prove suitable for transponder downlinks on future low-altitude spacecraft, and led to its use on OSCARs 6, 7 and 8. As the battery became depleted, the transmitters shut down: The 144-Mhz beacon went dead 23 days into the mission, and the 29-Mhz beacon, operating at greatly reduced power levels, was usable for propagation studies until day 46.

     At AMSAT, the project manager responsible for final testing, modification, and integration of AO-5 was a young engineer named Jan King (W3GEY). It's difficult for people not directly involved in a program of this scope to imagine the pressure on the project manager. But Jan must not have minded too much, as he went on to oversee the design and construction of several AMSAT spacecraft over the next quarter century.

     AO-5 met its three primary mission objectives. In addition, careful analysis of reports submitted by ground stations that monitored the mission showed that such stations were capable of collecting reliable quantitative data from a relatively complex telemetry format. All in all, AO-5 was a solid success.

 

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A united voice for Australian Amateur Satellite operators.