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www.southgatearc.org
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Oscar-11 reportReception reports requested! Any reception reports would be appreciated. Please e-mail xxxxx@amsat.org (replace xxxxx by g3cwv), or post to AMSAT-BB. If you are unfamiliar with the sound of OSCAR-11, there is an audio clip on my website http://www.users.zetnet.co.uk/clivew/ During the period 06 May to 15 June 2006, nothing has been heard from the satellite. OSCAR-11's VHF beacon switched OFF on 05 May, as expected. This was just one day before the solar eclipses were due to start. These eclipses will continue until 04 August 2006, reaching a maximum duration of 22% around 19 June. If the satellite behaves in the same way as it did last year, the beacon may only be heard for very short times, during the eclipse season. Unfortunately, due to holidays, I was unable to monitor the satellite around 15 May, when the first transmissions during the eclipse season were expected. However, I am indebted to Jeff KB2M, Bob G4VRC and Gustavo LW2DTZ who listened for the satellite while I was away. The current status of the satellite is that all the analogue telemetry channels, 0 to 59 are zero, ie they have failed. The status channels 60 to 67 are still working. The spacecraft computer and active attitude control system have switched OFF, ie. the satellite' attitude is controlled only by the passive gravity boom gradient, and the satellite is free to spin at any speed. When telemetry was last received it showed that one of the solar arrays had failed, and there was a large unexplained current drain on the main 14 volt bus. After 22 years in orbit the battery has undergone around 100,000 partial charge / discharge cycles, and observations suggest that it cannot power the satellite during eclipses, or sometimes during periods of poor solar attitude. When last heard, the on-board clock showed a very large accumulated error. On 05 May it was 22.76456 days slow. The clock lost two hours during the last OFF period, and nine hours during the last transmission period. The observations of clock errors suggest that the clock may slow or stop when the battery voltage is low. The watchdog timer now operates on a 20 day cycle. During the three months before the eclipses started, the ON/OFF times have been very consistent, and the average of many observations show this to be 20.7 days, ie. 10.3 days ON followed by 10.4 days OFF. However, during the present solar eclipse season, power supply problems, may result in a low 14 volt line supply, which may cause the beacon to switch OFF prematurely, and reset the watchdog timer cycle. The Beacon frequencies are - VHF 145.826 MHz. AFSK FM ASCII Telemetry Listeners to OSCAR-11 may be interested in visiting my website which contains an archive of news & telemetry data. It also contains details about using a soundcard or hardware demodulators for data capture. There is software for capturing data, and decoding ASCII telemetry. The URL is http://www.users.zetnet.co.uk/clivew/
73 Clive G3CWV
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