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www.southgatearc.org
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Last Updated on:
Wednesday, April 23, 2008
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Final monthly OSCAR-11 reportFor over 12 years Clive G3CWV has been producing the monthly OSCAR-11 report. Due to the deteriorating health of the satellite, launched over 24 years ago, this will be his final report. This is the 144th monthly report for OSCAR-11. Unless there is an unexpected change of status (such as occured with OSCAR-7), I'm expecting this to be my last report. This report covers the period from 17 March to 21 April 2008. During this period the satellite has not been heard and no reports of reception have been received. Transmissions were expected to resume on 24 March, after the beacon switched-off on 14 March. However, permanent eclipses started a few days beforehand, which probably caused the transmission period to be terminated prematurely. It is now unlikely that the satellite will support any sustained period of operation, and will only transmit for a short time, possibly less than a single orbit, every 21 days. I am indebted to all those who sent reception reports during the last 12 years. Initially there was much interest in hearing the mode-S beacon, which was very weak. Recently, interest has changed to hearing when the two metre beacon switched on/off. Special thanks must go to Jeff KB2M who recorded telemetry during my holidays, and Peter ZL3TC, who has monitored the beacon daily, during recent months. Many thanks to everyone. The Beacon frequencies are - The satellite is now subject to eclipses during every orbit. Long term predictions indicate that eclipses will occur until 2019, when there will be some eclipse free periods until 2023. However these very long term predictions should be regarded with caution, as large tracking errors can accumulate over long periods of time. 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 24 years in orbit the battery has undergone over 100,000 partial charge/discharge cycles, and observations suggest that it cannot power the satellite during eclipses lasting more than about ten minutes, or sometimes even during periods of poor solar attitude. 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 real time clock is showing a large accumulated error, although over short periods timekeeping is accurate to a few seconds per month. When last heard the clock was 83.0958 days slow. The day of the month has a bit stuck at 'one' so the day of the month may show an error of +40 days for some dates. The time display has switched into 12 hour mode. Unfortunately, there is no AM/PM indicator, since the time display format was designed for 24 hour mode. 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. The watchdog timer now operates on a 20 day cycle. The ON/OFF times have tended to be very consistent. The average of many observations show this to be 20.7 days, ie. 10.3 days ON followed by 10.4 days OFF. However, poor solar attitude may result may result in a low 14 volt line supply, which may cause the beacon to switch OFF prematurely, and reset the watchdog timer cycle. When this occurs, the beacon is OFF for 20.7 days. OSCAR-11 was the second satellite from the University of Surrey, http://www.ee.surrey.ac.uk/SSC. Following the success of these satellites, in 1985 Surrey Satellite Technology Ltd. http://www.sstl.co.uk/ was formed, as a commercial venture. This grew into a major company that has produced over 27 small satellite projects for a global market.
The University of Surrey has recently agreed to sell it's major shareholding to EADS-Astrium. This agreement is now awaiting regulatory approval. The joint company will have the experience of manufacturing large and small satellites, for geo-synchronous and low earth orbits. In recognition of his work, Martin G3YJO, was appointed Professor at the University of Surrey. He received an OBE in the 1995 Queens birthday honours list, and in 2002 a knighthood in the New Year's honours list. Listeners to OSCAR-11 may be interested in visiting my website, which is being updated to reflect the current status of the satellite. If you need to know what OSCAR-11 should sound like, there is a short audio clip for you to hear. The last telemetry received from the satellite is available for download. The website contains an archive of news & telemetry data which has now been updated. 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 Reception Reports Requested! In the years ahead, it is possible that you may hear OSCAR-11, by accident, when tuning round the frequency. If you are able to record the satellite on audio tape or as a WAV file (not MP3), please do so, as it is unlikely that it will be heard on the next pass! Please send reception reports to xxxxx@amsat.org (replace xxxxx by g3cwv) or post to amsat-bb. If you have a file, please let me know what you have, before sending it! If you need to hear what the satellite sounds like, please visit my website http://www.users.zetnet.co.uk/clivew/ . The satellite transmits on 145.826 MHz. Set receiver to NBFM. Uosat-Oscar 11 1984 Launch Video (9.64 MB Windows Media file) http://personal.ee.surrey.ac.uk/Personal/L.Wood/ A 64.9 MB MPEG Video of the launch can be downloaded from http://personal.ee.surrey.ac.uk/Personal/L.Wood/ UoSAT-OSCAR 11 information Online Satellite Pass Predictions (Select UO-11)
The AMSAT-UK International Space Colloquium will be held at the University of Surrey in Guildford from Friday 25th to Sunday 28th July. All Radio Amateurs and SWL's are welcome. See http://www.uk.amsat.org/Colloquium/
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