OSCAR-11 REPORT

28 September 2006

NOTHING HEARD FROM OSCAR-11 DURING SEPTEMBER ... REPORTS REQUESTED! Please post reports to AMSAT-BB or e-mail to xxxxx@amsat.org (replace xxxxx by g3cwv).

During the period 14 August 2006 to 28 September, the satellite was heard from 16 to 26 August. The beacon was expected to switch ON ten days or 20 later, ie. around 05 or 15 September. However, it has not been heard since 26 August.

During the last ON period, the real time clock showed various errors. The date on 16 August was 51 July. By 26 August it had incremented to 60 July. The hours were also showing an erratic behaviour. Over short periods of time, ie. during a pass, the minutes and seconds appeared to be incrementing correctly

I am indebted to Jeff KB2M, Peter ZL3TC and Dave G1OCN, for their reports and for monitoring the satellite, especially during the last two weeks while I have been away on holiday. Many thanks.

The status of the satellite, when last heard, was that all the analogue telemetry channels, 0 to 59 are zero, ie they have failed. The status channels 60 to 67 were 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.

The watchdog timer now operates on a 20 day cycle. During the three months before May (when the eclipses started), the ON/OFF times were 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, 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.

The Beacon frequencies are -

VHF 145.826 MHz. AFSK FM ASCII Telemetry

UHF 435.025 MHz. OFF

S-band 2401.5 MHz. OFF

Listeners to OSCAR-11 may be interested in visiting my website. If you need to know what OSCAR-11 should sound like, there is a short audio clip for you to hear. The website 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 www.users.zetnet.co.uk/clivew/

If you place this bulletin on a terrestrial packet network, please use the bulletin identifier $BID:U2RPT125.CWV, to prevent duplication.

73 Clive G3CWV xxxxx@amsat.org (please replace xxxxx by g3cwv)