OSCAR-11 report

27 March 2006

On 01 March OSCAR-11 achieved 22 years in orbit, and inspite of numerous problems, it still continues to transmit good signals.

During the period 14 February to 26 March 2006 the VHF beacon on 145.826 MHz. has been heard from 22 February to 04 March, and from 14 to 24 March.

Signals have been very consistent and excellent copy has been obtained on all passes received. If the current mode of operation continues, the beacon should switch ON around 04 April 2006.

The on-board clock continues to show a very large accumulated error. On 24 March it was 22.14308 days slow. However, the clock is now very stable. During the last month it gained 2.5 seconds, which is approximately half the monthly gain, observed when the satellite was fully operational! The observations of clock errors suggest that the clock may slow or stop when the battery voltage is low.

All the analogue telemetry channels, 0 to 59 are zero, ie they have failed. The status channels 60 to 67 are still working.

The satellite is now in continuous sunlight until around 06 May, when eclipses will start again. This should help the satellite to continue transmitting, although continuous sunlight can cause problems due to excessive temperatures. Power supply problems can be caused by poor pointing attitude, ie the sunlight illuminating the ends of the satellite, instead of the solar arrays.

The watchdog timer now appears to have resumed operation on the 20 day cycle. During the last two months the ON/OFF times have been very consistent, and many observations show this to be 20.7 days, ie. 10.3 days ON followed by 10.4 days OFF. However, at any time, poor solar attitude, and battery 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.

I am indebted to Bob G4VRC, Gustavo LW2DTZ, Mike DK3WN, John K7RQN and John G4PWG for their reception reports. All have reported good signals from the VHF beacon. Many thanks for those reports.

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 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
www.users.zetnet.co.uk/clivew/

73 Clive G3CWV
g3cwv@<no spam>amsat.org

AMSAT-UK produces a newsletter Oscar News packed full of Amateur Satellite information. For membership details contact the secretary Jim Heck G3WGM Tel: +44 (0)1258 453959 Email: g3wgm@amsat.org Website: http://www.uk.amsat.org/ Online Satellite Pass Predictions: http://www.amsat.org/amsat-new/tools/predict/

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