OSCAR-11 REPORT

31 October 2006

OSCAR-11 is back! It was first heard by Peter ZL3TC, at 06:23 UTC on October 18. It had been silent since August 26.

During the period 28 September to 30 October, the satellite was heard from 18 to 28 October. Good signals have been heard on most passes, often very strong.

Further deterioration of the time/date stamp has occurred. Here is a frame of telemetry captured on 27 October at 08:43:51 UTC.

UOSAT-2 060=601033448

000000010001020002030003040004050005060006070007080008090009 100001110000120003130002140005150004160007170006180009190008 20000221000322000023000124000625000726000427000528000A29000B 30000331000232000133000034000735000636000537000438000B39000A 40000441000542000643000744000045000146000247000348000C49000D 50000551000452000753000654000155000056000357000258000D59000C 60800E615FC1620105633305644402651E0C662AC467000168000E69000F

The date/time stamp is the block of characters following 'UOSAT-2' having the format YYMMDDWHHMMSS (Year, month, day, day of week, hours, minutes, seconds).

The month, shown as '0=' in the date stamp is now in all telemetry frames. When the satellite was heard in August the month, had stuck at 07 and the day had incremented to 60. During the ten day reception period in October, the day had correctly incremented from 51 to 60. While the satellite was silent, it appears likely that the day may have incremented to 99 and then reset to zero. It will be interesting verify this theory on future passes.

During the last ten days of beacon transmission the time stamp incremented accurately, and no gain or loss was detected ( within one or two seconds). However, on one occasion, the most significant digit of the hours failed to change from zero to one, although it didn't cause a permanent error.

If the satellite continues to operate normally, the beacon should switch ON around 07 November. If nothing is heard, it may be worth listening ten days later, ie. around 17 November.

I am indebted Peter ZL3TC, Bob G4VRC, Paul KB5M, and Doug KA2UPW/5 for their reports and for monitoring the satellite. Peter listened for the satellite daily, often during several passes, while it was silent. 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. 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.

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:U2RPT126.CWV, to prevent duplication.

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