[amsat-bb] OSCAR-11 Report

Clive Wallis clivew at zetnet.co.uk
Fri Sep 29 02:29:57 PDT 2006

                    OSCAR-11 REPORT

                   28 September 2006

Please post reports to AMSAT-BB or e-mail to xxxxx at 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 at amsat.org (please replace xxxxx by g3cwv)

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