OSCAR-11 Report
29 December 2006
During the period 20 November to 29 December, the satellite was heard
from 28 November to 08 December and from 18 to 28 December. Good, steady,
often strong, signals have been heard on all passes, and excellent copy
of the telemetry obtained.
The date/time stamp has been of continued interest. Since the satellite
was heard on 18 October the on-board clock has maintained accurate time,
to within five seconds over a period of 71 days. This compares with the
average gain of five seconds per month, recorded when the satellite was
fully operational.
The date counter appears to be incrementing correctly, but the day of
the month is not reset to one, at the end of each month, and is not incrementing
the month counter correctly.
During the last OFF period the month counter changed from '10' to '11'.
On 28 December the date was shown as 61 November. However, the day of
the week counter appears to be incrementing correctly. Currently, 0 indicates
Thursday.
If the satellite's watchdog timer continues to operate normally, the
beacon should switch ON around 08 January 2007. The satellite is in full
sunlight at the present time, and will remain in this state until mid-April
2007, when eclipses start again.
I am indebted to Peter ZL3TC, Dean AL7CR,
Bob G4VRC and Ken W7KKE for their reports.
Reports around the times of the expected beacon switch ON/OFF, are especially
useful. Many thanks.
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 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 http://www.users.zetnet.co.uk/clivew/
73 Clive G3CWV
xxxxx@amsat.org (please replace xxxxx by g3cwv)
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
Web: http://www.uk.amsat.org/
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