OSCAR-11 report
During the period 21 November to 14 December 2005 the VHF beacon
on 145.826 MHz. has been heard from 05 to 10 December.
Signals have been very variable during this period. Sometimes received
at good strength, at other times they were inaudible, even with
the BFO switched ON (ie. in CW mode).
If the watchdog resets as expected, then the beacon should restart
around 31 December. However, more observations are needed to confirm
the timing of the watchdog timer, and whether it is being reset
prematurely. Therefore, it may be worth listening for the satellite
a few days before 31 December.
The on-board clock continues to show a very large error.
On 09 December it was 21.8 days slow.
All the analogue telemetry channels, 0 to 59 are zero, ie they
have failed. The status channels 60 to 67 are still working.
The eclipses have now ended, and the satellite should be in continuous
sunlight for the remainder of this year, and next year until early
May. 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 earth pointing attitude,
ie the sunlight illuminating the ends of the satellite, instead
of the solar arrays.
The watchdog timer appears to be operating on the 20 day cycle,
ie. approximately ten days ON followed by 10 days OFF. It appears
to be unaffected by problems of the on-board clock. However, poor
solar attitude, and battery problems, may be combining to produce
a low 14 volt line supply. This appears to be causing the beacon
to switch OFF prematurely, and resets the watchdog timer cycle.
It seems very likely that the battery is now unable to retain its
charge, due to having endured around 100,000 partial charge/discharge
cycles, always a problem with NiCad cells. When analogue telemetry
was transmitted, it showed an unexplained current drain from the
14 volt line. This just adds to the present problems.
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 http://www.users.zetnet.co.uk/clivew/
73 Clive G3CWV
g3cwv@<no spam>amsat.org
AMSAT-UK
produce a quarterly newsletter "Oscar News" which is full
of Amateur Satellite information. For membership details contact
the secretary Jim Heck G3WGM
Tel: +44 (0)1258 453959
E-mail: 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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