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OSCAR-11 Report



                  OSCAR-11 REPORT

                  14 December 2005

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

If you place this bulletin on a terrestrial packet network, please
use the bulletin identifier $BID:U2RPT116.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
----
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