[amsat-bb] OSCAR-11 Report

[Clive Wallis <clivew@xxxxxxxxxxxx>]

                  OSCAR-11 REPORT

                  17 April 2006

I have recently updated the software package for capturing OSCAR-11
telemetry, UCAP.ZIP.  The update includes two new programs. UTCAP, which
features an automatic time stamp, to aid unattended monitoring; and
TIME_DIFF which eases the task of calculating clock errors.  The software
can be downloaded from my website - www.users.zetnet.co.uk/clivew/

During the period 26 March to 16 April 2006 the VHF beacon on 145.826
MHz. has been heard from 04 April to 14 April.

Signals have not been as strong as during the previous ten day period,
although they were usually decoded without difficulty. However, on  one high
elevation pass (11 April), the signals couldn't be detected until the middle
of the pass, and then they were too weak to decode. If the current mode of
operation continues, the beacon should next switch ON around 25 April 2006.

The on-board clock continues to show a very large accumulated error. On
March it was 22.31086 days slow. The stability of the clock, mentioned in
the last report has not been maintained.  It lost 2.2 hours during the last
OFF period, and 1.8 hours during the transmission period. The observations
of clock errors suggest that the clock may slow or stop when the battery
voltage is low.

All the analogue telemetry channels, 0 to 59 are zero, ie they have
failed.  The status channels 60 to 67 are still working.

The satellite is now in continuous sunlight until around 05 May, when
eclipses will start again. This coincides with the time when the next ON
period is due to finish.  If the satellite behaves in the same way as it
did last year, the beacon may only be heard for very short times, during
the eclipse season, which ends around 05 August 2006.

The watchdog timer now appears to have resumed operation on the 20 day
cycle. During the last three months the ON/OFF times have been very
consistent, and many observations show this to be 20.7 days, ie. 10.3 days
ON followed by 10.4 days OFF. However, at any time, poor solar attitude,
and battery problems, may result in a low 14 volt line supply, which may
cause the beacon to switch OFF prematurely, and reset the watchdog timer
cycle.

I am indebted to Bob G4VRC and  Gustavo LW2DTZ  for their reception
reports. They have reported mixed signals from the VHF beacon. Many thanks
for those reports.

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:U2RPT120.CWV, to prevent duplication.

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