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OSCAR-11 Report




                OSCAR-11 REPORT   14 October 2003


During the period 06 September to 13 October 2003 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 11 to 21
September, and 02 to 12 October. During this period good signals have been
received. Telemetry transmissions are expected to resume around 22 October
for about 10 days.  Once again I am indebted to Jeff KB2M who has
provided telemetry from 13 to 21 September, while I have been on holiday.
Many thanks Jeff.

On 11 September at 17:11:37 UTC, while searching for a signal, I was
particularly fortunate to hear the beacon switch ON. Telemetry showed
the 145.826 MHz. beacon temperature rapidly rising, frame by frame,
immediately after it had switched ON.

The internal temperatures have increased by 12C during the period,
indicating that the eclipse times are continuing to decrease.  The
temperatures are now 17.0C, 14.4C, and 21.4C respectively, for battery,
telemetry electronics and command decoder, respectively. The external
temperatures have shown less variation than previously reported, and are
generally in the range 0 to 30C.

Temperatures are expected to increase, reaching a peak in November with
higher temperatures than in 2002.

The battery voltage observed during daylight passes has increased.
Observations have varied between 13.5 and 14.0 volts, with an average value
of 13.8 volts.

Spin periods of 430 to 720 seconds have been measured from the magnetometer
telemetry. This indicates a trend towards normal rotational speeds, and the
direction of rotation is normal.

The mode-S beacon has been heard by Christian F1AFZ. He reports S3-S4
signals with 85 cm dish, 3.5 turn helix, and AIDC 3733 converter.  Many
thanks for that report Christian.

Users of OSCAR-11 should note that the date in the telemetry is advanced by
three days.  The time is advanced by 19.0 minutes, and this error is
increasing by about one minute per year.

OSCAR-11 now operates in a default mode, controlled by the watch-dog timer.
The satellite transmits continuous ASCII telemetry for about 10 days on
145.826 MHz., followed by about 10 days of silence. This regular
sequence might be interrupted by ground control.

The mode-S beacon is ON continuously, even when the VHF beacon is
OFF, nominally transmitting an unmodulated carrier on 2401.5 MHz.
There is however a VERY low level of AFSK modulation, (now a constant
1200 Hz. audio tone), which has been detected on strong signals.
Telemetry indicates that the beacon has partially failed, and is
delivering half power.  This beacon is a useful test source for those
testing mode-S converters, as an alternative to OSCAR-40. However the
signals are very weak, and there is a lot of Doppler. Users should
also note that the polarisation of OSCAR-11 is LHC. Even if you can't
hear OSCAR-11, your equipment may still be OK for OSCAR-40. Any
reports of reception on 2401.5 MHz. would be most welcome.  Please
e-mail g3cwv@amsat.org.

The 435.025 MHz. beacon is normally OFF.  It can only be heard on the
very rare occassions when the satellite is being commanded by ground
control, ie. within range of Guildford, UK.  When the 435 beacon is
transmitting, the 145 beacon is normally OFF.  The data transmitted
is mainly binary.

Listeners to OSCAR-11 may be interested in visiting my web site.

The web site contains details about using a soundcard for data
capture, and also details about using hardware demodulators. There is
software for capturing data, and decoding ASCII telemetry and WOD.
There is an archive of raw data for analysis, which is continually
being expanded, as new data is captured.  Originally this was for
WOD, but it is now being expanded to include ASCII telemetry. At the
present time the telemetry covers 1996 to April 2003.  I will add
other years as time permits.  In parallel there is a news archive
which provides an overview of the state of the satellite, at the
times when the telemetry was captured.

If anyone out there can provide any data, particularly for the 1984
to 1993 years, this would be most appreciated.  Please e-mail me
with details.  However please DO NOT SEND ANY FILES, before futher
discussion.

Also included are some audio files, examples of each type of data
transmitted by OSCAR-11, each one plays for about ten seconds.  There
are also examples of mode-S reception.  All the audio files are
zipped, so that they can be played off-line.  These should help
listeners identify the various types of data, and give an indication
of the signal quality required for successful decoding.

The URL is -

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

If you place this bulletin on a terrestrial packet network, please
use the bulletin identifier $BID:U2RPT90.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
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