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OSCAR-11 Report







                OSCAR-11 REPORT    16 July 1999

During the period 15 June to 16 July 1999 consistent signals have
been received from the 145.826 MHz. beacon. The battery voltage
during daylight passes has remained fairly constant, the average
value observed was 13.5, with a range of 13.2 to 13.9 volts.

The internal temperatures have remainded fairly constant during this
period. They are now 0.2C and minus 1.0C for battery and telemetry
electronics respectively. The maximum eclipse time appears to have
been reached, and should decrease in the next few months. This should
result in increased internal temperatures and improved battery
voltage.

The magnetorquer spin correction counters have now resumed their
nominal counting rates, after their unusual behaviour during the last
few months. The counting rate for the negative spin counter is now
about 6.5 counts per day, whilst the Z axis counter increments at
about 11 counts per day.  During the last week the Z-axis counter
reached its maximum value of 1024, causing the attitude corrections
(magnetorquer firings) to stop.  When this happened the spin period
slowly started to increase. A value of -537 seconds was recorded
before ground control reset the counters on July 14.  The spin period
has now dropped to a normal value of -348 seconds.

The WOD survey dated 08-April-1999 of channels 39, 50, 52 & 63
(telemetry electronics temperature, battery charge current, battery
voltage, and BCR status), has been transmitted during this period.
This starts at 16:00 UTC.  at the end of the period a new WOD survey
of channels 1, 2, 3, 61 (magnetometers) dated 15 July 1999,was
started.  This should show the increased spin period mentioned above.

Reports of the mode-S beacon have been received from Ted WA2HKS and
Ken G8VR.  Ted reports strong signals from overhead passes using a
three foot corner reflector, and a Drake converter. On the other hand
Ken uses an 18 element helix (G3RUH design), and a DownEast
converter.  He commented that the antenna was very easy to construct,
and pointed out that although many stations use a dish for mode-S,
satisfactory results can be used with simpler antennas.  Many thanks
for those reports Ted & Ken.

The operating schedule is unchanged.

        ASCII status (210 seconds)
        ASCII bulletin  (60 seconds)
        BINARY SEU (30 seconds)
        ASCII TLM (90 seconds)
        ASCII WOD (120 seconds)
        ASCII bulletin (60 seconds)
        BINARY ENG (30 seconds)

The ASCII bulletin is currently a static message, detailing modes and
frequencies of all the amateur radio satellites.

There  are  additional  status  blocks  after  each bulletin is
transmitted, and between ASCII TLM and WOD.

The mode-S beacon is ON, transmitting an unmodulated carrier, but
telemetry indicates that it has partially failed, and delivering half
power.  This beacon is a useful test source for those testing mode-S
converters, prior to the launch of P3-D. 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 P3-D. Any reports of reception on
2401 MHz.  would be most welcome.  Please e-mail g3cwv@amsat.org.

The 435.025 MHz. beacon is normally OFF.  However it can sometimes be
heard 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 of hardware required and some software for
capturing data, and decoding ASCII telemetry and WOD.  There is an
archive of raw data (mainly WOD) for analysis, which is continually
being expanded, as new data is captured.  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:U2RPT39.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org



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