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OASCAR-11 Report





                OSCAR-11 REPORT    17 June 2000

During the period 16 May to 16 June 2000 fairly good signals have
been received from the 145 MHz. beacon.

The battery voltage during daylight passes has continued to
decrease. The average value observed was 13.4, with a range of 13.2
to 13.5 volts.

The internal temperatures have again decreased, by about one degree
C.  They are now -0.5C and -2.0C for battery and telemetry electronics
respectively.  Further reductions in temperature are expected until
July.

Ground control reset the magnetorquer attitude control counters at
the start of June.  During May the Z-axis counter remained at its
maximum value of 1024, which was reached towards the end of April.
This stopped further magnetorquer firings, the attitude being
controlled solely by the passive gravity gradient boom, without any
spin corrections. During May the spin period increased steadily from
286 to 450 seconds. After the counters were reset the spin period
quickly settled to an nominal -350 seconds.  It is interesting to
note that the negative spin correction counter is now incrementing at
about half the rate of the Z-axis counter.  The was the nominal rate
before October 1998, when the rate suddenly dropped to almost zero.
The cause of this anomaly remains a mystery.

Ground control has also corrected the software generated dates, but
the date in the hardware generated ASCII telemetry frames is still
advanced by three days.  Unfortunately the date in the hardware was
set up at the start of the mission and cannot be reset.

The single WOD survey of channels 10, 20, 30, 40 (+Y, -X, +X solar
array currents, array voltage), dated January 06 has been
transmitted. Note the year of this WOD survey is incorrectly
displayed as 99. This survey clearly shows the solar eclipses, and a
spin period of 340 seconds.

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:U2RPT50.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org


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