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OSCAR-11 Report







                OSCAR-11 REPORT    15 May 1999

During the period 15 April to 15 May 1999 reliable signals have been
received from the 145.826 MHz. beacon. The battery voltage during
daylight passes has continued to decrease, the average value observed
is 13.5, with 13.1 recorded on one occassion.

The internal temperatures have continued to fall, by about two
degrees C during this period, due to the increasing eclipse times.
They are now 2.4C and 0.6C for battery and telemetry electronics
respectively.

The magnetorquer spin correction counters have now started to show
some activity. During the last month the negative spin counter has
started to increment at about three counts per day, whereas
previously it was incrementing at about one count every three days.
At the beginning of April, there was a period when the Z-axis counter
reached 1024, causing the attitude control to stop. During this time
the spin rate remained fairly constant, indicating that the spin rate
did not require any corrections, rather than a fault condition. The
Z-axis counter continues to increment normally at around 10 counts
per day.

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.  This starts at 16:00
UTC.  A plot of channel 52 (battery voltage) shows that during
periods of sunlight the voltage can be seen rising and modulated by
the spacecraft spin. The shape of this modulation suggests that one
photo cell panel may be generating a smaller output than the others.
During the eclipse period the voltage steadily decreases from 13.3
down to 12.2 volts.

Channel 63, which contains the battery charge regulator (BCR) status
shows that the switch between A & B units occurs when the satellite
enters or exits from the eclipse state.  Channel 39 (telemetry
electronics) shows a very small change in temperature, about one
degree C, of the telemetry electronics unit, as the satellite passes
through the earth's shadow.

I will add this interesting WOD to my web site, details below.

The mode-S beacon has been heard by Victor OK1VKW. Victor uses a 40
element horizontal Yagi, with SSB UEK2000 converter into an IC275
receiver. Signals were S2-3 at a range of 700 Km. Thanks for that
report Victor.

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:U2RPT37.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org



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