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OSCAR-11 Report




                OSCAR-11 REPORT    11 June 2001


An uneventful time for OSCAR-11. During the period May 15 to 09 June
2001 reasonable signals have been received from the 145 MHz. beacon.

The battery voltage observed during daylight passes has continued to
decrease. The average value observed was 13.3 with a range of 13.1 to
13.5 volts.

The internal temperatures have continued to decrease by a further one
degree C. They are now -0.2C and -1.6C for battery and telemetry
electronics respectively.

The WOD survey of channels 1, 2, 3, 61 (X, Z, Y magnetometers and
status) dated 24 March, has been transmitted. This WOD may now been
downloaded from my web site (details below).

The magnetometer calibrations have steadily changed during the many
years in orbit. Although the changes are small and are not noticeable
on a plot of individual channels, they do have a considerable effect
when the total magnetic field is calculated.  UoS has recently
supplied some new calibrations, which give a good match when used
with the current WOD.  I have now posted them on my website, in the
'UPDATES' page.

The spin period has varied between 300 and 344 seconds, with the
attitude control working normally. During this period there have been
279 Z, one Spin+, and 111 spin- counts.

The mode-S beacon has been heard by Shlomo 4X1AS, Bob K6WL, and Neil
G4HLX.  Shlomo reports S3 signals with a modified Drake converter,
and G3RUH 60 cm dish.  Bob uses an SSB converter with a 16 dB
parabolic antenna. Signals are 3-7 dB above the noise. Neil uses a
Drake converter with minimum modifications and a 16 turn RHCP helix.
Signals are just above the noise. Many thanks for those reports.

Users of OSCAR-11 should note that the hardware generated time in the
ASCII telemetry is now 15.5 minutes ahead of UTC, and the date is
three days advanced.  Unfortunately these errors cannot be corrected.
There are also smaller errors in the software generated times,
advances of 3.5 in the status blocks, and 1.5 minutes in the binary
packets, which ground control should be able to correct. The dates in
the status blocks and binary packets are correct.

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 (number 115) 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, 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 when commissioning is
complete. 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:U2RPT62.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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