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OSCAR-11 Report




                OSCAR-11 REPORT    16 December 2001


During the period 17 November to 15 December 2001 good signals
have been received from the 145 MHz. beacon.

The internal temperatures have have been fairly static, with no
particular trend observed, indicating that the current eclipse cycle
has reached a minimum value. These temperatures are now 6.8C and 5.0C
for battery and telemetry electronics respectively.

The battery voltage observed during daylight passes has fallen
slightly. The average value observed was 13.8 with a range of 13.6 to
14.0 volts.

The rate at which the SEU counter increments has continued to
increase from 479 to 614 counts per day. Decoding the SEU binary
telemetry shows permanent memory failures at locations 3EC0, 37B1 and
21C0. Locations FF5A FF58 also fail less frequently.  I have now
added a package (U2PKT.ZIP) of software, sample files and
documentation to my website, for decoding the binary SEU packets. The
program is written in BBC BASIC, but the package includes a suitable
interpreter which runs well in DOS or Windows.

The WOD survey of channels 1, 2, 3, 61 (X, Z, Y magnetometers and
status) dated 16-August-2001 has been transmitted.  This WOD shows
the spin period to be 368 seconds, which was current at the time of
the survey.  I have now stopped capturing this WOD. It may now be
downloaded from my web site (details below).

Around October 21 the Z-axis magnetorquer counter reached it's
maximum count of 1024 pulses.  This has stopped further attitude
control, and the satellite's attitude is now being controlled by the
passive gravity boom gradient. Since saturation the spin period has
drifted between  203 and 242 seconds.   Ground control action to reset
the counters is now awaited.

The mode -S has been heard by Nels, W0TUP, who reports weak signals.
He uses a California down converter, Down East pre-amp and a 3ft BBQ
dish antenna.  Many thanks Nels for that report.

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, nominally transmitting an unmodulated
carrier. There is however a VERY low level of AFSK modulation 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 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:U2RPT68.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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