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OSCAR-11 Report




                OSCAR-11 REPORT    18 April 2001

I have now updated my processing software for OSCAR-11, as mentioned
in the January report.  This corrects a Y2K problem with the
Keplerian elements, and the removal of an unnecessary modification to
the PLAN13 code. The latest versions are SATILL.BAS v1.2, ORBILL.BAS
v1.1, ORBMAG.BAS v1.1.  If you have earlier versions ie. downloaded
before the end of March 2001, the updated packages can now be
downloaded from my web site, details below.

Ground control operations have now corrected the dates in ASCII
status blocks, reset the magnetorquer counters, and started an new
WOD survey. However, users should also note that there is still a
three day error in the hardware generated ASCII telemetry date. The
time in the ASCII telemetry continues to advance, and the error is
now about 18 minutes. Unfortunately these errors cannot be corrected.

During the period 14 March to 17 April 2001 reliable 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 13.6 with a range of 13.2 to
13.9 volts.

The internal temperatures have continued to decrease by another one
degree C. They are now 2.0C and 0.4C for battery and telemetry
electronics respectively.

The WOD survey of channels 10, 20, 30, 40 (+Y, -X, +X, solar array
currents, array voltage), dated 06 January, has now been replaced by
Channels 1, 2, 3, 61 (X, Z, Y magnetometers and status) dated 24
March. This WOD should be available available for download from my
web site (details below), in a few days time.

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.

Yoshi Hashida of UoS has now supplied some recent calibrations for the
magnetometer channels, optimised for the WOD dated 06-October-2000.
These give good results with the current data.
The new calibrations are -

        BX = 0.152*N - 69.8
        BZ = 0.146*N - 65.3
        BY = 0.155*N - 71.0

where N is the WOD value. BX, BZ, BY are the magnetic fields along
the X, Z, Y axes respectively, in micro-Tesla.

These calibrations should be used for the current data. The previous
calibrations should be used for data several years old.  Thanks
Yoshi.

The spin period has varied between 207 and 339 seconds. Ground
control has now reset the magnetorquer counters, and there have been
257 Z, 16 Spin+, and 1 spin- counts.

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:U2RPT60.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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