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OSCAR-11 Report




                OSCAR-11 REPORT    17 March 2002

On March 1st this satellite celebrated it's 18th birthday.  During
the past year OSCAR-11 has operated continuously on the VHF and S
bands, with very little ground control needed.  The single event
upset counter has detected several permanent memory location
failures, but these do not appear to be causing any malfunction at
the present time. Congratulations to the UoS team, past and present,
for a fantastic achievement.

Recently I have encountered some difficulty in receiving the near
perfect signals required for decoding the telemetry, from the 145.826
MHz. beacon.  High winds in this area have upset the antenna
alignment, and may have caused some damage. Local interference (QRN),
probably from an electric fence,has also been detected.

During the period 15 February to 15 March 2002 the internal
temperatures have decreased slightly They are now 3.8C and 2.2C
for battery and telemetry electronics respectively. The battery
voltage observed during daylight passes has decreased slightly.
The average value observed was 13.7 with a range of 13.3 to 13.9
volts.

The rate at which the SEU counter increments has continued to
increase, from 785 to 830 counts per day. Decoding the SEU binary
telemetry shows four permanent memory failures at locations 3EC0,
37B1, 21C0 and F96. Locations FF5A FF58 also fail less frequently.
These permanent memory failures tend to mask out the display of the
less frequent failures, owing to the limited storage for this data in
the satellite.

The WOD survey of channels 10, 20, 30, 40 ( +Y, -X, +X array
currents, & array voltage ) dated 06 January 2002 has been
transmitted.  This data may now be downloaded from my web site,
details below. Users should note that the date of this WOD survey in
the status messages is incorrectly listed as 2001. There is also an
error in the time of this survey due to satellite clock drift.  A
more accurate start time is 05-January-2002 23:49:30 UTC.

The spin period has drifted between 198 and 266 seconds, although no
particular trend is apparent. The attitude is controlled solely by
the gravity boom gradient, as the Z-axis magnetorquer counter has
reached saturation (1024). Ground control action is awaited to
reset the magnetorquer pulse counters.

The mode-S beacon on 2401.5 MHz. has been heard by Jerry K5OE, and
by Hans DL6KG. Jerry reports strong signals, and has managed to hear
the beacon at two degrees of elevation.  Hans reports signals one S
point above noise, using a G3RUH patch and dish, Kuhne converter, and
IC821 receiver.  Many thanks for those reports.

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 on 2401.5 MHz. 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 2401.5 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:U2RPT71.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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