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OSCAR-11 Report




                OSCAR-11 REPORT    15 January 2002


During the period 15 December 2001 to 14 January 2002 good signals
have been received from the 145 MHz. beacon. Occasional interference
from PCSat and distant ground stations trying to connect, has been
observed.

The internal temperatures have have been fairly static, with no
particular trend observed, although they have varied up and down
within a band of about one degree C. These temperatures are now 5.6C
and 4.0C for battery and telemetry electronics respectively.

The battery voltage observed during daylight passes is unchanged.
The average value observed was 13.8 with a range of 13.5 to 14.1
volts.

The rate at which the SEU counter increments has continued to
increase from 516 to 771 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. In
mid-December the SEU count rate steadied at around 620 counts per day
but suddenly increased in the first week of January as location F96
failed.

I have now added a package (U2PKT.ZIP) of software, sample files and
documentation to my website, for decoding these binary SEU packets.
The program is written in BBC BASIC, but the package includes a
suitable interpreter which runs well in DOS or Windows.

A new WOD survey of channels 10, 20, 30, 40 ( +Y, -X, +X array
currents, & array voltage ) dated 06 January 2002 has now replaced the
survey of channels 1, 2, 3, 61 (X, Z, Y magnetometers and status)
dated 16-August-2001.  Users should note that the year in the date of
the new survey is incorrectly given in the status frames as 2001.

The hardware generated time in the ASCII telemetry is now 16.5
minutes ahead of UTC, and the date is three days advanced.
Unfortunately these errors cannot be corrected. There are also errors
in the software generated time, which is advanced by 10.5 minutes in
the status blocks, and the binary packets. The year in the status
blocks is now 2001, instead of 2002. However, the date in the binary
packets is correct.  Ground control should be able to correct the
errors in the software generated times and dates.

The spin period has drifted between 179 and 247 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 Andy VK2AES.  He
reports weak signals.  Andy uses a MMDS down converter, and a
'BBQ Grill' antenna.  Many thanks 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 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:U2RPT69.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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