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OSCAR-11 Report




                OSCAR-11 REPORT    16 September 2001


During the period 14 August to 15 September reliable signals have
been received from the 145 MHz. beacon.

The internal temperatures have continued to increase as the solar
eclipse times decrease.  A rise of 2.5 degree C has been noted. These
temperatures are now 3.0C and 1.6C for battery and telemetry
electronics respectively.

The battery voltage observed during daylight passes has increased.
The average value observed was 13.8 with a range of 13.4 to 14.2
volts.  The improved battery voltage is also a result of decreasing
solar eclipse times, and this trend is expected to continue for
several months.

The WOD survey of channels 1, 2, 3, 61 (X, Z, Y magnetometers and
status) dated 24 March, has now been replaced by a survey dated
16-August-2001 of the same channels.  This WOD shows the spin period
to be 368 seconds, which was current at the time of the survey.  It
may now be downloaded from my web site (details below).

Ground control reset the magnetorquer Counters in mid August. After
this correction, the spin period has varied between 272 and 358 seconds,
and there have been 372 Z, 3 +ve, and 67 -ve counts.  Prior to the
ground control operations, while the satellite's attitude was
controlled solely by the passive gravity boom gradient, the spin
period drifted between 416 and 582 seconds.

The mode-S beacon has been heard by David 9M2DT, Jack W9JIU, DF4PV,
and Ken G8VR.  David reports signals 2 dB above noise. Jack reports
signals S1 to S3 above noise.  He uses a Drake converter, preamp, and
a Myers parabolic antenna.  DF4PV uses a massive six metre dish, and
receives the beacon at S7 to S9.  You can see mouth watering pictures
of his dish and equipment at www.goecities.com/df4pv. Ken is now
receiving the beacon at S4 after several improvements to his
equipment. He found an open circuit power supply to one stage of his
converter, now has a DB6NT pre-amplifier, and has replaced his helix
with a 60 cm dish.

In the July report I mentioned two reports of unusually strong
reception of the mode-S beacon when AFSK modulation had been
detected.  For the curious, I have now put the two files into a ZIP
package onto my web site ( details below).  It is located at the end
of the Audio Files section, on the OSCAR-11 page.

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, 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:U2RPT65.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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