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OSCAR-11 Report




                OSCAR-11 REPORT    22 March 2003

During the period 01 March to 21 March 2003 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 09 to 19
March. During this period good signals have been received.

The internal temperatures have continued to fall, by about one
degree C, with an up/down variation of half a degree. They are now
6.0 C, 4.8 and 11.2 C for battery, telemetry electronics, and command
decoder respectively. The temperatures are expected to fall slowly as
the solar eclipse times lengthen, reaching a minimum in the Summer,
and then increase in the Autumn. The solar eclipse times should be
shorter than last year,resulting in higher temperatures in 2003.

The battery voltage observed during daylight passes is unchanged.
Observations have varied between 13.5 and 14.0 volts, with an average
value of 13.7 volts.

The attitude is now being controlled solely by the passive gravity
boom gradient, and there is no control over spin rate. The continuous
telemetry has enabled the spin period to be calculated from the X & Y
magnetometer readings. The spin period has varied from 295 to 376
seconds. The attitude is normal.

Users of OSCAR-11 should note that the date in the telemetry is
advanced by three days.  The time is advanced by 18 minutes.

The mode-S beacon has been heard by Michael OH2AUE. He uses a home
brew feed horn antenna with a three stage pre-amp. Many thanks for
your report Michael.

OSCAR-11 now  operates in a default mode, controlled by
the watch-dog timer.  The satellite transmits continuous ASCII
telemetry for about 8 - 9 days on 145.826 MHz., followed by about 10
- 12 days of silence.  These times appear to be somewhat variable.

The mode-S beacon is ON continuously, even when the VHF beacon is
OFF, nominally transmitting an unmodulated carrier on 2401.5 MHz.
There is however a VERY low level of AFSK modulation, (now a constant
1200 Hz. audio tone), 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. 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.  It can only be heard on the
very rare occassions 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 about using a soundcard for data
capture, and also details about using hardware demodulators. There is
software for capturing data, and decoding ASCII telemetry and WOD.
There is an archive of raw data for analysis, which is continually
being expanded, as new data is captured.  Originally this was for
WOD, but it is now being expanded to include ASCII telemetry. At the
present time the telemetry is just for 2002, and 2001.  I will add
other years as time permits.  In parallel there is a news archive
which provides an overview of the state of the satellite, at the
times when the telemetry was captured.

If anyone out there can provide any data, particularly for the 1984
to 1993 years, this would be most appreciated.  Please e-mail me
with details.  However please DO NOT SEND ANY FILES, before futher
discussion.

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:U2RPT83.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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