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OSCAR-11 Report




                OSCAR-11 REPORT    19 January 2003

OSCAR-11 has continued to operate in a default mode, controlled by
the watch-dog timer.  The satellite transmits continuous ASCII
telemetry for about seven days on 145.826 MHz., followed by about 14
days of silence.  These times appear to be somewhat variable, and on
the last occasion the sequence was ten days off and nine days ON.
The mode-S beacon on 2401.5 MHz. transmits continuously.

During the period 16 December 2002 to 18 January 2003 the 145.826
MHz. beacon has been heard transmitting continuous ASCII telemetry
from 18 to 26 December, and 06 to 15 January.

The internal temperatures after reaching a peak in mid November, and have
now fallen by about one degree C. They are now 7.8C, 5.8C and 12.2C
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 has remained
constant. Observations have varied between 13.6 and 14.0 volts, with
an average value of 13.8 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 223 to 305
seconds. Comparison with WOD taken some time ago indicates that the
spin direction is unchanged, ie Y-axis leading in phase. The
attitude is normal.

The mode-S beacon has been heard by Ferruccio IW1AM. He uses a 100
cm prime focus dish, with 3.5 turn helix, and 0.9 dB down converter.
Signals peaked at S5-6. Many thanks for that report.

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 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. 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
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 of hardware required and some 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.

Telemetry from 1993 to 2000 should be relatively easy to archive, as
I already have the data on disk. Data prior to 1993 will take a lot
longer to archive, as I have to convert it from tape to disk.  A
tedious process!  The early data is often of poor quality, and there
are many long gaps where no recordings were made.

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:U2RPT81.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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