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OSCAR-11 Report

                OSCAR-11 REPORT   14 April 2004

OSCAR-11 celebrated its 20th birthday on 01 March. After 20 years in orbit,
it is still transmitting useful data. To commemorate this event, AMSAT-UK
issued a special QSL for reports of reception, during March. 320 reports
from 37 different countries were received, 122 for reception on 01 March.
57 reports were for mode-S reception.

For full details of the reports received, visit the AMSAT-UK website at

Many thanks Jim G3WGM, Secretary of AMSAT-UK, who organised this event,
Martin G3YJO and his UoSAT team for their support, and all those who sent
reception reports.

During the period 08 March to 14 April 2004 the 145.826 MHz. beacon has
been heard transmitting continuous ASCII telemetry from 09 to 19 March, and
from 30 March to 09 April.  Ground control turned the beacon ON during 09
March, to minimise the OFF time during March.  It now operates under
control of the watchdog timer, approximately 10 days ON followed by 10 days
OFF. If the current 20 day cycle continues, the beacon should switch OFF
on around 19 March. During this period good signals have been received.

The internal temperatures have decreased by about 2C. They are now 12.0C,
9.6C and 15.6C for battery, telemetry electronics and command decoder,
respectively. Solar eclipse predictions indicate that temperatures are
now expected to decrease, from the peak reached in March, towards a trough
in June/July and then increasing until the end of September, when the
satellite will encounter continuous sunlight for the remainder of the year.
Higher temperatures and greater temperature changes are expected this year,
compared to 2003.

The battery voltage observed during daylight passes has decreased, during
the second ON period. Observations have varied between 13.2 and 13.7 volts,
with an average value of 13.5 volts for 09 March to 19 March.  From 29
March to 09 April the voltage varied from 13.3 to 13.6 with an average
value of 13.4 volts.

Spin periods of 390 to 626 seconds have been measured from the magnetometer
telemetry. The rotational speed has decreased steadily during the reporting
period, but recovered at the end. The direction of rotation is normal.

Users of OSCAR-11 should note that the date in the telemetry is now
advanced by FOUR days.  The time is advanced by 19.6 minutes, and this
error is increasing by about one minute per year.

OSCAR-11 now operates in a default mode, controlled by the watch-dog timer.
The satellite transmits continuous ASCII telemetry for about 10 days on
145.826 MHz., followed by about 10 days of silence. This regular sequence
might be interrupted by ground control, at any time.

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
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 MHz beacon is
transmitting, the 145 MHz 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.
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 covers 1996 to April 2003.  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

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 -


If you place this bulletin on a terrestrial packet network, please
use the bulletin identifier $BID:U2RPT96.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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