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OSCAR-11 Report




                OSCAR-11 REPORT   16 March 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
are issuing a special QSL for reports of reception during March. There are
special endorsements for hearing the satellite on it's birthday, and for
mode-S reception.  It's still not too late to apply for a QSL, but all
reception reports must be received by 07 April. For full details visit the
AMSAT-UK website at http://www.uk.amsat.org/

At the present time the satellite is operating in a default mode,
transmitting continuous ASCII telemetry on 145.826 MHz., for ten days
followed by ten days of silence.  However, during March ground control are
hoping to reset the timer each time the VHF beacon switches OFF.  This
should minimise the OFF time, but there may be some gaps in the
transmissions.  The mode-S beacon is ON continuously.

For the latest news, visit my website   http://users.zetnet.co.uk/clivew

During the period 16 February to 15 March 2004 the 145.826 MHz. beacon has
been heard transmitting continuous ASCII telemetry from 25 February to 06
March, and from 09 March.  If the current ten day cycle continues, the
beacon should switch OFF on around 19 March. During this period good
signals have been received.

Around 27 February the date in the ASCII telemetry incremented, giving an
error of four days.  This appears to be a leap year problem, which first
occurred in 1992.

The internal temperatures have increased by about 1.5C. They are now 14.6C,
11.8C and 17.8C for battery, telemetry electronics and command decoder,
respectively. Solar eclipse predictions indicate that temperatures are
expected to increase, reaching a peak in March, 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.  This is
because the S-band beacon was switched OFF during the previous reporting
period. The reduction in line current causing higher than usual battery
voltage. Observations have varied between 13.2 and 13.5 volts, with an
average value of 13.35 volts for 25 February to 06 March.  From 09 to 15
March the voltage varied from 13.6 to 13.7 with an average value of 13.6
volts.

Spin periods of 344 to 453 seconds have been measured from the magnetometer
telemetry. The rotational speed is nominal and variations random. 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 19.5 minutes, and this
error is increasing by about one minute per year.

The mode-S beacon on 2401.5 MHz. has been heard by Ferrucio IW1AM, Dean
AL7CR, Mark CT1JFC/G4MAW, Ken W7KKE, Ferracio & Piero IW1AM/IZ1ERR, Martin
G7MRF, Mirek OK2AQK and Bill GM0ICF.  Also, many more reports have been
submitted to the AMSAT-UK website for the special birthday QSL endorsement.
Many thanks for all those reports.

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, especially during March,
when ground control will attempt to minimise OFF periods.

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
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:U2RPT95.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
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