[amsat-bb] OSCAR-11 Report

[Clive Wallis <clivew@xxxxxxxxxxxx>]

                  OSCAR-11 REPORT

                   25 September 2004

During the period 14 August to 24 September 2004 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 22 August to 01
September, and from 13 to 22 September. During this period reliable signals
have been received.  Once again I am indebted to Jeff KB2M who supplied
telemetry for 13 to 22 September, while I was away on holiday.

The beacon operates under control of the watchdog timer. Observations have
indicated that the cycle is approximately 10.3 days ON followed by 10.4
days OFF. Assuming that this cycle continues, the beacon should switch ON
around 03 October.

The internal temperatures have increased by massive 14 degrees C. They are
now 19C, 15C and 24C for battery, telemetry electronics and command
decoder, respectively. Solar eclipse predictions indicate that the
temperatures will continue to increase 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 varied between 12.7
and 13.8 volts.  The average voltage has agsin dropped slightly, to 13.3
volts.

The rotational speed of the satellite has remained very low, making it
difficult to measure the speed accurately from telemetry, during a ten
minute pass. Spin periods of between 500 and 1300 seconds have been
observed.  The direction of rotation has reversed several times and the
Z-axis magnetometer indicates that sometimes the satellite's antennas are
pointing away from the earth. When the spin was being controlled by the
magnetorquers the target spin period was 300 seconds, with the antennas
nominally earth pointing.

The mode-S beacon on 2401.5 MHz. has been heard by Willi OE6AG, Bill W0OQC
and David VK5DG. Willi reports signals 15 to 20 dB above noise.  Bill
reports strong signals for part of the pass.  He uses a one metre BBQ dish,
and SSB 2000 converter. David reports signals S6 above the noise, with an
18 inch BBQ grill, dipole feed and an unmodified MMDS converter. Many
thanks for those reports.

Users of OSCAR-11 should note that the date in the telemetry is now
advanced by FOUR days.  The time is advanced by 20.2 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 approximately 10.3
days on 145.826 MHz., followed by 10.4 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. 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.  Any reports of reception
on 2401.5 MHz. would be most welcome, however please DO NOT send sound
files.  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:U2RPT101.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
----
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