[amsat-bb] OSCAR-11 Report

[Clive Wallis <clivew@xxxxxxxxxxxx>]

                  OSCAR-11 REPORT

                  25 November 2004

Recent telemetry has indicated that there has been a serious problem with
OSCAR-11, which occurred sometime between 16:50 UTC on 13 November and
15:40 UTC 15 November.  The status telemetry shows that the S-band beacon
has switched OFF, also confirmed by temperature and current telemetry. The
status telemetry also shows that the digitalker has switched OFF (although
this hasn't been operational for many years).

Several of the analogue channels appear to have failed. Previously seven
channels were showing raw data values of zero, now 16 channels are set to
zero.  Among these are the important magnetometer channels.

Ferruccio IW1AM and Mineo JE9PEL have confirmed that they have been
unable to receive the S-band beacon. Many thanks for those reports.

During the period 15 October to 24 November 2004 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 23 October to 02
November, and from 13 to 23 November. During this period good signals have
been received, inspite of the problems.

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 04 December.

Variations in the 14 volt line current have continued, with the highest
value of 1070 mA recorded on 13 November.  It has now decreased to 815 mA
since the recent fault. The line current changes appear to be consistent
with changes in array current and battery current, so they are probably
correct.

Before the magnetometer channels failed, they indicated that the satellite
was pointing in the correct direction, ie antennas towards the earth.
Periods observed were around 400 seconds, although at times, unusual
motions were noted.  Since the magnetometer channels failed, the solar
array currents have been used as an indication of the satellite's motion
and attitude.  This shows that the spin rate has increased, with a period
of 73 seconds on 18 November, with some movement in the Z axis. This has
prevented excessive external temperatures, and may have caused the
internal temperatures to fall, (see below).

The internal temperatures have remained fairly constant, until the recent
problem occurred, after which they fell by about four degrees C. They are
now 18.2C, 17C and 22.8C for battery, telemetry electronics and command
decoder, respectively. Solar eclipse predictions indicate that the
satellite is now in continuous sunlight, which will continue until the end
of April next year.

The battery voltage has varied between 11.6 and 12.9 volts.  The average
voltage has increased marginally to 12.6 volts. Variations have been caused
by changes in the current being taken from the 14 volt line, and poor
attitude.

Users of OSCAR-11 should note that the date in the telemetry is now
advanced by FOUR days.  The time is advanced by 20.3 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.

At the present time the mode-S beacon 2401.5 MHz. is OFF. Also the UHF
beacon 453.025 is OFF.


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 August 2004.  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:U2RPT103.CWV, to prevent duplication.

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