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OSCAR-11 Report



                OSCAR-11 REPORT   24 July 2004

During the period 14 June to 24 July 2004 the 145.826 MHz. beacon has been
heard transmitting continuous ASCII telemetry from 21 June to 01 July and
from 12 July to 22 July. During this period consistent signals have been
received.

The beacon operates under control of the watchdog timer, approximately 10
days ON followed by 10 days OFF. Assuming that the 20 day cycle continues,
the beacon should switch ON around 01 August.

The internal temperatures have increased by about one degreec C, having
reached a trough during June. They are now 3.8C, 2.0C and 7.8C 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 13.0
and 14.0 volts.  The average voltage has increased by 0.3 to 13.5 volts.

Examination of the power supply telemetry channels during 2004 has shown
some interesting changes, which are difficult to explain. Recent telemetry
shows a reduction of 40 Ma in the main 14 volt bus current. This occurred
between 10 and 21 June 2004. No change in status telemetry has occurred,
which might indicate that a unit had switched OFF, during this period.
Examination of the telemetry for various power supply current channels
shows a change in channels 14, 15 and 16, the DCE (digital communications
experiment) currents, between 10 and 21 June.  The telemetry originally
showed a total current of 89 mA, but now shows negative currents for these
channels, so it is difficult to determine exactly what is happening.

Between 07 and 25 February two other telemetry channels changed. These were
channel 21, +10 volt line current, which decreased from 226 to 106 mA, and
channel 54, telemetry current, which decreased from 15 mA to near zero.
There was no related change in total 14 volt line current, but the status
telemetry showed that the primary spacecraft computer had switched to OFF.
Recently the telemetry current has increased to 19 mA.

The rotational speed of the satellite has remained very low, often making
it impossible to measure the speed accurately from telemetry, during a ten
minute pass. When measurements have been possible spin periods of between
840 and 1400 seconds have been observed.  When the spin was being
controlled by the magnetorquers the target spin period was 300 seconds.

The mode-S beacon on 2401.5 MHz. has been heard by Mike KE4AZN.  He used a
one metre dish with helix feed, DB6NT converter, and IC-910 receiver.
Mike's interest was to check out his equipment, in preparation for
receiving signals from ECHO. Thanks for the report Mike, and pleased to
hear that UO-11 was of use.

Users of OSCAR-11 should note that the date in the telemetry is now
advanced by FOUR days.  The time is advanced by 20.0 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. 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:U2RPT99.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
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