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OSCAR-11 Report




                OSCAR-11 REPORT    19 August 2002

The period from 15 July to 18 August has been an eventful one for
OSCAR-11.  The normal diary sequence was heard on 145.826 MHz., up to
and including 22 July.  On 24 July to 01 August the beacon was heard
transmitting continuous ASCII telemetry only.  On 05 August the VHF
beacon was silent.  This was the first interuption of continuous
service since March 1998.

Initial attempts by ground control to command the satellite failed.
They had noted some difficulties in the past, when the satellite was
cold (which it is at the present time). However, on 17 & 18 August
the VHF beacon was heard once again, transmitting ASCII telemetry
only.

Throughout this eventful period, the telemetry has been nominal, and
the mode-S beacon has been heard normally.

The internal temperatures have increased by two degree C. They are
now +1.2 C and 0 C for battery and telemetry electronics
respectively. These temperature rises are expected to continue during
the next few months, due to the reduction in solar eclipse time.

The battery voltage observed during daylight passes has increased by
0.6 volts. The average value observed was 13.4 with a range of 13.1
to 13.8 volts.

While the diary cycle was operating, the spin period varied between
353 and 373 seconds.   There were 76 Z axis, zero plus spin, and
67 negative spin magnetorquer firings during these nine days.
Examination of the magnetometer channels of recent telemetry
indicates that the spin period is now around 950 seconds, indicating
that the attitude control is not operating.

While the diary cycle was operating the SEU count rate has continued
to remain stable at 1150 counts per day. Decoding the SEU binary
telemetry shows six memory locations 39C0, 21C0 3EC0, 37B1, 180 and
F96 have failed.

The WOD survey of channels 1, 2, 3, 61 (X, Z, Y magnetometers and
status) dated 22 May 2002 was transmitted until the diary cycle
stopped.  This survey shows an unusually long spin period of 1800
seconds.  The WOD may now be downloaded from my web site, details
below.

The mode-S beacon on 2401.5 MHz. has been heard by many stations
including KA4YMY, WA6FWF, Wl7BQM, OZ1MY, Laurent F-SWL, OE6AG, ZL2MN,
OE1VKW, GM3OGI, G8VR, VE7BPB and K3EL.  These reports indicate that
the recent problems on OSCAR-11 have not effected the operation of
this beacon.  Roy VE7BPB has detected weak sidebands 2400 Hz. either
side of the main carrier, with his Spectran program.  This suggests
that the modulation may be a continuous tone of 2400 Hz., instead of
AFSK.   Mnay thanks for all those reports.

Some time ago, Joe G3ZCZ/VK suggested that a telemetry archive for
OSCAR-11 would be useful, especially for educational projects.

I agreed, and have now started the archive on my website. Initially
it is just for the current year, and 2001.  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.

Telemetry from 1993 to 2000 should be relatively easy to archive, as
I already have the data on disk. Data prior to 1993 will take a lot
longer to archive, as I have to convert it from tape to disk.  A
tedious process!  The early data is often of poor quality, and there
are many long gaps where no recordings were made.

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.

The telemetry archive is at www.users.zetnet.co.uk/clivew/ Visit the
OSCAR-11 page.

The normal operating schedule for OSCAR-11 is currently suspended, and the
VHF beacon transmits continuous ASCII telemetry.

The mode-S beacon is ON, nominally transmitting an unmodulated
carrier on 2401.5 MHz. There is however a VERY low level of AFSK
modulation 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.  However it can sometimes be
heard when the satellite is being commanded by ground control, ie.
within range of Guildford, UK.  When the 435 beacon is transmitting,
the 145 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 of hardware required and some software
for capturing data, and decoding ASCII telemetry and WOD.  There is
an archive of raw data (mainly WOD) for analysis, which is
continually being expanded, as new data is captured.  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:U2RPT76.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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