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OSCAR-11 Report




                OSCAR-11 REPORT    01 March 2003

OSCAR-11 celebrates its 19th Birthday today! It achieved 100,000
orbits on 31 October 2002.  The satellite continues to output
consistent signals on its 145.826 and 2401.5 MHz. beacons. Once again
congratulations to the UoSAT team, past & present for a very fine
achievement.

During the last few years I have received many enquiries regarding
soundcard software for decoding OSCAR-11 signals, and from time to
time there has been some discussion on AMSAT-BB about the need for
this software.

I am pleased to say that a suitable Windows program for displaying
and capturing OSCAR-11 data is now available.   This is MIXW2, a
general purpose Amateur Radio data communication program written by
Nick Fedoseev UT2UZ.

You can download the program from Nick's website - www.mixw.net
or if this is not available, a google search for MIXW will yield
alternative sites.  You need the latest version, 2.07.

The OSCAR-11 feature is un-documented at present in MIXW. I have
therefore prepared a package of instructions and sample files, to
help users. This is on the OSCAR-11 page of my website
-www.users.zetnet.co.uk/clivew/ Also included is a filter program
which enables the data captured by MIXW to be used with the ASCII
telemetry & WOD programs on the website.

I have found that MIXW2 works very well on OSCAR-11, and gives
excellent results, comparable to a hardware decoder.

OSCAR-11 has continued to operate in a default mode, controlled by
the watch-dog timer.  The satellite transmits continuous ASCII
telemetry for about 8 - 9 days on 145.826 MHz., followed by about 10
- 12 days of silence.  These times appear to be somewhat variable.
The mode-S beacon on 2401.5 MHz. transmits continuously.

During the period 18 January to 28 February 2003  the 145.826
MHz. beacon has been heard transmitting continuous ASCII telemetry
from  27 January to 05 February, and from 16 to 27 February.

The internal temperatures have continued to fall, by about half a
degree C, with an up/down variation of half a degree. They are now
7.4C, 5.4C and 11.4C for battery, telemetry electronics, and command
decoder respectively. The temperatures are expected to fall slowly as
the solar eclipse times lengthen, reaching a minimum in the Summer,
and then increase in the Autumn. The solar eclipse times should be
shorter than last year,resulting in higher temperatures in 2003.

The battery voltage observed during daylight passes has decreased by
about 0.2 volts. Observations have varied between 13.4 and 13.9
volts, with an average value of 13.6 volts.

The attitude is now being controlled solely by the passive gravity
boom gradient, and there is no control over spin rate. The continuous
telemetry has enabled the spin period to be calculated from the X & Y
magnetometer readings. The spin period has varied from 306 to 425
seconds. Comparison with WOD taken some time ago indicates that the
spin direction is unchanged, ie Y-axis leading in phase. The
attitude is normal.

Users of OSCAR-11 should note that the date in the telemetry is
advanced by three days.  The time is advanced by 18 minutes.

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, (now a constant 1200 Hz. 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
rare occassions 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 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 is just for 2002, 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.

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:U2RPT82.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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