[amsat-bb] FINAL MONTHLY OSCAR-11 REPORT

[Clive Wallis]

                    FINAL MONTHLY OSCAR-11 REPORT

                            21 April 2008

RECEPTION REPORTS REQUESTED!

In the years ahead, it is possible that you may hear OSCAR-11, by accident,
when tuning round the frequency. If you are able to record the satellite on
audio tape or as a WAV file (not MP3), please do so, as it is unlikely
that it will be heard on the next pass!

Please send reception reports to xxxxx at amsat.org (replace xxxxx by
g3cwv) or post to amsat-bb.  If you have a file, please let me know what
you have, before sending it!

If you need to hear what the satellite sounds like, please visit my website
www.users.zetnet.co.uk/clivew/  The satellite transmits on 145.826 MHz. set
receiver to NBFM.

                   ----------------------------

This is the 144th monthly report for OSCAR-11. Unless there is an
unexpected change of status (such as occured with OSCAR-7), I'm expecting
this to be my last report.

This report covers the period from 17 March to 21 April 2008.  During
this period the satellite has not been heard and no reports of reception
have been received.

Transmissions were expected to resume on 24 March, after the beacon
switched-off on 14 March.  However, permanent eclipses started a few days
beforehand, which probably caused the transmission period to be terminated
prematurely. It is now unlikely that the satellite will support any
sustained period of operation, and will only transmit for a short time,
possibly less than a single orbit, every 21 days.

I am indebted to  all those who sent reception reports during the last 12
years.  Initially there was much interest in hearing the mode-S beacon,
which was very weak. Recently, interest has changed to hearing when the
two metre beacon switched on/off. Special thanks must go to Jeff KB2M who
recorded telemetry during my holidays, and Peter ZL3TC, who has monitored
the beacon daily, during recent months. Many thanks to everyone.

The Beacon frequencies are -

VHF 145.826 MHz.  AFSK FM  ASCII Telemetry

UHF 435.025 MHz.  OFF

S-band 2401.5 MHz. OFF

The satellite is now subject to eclipses during every orbit.  Long term
predictions indicate that eclipses will occur until 2019, when there will
be some eclipse free periods until 2023.  However these very long term
predictions should be regarded with caution, as large tracking errors can
accumulate over long periods of time.

When telemetry was last received it showed that one of the solar arrays had
failed, and there was a large unexplained current drain on the main 14 volt
bus. After 24 years in orbit the battery has undergone over 100,000 partial
charge/discharge cycles, and observations suggest that it cannot power the
satellite during eclipses lasting more than about ten minutes, or
sometimes even during periods of poor solar attitude.

The current status of the satellite, is that all the analogue telemetry
channels, 0 to 59 are zero, ie they have failed. The status channels 60 to
67 are still working. The real time clock is showing a large accumulated
error, although over short periods timekeeping is accurate to a few
seconds per month. When last heard the clock was 83.0958 days slow.  The
day of the month has a bit stuck at 'one' so the day of the month may show
an error of +40 days for some dates.  The time display has switched into 12
hour mode. Unfortunately, there is no AM/PM indicator, since the time
display format was designed for 24 hour mode.

The spacecraft computer and active attitude control system have switched
OFF, ie. the satellite' attitude is controlled only by the passive gravity
boom gradient, and the satellite is free to spin at any speed.

The watchdog timer now operates on a 20 day cycle. The ON/OFF times have
tended to be very consistent. The average of many observations show this to
be 20.7 days, ie. 10.3 days ON followed by 10.4 days OFF. However, poor
solar attitude may result may result in a low 14 volt line supply, which
may cause the beacon to switch OFF prematurely, and reset the watchdog
timer cycle. When this occurs, the beacon is OFF for 20.7 days.

OSCAR-11 was the second satellite from the University of Surrey,
www.ee.surrey.ac.uk/SSC.  It was designed, built and launched, within a
time scale of six months, by a team headed by Martin Sweeting G3YJO.
Amateur radio groups working at various locations in the world, also
contributed to the project. It used commercially available 'off the shelf'
components (COTS). Following the success of these satellites, in 1985
Surrey Satellite Technology Ltd. www.sstl.co.uk was formed, as a commercial
venture. This grew into a major company which has produced over 27 small
satellite projects for a global market.

The University of Surrey has recently agreed to sell it's major
shareholding to EADS-Astrium. This agreement is now awaiting regulatory
approval. The joint company will have the experience of manufacturing
large and small satellites, for geo-synchronous and low earth orbits.

In regognition of his work, Martin G3YJO, was appointed Professor at the
University of Surrey.  He received an OBE in the 1995 Queens birthday
honours list, and in 2002 a knighthood in the New Year's honours list.

Listeners to OSCAR-11 may be interested in visiting my website, which is
being updated to reflect the current status of the satellite. If you need
to know what OSCAR-11 should sound like, there is a short audio clip for
you to hear. The last telemetry received from the satellite is available
for download. The website contains an archive of news & telemetry data
which has now been updated. It also contains details about using a
soundcard or hardware demodulators for data capture.  There is software for
capturing data, and decoding ASCII telemetry.  The URL is
www.users.zetnet.co.uk/clivew/

If you place this bulletin on a terrestrial packet network, please
use the bulletin identifier $BID:U2RPT144.CWV, to prevent duplication.

73 Clive G3CWV   xxxxx at amsat.org (please replace xxxxx by g3cwv)