[amsat-bb] OSCAR-11 Report ... Revision

Clive Wallis clivew at zetnet.co.uk
Sun Dec 23 05:11:43 PST 2007


Ooops, I missed an important bit of news from my recent report! Many
thanks to Armando N8IGJ for bringing it to to my attention.  My
apologies for the omission. Here is the corrected report -


                    OSCAR-11 REPORT

                   20 December 2007


Please send reception reports to xxxxx at amsat.org (please replace xxxxx by
g3cwv) or post to amsat-bb. If you are able to record the satellite as a
WAV file, please do so, but 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.


During the period 15 November to 19 December 2007 the satellite has
been heard from 18 to 20 November. Signals were variable in strength,
mostly weak.

The real time clock has lost a further 4.29 days since 08 October. When
last heard it was 74.26876 days slow.

I am indebted to Kevin WA6FWF, Peter ZL3TC, Armando N8IGJ and Thomas
HB0SKA for their reports.  Many thanks.

Eclipses have continued and are expected until mid January 2008.  Although
the maximum duration of the current eclipses is less than those earlier
this year, it is doubtful whether the satellite will be heard for any
sustained period. Even in continuous sunlight during September and
October the satellite was unable to support continuous operation.

It is likely than the satellite will only be heard by chance, by stations
listening for other satellites on 145.826 Mhz.

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.  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.
More data is required to determine exactly when the date changes.

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. 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 23 years in orbit the battery has undergone around 100,000
partial charge/discharge cycles, and observations suggest that it cannot
power the satellite during eclipses, or sometimes during periods of poor
solar attitude.

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.

The Beacon frequencies are -

VHF 145.826 MHz.  AFSK FM  ASCII Telemetry

UHF 435.025 MHz.  OFF

S-band 2401.5 MHz. OFF

Listeners to OSCAR-11 may be interested in visiting my website. If you need
to know what OSCAR-11 should sound like, there is a short audio clip for
you to hear. There is an example of the latest telemetry received from the
satellite. The website contains an archive of news & telemetry data. 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:U2RPT140.CWV, to prevent duplication.

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

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