OSCAR-11 REPORT 22 May 2004
Once again I am indebted to Jeff KB2M and Ron VK5AKJ who provided telemetry during the period 20 April to 04 May, while I was on holiday. Many thanks for the files.
During the period 15 April to 22 May 2004 the 145.826 MHz. beacon has been heard transmitting continuous ASCII
telemetry from 23 to 29 April, and from 11 May to 21 May. 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 31 May.
The internal temperatures have decreased by 7.5C. They are now 4.6C, 1.6C and 8.0C for battery, telemetry electronics and command decoder,respectively. Solar eclipse predictions indicate that the temperatures will continue to decrease towards a trough in June/July and then 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 decreased by 0.4volts. Observations have varied between 12.5 and 13.4 volts, with an average value of 13.0 volts.
Spin periods of approximately 690 to 2500 seconds have been measured from the magnetometer telemetry. The rotational speed has decreased since the last the reporting period, and at the current very low rates, is difficult to determine with any accuracy. The direction of rotation has reversed.
Users of OSCAR-11 should note that the date in the telemetry is now advanced by FOUR days. The time is advanced by 19.8 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 on145.826 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 u 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 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 thetimes 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:U2RPT97.CWV, to prevent duplication.
73 Clive G3CWV g3cwv@amsat.org
Klla: amsat