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ZS6FB > SAT 06.07.03 10:46l 109 Lines 5104 Bytes #999 (0) @ AMSAT
BID : ANS-187.03
Read: GUEST
Subj: OSCAR-11 REPORT 02 July 2003
Path: DB0ZKA<DB0FSG<DB0SIF<DB0SON<DB0ERF<DB0EAM<DB0SMG<DB0RES<ON0AR<7M3TJZ<
ON4HU<F6GGY<F4CEP<F3KT<TU2BB<ZS6FB
Sent: 030706/0614Z @:ZS6FB.MPU.ZAF.AF #:4940 PACTOR-2: XFBB7.04 $:ANS-187.03
From: ZS6FB@ZS6FB.MPU.ZAF.AF
To : SAT@AMSAT
AMSAT News Service Bulletin 187.03 From AMSAT HQ
SILVER SPRING, MD. July 6, 2003
To All RADIO AMATEURS
BID: $ANS-187.03
During the period 21 May to 01 July 2003 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 31 May
to 09 June, and from 21 June to 30 June. During this period good
signals have been received. Telemetry transmissions are expected to
resume around 12 July for about 9 - 10 days.
I am indebted to Jeff KB2M and Ron VK5AKJ who monitored the
satellite while I was on holiday, during part of this period. Ron
also provided some night time telemetry, during a solar eclipse,
which gave useful information about the state of the battery. Many
thanks Jeff & Ron, for your help.
The internal temperatures have continued to fall. Usually they
change by the same amount, however during this period the battery,
telemetry electronics, and command decoder have decreased by 3.2C,
1.8C and 4.6C respectively. The temperatures are now -0.4C,
-0.8C, and +2.6C respectively. The temperatures are expected to
continue 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.
Observations have varied between 13.5 and 12.3 volts, with an
average value of 13.0 volts.
Examination of the magnetometer telemetry shows that the satellite
is now rotating very slowly ie. the spin period is very long.
Accurate determination of the spin period is very difficult when
the spin period exceeds the time of a pass. However, approximate
periods of 1000 to 1500 seconds have been measured. The direction
of rotation appears to have reversed. The slow spin rate has also
caused some uneven heating of the external surfaces, and
temperatures up to 45C have been observed.
Users of OSCAR-11 should note that the date in the telemetry is
advanced by three days. The time is advanced by 18.5 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 8 - 9 days on 145.826 MHz., followed by about 10 - 12 days
of silence. These times appear to be somewhat variable, and this
regular sequence might be interrupted by ground control.
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 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 polarization 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
the very rare occasions 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 about using a soundcard for data
capture, and also details about using hardware demodulators.
There is 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 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 the times 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 further
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:U2RPT86.CWV, to prevent
duplication.
[ANS thanks Clive, G3CWV, for the above information]
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