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CX2ACB > SAT 08.09.03 05:26l 112 Lines 5303 Bytes #999 (0) @ AMSAT
BID : ANS-250.03
Read: GUEST
Subj: OSCAR-11 REPORT
Path: DB0ZKA<DB0FSG<DB0SL<DB0RGB<OK0PPL<DB0RES<ON0AR<7M3TJZ<CX2ACB
Sent: 030908/0319Z @:CX2ACB.MVD.URY.SA #:18919 [Montevideo] $:ANS-250.03
From: CX2ACB@CX2ACB.MVD.URY.SA
To : SAT@AMSAT
AMSAT News Service Bulletin 250.03 From AMSAT HQ
SILVER SPRING, MD. September 7, 2003
To All RADIO AMATEURS
BID: $ANS-250.03
OSCAR-11 REPORT 06 September 2003
During the period 13 August to 06 September 2003 the 145.826 MHz. beacon
has been heard transmitting continuous ASCII telemetry from 22 August to 01
September. During this period good signals have been received. Telemetry
transmissions are expected to resume around 11 September for about 9 - 10
days.
The internal temperatures have increased by 3.2C during the period,
indicating that the eclipse times are continuing to decrease. The
temperatures are now 5.0C, 4.0C, and 9.8C respectively, for battery,
telemetry electronics and command decoder, respectively. However, there is
a considerable variation in the temperature changes between the three
units. This may due to the very low spin rate producing uneven heating. The
slow spin rate has also caused some uneven heating of the external
surfaces, and temperatures of +32C and down to 0C have been observed. The
range of temperatures was less than those reported last month.
Temperatures are expected to increase, reaching a peak in the Autumn with
higher temperatures than in 2002.
The battery voltage observed during daylight passes was unchanged.
Observations have varied between 14.0 and 13.3 volts, with an average value
of 13.5 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. Spin periods of 582 to 716 seconds have been
measured. On one occasion no spin was observed, and on another the X & Y
axes indicated an unusual motion.
The mode-S beacon has been heard by Ken W7KKE. He uses a one metre dish,
with a G3RUH patch, RHCP, 0.7 dB pre-amp, and Drake converter. The
measured frequency, after correction for Doppler, but not CW beat, was
2401.5023 MHz. The equipment was calibrated before and after the
measurement. Ken also noticed two weak 1200 Hz. sideband tones. At the
time the 145 MHz. beacon was OFF. Many thanks for that report Ken.
Users of OSCAR-11 should note that the date in the telemetry is advanced by
three days. The time is advanced by 18.6 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. 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:U2RPT89.CWV, to prevent duplication.
[ANS thanks Clive, G3CWV, for the above information]
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