[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

OSCAR-11 Report




                OSCAR-11 REPORT   14 June 2004

During the period 22 May to 14 June 2004 the 145.826 MHz. beacon has been
heard transmitting continuous ASCII telemetry from 31 May to 10 June.
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 21 June.

The internal temperatures have decreased by 2.5C. They are now 2.8C, 0C
and 6.6C 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 varied between 12.5
and 13.9 volts. However the higher value was a single observation recorded
shortly after the beacon switched ON.  The average of the other readings
was 13.2 volts, a small increase on last month's values.

The rotational speed of the satellite has remained very low, making it
impossible to measure the speed accurately from telemetry, during a ten
minute pass. The spin period appears to be around 1500 seconds, ie. one
revolution every 25 minutes.  When the spin was being controlled by the
magnetorquers the target spin period was 300 seconds.

The mode-S beacon has been heard by Hans DL6KG and Jean-Jacques ON7EQ.
Hans reports S3-S4 signals, with G3RUH antenna, Kuhne converter, and IC910
receiver. Jean has received S8 signals using a one metre dish, G3RUH
patch, and DB6NT converter. Many thanks for those reports.

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 on
145.826 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 reports of reception
on 2401.5 MHz. would be most welcome, however please DO NOT send sound
files.  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 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 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:U2RPT98.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home