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

OSCAR-11 Report





                OSCAR-11 REPORT    16 January 2000

It's been an interesting time for OSCAR-11. I'm pleased to report
that the satellite has survived the Y2K change-over and continues to
work well. During the period 14 December 1999 to 15 January 2000 good
signals have been received from the 145.826 MHz. beacon. A revised
bulletin No. 115 from Richard G3RWL, has been uploaded by ground
control. This is a brief list of modes and frequencies of the
Amateur Radio satellites, and has been updated to include recent
additions.

Users of OSCAR-11 will know that the date in the ASCII telemetry
frames has been advanced by two days for a number of years now, and
that the displayed time has been slowly drifting over the years. The
first one day advance of the date occurred early in July 1992, and
the second at the start of March 1996.  The satellite makes
extensive use of two digits to designate the year in its status
display and data blocks.  I have therefore been looking at the dates
and times on UO-11 during the Millennium change-over period, with
interest.

On 30 December the date in the ASCII TLM switched over to 00
correctly. On January 01 the day and month in the ASCII status block,
binary SEU and ENG frames also changed over correctly, but the year
remained at 99. The time in the ASCII TLM frames was approximately
13.5 minutes ahead of UTC, and the time in the ASCII status
and binary SEU/ENG frames was approximately three minutes ahead of UTC.

Ground control operations early in January corrected the year in the
ASCII status block, and in the binary data. The time in these
displays was also set correctly. Chris Jackson, the UoS ground
controller, reminded me that the time is derived from a hardware
clock, set up in the early stages of the satellite's life, and cannot be
adjusted. This time and date is displayed in the ASCII Telemetry,
also a hardware function. However the time in the status block and binary
data frames is processed by the Diary software, and therefore can be
adjusted. Time errors won't have any effect on the functioning of the
satellite.

The battery voltage during daylight passes is unchanged. The average
value observed was 13.9, with a range of 13.7 to 14.0 volts.

The internal temperatures have been fairly constant during
this period. They are now 5.8C and 3.8C for battery and telemetry
electronics respectively.

Temperatures observed on the satellite during 1999 showed a steady
fall during the first half of the year, followed by an increase
during the second half.  It seems likely that this pattern will be
repeated this year, but with less temperature variation. At the
present time there appears to be an annual trend towards slightly
longer eclipses, with less variation between maximum and minimum
amounts of sunlight.  This year's forecast was based on the 1999 day
363 Keplerian element set, and is only as good as that data.

The Z-axis magnetorquer counter is now incrementing normally, at
about 10 counts per day. The spin period has slowly drifted from -295
seconds to -349 seconds at the start of the year, and has now drifted
back to -266. However very few spin correction counts have been
observed during this time.

The WOD survey of channels 1, 2, 3, 61 (magnetometers) dated 17
November 1999 has now been replaced by channels 10, 20, 30, 40 (+Y,
-X, +X solar array currents, array voltage), dated January 06.  Note
the year of this WOD survey is incorrectly displayed as 99. This
survey clearly shows the solar eclipses, and a spin period of 340
seconds.

A report of the mode-S beacon has been received from Jerry K5OE.
Jerry uses a Drake converter, a 10 turn helix with a ring reflector.
Signals were S3. Further details of Jerry's experimental antennae are
available on his web site URL - http://members.aol.com/k5oe/ Many
thanks for that report Jerry.

The operating schedule is unchanged.

        ASCII status (210 seconds)
        ASCII bulletin  (60 seconds)
        BINARY SEU (30 seconds)
        ASCII TLM (90 seconds)
        ASCII WOD (120 seconds)
        ASCII bulletin (60 seconds)
        BINARY ENG (30 seconds)

The ASCII bulletin is currently a static message, detailing modes and
frequencies of all the amateur radio satellites.

There  are  additional  status  blocks  after  each bulletin is
transmitted, and between ASCII TLM and WOD.

The mode-S beacon is ON, transmitting an unmodulated carrier, but
telemetry indicates that it has partially failed, and delivering half
power.  This beacon is a useful test source for those testing mode-S
converters, prior to the launch of P3-D. 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. Even if you can't hear OSCAR-11,
your equipment may still be OK for P3-D. Any reports of reception on
2401 MHz.  would be most welcome.  Please e-mail g3cwv@amsat.org.

The 435.025 MHz. beacon is normally OFF.  However it can sometimes be
heard 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 of hardware required and some software for
capturing data, and decoding ASCII telemetry and WOD.  There is an
archive of raw data (mainly WOD) for analysis, which is continually
being expanded, as new data is captured.  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:U2RPT45.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org


----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home