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

OSCAR-11 Report




                OSCAR-11 REPORT    17 October 2001

Within the last few days my antenna rototor has failed, and at the
time of writing I am unable to receive the satellite while I'm
fitting a replacement. However, Jeff KB2M has very kindly offered to
provide some regular telemetry while my antenna is dismantled. Jeff
has provided some excellent ASCII data but he may have a problem with
the 8-bit binary data, which is of interest at the present time (see
below). If any one out there can help capture and decode the binary
data please e-mail me at g3cwv@amsat.org.  PLEASE DO NOT SEND any
data or files before first discussing details with me.

In the July report I mentioned that the rate at which the SEU counter
increments had approximately doubled, to about 390 counts per day.
Since then the rate has steadily continued to increase and is now
around 420 counts per day. Decoding the SEU binary telemetry shows
permanent memory failures at locations 3EC0 and 37B1. Frequent faults
at FF5A and FF58 appear to be causing the increase in count rate.  I
am not aware of any readily available software for decoding the SEU
packets, other than my own program U2PKT (please e-mail me if you
know differently).  I hope to add U2PKT to my web site in the near
future.  The program is written in BBC BASIC, but the package will
include a suitable interpreter which runs well in DOS or Windows.

During the period 15 September to 16 August consistent signals have
been received from the 145 MHz. beacon.

The internal temperatures have continued to increase as the solar
eclipse times decrease.  A further rise of 2.5 degree C has been
noted. These temperatures are now 5.8C and 4.0C for battery and
telemetry electronics respectively.

The battery voltage observed during daylight passes has increased.
The average value observed was 14.05 with a range of 14.0 to 14.1
volts.  The improved battery voltage is also a result of decreasing
solar eclipse times, and this trend is expected to continue for
several months.

The WOD survey of channels 1, 2, 3, 61 (X, Z, Y magnetometers and
status) dated 16-August-2001 has been transmitted.  This WOD shows
the spin period to be 368 seconds, which was current at the time of
the survey.  It may now be downloaded from my web site (details
below).

The spin period has varied between 208 and 276 seconds. There have
been 288 Z axis, six positive spin, and zero negative spin
magnetorquer correction pulses.

The mode-S beacon has been heard by Jerry K5OE and Micheal KD9KC.
Jerry reports S5 signals at TCA. He uses a 65 cm dish, helix feed,
DEM pre-amp, and Transystem 3733 converter.   Micheal reports signals
S4 above noise using a 66*106 cm parabolic section dish, 3733
converter, and IC820H receiver.  Many thanks for those reports.

Users of OSCAR-11 should note that the hardware generated time in the
ASCII telemetry is now 15.5 minutes ahead of UTC, and the date is
three days advanced.  Unfortunately these errors cannot be corrected.
There are also smaller errors in the software generated times,
advances of 3.5 in the status blocks, and 1.5 minutes in the binary
packets, which ground control should be able to correct. The dates in
the status blocks and binary packets are correct.

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 (number 115) 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, nominally transmitting an unmodulated
carrier. There is however a VERY low level of AFSK modulation 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
polarisation of OSCAR-11 is LHC. Even if you can't hear OSCAR-11,
your equipment may still be OK for OSCAR-40 when commissioning is
complete. 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:U2RPT66.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