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OSCAR-11 Report






                OSCAR-11 REPORT    14 July 1998


A potential problem occurred at the end of June, after a long  period
of   uneventful   operation.   The  status  blocks  showed  that  the
magnetorquer firing counters had stopped incrementing. and  the  spin
period  was  steadily  increasing  ie.   the  satellite  rotation was
slowing down.  Normally the Z counter increments at about ten  counts
per day, and the minus spin counter about five counts per day.  These
firings  maintain  the  spin  period  at  around 360 seconds (ie. one
revolution every six minutes, and keep the satellite pointing towards
the earth.  The Z-axis counter had stuck at 1024 and the  minus  spin
counter was stuck at 486. After six days the spin period had risen to
640 seconds.

Ground control reset the counters on 1st July, and started a new  WOD
of  the  magnetometer channels. After three days, the spin period had
returned to its nominal value.  I understand  that  the  magnetorquer
control  system stops working when a counter reaches 1024.  This is a
feature  to  protect  the  satellite   from   malfunctions   of   the
magnetorquer control system.

During the period 15 June to 14 July  reasonable  signals  have  been
received  from  the  145.826  MHz.   beacon.   Telemetry nominal. The
battery voltage has tended to be rather low,  averaging  13.5  volts,
with  13.4  volts observed on several occasions.

The  internal  temperatures  have  remained constant and are now 1.8C
and 0.4C for battery and telemetry electronics respectively.

The WOD survey,  of  channels  1,  2,  3,  61  (magnetometers)  dated
19-March-98  has been been replaced by a survey of the same channels,
dated 01-July-1998, starting at  16:24:09  UTC.   This  was  probably
started  at  the  same time as the counters were reset, and shows the
unusually high spin period of 640 seconds.

Reports of the OSCAR-11 mode-S beacon  have  been  received  from  Ed
K9EK,  Rick  VE7SME, and Mike WL7BQM. Rick's report was of particular
interest, as he was using OSCAR-11 as a  signal  source  while  doing
some RFI tests at the Australian National Telescope Facility.

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.  It is  considerably  weaker
than  DOVE,  which should be used for initial testing. 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:U2RPT27.CWV, to prevent duplication.

73 Clive G3CWV   g3cwv@amsat.org

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