[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[jamsat-news:569] * SpaceNews 16-Jun-97 *

* SpaceNews 16-Jun-97 *

BID: $SPC0616


			  MONDAY JUNE 16, 1997

SpaceNews originates at KD2BD in Wall Township, New Jersey, USA.  It
is published every week and is made available for non-commercial use.

Regular users of FO-20 may have been puzzled by a strange buzzing sound on
its mode JA transponder over the last couple of weeks.  This was due to
command stations testing the new P3D Range Determination software and

P3D's orbit will change significantly after motor firings, and NORAD will
lose track of us.  So would we!  The P3 ranging system enables our world
wide network of Command Stations to measure distance to the satellite from
different locations and at different times and so compute the new orbit's
Keplerian elements.  This information is used by us, the AMSAT community,
and of course given back to NORAD so that they can re-acquire our satellite
by radar.  This methodology was used to remarkable effect in picking up
OSCAR-13 after both its motor firings.

Back in 1988, the P3C engineering software was still based on the Atari-800XL
computer.  This was a legacy from the very successful designs originating as
far back as 1979 and the ill-fated P3A satellite (1981).

However, the prospect of working on P3D yet again using a dual audio cassettes
for storage and 8-bit 2 MHz processors has never been very attractive, and a
re-engineering of many of the tools has been undertaken by James Miller G3RUH
over the last couple of years.

The P3 Range Determination package marks the successful completion of a
substantial development programme that includes the following principal

  - Tracking
  - Telemetry Display
  - Command Uploader
  - IPS-X1802
  - Ranging
  - OrbitFit
Tracking of course needs no introduction.

Telemetry Display is essentially as already available for AO-13, but with P3D
specific changes.  This will be publicly released for several platforms when
P3D is finally "nailed down".

Command Upload software is used for commanding the spacecraft both during
lab-testing and in space.  These first three packages were used for AO-13.

P3D, like its predecessors, has a flight computer based on a radiation
hardened CDP-1802 microprocessor.  It runs an operating system called IPS.
But generation of the flight operating system and on-board control software
is done on a ground-based host computer.  The IPS-X1802 package is, as its
name suggests, a cross compiler.

Source files for P3D are written using the IPS language.  They are compiled
by the IPS-X1802 development system (itself written in IPS) which outputs a
target binary in 1802 machine code.  In the days of P3A/B/C, this compilation
used to take half an hour on the Atari-800XL.  Imagine how tedious a simple
edit used to be.  Flight software compilation, from source files to
uploadable binary, now takes half a second.

The IPS-X1802 cross-compiler is a major part of the P3D development
programme.  Without it, the flight software which controls the spacecraft,
and is much different than that of P3A/B/C, would be impossible to produce
efficiently in the short timescales left to us.

The Ranging software, mentioned earlier, measures range to the satellite
with a basic accuracy of about 150m (1 microsecond).  Comparison of ranges
measured via FO-20, with ranges displayed by regular tracking programs, shows
agreement within 5 km, often better.  During tests, signal strengths have
been kept to the absolute minimum needed for "lock", and are weaker than
AO-13's general beacon used to be.  The uplink power to FO-20 is typically
under 1 watt to a KLM14C antenna, rather less than a typical SSB user's.
The ranging software can track down to a level where the signal is virtually
inaudible.  Sample GIF (5 kbytes) taken during an FO-20 pass is at:


The final program OrbitFit takes range measurements from the network of
command stations, and computes an orbit that best fits the data.  It was
written 10 years ago by Stefan Eckart DL2MDL, and has been adapted for our
current needs by G3RUH.  Tests processing FO-20 ranging data have been
completely successful.

Software is written in BASIC and ARM assembler for the Acorn Risc Computer.
Current machines use the DEC SA-110 processor at typically 200 MHz/700 mW/$50,
representing the highest MIPs/mW and MIPs/$$ (taken together) in the business
and currently the embedded systems processor of choice.  It makes a cool
personal computer too.

  Acorn Risc Computer:
  DEC SA-110 information:

Software is not as photogenic or as sexy as hardware, and thus gets little
or no exposure.  Yet it is hoped that this short precis provides a better
understanding of how the backroom boys have been keeping busy.  There are
many such heroes in the P3D program, but special recognition is given to
P3 command stations Peter Guelzow DB2OS, Graham Ratcliff VK5AGR, Stacey
Mills W4SM and Ian Ashley ZL1AOX for enthusiastically thrashing every
development as it has staggered off the production line.

Notes by James Miller G3RUH
1997 Jun 10 [Tue] 0653 UTC

The following notice was posted to the packet radio BBS on the Mir space
station by Mike Foale, KB5UAC, and was downloaded by Miles Mann:

  Stat   : PR   
  Posted : 06/07/97 13:10
  To     : ALL    
  From   : R0MIR  

  @ BBS  :        

  BID    : 
  Subject: SAFEX is ON

  Turning SAFEX II on today.  Repeater mode tx 437.950,  rx 435.750 
  ctcss 141.3.  SAFEX is turned off during all joint ops missions with
  soyuz, shuttle because of interference.

  Mike kb5uac

BJ Arts, WT0N, reports the Mir 70 cm repeater is up and running, and several
stations were worked during the 0030 UTC pass on June 8th.  Strong downlink
signals were reported while Mir was over north America.  BJ's uplink was
435.750 MHz FM, while he received downlinks on 437.950 MHz.  A CTCSS tone
of 141.3 Hz is required for access.

A brief description of the SCOPE project is now available in Japanese and
English.  The SCOPE Home Page is located at:


SCOPE is an experiment flying on the Phase 3D satellite that will provide
images of celestial objects through the use of a CCD imaging camera.

[Info via Tak Okamoto and the JAMSAT SCOPE Project Team]

STS-94 Nominal orbital data is now available on the AMSAT Web Page.  The
time-independent State Vector and the Keplerian elements corresponding to
the scheduled launch time of 01-JUL-97 / 18:37 UTC are available at:


The full set of nominal state vectors and mission profile schedule is also
available on the AMSAT Web page at:


As in the past, updates will be made to the AMSAT Web page using actual
orbital data during the mission.

E-Mail updates are no longer made to the SAREX mailing list during the
mission.  These updates were discontinued when NASA Spacelink began
sponsoring a mailing list called *STSTLE* for this specific purpose.
Subscriptions to STSTLE are available on request.  To subscribe send
a E-Mail message to the following address:


The text of the mail message should be as follows:

	subscribe STSTLE FirstName LastName

Where "FirstName" and "LastName" provide the list manager with your name.

Those considering subscribing to STSTLE should be cautioned that the list
typically provides three to four updates per day on the Shuttle (and also
for any satellites deployed by the Shuttle).  The frequency of updates
ensures current data for several NASA agencies that subscribe to this
mailing list.  If this many updates are undesirable, you should get your
Keplerian elements from a different source.

I created one additional source for Shuttle orbital data.  In some
high-interest SAREX missions, I received E-Mail messages from individuals
having difficulty accessing the AMSAT Shuttle Orbital Data Web page.  These
individuals did not want to subscribe to STSTLE because of the frequency of
updates.  Therefore, I provide a backup source of a current STSTLE update
message on my personal Web page.  This page may be accessed at:


Because of the workload in providing updates to both the AMSAT Web page and
the STSTLE mailing list, my personal Web page is sometimes only updated with
the STSTLE message at ~13:00 UTC and ~20:00 UTC during the missions.  Thus,
the AMSAT page is the primary data source on the World Wide Web.

Ken Ernandes, N2WWD

It is with sadness that the death of Dennis Caton, KF0JT, author of UP/DOWN
is reported.  Dennis lost a three year battle with cancer June 4 at his home
near Colorado Springs.  He was a native of England and is survived by his
wife and two grown children.  Dennis was a long time supporter of AMSAT and
satellite projects.  For a time he was AMSAT's coordinator for activities at
the Air Force Academy.  When he hit upon the idea for the UP/DOWN program he
was delighted to have found a way to contribute to AMSAT and satellite
operations.  A service was held at Our Lady of The Pines in Black Forest,
Colorado on June 11.  Messages may be sent to Jim White, WD0E (wd0e@amsat.org)
for forwarding to the family.

Jim White

Comments and input for SpaceNews should be directed to the editor (John,
KD2BD) via any of the paths listed below:
WWW       : http://www.njin.net/~magliaco/
INTERNET  : kd2bd@amsat.org, magliaco@email.njin.net

       <<=- SpaceNews: The first amateur newsletter read in space! -=>>