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From: john@aplcomm.jhuapl.edu (John Hayes)
Newsgroups: comp.lang.forth
Subject: Re: Forth and Astronomy
Message-ID: <1990Dec13.221406.15664@aplcen.apl.jhu.edu>
Date: 13 Dec 90 22:14:06 GMT
References: <2109.UUL1.3#5129@willett.pgh.pa.us>
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Reply-To: john@aplcomm.jhuapl.edu (John Hayes)
Organization: JHU/APL, Laurel, MD
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Gary writes in reference to the recent shuttle flight:
>  That would indeed be extremely _BAD_ publicity. Forth was invloved in
>  this mission. I refer you to John Hayes rather detailed report of two
>  days ago for specifics. I will also have to defer to John Hayes or
>  perhaps Marty Fraeman for an accounting if the mission snafus were
>  contributed to and/or caused by Forth based programs. From the reports
>  I read and John's net message I am thinking Forth is not the culprit,
>  but lacking specifics I am obviously guilty of speculation, and it may
>  be wishful speculation.

I have just returned from Huntsville and can give a complete report
on the recent space shuttle Columbia flight.  As I reported earlier
this flight carried three ultraviolet telescopes, each programmed
in Forth.  Two astronauts on the aft flight deck control the telescopes
using the Experiment Computer (EC) built by the ESA.  This computer
can be seen as an I/O multiplexer for the computers in the telescopes
and for the Instrument Pointing System (IPS).  The two astronauts
interact with the EC via two Dedicated Display Units (DDUs).
These are just color display terminals.

				+-----+   +-----+   +-------+   +-----+
				| IPS |   | HUT |   | WUPPE |   | UIT |
				+--+--+   +-----+   +-------+   +-----+
+-----+        +------+		   |         |	        |	   |
| DDU |----+   |      +------------+	     |		|	   |
+-----+    |   |      |			     |		|	   |
           +---|  EC  +----------------------+		|	   |
+-----+    |   |      |					|	   |
| DDU |----+   |      +---------------------------------+	   |
+-----+        |      |						   |
	       |      +--------------------------------------------+
	       +------+

On the first day one of the DDUs died.  This was not disastrous but
inconveniant since the astronauts had to share the remaining DDU.
A couple of days later the second DDU died.  This left the astronauts
with no way to communicate with the telescopes.  However, the command
uplink capability from Huntsville (via many satellites) to the shuttle
was still working.  Each instrument team controlled their
telescope from the ground.  The astronauts still had some control
of the IPS with a joy stick.  The astronauts were able to find
the targets with some help from the ground, then the observation was
controlled entirely by command uplink.  Ben Ballard and I took
turned driving HUT.

The telescopes, for the most part, worked flawlessly.  During the
initial turn on, the team from the University of Wisconsin was
unable to load the WUPPE computer.  It was later found that a heater
had not been turned on for the interface between the EC and the WUPPE
computer.  Somehow this damaged the WUPPE computer.  Fortunately,
they had a backup computer.  Once this was brought up, they had
no further problems.

Despite what you hear from the media, the mission was a success.
These apparently severe problems were circumvented in a remarkably
short amount of time.  By the time things settled down, we acquired
almost every target attempted and collected large amounts of data
(1.5 Gbytes for HUT).  All of the scientists were grinning
ear to ear by the end of the flight.  Several cataclysmic variables
were fortuitously in outburst during the mission and HUT observed
some of these.  The HUT scientists are also interested in quasi-stellar
objects (or quasars) and several were observed doing "strange" things.
Once the data has been reduced, many papers will be forthcoming.


John R. Hayes			john@aplcomm.jhuapl.edu
Applied Physics Laboratory
Johns Hopkins University