Re: Mars Observer (Neumann, RISKS-14.87)

[Lee Mellinger <leem () tsunami Jpl Nasa Gov>]

Just a few comments.  I'm on the Mars Observer project, and some of the
information published in public sources has been somewhat misleading or
incorrect.  First, the spacecraft did not cost $1B, is was about $300M, the
Titan booster was about $500M and ground systems and ops about $200M.  In
NASA's new way of doing business all costs are lumped together, so to make a
fair comparison to other projects, you must understand that the costs quoted
in the past did not cover the launch and sometimes not the ground system.
Second, the communications with the spacecraft were not "disrupted" [actually
David Perlman in the Chron said Pike noted that Mission Control engineers at
JPL had ``lost contact with the Mars Observer'' --- PGN] as John Pike has
said, nor "interrupted", they were intentionally turned-off.  The transmitter
beam voltage was shut down to protect the filament when the fuel and oxidizer
pyro valves were blown to pressurize the tanks.  The beam voltage was supposed
to be turned back on after the tank pressurization event by the command
sequence stored in the SCP, the spacecraft control processor.  We do not konw
what happened after the beam-off was executed because the downlink was not
seen again, and that is all we know for sure.

We have been commanding a series of events, presuming that certain scenarios
have occurred.  None has been successful as far as we know.  We continue to
send commands because the Command Detector Unit is connected to the Low
Gain Antennas and do not require precise pointing by the spacecraft to 
achieve command reception.


We do not know that whatever happened, happened when the pyro valves were fired
because that did not occur until sometime after the beam voltage was turned
off.  There was a time interval to allow sufficient cooling of the filament.

We are at this moment waiting for the expiration of the the secondary 
command loss timer, which will reconfigure the spacecraft telecom to 10bps
and the Low Gain Antennas for downlink.  That will occur (assuming that
no commands have be accepted since last Friday) at 93/238-21:56:35 UTC,
that is today, the 27th at 14:56:35 PDT. 

Lee F. Mellinger, Caltech/Jet Propulsion Laboratory - NASA, 4800 Oak Grove Dr.
Pasadena, CA 91109 818/354-1163      leem () jpl-devvax JPL NASA GOV

------------------------------
Date: Thu, 26 Aug 1993 17:15:33 -0400
From: stern () deshaw com (Michael Stern)
Subject: Re: Mars Observer (RISKS-14.87)

Unfortunately I can not provide the names of my sources for this material,
as it would not be fair to them. Treat anonymous sources with appropriate
skepticism; I think you'll find this an interesting tidbit nonetheless.

Apparently the tank pressurization system on the Observer was tested
exactly once, and it "blew up." Whether this phrase is meant to imply
an explosion or merely a bad leak is an exercise left to the reader.

NASA had one spare tank.

Result: the Observer was launched with the second tank, with no further
testing or development.

/stern