11/24/93:  Mars Observer Concludes Operations

Wed, 24 Nov 1993 00:22:59 GMT

Excerpted from Jet Propulsion Laboratory UNIVERSE

By Diane Ainsworth

With no results from the last set of commands sent to the Mars Observer
spacecraft on Oct. 29, flight controllers concluded scheduled operations.

"The flight team has sent all of the commands that support recovery from the
plausible failure modes we have been able to put together," said Project
Manager Glenn Cunningham. "Since there is little more to do, the majority of
the flight team has been reassigned to other projects.  A small staff has been
retained for the Mars Recovery Study Team effort, which is currently under
way."

JPL dissolved the Mars Observer flight team as a technical review board
concluded an investigation into the probable causes of the apparent loss of the
spacecraft.  Meanwhile, the Deep Space Network will continue to listen for the
spacecraft through mid-February 1994.

"We have put forth our best guesstimates about what might have happened to the
Mars Observer spacecraft, but without data to work with, we will never be able
to say definitively what happened," said Dr. R. Rhoads Stephenson, chairman of
the JPL technical review board.

"It's time to move on to possible return missions to Mars and use our best
instincts to come up with alternatives that can recover the Mars Observer
science in the very near future."

Flight controllers lost contact with the Mars Observer spacecraft at
approximately 6 p.m. on Aug. 21, three days before the spacecraft was set to
fire its main rocket engines and decelerate into orbit around Mars.

The spacecraft was about to begin pressurizing its fuel tanks in preparation
for the Aug. 24 orbit-insertion maneuver when its transmitters were turned off
and the spacecraft was never heard from again.

Flight controllers attempted the most critical and probable commanding
strategies to try to restore communications before the spacecraft was to be
captured in orbit around Mars at about 1:30 p.m. on Aug. 24.

Commanding strategies during the weeks following the orbit- insertion maneuver
addressed more unlikely anomalies that could have occurred onboard the
spacecraft.

The last realistic chance to validate that the spacecraft still existed and was
properly operating--except for its telemetry transmitter--occurred in late
September, during a search for a beacon from a radio relay system onboard the
spacecraft by radio astronomy antennas at Jodrell Bank in England, at Stanford
University, and at the Goldstone tracking facility near Barstow.

"Had the spacecraft been in either of its predicted locations--in orbit around
Mars or in a flyby orbit around the sun--and had it been able to receive and
process commands from the ground, we fully expected that a signal from its
independent radio transmitter would have been detected," said Dr. Sam Dallas,
Mars Observer mission manager.

While minimal support for ground-tracking of Mars Observer will continue
through mid-February, JPL has begun a Mars Recovery Study Team effort to
explore the most cost-effective, low-risk ways of recovering the Mars Observer
science during the next Mars launch opportunities in 1996, 1998 and 2000.

The study team, chaired by Dr. Charles Elachi, assistant Laboratory director
for the Office of Space Science and Instruments, will evaluate all of the
possible options, including those that would involve international cooperation,
and hear proposals from U.S. industry in November. Formal recommendations are
expected to be presented to NASA Headquarters on Nov. 18.

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