The Loss of Mars Observer
The Coffey Board report stated that the most probable cause of the
loss of communications with the spacecraft on Aug. 21, 1993, was a
rupture of the fuel (monomethyl hydrazine (MMH)) pressurization side
of the spacecraft's propulsion system, resulting in a pressurized leak
of both helium gas and liquid MMH under the spacecraft's thermal
blanket. The gas and liquid would most likely have leaked out from
under the blanket in an unsymmetrical manner, resulting in a net spin
rate. This high spin rate would cause the spacecraft to enter into
the "contingency mode," which interrupted the stored command sequence
and thus, did not turn the transmitter on.
The board also identified three other possible causes:
- failure of the electrical power system, due to a
regulated power bus short circuit;
- NTO tank over-pressurization and rupture due to
pressurization regulator failure;
- the accidental high-speed ejection of a NASA standard
initiator from a pyro valve into the MMH tank or other
spacecraft system.
The JPL board report added two additional failure scenarios:
- Loss of function that prevented both the spacecraft's main and
backup computers from controlling the spacecraft;
- Loss of both the main and backup transmitters due to failure of
an electronic part.
Additional information relevant to the loss of Mars Observer includes:
Copyright © 1995 by Malin Space Science Systems, Inc.
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