Mishap Board Completes Investigation: First Impression Probably
Correct
NASA's Comet Nucleus
Tour (CONTOUR) Mishap Investigation Board (MIB) identified four
possible causes for the failure of the comet-rendezvous mission
launched (right) in July 2002. The Board concluded the
probable proximate cause for this accident was structural failure
of the spacecraft due to plume heating during the embedded
solid-rocket motor burn.
However, the lack of telemetry and observational data,
immediately prior to and during the burn, and the lack of
recoverable debris, leave open the possibility that one of several
other problems could have led to the accident. The alternate
possible causes are catastrophic failure of the solid rocket motor;
collision with space debris or meteoroids; and loss of dynamic
control of the spacecraft.
NASA was not able to re-establish contact with the spacecraft on
August 15, 2002, following a propulsive maneuver involving the
solid rocket motor.
On August 22, 2002, the Associate Administrator for Space
Science established the NASA CONTOUR Mishap Investigation Board
with Theron Bradley Jr., NASA Chief Engineer, as chair. The purpose
of the Board was to examine the processes, data and actions
surrounding the events of August 15; to search for proximate and
root causes; and develop recommendations that may be applicable to
future missions.
Based on various facts and data, the MIB concluded the alternate
possible causes were less likely than the identified proximate
cause. Nonetheless, in the spirit of constructively improving
future mission reliability, the Board drew conclusions, identified
lessons learned, and made recommendations based on the broader
range of possible causes, according to Bradley.
Launched on July 3, 2002, CONTOUR was intended to encounter at
least two comets and perform a variety of investigations and
analyses of the comet material. It remained in Earth orbit until
August 15, 2002, when an integral Alliant Techsystems STAR 30BP
solid rocket motor was fired to leave orbit and begin the transit
to the comet Encke.
CONTOUR was programmed to re-establish telemetry contact with
the ground following the burn, however, no signal was received. The
mission design did not provide for telemetry coverage during the
solid rocket motor burn and no provision was made to optically
observe the burn.
Active attempts to
contact CONTOUR were unsuccessful. On August 16, 2002,
limited ground observations identified what appeared to be three
separate objects (below) on slightly divergent trajectories near,
but behind, CONTOUR's expected position. Further attempts to
contact CONTOUR were made through December 20, 2002, when NASA and
Johns Hopkins University/Applied Physics Laboratory (APL), Laurel
(MD), concluded the spacecraft was lost.
The project manager at APL oversaw the technical implementation
of the project and was responsible for the design, development,
test and mission operations.
The MIB established Root Causes and Observations contributing to
the failure, and recommendations for each in the Report.
"NASA will apply the lessons from CONTOUR to future missions,"
Bradley said. He stated the report represented a lot of tough
detective work by the many individuals and organizations involved
in the investigation. "The lack of data meant the investigators
could leave no stone unturned in their search for possible causes,"
he said.
The CONTOUR Mishap Investigation Board Report is available
online at the NASA site.
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