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Review Board Reports on Mars Orbiter Loss

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The Mars Global Surveyor (MGS) spacecraft unexpectedly lost radio contact in November, 2006.  When attempts to reconnect with MGS were unsuccessful, NASA convened an internal review board. The board was formed to determine why NASA's Mars Global Surveyor went silent and to make recommendations about any processes or procedures changes that could increase safety for other spacecraft.

The results of the internal review board were published on April 13th, 2007. The root cause of the spacecraft loss was complete discharge of the spacecraft's batteries.  When a command was sent to MGS on November 2nd, 2006 to reorient its solar panels, the spacecraft transmitted a series of alarms, followed by a message indicating MGS had stabilized.  This was the last message the MGS ground controllers received from the spacecraft.

Investigators now believe that although the spacecraft indicated it was in a stable position, in reality it had oriented itself into a position that exposed one of its two batteries to direct sunlight.  The unrelenting sunlight caused the battery to overheat and fail leading to mars_global_surveyorthe depletion of the second battery.  The programmed attitude MGS was to assume in case of a problem was not a thermally safe orientation.  The spacecraft's antenna was not aimed at Earth so the spacecraft could not communicate its status or accept commands. Eleven hours later the battery system depleted completely.

These failures were traced back to a software update transmitted to MGS in June of 2006. The directions for pointing the spacecraft antenna in case of a problem on board the spacecraft were written to the wrong memory address in MGS's computer.  When the November 2nd command was received by MGS it triggered a sequence of events that resulted in the loss of power to the spacecraft.

The internal review board findings were made in three key areas: Operational Procedures and Processes, Spacecraft Design Weaknesses and Lifetime Management Considerations.  The processes and procedures were inadequately written, providing no guidance for the errors that occurred.  The spacecraft's on board fault protection was insufficient to handle the faults that were most likely encountered. Finally, the risk for errors was increased by the staff and other cost reductions made to the MGS Mission as it entered its fourth extended mission phase.

The full text of the Interim Report is available NASA's web site.

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