Faulty Software May Have Doomed Mars Orbiter

NASA’s venerable Mars Global Surveyor. Search is on for silent spacecraft. Image CREDIT: NASA/JPL/Corby Waste

WASHINGTON -- NASA is forming an internal investigative board to look into why the Mars Global Surveyor spacecraft stopped responding to commands in November, the agency announced Jan. 10.

The announcement comes a day after one of the U.S. space agency's senior Mars program officials told a public gathering of scientists here that faulty software uploaded to the spacecraft last summer may have doomed the spacecraft.

As first reported by the Web site NASA Watch and confirmed by sources who attended the Mars Exploration Program Analysis Group meeting here Jan. 9, John McNamee, NASA deputy program manager for Mars Exploration at the Jet Propulsion Laboratory, said it appears that improperly-coded software caused the Mars Global Surveyor to point its heat-shedding radiator toward the Sun, causing the battery to overheat to the point of failure.

"We think that the failure was due to a software load we sent up in June of last year," NASA Watch quoted McNamee as saying. "This software tried to synch up two flight processors. Two addresses were incorrect -- two memory addresses were overwritten. As the geometry evolved, we drove the [solar] arrays against a hard stop and the spacecraft went into safe mode. The radiator for the battery pointed at the Sun, the temperature went up, and battery failed. But this should be treated as preliminary."

Doug McCuistion, director of NASA's Mars Exploration Program, said in a Jan. 10 phone interview that the software problem McNamee discussed at the meeting is one of several scenarios the board would investigate. Other possible explanations include a problem with the spacecraft's solar array, which jammed in November. 

"All kinds of things can happen to a 10-year-old spacecraft," McCuistion said.

McCuistion added that he expects the investigative board to deliver its report in couple of months, but noted that the actual cause of the failure may never be known.

Space News staff writer Brian Berger contributed to this story.

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