After nine years and 52 days, the Mars Global Surveyor orbiter broadcast its last communication with Earth on Nov. 2, 2006. Eleven hours later, depleted batteries left the spacecraft unable to control its orientation. Now, an internal NASA review of the mission has determined why those batteries failed.
On Nov. 2, the spacecraft was ordered to perform a routine adjustment of its solar panels. It then reported a series of alarms but indicated that it had stabilized in what would be its final transmission. The orbiter next reoriented and exposed one of its two batteries to direct sunlight, overheating that battery and eventually depleting both batteries.
The orbiter couldn’t report its status because its antenna wasn’t pointing in the right direction. Also, its programmed safety response didn’t check to see if the spacecraft’s orientation was in any thermal danger. While the review board concluded that the Mars Global Surveyor team followed existing recovery procedures after failing to make contact with the orbiter, these procedures failed to catch the errors that led to the loss of the orbiter.
“The loss of the spacecraft was the result of a series of events linked to a computer error made five months before the likely battery failure,” said board chair Dolly Perkins, deputy director-technical of the NASA Goddard Space Flight Center. The board attributed the breakdown to a specific incorrect parameter upload in June 2006, as a direct memory command to update positioning for contingency operations was written to the wrong memory address in the orbiter’s onboard computer.
“We are making an end-to-end review of all our missions to be sure that we apply the lessons learned from Mars Global Surveyor to all our onging missions,” said Fuk Li, Mars Exploration Program manager at NASA’s Jet Propulsion Laboratory. These lessons include the need for more thorough reviews of all non-routine changes to stored data before uploading as well as the need to evaluate contingency modes for overheating risks.
Despite this catastrophic end, the mission lasted about four times longer than expected. Among its discoveries, it revealed interweaving, curved ridges that could be the location of an ancient river delta. Its magnetometer observed remnant magnetic fields indicating that Mars once had a field like Earth’s that could shield the planet’s surface from cosmic rays. And perhaps most significantly, before and after images of two gullies suggest the presence of liquid water sometime in the past seven years.
NASA
www.nasa.gov/mission_pages/mgs/index.html
