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The Planetary Society Blog

By Emily Lakdawalla

Arizona Daily Star reports MRO managers working to avoid "unlikely but potentially fatal scenario"

Oct. 28, 2009 | 10:53 PDT | 17:53 UTC

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Mars Reconnaissance Orbiter has been in safe mode for nine weeks, since August 26, the date of the fourth in a series of safing events. A JPL update on the situation dated to September 4 said that analysis had "identified one possible but unlikely scenario jeopardizing the spacecraft. This scenario would require two computer resets, each worse than any so far, occurring within several minutes of each other in a certain pattern." Today's Arizona Daily Star contains a bit more information on this possible failure scenario:

While the engineers have not been able to find the root cause of why the orbiter [rebooted] on Aug. 26, they are seeing a pattern among the four occurrences this year.

"In all four cases the most likely scenario is that ... either one of the voltages wasn't right or the part of the device that measures voltages indicated there was a problem and there wasn't one," [project manager Jim] Erickson said.

The unclear voltage signals have caused the orbiter in one instance to switch to a backup computer and in the three other instances to reset the computer. Engineers worry that if these actions happen in a short enough time frame, the memory of the main computer as well as the memory of the backup computer could be reset.

"There's a case where the spacecraft may not remember that it is in mapping mode," Erickson said. "It might think it's on the ground waiting to be turned on."

Engineers are now working to create a safeguard against that worst-case scenario as well as finding the cause of the mysterious voltage signals.

Since they haven't figured out a cause yet, it's no surprise that Erickson can't currently give a date as to when MRO will be able to return to normal operations. Now that it's in its extended mission, its highest priority is to serve as a communications relay for future landers -- I wonder if there are possible recovery scenarios that include return to relay operations but not return to science? We'll have to wait for further updates to come out of the mission.

Meanwhile, spring continues to arrive to Mars' northern plains...

Click to enlarge >

MRO in Orbit
Credit: NASA / JPL

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