NASA’s Mars Reconnaissance Orbiter unexpectedly rebooted its computer Monday morning, Feb. 23, and put itself into a limited-activity mode, an automated safety response to an anomalous event such as a cosmic ray hit on part of the electronics on board the spacecraft. This is the fifth time since August of 2005 that the spacecraft has gone into safe mode. However, the symptoms from this week’s event do not match any of the prior safe-mode events. “We are going to bring the spacecraft back to normal operations, but we are going to do so in a cautious way, treating this national treasure carefully,” said Jim Erickson of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., project manager for the Mars Reconnaissance Orbiter. “The process will take at least a few days.”
Safe Mode is a precaution programmed for the spacecraft when it senses a condition for which it does not know a more specific response.
MRO engineers are examining possible causes of the event while planning to prepare the spacecraft to resume its scientific investigations of Mars. There has been no reoccurrence of the reboot event.
The spacecraft is in communication with and under control by the flight team. Its batteries are charged and its solar panels are properly generating electricity. The team successfully commanded an increase of more than 10,000-fold in the communication rate Monday afternoon from the rate of 40 bits per second that the orbiter initially adopted when it went into the precautionary “safe” mode.
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From the spacecraft data received after communications accelerated, the team gained a preliminary indication that the cause of the reboot might have been a measurement — possibly erroneous — of a brief increase in power load. The event lasted between 200 nanoseconds and 41 seconds. That leads engineers to identify one possible scenario as a cosmic-ray hit that could have caused an erroneous voltage reading that would last 9 microseconds, enough to trigger the reboot.
The reboot occurred at about 4:25 a.m. Pacific Standard Time on Monday, while the orbiter was behind Mars from Earth’s perspective. Engineers hope to have MRO back functioning normally by early next week.