A recent self-portrait of Curiosity on Mars. via
Even the most charmed missions run into problems. Case in point: Curiosity, the centerpiece of NASA's Mars Science Laboratory mission, just had to shut down. Over the weekend, a computer glitch unexpectedly forced the rover into safe mode. As far as we know, neither Chinese hackers nor tentacled Martians were to blame.
It was a routine glitch: On Saturday night, March 16, Curiosity was busily radioing data back to its Earth bound teach of engineers. It was operating on its B-side computer, one of two redundant onboard units, when a single command file failed a size-check by the rover's protective software. It was this mismatch that triggered Curiosity to go into safe mode.
This isn’t the first computer problem to hit the mission; it’s actually compounding a previous problem. On February 27, a memory glitch in the A-side computer – the primary unit that serves as a backup to the B-side computer – forced the rover team to order a switch. It put the A-side in safe mode then transferred all activity to the B-side. The ordered swap put the rover into safe mode for two days while the team worked the problem. They were eventually able to restore the A-side computer, bringing it up as a backup while the B-side computer resumed full operations.
Last Monday, Curiosity was supposed to resume full operations following this February glitch. But this second glitch over the weekend has extended the forced unplanned work break. The team will keep the transfer of Curiosity’s next batch of science results on hold while the rover stays on standby for at least two days, then longer as the team brings the computer back online.
Unfortunately, these sequential glitches are coming right before another planned work break. The Earth, Mars, and the Sun are about to align in such a way that the red planet will pass behind the sun from the Earthly perspective. Beginning on April 4, there were will be a four-week moratorium on sending commands to the rover. It’s a precaution against the Sun’s possible interference and corruption of commands sent to the rover.
Thankfully, this latest glitch has a really easy fix: delete the problematic file. This type of problem isn’t rare or uncommon, says the mission’s lead scientist John Grotzinger of the California Institute of Technology. And its resolution should teach engineers how to deal with the issue in the future. Or, better yet, prevent it from happening again.
The forced break from work isn’t ideal for the mission, but Curiosity has enough power to take a rest for a couple of weeks. Though its only about 7 months into its two-year primary mission, the rover has enough plutonium in its radioisotope thermoelectric generator (RTG) to run for about 14 years. The important thing is that the rover is stable, healthy, and communicating with its Earthly engineers. And doing some awesome science.