January 2, 2015

Eric Hopton for redOrbit.com Your Universe Online

In December, NASA reported that its Mars rover Opportunity, which has been working the surface of Mars for over 10 years, was experiencing continuing Flash memory problems. As a result, the project team decided to operate the rover without using the non-volatile Flash storage system. Instead, they had to rely on the volatile random access memory (RAM) for temporary storage of telemetry and rover data. NASA said at the time that its longer term plan was to implement a strategy to mask off the troubled sector of Flash and resume using the remainder of the Flash file system in normal operations.

The fault, thought to be due to the robots age, has resulted in the six-wheeled vehicle resetting unexpectedly.

According to the BBC, NASA now believes it has found a way to hack the rovers software which will enable it to disregard the faulty part. NASA project manager John Callas told Discovery News how his team intended to solve the issue.

Callas explained that the rover has two key types of memory volatile and non-volatile. Non-volatile memory remembers information even when powered down. This makes it perfect for longer term storage. Volatile memory is more like PC RAM data is lost when power is lost or turned off.

Opportunitys memory fault means that it cannot save telemetry data to the flash memory. It then writes it to the volatile memory instead and any data is lost when the rover powers down.

Callas describes this problem as amnesia. Essentially, each time it powers down it forgets what it has done. The problem was relatively minor and benign at first but is now becoming much worse. NASA now reports that the fault is causing the rover to reset itself. On occasions, it even stops communicating with mission control altogether. The rover keeps attempting to save data to the flash memory but repeatedly fails. As a consequence, its software keeps forcing the rover to reboot time and time again and to forget what the previous command instructed it to do. Callas likens this to your car stalling every five minutes on a family day out. The situation took a turn for the worse when Opportunity failed to communicate with mission control over the Christmas period.

NASAs hack involves persuading the rovers software to ignore the faulty part of its flash memory and to write to the healthy hardware instead. The fix will probably take around two weeks. Longer term prospects for Opportunity are not great, however, and its life on Mars may be coming to an end. Callas believes that it could suffer terminal failure at any time. Nevertheless, the rover has lasted much longer than its expected three months on the Red Planet. In its ten years on Mars, Opportunity has roamed over 26 miles across the surface of Mars surface. The data it has gathered has provided vital understanding of the biological make-up of Mars.

The team would dearly love to keep the mission going a little longer. Callas says that the most exciting part of the mission is still ahead. The rover is only about 650 meters away from Marathon Valley, so-called because, if the rover ever makes it there, it will have exceeded the length of a marathon while on Mars. Marathon Valley contains a variety of clay minerals from a time when Mars held pH-neutral water on its surface. The Valleys geology could give fascinating clues to the potential for life on the ancient Mars environment. Whatever happens though, Opportunity already holds the current off-world record forarover.

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NASA hacks Mars Rover to cure system amnesia