NASA’s Mars Exploration Rover Opportunity can be considered a veteran of Mars exploration, investigating the planet’s surface since January 2004. Although the rover is still performing well, it has been showing signs of old age the past few weeks. As memory issues become more and more frequent, engineers need to find a way to solve Opportunity’s increasingly problematic episodes of amnesia.
The rover uses two types of memory in order to store data and measurements acquired during its investigation across the Meridiani Planum region of Mars. One is known as “volatile memory” and the other one is a “non-volatile” type. The difference between these two is that data stored on non-volatile memory will be kept even after the system restarts while the other type of memory deletes data once the system powers off.
So, one could compare volatile memory to the RAM found in all PCs while non-volatile memory is similar to a flash-memory device. Flash memory is responsible for storing all data, so that it won’t be lost when the rover shuts down overnight or while it restarts. This type of memory does have its limitations as it can store and send data a limited number of times, each usage also contributing to its fray.
Due to increasingly frequent flash memory issues, engineers noticed loss of data and Opportunity resetting without being programmed to do so. John Callas, the mission’s Project Manager at NASA’s Jet Propulsion Laboratory in Pasadena, California stated that the problem was initially benign, comparing it to a disease: “the symptoms were mild, but now with the progression of time things have become more serious.”
The problem evolved to the point where the rover goes through amnesia-like episodes. This happens when it tries to store data on flash memory but is unable thus being forced to use RAM. As a result, once Opportunity shuts down, the newly stored data will be deleted, making research quite difficult.
Engineers attempted to reformat Opportunity’s system, just like they tried with its sister – Spirit – that couldn’t face the Red Planet’s conditions and died in March 2010 after six years into its mission. Engineers’ first solution to fixing Opportunity failed due to temporary loss of communication during Christmas.
NASA is now developing their second solution, a software that will avoid the 7th bank of flash memory which is causing all the problems. The program is expected to be complete in a few weeks.
The agency hopes Opportunity will pull through and reach its designated destination, the so-called Marathon Valley, an area located 650 meters from the rover’s current location. That is the place where Curiosity found clay minerals, evidence that liquid water once existed in the area.
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