Europe's Mars Express resumed full science operations in early February, four months after scientists suspended research following persistent glitches in the probe's solid-state mass memory unit, according to the craft's mission manager.

Artist's concept of Mars Express. Credit: ESA
 
"Mars Express has now been restored to full operational capability and its potential mission lifetime remains unchanged," a European Space Agency statement said.

Problems with the 12-gigabit memory unit, which contains data and commands necessary for instrument operations, put Mars Express in safe mode four times. The data system is required for the spacecraft to conduct scientific reesearch, storing up to 50 individual commands for each observation.

The safe mode events forced Mars Express to rapidy point toward the sun, consuming six months' worth of propellant in a short time, according to ESA.

After the data storage glitch showed up using two redundant controllers, engineers halted scientific observations Oct. 16 to avoid burning more propellant and preserve the mission's expected lifetime.

Officials turned to a hardware-based timeline store in a different computer, bypassing the issue believed to have caused the safe modes last year.

But the backup timeline store can only hold 117 commands, much less than the thousands executable in the timeline in the faulty solid-state mass memory unit.

Engineers found a way to write much shorter command sequences to fit in the hardware-based short timeline, and although the suspect memory unit continues to experience errors, none of them have triggered a safe mode, according to ESA.

"This has recently been tested in real life, as the spacecraft encountered a [solid-state memory unit] anomaly exactly like those in late 2011, but this time was able to complete the observation and return to Earth pointing without entering safe mode," an ESA statement said. "This allowed a much faster recovery to nominal operations and avoided wasting precious propellant."

Controllers continue working on a command scheduler to allow Mars Express to function autonomously for up to a week, reducing the workload for ground operators.

Fred Jansen, Mars Express mission manager, said the spacecraft has more than 8 pounds of maneuvering propellant left in its tank, which should be enough fuel to continue the mission for up to 14 more years.