14 DAY TRIAL // Mission controllers at the NASA Jet Propulsion Laboratory (JPL), in Pasadena, California, say that the Mars Science Laboratory (MSL) rover Curiosity is on a hiatus from scientific investigations, pending the results of an analysis of issues detected on Sunday, November 17.
During the weekend, JPL scientists discovered an unexpected voltage change in one of the rover's systems, and they are now investigating the possible causes of this phenomenon. In the meantime, a decision has been taken to suspend scientific operations for a few days, until the issue is fixed.
A possible explanation for what happened is that Curiosity experienced a soft short, a phenomenon that can easily cause voltage swings. If that is the case, then the 1-ton robotic explorer could now be at higher risk of damage from future shorts.
According to Curiosity operators, a soft short occurs when electricity flows through partially conductive materials, as opposed to when two cables touch each other (hard short). Soft shorts have a tendency to lower the resistance of electrical circuits in the future.
“The vehicle is safe and stable, fully capable of operating in its present condition, but we are taking the precaution of investigating what may be a soft short,” says JPL expert Jim Erickson, who is the project manager for the MSL.
The voltage difference between the robot's chassis and its 32-volt power bus – the structure used to distribute current throughout the vehicle – has been 11 volts since Curiosity landed, around 460 Martian days ago. On Sunday, this level dropped to 4 volts. The rover is not in any immediate danger.
When the nuclear-powered robot was constructed, engineers included a design feature called floating bus, which enables the electrical systems on Curiosity to operate properly even under significant voltage swings. The difference currently being recorded is within that operating range.
The voltage error was not sufficiently significant to force the rover into a safe mode, where all non-essential activities are suspended to prevent damage. Curiosity exited safe mode last week, following a warm computer reboot caused by a software update.
At this point, there is no way of knowing whether or not the update had anything to do with the voltage swing. JPL scientists say that the event first started as a series of 3 swings from 11 to 4 volts, which eventually settled at 4 volts.