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November 21, 2013

Electrical Problems Temporarily Suspend Curiosity's Scientific Activity

by VOA News

Electrical problems have caused NASA to suspend scientific operations on its Mars rover Curiosity “for a few days."

According to the U.S. space agency, there was a voltage change detected November 17.

"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," said Mars Science Laboratory Project Manager Jim Erickson at NASA's Jet Propulsion Laboratory, Pasadena, California.

A "soft" short is a leak through something that's partially conductive of electricity, rather than a hard short such as one electrical wire contacting another.

NASA said there had been a voltage difference between the chassis and the 32-volt power bus that distributes electricity on the rover. On Curiosity’s 456th Martian day, the rover sent back data that the voltage had fallen to 4 volts. The voltage level had been around 11 volts since the probe first landed on Mars.

The bus-to-chassis voltage was designed to be 16 volts. However another soft short caused by the explosive-release devices used to land the rover lowered it to 11 volts.  The lower voltage has not affected rover operations.

Soft shorts reduce the level of robustness for tolerating other shorts in the future, and they can indicate a possible problem in whichever component is the site of the short, NASA said. Operations planned for Curiosity for the next few days are designed to check some of the possible root causes for the voltage change. Analysis so far has determined that the change appeared intermittently three times during the hours before it became persistent.

The electrical issue did not cause the rover to enter a safe-mode status, in which most activities automatically cease pending further instructions. And there is no indication the issue is related to a computer reboot that triggered a "safe-mode" earlier this month.