[meteorite-list] Curiosity Rover Team Working to Diagnose Electrical Issue

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 20 Nov 2013 12:36:12 -0800 (PST)
Message-ID: <201311202036.rAKKaCdK006055_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2013-337

Rover Team Working to Diagnose Electrical Issue
Jet Propulsion Laboratory
November 20, 2013

Mars Science Laboratory Mission Status Report

Science observations by NASA's Mars rover Curiosity have been suspended
for a few days while engineers run tests to check possible causes of a
voltage change detected on Nov. 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, Calif.

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.

The team detected a change in the voltage difference between the chassis
and the 32-volt power bus that distributes electricity to systems
throughout the rover. Data indicating the change were received on
Sunday, during Curiosity's 456th Martian day. The level had been about
11 volts since landing day, and is now about 4 volts. The rover's
electrical system is designed with the flexibility to work properly
throughout that range and more -- a design feature called "floating bus."

A soft short can cause such a voltage change. Curiosity had already
experienced one soft short on landing day in August 2012. That one was
related to explosive-release devices used for deployments shortly before
and after the landing. It lowered the bus-to-chassis voltage from about
16 volts to about 11 volts but has not affected subsequent 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. 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.

NASA's Mars Science Laboratory Project is using Curiosity inside Gale
Crater to assess ancient habitable environments and major changes in
Martian environmental conditions. JPL, a division of the California
Institute of Technology in Pasadena, built the rover and manages the
project for NASA's Science Mission Directorate in Washington.

More information about Curiosity is online at
http://www.jpl.nasa.gov/msl , http://www.nasa.gov/msl and
http://mars.jpl.nasa.gov/msl/ . You can follow the mission on Facebook
at: http://www.facebook.com/marscuriosity and on Twitter at:
http://www.twitter.com/marscuriosity .

Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

2013-337
Received on Wed 20 Nov 2013 03:36:12 PM PST


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