[meteorite-list] Curiosity Rover Resumes Science After Analysis of Voltage Issue

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 25 Nov 2013 13:23:47 -0800 (PST)
Message-ID: <201311252123.rAPLNmlx023156_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2013-340

Curiosity Resumes Science After Analysis of Voltage Issue
Jet Propulsion Laboratory
November 25, 2013

Mars Science Laboratory Mission Status Report

NASA's Mars rover Curiosity resumed full science operations on Saturday,
Nov. 23.

Activities over the weekend included use of Curiosity's robotic arm to
deliver portions of powdered rock to a laboratory inside the rover. The
powder has been stored in the arm since the rover collected it by
drilling into the target rock "Cumberland" six months ago. Several
portions of the powder have already been analyzed. The laboratory has
flexibility for examining duplicate samples in different ways.

The decision to resume science activities resulted from the success of
work to diagnose the likely root cause of a Nov. 17 change in voltage on
the vehicle. The voltage change itself did not affect the rover safety
or health. The vehicle's electrical system has a "floating bus" design
feature to tolerate a range of voltage differences between the vehicle's
chassis -- its mechanical frame -- and the 32-volt power lines that
deliver electricity throughout the rover. This protects the rover from
electrical shorts.

"We made a list of potential causes, and then determined which we could
cross off the list, one by one," said rover electrical engineer Rob
Zimmerman of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Science
operations were suspended for six days while this analysis took priority.

The likely cause is an internal short in Curiosity's power source, the
Multi-Mission Radioisotope Thermoelectric Generator. Due to resiliency
in design, this short does not affect operation of the power source or
the rover. Similar generators on other spacecraft, including NASA's
Cassini at Saturn, have experienced shorts with no loss of capability.
Testing of another Multi-Mission Radioisotope Thermoelectric Generator
over many years found no loss of capability in the presence of these
types of internal shorts.

Following the decision to resume science activities, engineers learned
early Nov. 23 that the rover had returned to its pre-Nov. 17 voltage
level. This reversal is consistent with their diagnosis of an internal
short in the generator on Nov. 17, and the voltage could change again.

The analysis work to determine the cause of the voltage change gained an
advantage from an automated response by the rover's onboard software
when it detected the voltage change on Nov. 17. The rover stepped up the
rate at which it recorded electrical variables, to eight times per
second from the usual once per minute, and transmitted that engineering
data in its next communication with Earth. "That data was quite
helpful," Zimmerman said.

In subsequent days, the rover performed diagnostic activities commanded
by the team, such as powering on some backup hardware to rule out the
possibility of short circuits in certain sensors.

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

2013-340
Received on Mon 25 Nov 2013 04:23:47 PM PST