Keep the shuttle flying: Fwd: Curiosity Bounces Back from Electrical Glitch

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Subject: FW: Curiosity Bounces Back from Electrical Glitch

Curiosity Resumes Science After Analysis of Voltage Issue

This artist concept features NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or present ability to sustain microbial life. Image credit: NASA/JPL-Caltech
› Full image and caption
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@jpl.nasa.gov

2013-340

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Mars Rover Curiosity Bounces Back from Electrical Glitch
By Mike Wall, Senior Writer | November 26, 2013 07:46am ET
NASA's Mars rover Curiosity took this self-portrait, composed of more than 50 images using its robotic arm-mounted MAHLI camera, on Feb. 3, 2013. The image shows Curiosity at the John Klein drill site. A drill hole is visible at bottom left.
Credit: NASA/JPL/MSSS/Marco Di Lorenzo/Ken Kremer View full size image
NASA's Mars rover Curiosity is back in action after being sidelined for nearly a week by an electrical problem.
The 1-ton Curiosity rover resumed science operations on Saturday (Nov. 23), six days after mission engineers noticed an odd voltage change and stood the robot down to investigate.
"We made a list of potential causes, and then determined which we could cross off the list, one by one," rover electrical engineer Rob Zimmerman, of NASA's Jet Propulsion Laboratory in Pasadena, Calif., said in a statement.
The mission team eventually determined that the likely cause of the change in voltage was an internal short in Curiosity's radioisotope thermoelectric generator, which powers the rover by converting the heat of radioactive decay to electricity.
The electrical glitch shouldn't have any lasting effects, mission team members say.
"Due to resiliency in design, this short does not affect operation of the power source or the rover," NASA officials wrote in a Curiosity status update today (Nov. 25). "Similar generators on other spacecraft, including NASA's Cassini at Saturn, have experienced shorts with no loss of capability."
The voltage difference between Curiosity's chassis and power bus had been about 11 volts since the rover touched down inside Mars' Gale Crater in August 2012. On Nov. 17, engineers noticed that it had dropped to just 4 volts and called a halt to the rover's science operations in response. But the difference returned to 11 volts on Nov. 23, officials said.
Curiosity's main task is to determine if Mars has ever been capable of supporting microbial life. The mission has already answered that question in the affirmative, finding that a site in Gale Crater called Yellowknife Bay was indeed habitable billions of years ago.
Curiosity is now engaged in a long trek to the base of the towering Mount Sharp, whose many layers record a history of Mars' changing environmental conditions over time. The rover should reach Mount Sharp sometime around the middle of next year, mission team members have said.
In its return to science operations over the weekend, Curiosity used its robotic arm to deliver powdered rock to some of its onboard instruments. The rover had stored this powder in its arm since drilling into a target rock called "Cumberland" six months ago, NASA officials said.

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