[meteorite-list] Mars Exploration Rover Mission Status - October 5, 2004

[Ron Baalke]

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109.  TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov 

Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Don Savage (202) 358-1727
NASA Headquarters, Washington

News Release: 2004-249            October 5, 2004

Mars Exploration Rover Mission Status

Engineers on NASA's Mars Exploration Rover team are 
investigating possible causes and remedies for a problem 
affecting the steering on Spirit.

The relay for steering actuators on Spirit's right-front 
and left-rear wheels did not operate as commanded on Oct. 1. 
Each of the front and rear wheels on the rover has a steering 
actuator, or motor, that adjusts the direction in which the 
wheels are headed independently from the motor that makes the 
wheels roll. When the actuators are not in use, electric 
relays are closed and the motor acts as a brake to prevent 
unintended changes in direction.

Engineers received results from Spirit today from a first 
set of diagnostic tests on the relay.  "We are interpreting 
the data and planning additional tests," said Rick Welch, 
rover mission manager at NASA's Jet Propulsion Laboratory, 
Pasadena, Calif. "We hope to determine the best work-around 
if the problem does persist."

Spirit and its twin, Opportunity, successfully completed 
their three-month primary missions in April and five-month 
mission extensions in September. They began second extensions 
of their missions on Oct. 1. Spirit has driven more than 3.6 
kilometers (2.2 miles), six times the distance set as a goal 
for mission success. It is climbing into uplands called the 
"Columbia Hills."

JPL's Jim Erickson, rover project manager, said, "If we do 
not identify other remedies, the brakes could be released by 
a command to blow the fuse controlling the relay, though that
would make those two brakes unavailable for the rest of the 
mission." Without the steering-actuator brakes, small bumps 
or dips that a wheel hits during a drive might twist the 
wheel away from the intended drive direction.

"If we do need to disable the brakes, errors in drive direction 
could increase. However, the errors might be minimized by 
continuing to use the brakes on the left-front and right-rear
wheels, by driving in smaller segments, and by adding a 
software patch to reset the direction periodically during a 
drive," Erickson said. Engineers believe the steering-brake 
issue is not related to excessive friction detected during 
the summer in the drive motor for Spirit's right-front wheel, 
because the steering actuator is a different motor.

Meanwhile, the team continues to use Spirit's robotic arm and 
camera mast to study rocks and soils around the rover, without 
moving the vehicle until the cause of the anomaly is understood
and corrective measures can be implemented.

JPL, a division of the California Institute of Technology in 
Pasadena, manages the Mars Exploration Rover project for NASA's 
Science Mission Directorate, Washington.

Additional information about the project is available from JPL at

 http://marsrovers.jpl.nasa.gov/ 

and from Cornell University, Ithaca, N.Y., at

 http://athena.cornell.edu .

-end-