Rover Works with Bad Arm

As we get older we find our joints don't work as well as they once did. Our minds may still be able to contain and understand knowledge, but our body's motor is not quite functioning as it once did. And so it is with the soon-to-be Martian-year-old Mars Rover, Opportunity.

Opportunity, one of two Rovers launched one Martian year ago, has a bad arm. A Martian year is equivalent to 687 Earth days. Opportunity has traveled about 6,446 meters, a little more than four miles, since its landing. On the weekend of Nov. 26 scientist noticed a problem with extending Opportunity's arm.

"We don't know what the problem is," said John Callas, deputy project manager of Mars Exploration Rover Project at JPL. "The robotic arm is the most complex piece of the rover."

Callas said his team is working on analyzing the arm's problem with special attention being paid to the motor. The arm is not moving at all, when it stalls usually the motor is drawing its maximum current but that is not happening in this case, he said.

On Wednesday the team will be trying to see if the motor can spin. They have done a few tests so far and will attempt to change the voltage that gets applied to the motor to see if it moves it. They will not know the results until late Friday or next week.

In addition to traversing the Martian landscape, the rovers have had to endure extreme Martian temperature changes from daily averages of 0 degrees Celsius to a negative 100 degrees Celsius at night. Despite the sand, the winds, and the temperature, Callas does not believe the arms defect is from the environment, however, nothing has been ruled out yet, Callas said.

At a year old, Opportunity has gone above and beyond all expectations. Both rovers have gone over seven times their mission design, Callas said, he compared the break down in Earthly terms.

"Think about that old car in your driveway with over 100,000 miles on it. The air conditioner breaks down and the CD player broke down a long time ago," Callas said.

Scientist however are continuing to repair Opportunity. The arm has been of great value to scientist.

"It is like a field geologist," Callas said.

The arm has four robot instruments, one is a microscope, the second is a spectrometer for chemical, the third for mineral. And the fourth is a rock abrasion tool. If they are used completely, it would make a difference in the science they are discovering.

As of press time, Opportunity is on the edge of the crater Erebus where scientist had planed to do some measurements and then move on to the large crater name Victoria.

Callas hopes that if they cannot get the arm to work as it once did they will be able to at least extend the arm so they can continue some of its robotic function. If the arm does not respond to any of the repair attempts, Opportunity will still continue to explore on the Martian service.

"We can do a huge amount of exploration. We can do a tremendous amount of observing," Callas said.