- The Washington Times - Saturday, April 9, 2005

NASA’s two Mars exploration rovers - Spirit and Opportunity - have defied all expectations by lasting much longer than expected after landing on Mars in January 2004 with an anticipated lifetime of about three months.

And they continue to work.

“We are extending their mission through September 2006 to take advantage of having such capable resources still healthy and in excellent position to continue their adventures,” said NASA manager Ghassem Asrar.

In two previous cases, NASA authorized five-month extensions to the mission, budgeting $15 million per extension. This time NASA authorized an 18-month extension, and if both rovers last the entire year and a half it would come to $52.8 million.

That money pays for about 100 personnel at the Jet Propulsion Laboratory in California, scientists around the country and maintenance for equipment. The original cost for the design, development and launching of the two spacecraft was $820 million.

Spirit, scientists say, actually is in better shape now than it was a month ago.

One of the key limiting factors that determines the rovers’ performance is the amount of dust that builds up over time on their solar arrays. As dust accumulates it reduces the amount of sunlight on the arrays and the power that is generated.

Mars scientist Steve Squyres said before the launch that a windstorm on Mars could remove the dust and rejuvenate the solar arrays. Opportunity had such an event earlier, permitting it to travel farther and perform more science than Spirit.

Spirit’s cleaning event occurred April 9, giving it more power.

“We’ve doubled our power,” said mission manager Emily Eelkema. “It has given us extra hours of operations every day, so we can drive longer and we’ve used more time for observations.”

It’s going to need the power since it’s traveling up hilly slopes - up to a 20 degree grade. Spirit is exploring Husband Hill, named after astronaut Rick Husband who died in the space shuttle Columbia accident.

“This is very tough terrain; the rover was not designed for this stuff at all,” Mr. Squyres said. “The hard part is it’s very rugged terrain; there’s lots of slippery spots.”

Sometimes rover engineers will send instructions to go forward by a certain amount and then find out that the rover did move forward, but then slipped backward near the spot where it started.

The rovers have shown some signs of aging. One of the scientific instruments uses a radioactive source for its detector. A scientific measurement that took four hours when the rover landed on Mars now takes twice as long.

“Either mission could end tomorrow with a random part failure,” said rover project manager Jim Erickson. “We’re going to work them hard to get as much benefit from them as we can, for as long as they are capable of producing worthwhile science results.”

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