NASA follows Mars successes with plans for $2B super rover

Pair of rovers on Martian soil among agency's most successful technology

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The Mars Spirit Rover has traveled 4.5 miles across the surface of the planet, while its counterpart, Opportunity, has ventured more than seven miles.

"It may not be that far for a person to walk, but try it holding your breath for four and a half years," said John Callas, project manager of the Mars Exploration Rover Project. "Remember, these rovers are hundreds of millions of kilometers away in a hostile environment, exploring. They operate autonomously on Mars."

Callas explained that in order for the rovers to accomplish their tasks, they have to be aware of their environment and then make judgments about it. To help them do that, they have many cameras arranged in stereo pairs to give them depth perception and a digital model of their world. They can calculate the size of rocks, the slope of the land and the distance to objects. They also are capable of deciding whether it's safe to go over a particular rock or if a slope in the ground is gentle enough to traverse.

"They do the same things we do with our eyes and brains when we're out walking," Callas told Computerworld.

Each rover runs on a single, radiation-hardened processor that's based on the PowerPC architecture. They're powered by an array of solar panels that feed energy into onboard rechargeable batteries. When the sun comes up, the machines wake up and go to work, and at the end of the day, they go back to sleep, saving their energy.

The problem, according to Callas, is dust, which accumulates on the solar arrays and could hinder them from capturing the sunlight they need. So far, though, wind has kept the dust from building up and becoming too much of a problem.

"Our greatest challenge was about a year ago, when they encountered a global dust storm that threatened to kill both [of the rovers]," said Callas, noting that the storm lasted about two months. "Without their solar power, they were at risk of freezing to death. We were able to manage the power very carefully and keep the rovers safe till the storm passed."

Banerdt noted that the two rovers have greatly extended scientists' understanding of Mars, and he's eager to get a third working machine up on Mars, especially one with five times the mass and more sophisticated equipment than the others.

"The rovers were designed to go down to the surface and look at the rocks, which contained evidence about the history of Mars," he said. "The minerals you find in a rock tell you a story about the environment in which the rocks were formed. ... The Mars rovers looked at the effects of water billions of years ago. We know there was quite a bit of water out there at that time. It maybe wasn't Earth-like, but it was more Earth-like than it is today.

"We can't say if life occurred there, but what we've been able to establish is that the conditions for life to survive were in place," he added.

The initial cost for the two 90-day rover missions rang in at about $650 million, according to Banerdt, who added that NASA is spending about $20 million annually to operate them. He estimated that the entire price tag for Spirit and Opportunity will be about $800 million.

Copyright © 2008 IDG Communications, Inc.

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