Anxiety over rover's Hollywood-style Mars landing

[August 04, 2012]  PASADENA, Calif. (AP) -- Seven minutes of terror.

It sounds like a Hollywood thriller, but the phrase describes the anxiety NASA is expecting as its car-sized robotic rover tries a tricky landing on Mars late Sunday.

Skimming the top of the Martian atmosphere at 13,000 mph, the Curiosity rover needs to brake to a stop -- in seven minutes.

The rover is headed for a two-year mission to study whether Mars ever had the elements needed for microbial life. Because of its heft, the 2,000-pound robot can't land the way previous spacecraft did. They relied on air bags to cushion a bouncy touchdown. This time NASA is testing a brand new landing that involves gingerly setting down the rover similar to the way heavy-lift helicopters lower huge loads at the end of a cable. How hard is it? "The degree of difficulty is above a 10," says Adam Steltzner, an engineer at NASA's Jet Propulsion Laboratory, which manages the mission.

And American University space policy analyst Howard McCurdy says: "It would be a major technological step forward if it works. It's a big gamble."

A communication time delay between Mars and Earth means Curiosity will have to nail the landing by itself, following the half-million lines of computer code that engineers uploaded to direct its every move.

After an 8 1/2-month, 352-million-mile journey, here's a step-by-step look at how Curiosity will land:

• Ten minutes before entering the Martian atmosphere, Curiosity separates from the capsule that carried it to Mars.

• Turning its protective heat shield forward, it streaks through the atmosphere at 13,200 mph, slowing itself with a series of S-curves.

• Seven miles from the ground at 900 mph, Curiosity unfurls its enormous parachute.

• Next it sheds its heat shield and turns on radar to scope out the landing site. Now it's 5 miles from touchdown and closing in at 280 mph.

• A video camera aboard Curiosity starts to record the descent.

• A mile from landing, the parachute is jettisoned.

• Curiosity is still attached to a rocket-powered backpack, and those rockets are used to slow it to less than 2 mph.

• Twelve seconds before landing, nylon cables release and lower Curiosity. Once it senses six wheels on the ground, it cuts the cords. The hovering rocket-powered backpack flies out of the way, crashing some distance away.

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Online:

NASA's Mars site: http://mars.jpl.nasa.gov/

NASA's YouTube video "Seven Minutes of Terror":
http://www.youtube.com/watch?vKi-Af-o9Q9s

[Associated Press; By ALICIA CHANG]

Follow Alicia Chang's Mars coverage at http://twitter.com/SciWriAlicia.

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