Mars rover Curiosity on course to land Monday

PASADENA, Calif. — After a journey of 354 million miles, a spacecraft approaching Mars at 13,200 mph is on course to land inside its sweet spot early Monday.

The landing is one of the riskiest ever tried, and the descent is what NASA officials call “seven minutes of terror.”

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The Washington Post’s Marc Kaufman, author of “Mars Landing 2012: Inside NASA’s Curiosity Mission,” explains why the Curiosity mission to Mars is being hailed by NASA’s chief scientist as the “mission of the decade.”

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NASA’s Mars Curiosity: 11 things you may not know: A multibillion dollar gamble, a most scary landing and possibly learning whether Mars once could have supported life — briefly, that’s what’s at stake in NASA’s Mars Curiosity mission.

Nonetheless, the spacecraft carrying the Mars rover Curiosity is on target “to fly through the eye of the needle” and touch down within its five-by-13-mile landing elipse, said Arthur Amador, mission manager of the Mars Science Laboratory. “We’re . . . in as good shape as we could hope for.”

Yet with so much riding on the $2.5 billion mission, he said at a news conference, “we’re often reminding each other to keep breathing.”

The spaceship is on course to enter the Martian atmosphere at 1:24 a.m. Eastern time on Monday.

Because the rover is so much larger, more complicated and more ambitious than earlier models, it has to land in a new and far more hazardous way. The landing, which could never be tested in full on Earth, includes a hovering rocket stage, a kind of sky crane, to lower it to the ground. NASA’s chief scientist John Grunsfeld has said that because of that heightened landing difficulty, in addition to the unprecedented sophistication of the instruments on board, Curiosity is “the most important NASA mission of the decade.”

Anxious engineers and scientists will be waiting for a touchdown “beep” — which comes as computer code — that will report a safe landing. It could come as early as 1:31 a.m.

Several hours of silence from Curiosity are quite possible, officials said, since the rover’s signals can be received only if the Mars orbiters that will relay its messages are in precisely the correct location.

But if nothing is heard from the orbiters or through the Deep Space Network after about 18 hours, said MSL deputy project manager Richard Cook, then it’s time to start worrying about the fate of the mission.

The Curiosity landing is shaping up to be an international spectacle. Formal “landing” parties have been scheduled from South Australia to Rome, from Israel to Crete; and in the United States from Atlanta to Seattle, Milwaukee to Honolulu.

NASA also has helped organize a landing gathering in New York’s Times Square, which will feature a large screen that will beam the streaming news from atop a building and high above the crowd.

Reaching, orbiting and landing on Mars is notoriously hard. In addition to the European Space Agency, nations including the United States, the former Soviet Union, Russia, China and Japan have sent missions to Mars since the late 1960s, but only about one-third of them have succeeded.

The United States is the only nation to land a vehicle on Mars and complete its mission, having done it six out of seven tries.

The Soviet Union was the first to touch down on the Martian surface, but that 1971 mission ended 14 seconds later when all communication ceased.

NASA’s confidence in the mission is reflected in the aggressive way it’s trying to bring it to the public, from landing-based X-box games to those many parties.