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NASA rover appears to survive descent to Mars

Posted on: Sunday, 4 January 2004, 06:00 CST

NASA rover appears to survive descent to Mars

Probe emits brief signal as it bounces on planet's surface

By THOMAS H. MAUGH II AND CHARLES PILLER Los Angeles Times

Sunday, January 4, 2004

Pasadena, Calif. -- NASA's rover Spirit apparently survived its fiery plunge through the thin Martian atmosphere Saturday evening, emitting a brief tone at 11:35 p.m. EST, indicating that it was bouncing on the surface at its Gusev Crater landing site.

Cheers and clapping erupted in the control room at Pasadena's Jet Propulsion Laboratory as landing manager Rob Manning announced, "We have signs of bouncing on the surface."

But the team lost the signal again as the rover continued to bounce, pointing its small antenna away from the Earth.

JPL officials weren't overly concerned because they had previously estimated that there was only about a 40% chance that they would hear from the craft on landing. Success depended on whether the tiny antenna on the craft's 15-watt transmitter ended up pointing in the general direction of Earth.

NASA's massive antenna farms at Goldstone in the Mojave Desert and in Canberra, Australia, were straining to hear the faint tones emitted by the probe.

In a precisely timed ballet, NASA's Mars Global Surveyor orbiter was flying over the Gusev Crater landing site at touchdown time, and it had about the same chance of contacting the rover. It too did not receive a signal.

The lack of a signal does not mean that the landing failed, said JPL's Jennifer Trosper, who is in charge of surface operations. It may simply mean that it has taken the craft longer than expected to right itself after the landing.

There will be more chances for contact Sunday. Later, after Earth has risen in the Mars sky, Spirit will again have the opportunity to communicate directly to Earthbound antennas.

"If we don't hear from Spirit by late Sunday night, there is a high probability of failure," said Ed Weiler, NASA's associate administrator for space sciences.

"We will not drag this out for weeks," he said. "It would wreak havoc on our ability to prepare for the second lander."

That lander, Opportunity, is scheduled to land on Mars on Jan. 24. Scientists say they will try to enhance its chances of survival by using information from Spirit's descent.

Spirit is the most ambitious effort yet to roam the surface of another planet. It is part of a small fleet of spacecraft sent toward Mars in an effort to answer one of the most captivating questions in science: Has there been life on other planets?

Spirit and its twin, Opportunity, are the most sophisticated of the spacecraft, and hopes are high that they will provide a bounty of information.

The stakes are even higher because NASA's last two Mars missions, the Mars Climate Orbiter and the Mars Polar Lander, failed in 1999. A third mission planned for 2001 was canceled when outside reviewers concluded the agency was attempting too much with too few resources.

The two new missions, costing $820 million, have consumed the energy of hundreds of scientists and engineers for the last four years.

A planned last-minute course correction proved unnecessary because the craft was already on a "bull's-eye" course for its targeted landing site in Gusev Crater.

"This is essentially perfect navigation," said JPL's navigation team chief, Louis D'Amario.

But the team did have to make some last-minute adjustments in the landing program to take into account a dust storm on the opposite side of Mars.

Because dust absorbs more sunlight than the planet's surface, Mars' upper atmosphere was about 10% to 15% warmer and thinner than normal, said mission manager Mark Adler.

The lander's parachute was reprogrammed to open 13 or 14 seconds earlier than originally planned to ensure that the craft didn't crash into the surface, he said.

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