MOUNTAIN VIEW, Calif MOUNTAIN VIEW, Calif. -- Taking a "rest stop" on another world.
That is the final assignment for NASAs Near Earth Asteroid Rendezvous (NEAR) Shoemaker spacecraft. The first asteroid touchdown in history is slated for Feb. 12 as NEAR Shoemaker attempts to gently drop itself onto the battered and boulder-strewn surface of Asteroid 433 Eros.
Scientists and engineers said Jan. 31 at a NASA press conference held in Washington, D.C. that all is ready for the touchdown. They underscored the fact that, because NEAR is not built to land, chances are slim that the probe will survive and continue to operate after the controlled descent.
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The probe is ready to camera click its way down to the surface, drawing to a close NEAR Shoemakers one-year-long mission. Digital images snapped during the attempted soft landing are expected to be five to 10 times better than anything received from the craft to date.
"We have an opportunity here for unprecedented bonus science,"
said Robert Farquhar, NEAR mission director at The Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. APL designed, built and is managing the NEAR mission for NASA."We have an ambitious plan to do a controlled descent onto Eros surface. Its a complicated and risky operation," Farquhar said.
Go out with a bang
NEAR Shoemaker has been orbiting Eros for almost a year, circling the giant hunk of space flotsam since Feb. 14, 2000.
As the first launch in NASAs Discovery program of low-cost planetary missions, the spacecraft has been
a literal "picture book" project. It has sent back well over 150,000 photos of the potato-shaped space rock that is about the size of the island of Manhattan in New York City.Furthermore, the probe has made millions of laser range finder measurements to establish Eros shape. X-ray/Gamma Ray Spectrometer equipment aboard the robot has provided unique data sets. NEAR's instruments and camera surveys have confirmed that Eros is a consolidated, primitive sample from the solar systems beginnings.
NEAR has recently completed a four-day series of flyovers of Eros, ending with the craft zipping over the asteroid on Jan. 28 at a distance of less than 2 miles (2.74 kilometers). The daring pass was the closest any spacecraft has come to an asteroid. The probe then swung out to a higher orbit around Eros, where it is staying until the controlled descent on Feb. 12.
Farquhar said that the primary goal of dropping onto the asteroid is to produce spectacular up-close-and-personal pictures of Eros during the last maneuver. The secondary goal is to soft land on the surface at a speed of 7 miles per hour (3 meters per second), and not go out with a bang by crashing, he said.
Settle down now
NEAR Shoemakers telescopic camera is set to image Eros as the craft approaches, until about 1,650 feet (500 meters) above the asteroid.
The spacecraft is being targeted to settle down near Eros distinctive "saddle" depression that is 6.2 miles (10 kilometers) in size. Images taken during the final moments should show significant detail of rocks and boulders.
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"Were out of money for operations. Were out of Deep Space Network tracking time. And were almost out of fuel," Farquhar said.
"This will be the first time that the United States has been to another body where we are the first ones to land," Farquhar said, ticking off earlier first robotic touchdowns on the Moon, Venus and Mars done by the former Soviet Union.
Could the spacecraft survive its encounter and broadcast data directly from Eros surface?
"NEAR was not designed to land. That is really problematical. The chances are less than 1 percent. We have hope...but thats about it," Farquhar told SPACE.com. "The only risk is not taking one."
"NEAR is a total success story, said Edward Weiler, NASA associate administrator for space science. "Its done the science it needed to do," he said.
Weiler said NEAR has returned 10 times more data than originally planned. Taking only 26 months to design and build, NEARs total mission price tag is $223 million, he said.
"For me, this mission has been a thrill of a lifetime," said Andrew Cheng, NEAR project scientist at APL. "Its been 10 years of my life and worth every moment," he said.
Cheng said Eros could be a source of
some class of meteorites recovered on Earth, although no connection has been firmly made.A mystery uncovered by NEAR is the nature of the regolith, busted up material that covers the surface of the asteroid. "When we get up close, we see very small craters, but a very large number of boulders. How the surface got that way is very much a mystery," Cheng said.
Jessica Sunshine, staff scientist at Science Applications International Corporation in Chantilly, Virginia said that studies of asteroids and comets are
windows into the early solar system.Sunshine said there were several unexpected results from the mission. "Eros is very bland in terms of its color, and thats surprising," she said. "To be honest, we dont quite understand why this is the case."
"Eros has become our frame of reference as we compare asteroids and comets" in the future, Sunshine said.
At missions end, NEAR will have looped Eros for 230 times, providing an unequaled view of the celestial body.
Eros has been found to be heavily cratered, full of cliffs and has craters filled with thick debris. Thousands of huge boulders litter the asteroids surface, said Mark Robinson, imaging team member at Northwestern University in Evanston, Illinois.
NEAR Shoemaker "is a really good start on understanding the early solar system," said Robinson.
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