COLUMBIA, Md. -- The NEAR spacecraft touched down on the barren, rocky surface of Eros, successfully completing history's first landing on an asteroid.
NEAR's landing at about 3:05 p.m. EST Monday was confirmed when Mission Control received a beacon signal from the craft resting on the surface of Eros, some 196 million miles from Earth.
"I am happy to report that the NEAR has touched down," said Robert Farquhar, mission director. "We are still getting signals. It is still transmitting from the surface."
Engineers watching from monitors from Mission Control broke into applause at confirmation of history's first landing of a manmade object on an asteroid. The mission, controlled by the Johns Hopkins University Applied Physics Laboratory, also was the first into deep space operated by a non-NASA center.
NEAR flawless performed five rocket firings, starting Monday morning, to drop it out of a 15-mile orbit of Eros and slow it toward the surface. Early indications are that Mission control completed its plan to guide NEAR to a feather-like touchdown by slowing its velocity, relative to the surface of the asteroid, to about the speed of a fast walk, 3 to 5 miles an hour.
The landing completes a five-year, 2-billion-mile mission for the robot craft and boosts the technical experience in putting spacecraft on objects with extremely light gravity.
"This gives us a lot of practice," said Ed Weiler, NASA's chief scientist. "We'll eventually want to land on comets because they hold the clues to beginnings."
Weiler said the experience gained in the NEAR landing attempt on Eros can be applied in about a decade when NASA may launch a landing mission to a comet.
NEAR became the first spacecraft to orbit an asteroid when it arrived at Eros, an object named for the Greek god of love, on Valentine's Day last year. The mission had been scheduled to end on Wednesday, anniversary of achieving orbit.
Farquhar said it was decided to attempt the landing to squeeze a final bit of science out of the $223 million mission.
No matter how the landing attempt ended, Weiler said, earlier, NEAR was "a total success. It returned 10 times more data than expected."
Officials targeted NEAR to land on Eros at the edge of a deep depression called Himeros. Scientists picked this spot because it is thought to be on the edge of two different geologic formations.
During the final hours of its descent, NEAR furiously took pictures of Eros' surface as it drew closer and closer. Scientists hoped the final shots before impact would clearly show rocks as small as a fist, an unprecedented close-up view of an asteroid.
"In those final images, we'll be seeing objects that are just a few inches in resolution," said Andrew Cheng, chief project scientist of NEAR.
Farquhar had warned in advance that landing NEAR on Eros is exquisitely "tricky."
NEAR was not designed to land anywhere. Shaped like tin can attached to four solar panels, the craft was not equipped with wheels or braces to absorb the landing force.
Weiler commented, "This is not a landing. It is a controlled crash."
Eros has very light gravity, about one-thousandth that of Earth, which means that an object, such as NEAR, weighing 1,100 pounds on Earth, would weigh only slightly over a pound in the gravity field of Eros. A quarter, dropped from head-high on Eros, would take five seconds to fall to the surface.
Weiler said the final descent of NEAR was actually slower than the asteroid's rotation and there was risk that the spinning space rock could actually swat the craft back into orbit.
NEAR traveled more than 2 billion miles during its five-year mission. It was launched Feb. 17, 1996, into an independent solar orbit. NEAR swung by the Earth once to pick up speed and then streaked outward toward Eros, an asteroid in an elongated orbit that nears Mars and approaches Earth's orbit.
In December 1998, a rocket firing designed to put the craft into orbit of Eros failed and NEAR sped past the asteroid. A second rocket firing series was successful and the spacecraft eventually returned to Eros and slipped into history's first orbit of an asteroid.
The craft spent the last year snapping photos of Eros, second- largest of the asteroids that approach the Earth's orbit. The NEAR instruments also gathered information about the asteroid's composition, structure, size and shape.
NEAR was built and operated under a faster-better-cheaper space exploration philosophy developed at NASA. Under the direction and control of the Johns Hopkins University Applied Physics Laboratory, the spacecraft was designed, built and launched in just 26 months. Some deep space explorations have taken a decade or more to mount. NEAR is also the first deep-space mission to be operated by a non-NASA space center.
Mission site: http://near.jhuapl.edu/media/index.html
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