10:50 AM
LAUREL, Maryland - The space probe NEAR Shoemaker set down on the asteroid Eros this morning, the first time in history that any craft has landed on this kind of space rock.
Against tremendous odds, the craft kept sending signals even after it touched down on the cosmic object, 196 million miles from Earth.
"I'm happy to report that the NEAR spacecraft has touched down on the surface of Eros," a jubilant mission director, Robert Farquhar, announced from the control room in Laurel, outside Washington.
"We are still getting some signals, so evidently it's still transmitting from the surface itself," Farquhar said. "The pictures are still coming in. This is the first time that any spacecraft has landed on a small body."
Farquhar and other scientists had given the craft less than a 1 per cent chance of being able to send signals back to Earth, after it reached the asteroid's boulder-strewn surface.
The landing - some NASA officials dubbed it a controlled crash - took place almost exactly on schedule shortly after 9 am today (NZ time). But it will take years for astronomers to analyse all the data provided by this bus-sized $223 million robotic craft.
NEAR was never meant to land - it orbited the 21-mile-long asteroid for a year, taking some 160,000 images and beaming them back to Earth - but it was at the end of its expected life and had satisfied all its objectives, so Farquhar and others decided a landing attempt could provide some "bonus science."
To get the solar-powered ship out of its 21-mile-high orbit, thrusters were fired around 4:30 am NZ time to send it toward the asteroid. Four subsequent braking burns aimed to slow the craft to a soft landing.
The braking burns were to bring NEAR to a speed ranging from 3 to 11 kmh - or as slow as about 1 metre per second. The asteroid rotates faster than that, and because there are boulders, hills and valleys on the Erosian surface, it was possible that the asteroid could slam into the spacecraft before it had completely descended.
Because it takes 17.5 minutes for light to travel from the craft to Earth, scientists had little information at the time of touchdown, except that the craft was still functioning.
Ed Weiler, the head of space science at NASA, hesitated to even call the event a landing; without landing gear on the craft, he maintained, NEAR could only end in a controlled crash.
"We cannot measure NEAR's success by whether we hear it or not after it lands, because we do not expect to hear it," Weiler said in a conversation with reporters. The most scientists should hope for is a faint signal that the craft is still "alive," Weiler said, and even this was highly unlikely.
The spacecraft's camera was to go out of focus at about 100 to 450 metres, Weiler said, but even so, its last pictures were expected to have a resolution of about 10 cm.
Weiler was basking in the success of the mission, which he said would give space voyagers practice for future landings on asteroids and even on comets. Asteroids and comets are primordial bodies that could give clues to the very beginning of the solar system.
NEAR Shoemaker - short for Near Earth Asteroid Rendezvous and in honour of the late astronomer Gene Shoemaker - could have been flattened on impact if manoeuvres went awry. But even if that had occurred, the mission had accomplished its objectives of getting a close look at Eros.
It took NEAR about four years to travel a 3.2 billion-mile, looping route to Eros, named for the Greek god of love. At a cost of $223 million, the mission is considered a model for the cheaper, faster space flights envisioned by NASA.
The National Aeronautics and Space Administration rated the mission a success for the data it collected about Eros, a so-called near-Earth asteroid that has the potential to collide with the planet in 1.5 million years or so.
If Eros ever did hit Earth, the results would be catastrophic; indeed, a much smaller space rock is thought to have been responsible for wiping out the dinosaurs 65 million years ago.
Astronomers are also interested in the composition of this rock because it is probably a remnant from the formation of the rocky inner planets of our solar system some 4.5 billion years ago.
- REUTERS
Surface photo from the asteroid Eros
NASA
Space probe makes history by landing on asteroid
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