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Asteroid Update
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| Asteroid Update |
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This Just In Wednesday January 31 2001 Craft To Land on an Asteroid By PAUL RECER, AP Science Writer WASHINGTON (AP) - Mission controllers, in history's first attempt to land a spacecraft on an asteroid, hope to drop the NEAR Shoemaker craft to a soft landing on Eros, a barren space rock. The Feb. 12 maneuver will not be easy: The craft was not designed to land. If all goes perfectly, the 1,100-pound craft will drop from its asteroid orbit and slide gently onto Eros' rocky surface, perhaps bouncing slightly before resting on its side. Officials said Wednesday they hope the craft's antenna will still point toward Earth after landing, and its solar power panels will make electricity. That would allow the robot craft to send back a beacon signal. If the landing maneuver should fail, officials said the NEAR could smash into Eros and be forever silent. ``If the burns (braking rocket firings) don't go properly, it would hit at about 20 miles per hour,'' said Robert Farquhar, the NEAR mission director. ``That would do us in.'' Farquhar said the ideal result would be for the spacecraft to drift to surface contact at the speed of 2 to 7 mph. ``That would be a soft impact,'' he said. Farquhar, a former paratrooper, said the World War II parachutes he used descended at about 7 miles an hour, a survivable jolt. ``If you were an Erosian watching this thing come in, it would have a velocity about that of a walking individual,'' said Ed Weiler, NASA (news - web sites)'s chief scientist. Landing on an asteroid has never been attempted before and is exquisitely tricky. Eros, a potato-shaped object about 21 miles long, has gravity just one-thousandth that of Earth. If NEAR hits at a wrong angle or speed, it could bounce off the asteroid back into space or smash to bits on the rock. A series of six braking rocket firings will drop the craft from a 15.5-mile orbit and slow its descent. The last of the firings must be done automatically, based on instructions stored in the craft's computer. NEAR is so far from Earth that it takes 35 minutes for a roundtrip radio signal. NEAR is shaped like a tin can. Attached to its top is a dish antenna surrounded by four solar panels, rather like a flower with four petals. When the craft lands, Farquhar said, it could tip into an ``ostrich mode'' which would bury the antenna and the solar panels. That, most likely, would silence the craft, he said. However, if it stops in a tripod-like stance, supported by two solar panels and the bottom of the craft, then it could continue transmitting a beacon signal for several months, he said. NEAR was launched Feb. 17, 1996, into an independent solar orbit. It swung by the Earth once to pick up speed and then streaked outward toward Eros, an asteroid in an elongated orbit that swings out to near Mars and back close to Earth's orbit. In December 1998, a rocket firing designed to slow the craft and put it into orbit of Eros failed and NEAR sped past the asteroid. A second rocket firing series was successful and the spacecraft eventually slipped into its orbit of Eros, named for the Greek god of love, on Valentine's Day, Feb. 14, 2000. The craft has spent the last year snapping photos of Eros, the 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 has been a total success story,'' said Ed Weiler, NASA chief scientist. It was the first spacecraft to orbit an asteroid and the first craft to operate on solar power so far from the sun. NEAR gathered about 160,000 images of Eros, about 10 times more than planned. The whole project was built and operated under a faster-better-cheaper philosophy developed at NASA. Under the direction and control of the Johns Hopkins University Applied Physics Laboratory, it took only 26 months to design, build and launch the craft. NEAR is also the first deep-space mission to be operated by a non-NASA space center. The mission cost $223 million, a modest amount by space-exploration standards. Weiler said NEAR has significantly advanced the scientific understanding of asteroids, knowledge that could one day be invaluable for the Earth's safety. He noted that it was an asteroid ``that caused some bad days'' for the dinosaurs. A large asteroid smashed to Earth 65 million years ago and is thought to have caused the extinction of the dinosaurs. Such an asteroid impact on Earth could happen again, said Weiler. ``We consider it our responsibility to learn as much as we can about these objects,'' he said. - Monday September 18, 2000 Scientists Eye Dangerous Asteroids By IAN PHILLIPS, Associated Press Writer LONDON (AP) - They may only strike every 100,000 years on average, but life-threatening asteroids could be heading Earth's way, and scientists said Monday they want a closer look. A panel set up this year by the British government to assess the risk of asteroids slamming into the planet called for an international program to build a powerful $22.5 million telescope in the southern hemisphere. ``The risk is very real - and very tiny - but with awful consequences, and we ought to be doing something about it,'' said Sir Crispin Tickell, Britain's former ambassador to the United Nations (news - web sites) and a member of the panel, which published its report on Monday. Although millions are already being spent trying to track Near Earth Objects, or NEOs, scientists acknowledge they're very much in the dark. Asteroids near Earth travel at between 10 and 20 miles per second, making them hard to detect. As a result, scientists watch their orbits to predict their expected course. According to the U.S. space agency NASA (news - web sites), at the beginning of 2000, only about half the estimated 500-to-1,000 near-Earth asteroids measuring half a mile across or larger - big enough to cause a global catastrophe - had been detected. The proposed 10-foot telescope would see further and wider and be able to pick up the faintest of glows, the panel said. Operated robotically, it would supplement the coverage of other telescopes in operation in the northern hemisphere. ``It's a question of giving ourselves a chance,'' said Robert Massey, an astronomer at Britain's Royal Observatory in Greenwich. ``We would be able to spot trouble 10 to 100 years away and could take steps accordingly.'' ``On the other hand, if it were a year away, probably the best we could do would be to duck,'' Massey said. Objects hitting the Earth have caused devastating damage over millions of years. One impact off the coast of what is now Mexico 65 million years ago is thought to have led to the extinction of the dinosaurs. Another impact in 1908 in Siberia knocked down trees with its shock waves over hundreds of square miles. The report listed nine objects that have come within two lunar distances of the Earth - about 497,120 miles - since 1991. In May 1996, an object 984 feet wide, called JA1, came as close as about 298,000 miles to the planet. It also called for further study into how to destroy a sizable object on a collision course with the planet. One possibility is a nuclear explosion by the side of an asteroid to divert it from its course. Recent Hollywood blockbusters ``Armageddon'' and ``Deep Impact'' have heightened public awareness about asteroid disasters. NASA has already earmarked more than $1 billion to gain a better scientific understanding of asteroids, which are rocky or metallic bodies hurtling through space mostly in a band between Jupiter and Mars. One British lawmaker, whose grandfather had an asteroid named after him to acknowledge his lifelong campaign to warn of impending disaster, welcomed Monday's proposal. ``We are playing Russian roulette with the future of the planet if we do nothing about it,'' said Lembit Opik. ``It would be a bit like Armageddon, but probably we would not want to send Bruce Willis.'' The panel is chaired by Dr. Harry Atkinson, formerly of the Science and Engineering Research Council and a past chairman of the European Space Agency's council. |
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