NASA eyes lasers to divert asteroids

By DEE ANN DIVIS, Science and Technology Editor   |   Oct. 23, 2002 at 9:47 AM

HOUSTON, Oct. 18 (UPI) -- Although there is only a remote chance an asteroid will strike Earth in the near future, the spectacular crash of the Shoemaker-Levy comet into the planet Jupiter in 1993 and a razor-thin miss between an asteroid and Earth only last year have sharpened attention on work NASA has been doing to prevent impacts and their devastating results.

Even a small asteroid or comet only about 100 meters across could cause tremendous damage. An asteroid of that size flattened 2,000 square miles of forest in Siberia in 1908. Though there is only a 1-in-250,000 chance of impact, an asteroid roughly 1.2 kilometer across -- big enough to destroy a continent on impact -- is expected to pass near Earth on Feb. 1, 2019.

It was a comet that did hit -- actually a string of comet fragments -- that really caught the world's attention. When comet Shoemaker-Levy struck about 10 years ago, scientists had a ring-side seat as it tore planet-size holes in the golden surface of Jupiter in a series of impacts -- impacts big enough to destroy Earth.

"I think it made an impression," Jonathan Campbell, a NASA researcher at Marshall Space Flight Center, told United Press International.

There are roughly 1,000 to 2,000 Earth-orbiting asteroids in the 1-to-10-kilometer class -- that is, if they were a smooth ball instead of large lumpy rocks they would be about 1 km across. There are far more smaller asteroids, about 200,000 in the 100-meter class.

Campbell, whose work at NASA is part of Marshall's new National Space Science and Technology Center, is studying the use of lasers to shift the orbit of such dangerous asteroids. Carlos Roithmayr, a scientist at NASA's Langley Research Center in Hampton, Va., also is looking at lasers. Both scientists have presented their projects to attendees at the World Space Congress.

The lasers could divert -- not destroy -- the threatening rocks, the scientists said. Pulses from the laser would heat an asteroid's surface to the point where a small part of the surface explodes. The explosion does not remove enough of the asteroid to render it harmless, but it does give it a tiny kick to one side. A long series of such little kicks would be enough to push an asteroid off a collision course with Earth.

Campbell suggested basing a laser either on the Moon or at one of the libration points -- spots in space where the gravity of Earth and the Sun cancel each other out and laser-carrying spacecraft could sit relatively motionless. Roithmayr said he envisions an option where a laser-bearing spacecraft would travel to asteroids and use their lasers to turn them aside.

Either system would require extensive advance notice, however, because the lasers would need to fire continuously at an asteroid for a month or two -- at least to divert it. Such notice involves scanning the skies constantly with telescopes to identify and map the orbits of asteroids and comets zooming too near our planet.

One good place to place such telescopes would be the moon. Roithmayr described the Comet/Asteroid Protection System, or CAPS, which would include, as part of an overall protection system, a set of telescopes, each with apertures larger than 3 meters, placed on the moon. The large telescopes could be placed on tracks to allow them to be configured more flexibly.

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