A NEAT Search for Nearby Asteroids

SAN DIEGO--An automated telescope built to track satellites is helping astronomers pick up the pace of finding asteroids that approach Earth's orbit. By building into the loop two more such telescopes, scientists could spot 90% of all hazardous space rocks within a decade, according to a report released here this week at a meeting of the American Astronomical Society. However, Hollywood doomsday scenarios notwithstanding, odds are slim that any of the newly detected asteroids will threaten civilization.

Astronomers estimate that about 2000 kilometer-sized chunks wander close enough to Earth's orbit that they could someday hit the planet. Researchers have found perhaps 10% of these dim boulders, but today's modest search efforts would require decades of trolling the sky to uncloak the rest. Planetary scientists at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, aim to change that with their Near-Earth Asteroid Tracking project (NEAT).

NEAT uses an automated satellite-tracking telescope operated by the U.S. Air Force atop an extinct volcano on Maui, Hawaii. The 1-meter telescope sweeps across a swath of sky equal in size to 4000 full Moons in one night, taking three images each of the patches at different times. Computer programs sift the images to search for objects that move faster than distant asteroids but slower than satellites. Most detections are known objects, but NEAT finds one or two new near-Earth asteroids during its six nights of observation each month, says JPL astronomer David Rabinowitz. "We would expect to find 20 to 40 per month" by operating three identical systems on existing Air Force telescopes for 18 nights a month--a proposal that NASA and the Air Force are now considering, Rabinowitz says.

NEAT is one of three projects that are spotting the inner solar system's asteroids at a rate 5 to 10 times higher than a few years ago, says Gareth Williams, associate director of the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. The others are Spacewatch, based at the University of Arizona, Tucson, and LINEAR, a joint effort between Lincoln Laboratory in Lexington, Massachusetts, and the Air Force. But even with these heightened efforts, Williams maintains, finding most near-Earth nomads within a decade is an overly optimistic goal because of the vast volumes of space through which they migrate.