Satellite to find "things nobody has imagined"

12:35 PM, Dec 1, 2009   |    comments
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Somewhere out in space are thousands of asteroids, some of them potentially hazardous to Earth, that are so dark they have escaped detection by telescopes. They may not be able to hide much longer. Later this month, a satellite the size of a race car is scheduled to launch and begin orbiting the Earth 325 miles above the surface.  Its eight-month mission is simple: Take infrared images over a wider swath of the sky in greater detail than ever before.

The Wide-field Infrared Survey Explorer, called WISE for short, is expected to photograph never-before-seen asteroids, stars and galaxies and reveal sharper details on already-discovered places in the solar system and the Milky Way. "We're going to find things nobody has imagined," said Jon Morse, director of NASA's astrophysics division. An exact launch date has not been set, but it's expected to be after Dec. 8 at Vandenberg Air Force Base in California.

The University of Arizona is playing a key role in the $320 million project. Bob McMillan, an associate research scientist with UA's Lunar and Planetary Laboratory , is a member of the science team and an expert in hazardous asteroids. He plans to study any new asteroids in more detail using information from the WISE satellite and a ground telescope at Kitt Peak National Observatory , southwest of Tucson.

Most people are familiar with infrared technology through the night-vision goggles used in movies. All objects hotter than absolute zero, or 0 degrees Kelvin, emit some amount of infrared radiation. The WISE satellite has a telescope designed to measure these infrared waves, which will allow scientists to detect dark objects that traditional light telescopes miss. Infrared telescopes can also determine how big the objects are. Knowing the diameter is important, McMillan said, because the bigger the object, the more hazardous it would be if it collided with Earth.

Asteroids are usually made of rock or metal, and most reside in the so-called asteroid belt between Mars and Jupiter. Some have orbits that whip them close to Earth, a designation that earns them the title of "near Earth objects" and more scientific scrutiny. Scientists expect WISE to identify 100,000 new asteroids in the asteroid belt and several hundred more near Earth. In recent years, Congress has had an increased interest in identifying objects that could pose a threat to Earth.

The chance of a catastrophic impact is extremely unlikely, NASA says. You have a better chance of getting swept up by a tornado. But asteroid-Earth impacts are not out of the question, and the impact could be devastating. If a large asteroid smashed into the planet, scientists envision its debris would spread through the atmosphere, creating firestorms and pelting the surface with acid rain. Scientists believe an asteroid or comet impact wiped out the dinosaurs 65 million years ago.

Identifying asteroids on a collision course with Earth would force scientists to figure out ways to avert a collision, possibly by using some sort of weapon to divert the asteroid. NASA is doing an inventory of hazardous asteroids that are larger than about a half-mile in diameter. These could be civilization-ending if they hit the planet.

There is also increasing interest among scientists in identifying smaller asteroids at least 460 feet in diameter, a size that could still cause lots of damage. Most asteroids that have recently come close are much smaller. Last month, a newly discovered asteroid called 2009 VA came within 9,000 miles of the Earth. The asteroid was about 22 feet in diameter and was found about 15 hours in advance by the Catalina Sky Survey. In 2006, an asteroid estimated to be about a third of a mile wide hurtled past Earth at a distance of about 269,000 miles, or slightly farther away than the moon.

Once the WISE satellite mission is finished, scientists will publish a catalog of everything identified. Telescopes on Earth and in space can use the information to conduct more detailed studies. "Perhaps the greatest benefit . . . is you can keep coming back to it. There are objects likely to be discovered years after the WISE survey is complete," said Peter Eisenhardt, WISE's project manager.

The Arizona Republic

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