Infrared eye to help search for asteroids
NASA is preparing to launch an infrared telescope that will hunt down dark asteroids that have slipped beneath our radar.
The Wide-field Infrared Survey Explorer (WISE) spacecraft recently arrived at Vandenberg Air Force Base in California ahead of its launch later this year.
But hunting asteroids wasn't in the original plan for the telescope.
"I was recruited when the team realised they would be seeing a lot of asteroids, some of which may be new," says University of Texas astronomer Dr Robert McMillan who leads Spacewatch, an asteroid-survey project.
"They wanted someone who had connections with the ground-based telescope community who'd be able to do follow-ups," says McMillan.
With a quartet of infrared sensors and a wide view, WISE is designed to survey the whole sky in infrared light.
It's not the first telescope to do so, but scientists expect WISE's observations will be 500 times sharper than a survey conducted in 1980s by IRAS, the Infrared Astronomical Satellite, according to astronomer Martin Cohen of the University of California at Berkeley.
The data will be complied into an all-sky infrared atlas, a tome that is expected to include about 300 million objects, including around 100,000 asteroids.
Many of the asteroids seen by WISE will be known objects. Scientists hope to use the new observations to nail down details, such as an asteroid's diameter and surface reflectivity.
"With ground-based scopes, it's just a point source. You can't tell size directly," says McMillan. "A big object that is dark and a small object that is bright are going to look like they have the same brightness."
The solar system contains several million asteroids, most of which reside in the main asteroid belt between Mars and Jupiter. About 7000 asteroids have been identified that cross or come close to Earth's orbit.
WISE will be able to spot asteroids emitting heat due to direct exposure from the Sun, as opposed to visible-light searches that find asteroids that are reflecting sunlight.
"Those are two different physical effects," says McMillan. "An asteroid that has very dark colour in invisible light is going to get heated up more, just like a black car in a parking lot is going to get heated up more than a white car."
Scientists hope to get enough positioning information to follow up targets with ground-based observations.
McMillan expects that WISE will discover a few hundred new asteroids. The information will be folded into ongoing surveys to map asteroids that could impact Earth and cause widespread damage.
Other WISE targets include brown dwarfs, which are Jupiter-sized stars that never got their nuclear fusion engines running, and ultra-luminous galaxies, which pump out the equivalent of about 1000 Sun-sized stars every year.
These galaxies are among the most luminous objects in universe, says WISE lead scientist dr Edward Wright.
WISE should be able to spot these galaxies back to when the universe was about two billion years old.
The telescope is scheduled to be launched on 7 December 2009. The US$300 million (A$365 million) mission covers a month-long checkout and six months of science operations. The spacecraft is designed to last two years.