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Hunt for near-Earth asteroids is new mission for slumbering NASA craft

NASA's WISE telescope ran out of coolant for two of its four infrared detectors, but the remaining ones can operate in a way that is suitable for the detection of near-Earth asteroids.

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An artist's concept of Wide-field Infrared Survey Explorer (WISE) is shown in this illustration.

JPL-Caltech/NASA/Reuters

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NASA is getting set to rouse a slumbering spacecraft after a nearly three-year nap and hand it a new assignment: hunting for near-Earth asteroids.

The craft not only would keep a keen eye out for objects that could threaten Earth; it also would hunt for objects that might make a good target for a manned mission.

The center of attention is NASA's Wide-field Infrared Survey Explorer. The agency launched it in December 2009 to survey the entire sky in a kind of reconnaissance mission for orbiting observatories such as the Spitzer Space Telescope – a far more powerful infrared observatory that could conduct the detailed follow-up observations of objects that WISE detected.

Much of WISE's science program focused on hunting for nearby brown dwarfs, dim star wannabes whose internal furnaces never quite got hot enough to ignite the stars. WISE also hunted for galaxies with high rates of star formation – galaxies typically obscured at optical wavelengths by thick cocoons of dust. And the craft was to provide data that would shed additional light on the formation and evolution of stars, planets, and galaxies.

The mission "was not originally designed to look for asteroids and characterize them," says Amy Mainzer, deputy project scientist for WISE during its initial mission and now the lead scientist for the dedicated asteroid hunt.

But it's well suited to the task. Near-Earth asteroids can approach Earth from all directions, so having a telescope that surveys the entire sky is a plus.

In addition, the telescope operates at infrared wavelengths, in essence detecting heat. This allows it to pick up dark asteroids that might be difficult or impossible for ground-based telescopes to spot, since such asteroids still re-radiate as heat the energy they receive from the sun.

Using infrared data, scientists can get a better idea of how many of these darker objects are out there. And it helps reduce uncertainties in estimates of the size of an object – estimates typically based on brightness. A small but highly reflective asteroid can have a similar brightness to a much larger but darker asteroid when viewed only at optical wavelengths, Dr. Mainzer explains.

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