How WISE Works

To co-opt a phrase from the fictional Captain James Kirk of "Star Trek," when WISE was launched in 2009 into a polar orbit 326 miles (525 kilometers) above the Earth's surface, it was designed to boldly look where no one had looked before. WISE wasn't the first infrared orbital observatory, but unlike previous probes, it was designed to survey the entire expanse of the sky, looking farther into space to spot faint and/or distant objects [source:NASA].

To accomplish that, WISE relied upon a sophisticated design and state-of-the-art technology. The satellite was equipped with a sensitive telescope and infrared light detectors mounted inside a tank of solid frozen hydrogen — imagine a giant Thermos, and you've basically got the idea — that kept the instruments a frigid -429 degrees Fahrenheit (-256 Celsius). That chilling effect prevented WISE from picking up the heat signature of its own gadgetry, making its observations even more precise [source:NASA].

In the course of its 13 months of work, WISE scanned the sky 1 1/2 times, taking about 1.8 million images that scientists are stitching together to create a composite map of the cosmos [source:Klotz]. Some of the glimpses of previously unseen details of the universe that it provided were astonishing. For example, one snapshot revealed that a vast red and green cloud in deep space was brimming with newly formed stars, just a few million years old, inside flower-like wisps of interstellar dust [source:Space.com].

But WISE wasn't designed to run forever at full capacity. In September 2010, the spacecraft began to run out of the coolant needed to chill its infrared detectors. At that point, scientists shut down two of the four detectors and stopped looking out into the distant reaches of space [source:Chow]. But the orbital observatory's gadgetry worked well enough that it was eminently suitable for another important mission.

After finishing its original mission, WISE actually got a trial run of sorts on what eventually would become its second act. After NASA shut down much of its infrared equipment when the coolant began to run down, scientists utilized what was still operating to work on a project called NEOWISE between January 2010 and February 2011. The spacecraft began scanning the sky for closer objects. During 2010, it observed about 158,000 rocky bodies, including 34,000 asteroids in the solar system's main belt between Mars and Jupiter, and spotted 135 potentially hazardous near-Earth objects — that is, ones close enough to Earth's orbit that they might present a collision hazard [source:NASA].

When NASA reactivates WISE again, it will use the satellite's 16-inch (40-centimeter) telescope and its infrared sensors to look for additional near-Earth objects. Because the sensors no longer are being super-cooled, they don't all work, and thus the satellite isn't as good at detecting radiation from distant, faint objects as it once was. But it still has enough capability left to spot infrared radiation from nearer objects. "Two of our four infrared detectors still work even at warmer temperatures, so we can use those bands to continue our hunt for asteroids and comets," Amy Mainzer of NASA's Jet Propulsion Laboratory told Space.com in October 2010 [source:Malik].

Infrared sensing is a particularly useful tool, not only for spotting asteroids but for accurately calculating their size. Asteroids reflect light but don't emit it, and they vary inalbedo, or the ability to reflect visible light. That means that to a regular optical telescope, a small, light-colored space rock can look as big as a much larger dark one. An infrared telescope, however, picks up a part of the non-visible spectrum that a regular telescope misses, and can give a more complete picture of an asteroid [source:NASA].

Scientists are betting that capacity will enable WISE to give us a better idea of which asteroids are big enough and close enough to be a problem — and which might be the right size to be captured by a robotic spacecraft.

WISE should be a big help in two important NASA missions: tracking near-Earth objects and devising a way to protect the Earth from them, and staging a manned mission to an asteroid by 2025.

识别和跟踪asteroids that might venture within the vicinity of Earth is an especially high-priority NASA mission. Its urgency was driven home by the February 2013 explosion of an 18-meter- (60-foot)-across, 11,000 metric-ton (12,125-ton) meteor over the Russian city of Chelyabinsk. That hunk of space rock released nearly 30 times the energy of one of the atomic bombs exploded at the end of World War II, and more than 1,200 people were injured by flying debris [sources: Yeager,Klotz].

Compiling a database of near-Earth objects and tracking their movements hopefully will give NASA advance warning of an object on a collision course — and time to implement a defensive strategy, whether that means diverting the asteroid with gravity tractors, solar sails or other future technologies, or breaking it apart with a nuclear blast [source:Messier].

NASA also envisions using robotic spacecraft to capture a small near-Earth asteroid and redirect it safely to a stable orbit in the vicinity of the Earth and moon. A NASA video depicts one possible method: A robotic probe powered by solar sails could overtake the asteroid, lasso it with cables, and then slip it into a giant "asteroid capture bag," which will enable the craft to control and direct its movements.

Once the asteroid is where NASA wants it, astronauts would fly to it in the Orion spacecraft, a deep-space vehicle that is still under development, and then spacewalk to its surface. They would remove rock samples that would be brought back to Earth for further study [source:Moscowitz,NASA]. Eventually, captured asteroids might be a source of valuable materials such as nickel, platinum and palladium, or even sites for manufacturing [source:Mann].