By comparing the amount of visible light an asteroid reflects to the amount of infrared radiation it emits, researchers also can glean in general terms the asteroid's composition.
Toward the end of the original WISE mission, the craft ran out of coolant for two of its four infrared detectors. That left two others, which could operate at warmer temperatures. The infrared wavelengths that these two detectors covered were suitable for asteroid detection, so WISE became NEOWISE for the craft's near-Earth object search.
By the time the National Aeronautics and Space Administration put the craft to sleep in February 2011, the craft had discovered 21 comets, more than 34,000 asteroids out in the main asteroid belt between Mars and Jupiter, and 135 near-Earth asteroids.
Other than running out of the hydrogen ice needed to cool two of the detectors, the solar-powered craft had no other "expendables" left to lose and two good detectors remaining, making it a prime candidate for revival.
In the meantime, the Obama administration's budget for fiscal year 2014 included money for NASA to begin work on what's come to be known as the Asteroid Initiative. This combines a robotic mission to capture and park an asteroid in an orbit between Earth and the moon for later human exploration with efforts to find all the near-Earth asteroids that threaten Earth.
The threat struck home in a dramatic way in February, when a small asteroid entered Earth's atmosphere and exploded high over the Chelyabinsk region of Russia. The blast damaged more than 7,200 buildings and by some estimates injured nearly 1,500 people.
Against that backdrop, "a few months ago NASA came to us and asked us for a proposal to reactivate" NEOWISE, Mainzer says.
Within the first two weeks of September, her team hopes to wake up the craft and check out its telescope for a three-year mission.
Time is not on the mission's side, however. The craft is in an orbit uniquely suited for its original mission – one that keeps the telescope pointed at deep space and the solar panels always facing the sun. Over time, however, this sun-synchronous orbit undergoes subtle changes. By 2017, the orbit will have changed enough to prevent the team from keeping the sun out of the telescope, rendering it useless.