科学美国人60秒:Sky Map Satellite Becomes Asteroid Hunter

Last week we told you about the end of an era: NASA ended the Kepler spacecraft's exoplanet-hunting mission, following an irreparable mechanical failure.

This week, news of rebirth. NASA's WISE satellite is a space telescope that carefully surveyed the universe in infrared light. In 2010 it ran out of the cryogenic coolant that enabled its primary mission of mapping the skies. But WISE still found work, scanning for asteroids near Earth. Finally in 2011 NASA put the orbiting observatory into hibernation.

Now NASA is planning to reboot WISE to find more asteroids. The space agency will fire it up in September for a three-year run. WISE should be able to find some 150 new near-Earth asteroids and get a better handle on another 2,000.

Altogether more than 10,000 near-Earth asteroids, and almost 100 near-Earth comets, have been discovered by astronomers. That census includes most of the really big ones, but the vast majority of smaller asteroids remain to be discovered. And as we saw in February—when a small asteroid exploded over Russia, breaking windows in thousands of buildings—even the little ones can still do big damage.

—John Matson