A space explorer spotted a never-before-seen near-Earth asteroid after being put back into service, the U.S. space program said. The Near-Earth Object Wide-field Infrared Survey Explorer's first discovery of its renewed mission came on Dec. 29 when it reveals a near-Earth asteroid, designated 2013 YP139, picking out the moving object against a background of stationary stars by using sophisticated hardware, NASA said. 2013 YP139 is about 27 million miles from Earth. Based on its infrared brightness, scientists estimate it to be roughly 0.4 miles in diameter and extremely dark. The explorer spacecraft originally was known as the Wide-field Infrared Survey Explorer, which had made the most comprehensive survey to date of asteroids and comets, NASA said. The spacecraft was shut down in 2011 after its primary mission was completed but reactivated in September, renamed and given the mission of assisting NASA's efforts to identify the population of potentially hazardous near-Earth objects. NASA said Tuesday the spacecraft also can help characterizing previously detected asteroids that could be considered potential targets for future exploration missions. "We are delighted to get back to finding and characterizing asteroids and comets, especially those that come into Earth's neighborhood," said Amy Mainzer, the mission's principal investigator from NASA's Jet Propulsion Laboratory in Pasadena, Calif. "With our infrared sensors that detect heat, we can learn about their sizes and reflectiveness."