Nasa will reactivate a mothballed infrared space telescope for a three-year mission to search for potentially dangerous asteroids on a collision course with earth, officials said.
The Wide-field Infrared Survey Explorer, or WISE, telescope also will hunt for targets for a future mission to send a robotic spacecraft to rendezvous with a small asteroid and relocate all or part of it into a high orbit around the moon.
Astronauts would then visit the relocated asteroid during a test flight of Nasa's deep-space Orion capsule, scheduled for launch around 2021. Orion and a heavy-lift rocket called the Space Launch System are slated for an unmanned test flight in 2017.
Nasa is spending about US$3 billion a year for Orion and Space Launch System development.
Launched in December 2009, the WISE telescope spent 13 months scouting for telltale infrared signs of asteroids, stars, distant galaxies and other celestial objects, especially those too dim to radiate in visible light.
As part of its all-sky mapping mission, WISE observed more than 34,000 asteroids in the main asteroid belt between Mars and Jupiter and another 135 asteroids in orbits that come close to earth.
Overall, scientists catalogued more than 560 million objects with WISE.
Most of the telescope's instruments were turned off when its primary mission was completed in February 2011.
Nasa planned to bring WISE out of hibernation next month and operate it for another three years, at a cost of about US$5 million per year, Nasa spokesman Dwayne Brown said.
"After a quick checkout, we're going to hit the ground running," WISE astronomer Amy Mainzer, with Nasa's Jet Propulsion Laboratory in Pasadena, California, said in a statement.
Nasa already has found about 95 per cent of the near-earth asteroids that are one kilometre or larger in diameter.
The agency is about halfway through a 15-year effort to find 90 per cent of all near-earth objects that are as small as about 140 metres in diameter.
The search took on a note of urgency after a small asteroid blasted through the skies above Chelyabinsk, Russia, in February and exploded with 20 to 30 times the force of the Hiroshima atomic bomb. More than 1,500 people were injured by flying glass and debris.
Later that same day, a much larger but unrelated asteroid soared closer to earth than the networks of communication satellites that ring the planet.
The events prompted Congressional hearings and new calls for Nasa and other agencies to step up their asteroid detection initiatives.
The Obama administration proposes to double Nasa's US$20 million Near-Earth Objects detection programmes for the 2014 fiscal year.
About 66 million years ago, an object 10 kilometres in diameter smashed into what is now the Yucatan Peninsula in Mexico, leading to the demise of the dinosaurs, as well as most plant and animal life on earth.