WASHINGTON, Aug. 15 (Xinhua) -- U.S. space agency NASA said Thursday it is ending attempts to fix the planet-hunting Kepler Space Telescope and now is considering what new science research it can carry out at half-capacity.
Kepler needs three of its four gyroscope-like reaction wheels, which are used to precisely point the spacecraft, to search for Earth-sized planets outside our solar system but two of them have failed. The first was lost in July 2012, and the second in May this year.
"Engineers' efforts to restore at least one of the wheels have been unsuccessful," NASA said in a statement.
"An engineering study will be conducted on the modifications required to manage science operations with the spacecraft using a combination of its remaining two good reaction wheels and thrusters for spacecraft attitude control," the space agency said.
Since its launch in 2009, Kepler has confirmed 135 exoplanets and identified over 3,500 candidates.
NASA said it will continue to analyze all four years of data collected by Kepler, expecting "hundreds, if not thousands, of new discoveries including the long-awaited Earth-size planets" in the habitable zone of Sun-like stars.
"At the beginning of our mission, no one knew if Earth-size planets were abundant in the galaxy. If they were rare, we might be alone," said William Borucki, Kepler science principal investigator at NASA's Ames Research Center. "Now at the completion of Kepler observations, the data holds the answer to the question that inspired the mission: Are Earths in the habitable zone of stars like our Sun common or rare?"