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Efforts to save a $600 million tool in NASA’s quest for life elsewhere in the universe have been unsuccessful, the space agency said -- but there's still life left in the robotic planet hunter.
In May, a specialized gyroscopic wheel used to point the Kepler Space Telescope toward the sun failed, the second such failed wheel. And despite months of analysis and testing, the spacecraft will never be restored to working order. But despite the breakdown, Kepler has proven a remarkable success, NASA said.
"Kepler has made extraordinary discoveries in finding exoplanets including several super-Earths in the habitable zone," said John Grunsfeld, associate administrator for NASA's Science Mission Directorate in Washington. "Knowing that Kepler has successfully collected all the data from its prime mission, I am confident that more amazing discoveries are on the horizon."
NASA said its efforts will now turn to making the most of the research craft while it still can.
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. Launched in 2009, it has discovered thousands of such planets, including a pair just 1,200 light years away.
Called Kepler-62-e and Kepler-62-f, the news of their discovery came in April. But shortly after, Kepler’s mission ran into trouble.
Kepler is powered by four solar panels, and the spacecraft must execute a 90-degree roll every 3 months to reposition them toward the sun while keeping its eye precisely aimed. Kepler launched with four wheels to control that motion -- two of them have now failed.
On Aug. 8, engineers conducted a system-level performance test to evaluate Kepler's current capabilities. They determined that the wheel which failed last year can no longer provide the precision pointing necessary for science data collection. The spacecraft was returned to its point rest state, which is a stable configuration where Kepler uses thrusters to control its pointing with minimal fuel use.
"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 in Moffett Field, Calif. "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?"
Kepler will continue working, and NASA will look to reduce fuel consumption to extend the lifespan of the spacecraft. For example, a different mode of steering Kepler will enable NASA to extend its life by years, explained Charles Sobeck, deputy project manager with Ames Research Center.
“We’re not down and out. The spacecraft is safe, it is stable,” Sobeck said in May. And regardless, Kepler is already a win for NASA.
“The mission itself has been spectacularly successful,” he added. Most other scientists agree.
The quest for “exoplanets” has generated enormous interest among the public and with scientists. And it will continue. A second mission will launch in 2017 and will use the same method that Kepler has used to continue the mission; it will seek the closest exoplanet -- which may be under two dozen light years away.
The James Webb Space Telescope will also help in the quest for life in the universe.