NASA’s four year Kepler mission to search thousands of stars in the Milky Way galaxy for sun-like stars with planets that resemble the Earth has encountered a serious technical problem.
A second of the four rapidly spinning internal “reaction wheels” that aim and steady the observatory has stopped turning, NASA announced late Wednesday.
At least three “reaction wheels” are required to continue operations.
“Kepler is just one of those wonderful stories,” John Grunsfeld, the associate administrator of NASA’s science directorate, told a news teleconference. So far, the $600 million mission has produced evidence of 2,700 alien worlds circling stars in the galaxy. Of those, 132 discoveries have been confirmed as alien worlds so far, suggesting that exo planets are common and come in sizes ranging from the Earth’s moon to worlds larger than Jupiter, said William Borucki, Kepler’s chief mission scientist.
Some planets orbit multiple stars. Most significantly, some of these alien worlds circle their stars in the “habitable zone” — a region not too close and not too far. Like on the Earth — water, if present — would exist as a liquid.
Though Kepler has already fulfilled the mission it was launched March 2009 to carry out, engineers at NASA’s Ames Research Center in California are attempting to develop a recovery strategy, said Paul Hertz, director of NASA’s astrophysics division.
“I would not count Kepler down and out just yet,” said Hertz.
The small observatory is positioned 40 million miles from Earth. Unlike NASA’s Earth orbiting Hubble Space Telescope, Kepler is too distant to be repaired by NASA astronauts.
Kepler sustained its first reaction wheel failure in July 2012.
The second was discovered Tuesday, two days after Kepler slipped into “safe mode,” possibly triggered by the malfunction. In protective “safe mode,” spacecraft direct their solar arrays toward the sun to ensure they generate electricity and configure themselves to communicate with flight controllers on the Earth.
Kepler has thrusters and fuel, but not the quantities of propellant needed to continuously aim and steady the observatory for planet detection.
Charles Sobeck, Kepler’s deputy project manager at the Ames Research Center, said engineers will attempt to recover both of the stricken reaction wheels as well as devise possible pointing strategies that would permit some observations.
Astronomers are still making a first pass through the data generated by Kepler so far and could be for up to two more years, said Borucki. Astronomers around the world will likely find Kepler’s recorded observations useful for at least a decade, he predicted.
“We are not ready to call the mission over yet,” Grunsfeld insisted.
Last month, NASA selected a successor to Kepler, which makes its discoveries by detecting a slight dimming of the light from a star as a planet crosses or transits in front.
The Transiting Exoplanet Survey Satellite, or TESS, which will confine its planet search to the stars closest to Earth, should be ready to launch in 2017.
Meanwhile, the James Webb Space Telescope, the designated successor to the Hubble Space Telescope, is undergoing preparations for a late 2018 launch.
The powerful JWST is equipped to study alien planets as well. JWST will likely be trained towards planets detected by TESS.