NASA on Thursday will begin a long-shot operation to revive the planet-hunting Kepler space telescope, which was sidelined two months ago by a positioning system failure.
"I think the general feeling is that the odds are not good. We might see a wheel spin, but I suspect that it will not spin freely, that there will be vibrations, which would not make the science happy," said Charlie Sobeck, deputy project manager at NASA's Ames Research Center.
The attempt to resurrect Kepler will begin with detailed checkouts of two failed reaction wheels, which are part of a system needed to keep the observatory focused on its celestial targets.
GALLERY: Exquisite Exoplanetary Art
Kepler was launched in 2009 to hunt for Earth-like planets circling distant stars. It was designed to detect minute dips in the amount of light coming from the stars, changes that could be due to planets passing by relative to the telescope's line of sight.
So far, Kepler scientists have found and confirmed 134 planets beyond the solar system and are analyzing another 3,144 candidate planets.
To keep its gaze steady, Kepler needs at least three of its four reaction wheels spinning. One wheel failed last year. A second shut down in May.
When engineers last checked, the first wheel to fail could still move, but not freely.
"We would expect that it might very well seize up as soon as we try to spin it up again," Sobeck told Discovery News.
GALLERY: Top Exoplanets for Alien Life
The wheel that failed in May was completely stuck and likely will remain so.
Phase two of the Kepler revival effort will be to get one wheel moving again. Engineers will work first on the most recently failed wheel, though there is less of a chance that it can be restored.
"We'll learn any lesson on the wheel that's less likely to respond, and then we'll move on to the better bet," Sobeck said.
The options are pretty limited, he added. They include warming up the stuck wheels in the sunlight and then commanding them to spin clockwise and counter-clockwise to see if whatever is binding the wheel can be nudged out of the way.
ANALYSIS: How Habitable Are Kepler's New Worlds?
"I don't think that the odds are real great, but we could be surprised," Sobeck said. "We've got to at least try."
If Kepler's positioning system cannot be restored, its planet-hunting days likely will be over.
"Even if data collection were to end, the mission has substantial quantities of data on the ground yet to be fully analyzed, and the string of scientific discoveries is expected to continue for years to come," Kepler manager Roger Hunter wrote on the project's website.
Scientists also are mulling over other potential projects for Kepler that don't need such precise pointing.