NASA's planet hunting spacecraft is unlikely to make a full recoveryS

Attempts to rescue NASA's planet-hunting Kepler mission, which was sidelined in May due to a mechanical failure, have been met with limited success, according to the Agency.

Unlike Hubble Space Telescope, which astronauts have worked on several times, Kepler orbits the Sun, millions of miles from Earth. Sending a crew to repair the telescope by hand just isn't an option, which means troubleshooting has to be done entirely from the ground. To that end, NASA's had some success – but not enough to bring Kepler back to 100% functionality.

SPACE.com's Mike Wall has the details:

Kepler needs three functioning gyroscope-like reaction wheels to perform this precision work. It launched with four — three for immediate use and one set aside as a spare. But one wheel, known as number two, failed in July 2012. Then another (number four) gave up the ghost on May 11 of this year, halting Kepler's exoplanet search.

After the second failure, Kepler team members began devising ways to potentially bring the two wheels back. They performed recovery tests over the last week, commanding wheels four and two to spin on July 18 and July 22, respectively.

Wheel four rotated in one direction (counterclockwise), while wheel two spun in both directions, mission officials announced Wednesday (July 24). This was a victory of sorts, but a qualified one.

"Both wheels are showing substantially higher friction than a good wheel would show," Sobeck told SPACE.com. Those friction levels probably won't come down, he added, as the recovery team has already tried a number of strategies to this effect.

"Just saying that we could go back to science and operate normally, as we have — it's unlikely to happen," Sobeck said. "The question then becomes, Can you drive a wheel with substantial friction and still do science with it? We really don't know the answer to that question, so that'll be the next test that we run."

Everyone's obviously been pulling for a full recovery for Kepler, however unlikely. The telescope is among the Agency's most prolific projects in recent memory, having expanded the realm of possible worlds outside our solar system well beyond the boundaries of many people's wildest imaginations. That NASA's been able to corner even a qualified victory is really great news.

"We still have a great spacecraft, a great instrument," Sobeck said. "The instrument is working. We just have to figure out a way to get it pointed at the targets we want."

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