NASA engineers are still making efforts to get the crippled Kepler Space Telescope working again, but they're also seeking alternative plans in case that doesn't happen.
Engineers from the space agency have been working for nearly three months to fix the telescope, which was launched in 2009 to search for Earth-like planets. The telescope has been spinning out of control because of trouble with two of the four wheels that control its orientation in space.
NASA is no longer able to manipulate the telescope's positioning, and ground engineers have had a hard time communicating with the spacecraft since the communications link comes and goes as it spins.
Tests performed Friday showed that both of the problematic wheels are turning on command, according to Charles Sobeck, engineer and deputy project manager of NASA's Kepler mission. However, there now is friction when the two problematic wheels turn. If the friction doesn't remain at a constant level, the wheels will be unusable, Sobeck told Computerworld.
To hold the spacecraft at a steady state, the wheels need to move at a constant speed. If the friction level fluctuates, the torque that engineers calculate to keep the wheels spinning at a constant speed will be wrong. Sobeck said NASA cannot send up new software that would adjust the torque on the fly to the rate of friction.
The next test, scheduled for today, will check to see if the friction is constant or if it fluctuates.
Sobeck said that having just one of the two wheels perform well may give the telescope enough accuracy to deliver the high-precision photometry necessary for exoplanet detection.
He added that he has no idea of the odds of success. "All we can do is try and see," he said.
NASA, hedging its bets, issued a call for white papers on potential alternative scientific projects that a limited Kepler could work on.
"The purpose of this call for white papers is to solicit community input for alternate science investigations that may be performed using Kepler and are consistent with its probable two-wheel performance," reads the request. "If one of the two reaction wheels cannot be returned to operation, it is unlikely that the spacecraft will resume the nominal Kepler exoplanet and astrophysics mission."
Sobeck said he hopes the scientific community will come up with some intriguing scientific goals for Kepler.
"We're looking for ideas for science you might do with the Kepler mission that you might not be able to easily do from the ground," he said. "Maybe it could be used to find near-Earth asteroids, giving us a different perspective than we get from the ground."
Submissions are due to NASA by Sept. 3. The space agency plans to begin new science programs with Kepler by next summer.
The space telescope is considered one of NASA's great success stories. After wrapping up its primary three-and-a-half-year mission and entering a second phase of research last November, NASA scientists had hoped Kepler would continue working for another four years.
Since it began work on May 12, 2009, the telescope has searched more than 100,000 stars for signs of Earth-like planets in the habitable zone, an area that may have water and could potentially support life. The telescope has so far confirmed more than 100 such planets.
Even if Kepler cannot continue its search for Earth-like planets in the universe, it already has sent back enough data to keep scientists busy, Sobeck said.
"It's rewritten the textbooks on exoplanets," he said. "Even if Kepler never sends down any more data, you'll still see science coming out from this over the next several years."
This article, NASA seeks new science projects for crippled Kepler, was originally published at Computerworld.com.
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