The Kepler spacecraft suffered a catastrophic failure on May 14, leading to a possible loss of the mission. Scientists at NASA haven't given up hope for the orbiting space telescope, however, as there are a few ways that the craft may still be repaired.
Kepler was constructed with four reaction wheels that align the spacecraft so that its solar panels align with the Sun and stars do not blur during exposure. One of these four (the number two wheel) showed signs of metal-on-metal friction, and was shut down last year. The number four wheel failed on May 14, making it impossible to continue measurements. The next task will be to try to rescue the craft from Earth, 40 million miles away.
Charles Sobeck, Kepler's deputy project manager, said "We'll try the same things you'd do to unstuck a wheel on Earth... jiggling it... commanding it to move back and forth... forcing it through whatever might be holding it back."
Scott Hubbard was the director of NASA's Ames Research Center, where he helped direct the Kepler mission during its construction. According to an interview with him on the Stanford website, there are two ways that astronomers might try to repair the Kepler spacecraft from Earth.
The first of these possible methods involves turning the wheel that was switched off last year back on, and hoping that the lubricant within the wheel has settled in that time, fixing the original problem.
The second way the Kepler spacecraft might be repaired is challenging. The process would involve firing thrusters aboard the craft and pressure from the solar wind to behave like a thruster.
Hubbard said of this second plan, "[M]y impression is that it would require sending a lot more operational commands to the spacecraft."
The most famous repair job in space was the 1993 servicing mission to the Hubble Space Telescope, which repaired faulty optics aboard the orbiting observatory. In the case of Hubble, the telescope was in Low-Earth Orbit (LEO), easily within the reach of the Space Shuttle. Kepler, on the other hand, is in orbit around the Sun, as is the Earth, making a crewed repair mission impossible.
Even if Kepler can not be repaired, it will still take astronomers another year-and-a-half or more to interpret all the data it has collected. So, Kepler could still be delivering great science, even from a cold, silent grave.
