Last Tuesday NASA reported a failure of the reaction wheel number four onboard the Kepler Space Telescope. Sadly, this is the second of Kepler’s four reaction wheels used to keep the craft properly oriented to have failed. Wheel number two called it quits back in July 2012. While Kepler was able to maintain its orientation around the sun in the search for new exoplanets with only three wheels properly functioning, it is unlikely that the brave eye above the sky will be able to keep pointed in the same direction long enough to continue its mission of high-precision photometry. Currently Kepler is ‘parked’ in a “Thruster-Controlled Safe Mode” in orbit around the sun, much too far and dangerous for astronauts to reach and repair.
NASA hasn’t given up on the little guy yet. The spacecraft is stable and safe. Kept in Safe Mode, the telescope has enough fuel to last for years. Engineers are trying a number of possible software solutions, transmitted via an X-band communication downlink, to fix the error. One possibility is that of a hybrid operational state that would use thrusters in conjunction with the two working reaction wheels to control the craft. There is also some hope that the busted wheel two will come back to life again following a reset of the telescope’s systems. It is possible that wheel two didn’t function due to a lack of lubrication that may have finally settled into the correct spots. Charlie Sobeck of NASA’s Ames Research Center also has a backup plan, “Like with any stuck wheel that you might be familiar with on the ground, we can try jiggling it. We can try commanding it back and forth in both directions. We can try forcing it through whatever the resistance is that's holding it up.”
While disappointing, don’t feel too down about Kepler. The little guy has actually been working on overtime since November of 2012, having already completed its 3.5 year primary mission. The Kepler mission has returned data on the potential of more than 2700 previously unknown exoplanets. Scientists have only been able to confirm 132 of them thus far, but mission experts expect that 90% of Kepler’s findings to be real. Mission Principal Investigator Bill Borucki explains, “We have excellent data for an additional two years. So I think the most interesting, exciting discoveries are coming in the next two years. The mission is not over."
Then there is future missions in the realm of high-precision photometry. We have certainly learned a lot from both the successes and failures of the Kepler mission. In the words of Growing Up Otaku’s Lou Jorgl, “It may be most interesting to realize that this is our first generation of planet detecting equipment, techniques, and we are only focused on a small portion of the sky. The future will provide equipment that may much more easily find small planets or even moons around larger planets. One thing is for sure, eventually we will find another planet in our galaxy that we will be able to live on.”