Last year, it looked as though the Kepler space probe had nothing to look forward to but the scrap heap. After the failure of two of its reaction wheels, the unmanned spacecraft was incapable of maintaining the precision pointing needed to hunt planets beyond the Solar System. Now, however, NASA’s Kepler team has demonstrated that space telescope can still detect exoplanets thanks the K2 mission concept maneuver.
In May 2013, Kepler was a write-off. Launched in 2009, it was designed to seek exoplanets by studying the dip in light coming from other stars as their planets eclipsed them in transit. It proved to be an effective technique, with over 3,000 exoplanet candidates detected and hundreds confirmed. However, to do its job, Kepler had to keep its gaze fixed on one spot in the sky with minute precision – a precision that was lost when two of its reaction wheels malfunctioned.
That seemed to be the end of the story until NASA and Ball Aerospace engineers figured out that the pressure of sunlight falling on Kepler, which is the primary cause of its instability, could be used to save it. Dubbed the K2 mission concept, the idea was to angle the spacecraft in such a way that while the sunlight pressed the craft in one direction, the remaining two reaction wheels pressed in the opposite. This way, the forces balanced out and Kepler could remain relatively steady for at least part of its orbit.
NASA announced last week that this idea is now more than theoretical. Over a two-month period, the Kepler team conducted tests of the K2 concept and last month detected the transit of an already-known Jupiter-sized exoplanet called WASP-28b, which orbits its sun every three days.
According to NASA, Kepler hasn't anything near the precision that it previously had, but it is possible to use its star trackers to calibrate its aim to within a hundredth of a degree, while compensating for the spacecraft’s expansion and contraction due to uneven heating by the Sun. As to the future, the Kepler team has submitted a proposal to the 2014 Astrophysics Senior Review of Operating Missions to continue working on Kepler.
The team says that if Kepler can be brought back online, it can be used to search for planets orbiting nearby bright stars, study star formation, and use of gravity lensing for the study of galaxies and supernovae.
With the team’s proposals currently under review, the next round of observations called “Campaign 0” are scheduled to begin in March.