By Andrew Grant
The telescope that has discovered thousands of exotic, quirky worlds — and a few tantalizingly Earthlike ones — orbiting distant stars is no longer capable of finding planets, at least temporarily and probably for good. Officials with NASA’s $600-million Kepler space telescope announced May 15 that an essential piece of hardware on the spacecraft has failed.
Since May 2009, Kepler has been staring at 170,000 stars and looking for tiny shadows cast by planets crossing in front of them. To enable Kepler to make such precise measurements, engineers installed four pointing devices, called reaction wheels, that turn the telescope and keep it dialed in on its stellar targets. One of the wheels stopped working last July, but the telescope requires only three.
On May 14 Kepler scientists learned that the spacecraft had entered safe mode, which occurs when something is awry. When they tried to restore the telescope to normal operations, another reaction wheel failed to activate. That wheel had been behaving erratically for months, so its failure was not a total surprise. “This is something we’ve been anticipating for a while,” said John Grunsfeld, NASA’s associate administrator of the science mission directorate.
For now, Kepler will enter a fuel-saving mode that keeps the spacecraft in constant communication with Earth. Charles Sobeck, Kepler’s deputy project manager, said the mission team will take the next few weeks to put together a plan of action for trying to restore one of the failed reaction wheels. “We’re not ready to call the mission over,” Grunsfeld said. “I wouldn’t call Kepler down and out just yet.”