“Kepler’s not in a place where I can go up and rescue it, or any other astronaut,” said John Grunsfeld, the head of science at NASA who became famous as an astronaut for his missions to fix the Hubble Space Telescope.
The Kepler telescope, launched in 2009, seemed fine when NASA technicians and scientists communicated with it last Thursday. But on Sunday, the telescope signaled that it had gone into “safe” mode, as it is programmed to do when it has a problem. Although NASA didn’t know conclusively why that happened, on Tuesday engineers discovered that one of the reaction wheels used for steering wouldn’t spin.
The spacecraft has four such wheels. One had failed previously. Now two were inoperative. There is no way to control the pitch, roll and yaw of a spacecraft with just two reaction wheels.
That doesn’t necessarily mean Kepler is permanently crippled. NASA officials vowed in their news conference to try to restart the wheel or find a workaround to allow Kepler to resume planet-hunting. But they admitted that they were saddened by the malfunction, which may bring to an end a planet-hunting mission that, although it already has lived up to its promise and then some, could potentially have continued for a number of years.
In addition to finding 132 planets that have been confirmed by telescopes on the ground, Kepler has found more than 2,700 other candidate planets. The telescope uses the transit method, looking for the very slight dimming of starlight when a planet passes in front of the star when seen from the telescope.
Earlier this year, Kepler’s team of scientists announced that it had found three new planets, modestly larger than the Earth, in habitable zones around two stars.
Scientists still have two years’ worth of data to examine, and a truly Earth-sized planet in a habitable zone — an Earth twin, the ultimate potential discovery for Kepler — might be lurking in that data, said William Borucki, Kepler’s lead scientist and the driving force behind the telescope.
“I don’t think I’d be a pessimist here,” Borucki said. “The mission has been phenomenally successful, and I really wouldn’t write it off at this point.”
Asked at the end of the news conference how he felt about this latest turn of events, he sounded more emotional than before.
“It’s been a very long journey. Coming up with an idea that basically very few people believed in,” he said. “But right now, I’m really delighted with all it’s accomplished. It was designed to operate for four years. It operated for four year. . . . I’m just elated with what we’ve accomplished. I’m not feeling sorry at all.”
Emi Kolawole contributed to this report.