• The Washington Post


The Kepler space telescope, the celebrated discoverer of worlds around distant stars, may have found its last planet.

NASA scientists announced on Wednesday that the telescope, which to date has cost $600 million to build and operate, has lost the ability to point accurately.

It is not dead, but by going wobbly it can’t do the precision observations necessary for spotting signs of exoplanets.

Kepler is 65 million km from Earth, too far away to be fixed even if NASA still had a space shuttle and could throw together a repair mission.

“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 rescue 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.

On Sunday, however, the telescope signaled that it had gone into “safe” mode, as it is programmed to do when it has a problem.

Although scientists at 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 they 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-size planet in a habitable zone — a twin Earth, the ultimate potential discovery for Kepler — may 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,” he said.

Asked at the end of the news conference how he felt about this latest turn of events, Borucki sounded more emotional than before.

“It’s been a very long journey. Coming up with an idea that basically very few people believed in,” Borucki said.

“But right now, I’m really delighted with all it’s accomplished,” he said. “It was designed to operate for four years. It operated for four years. . . . I’m just elated with what we’ve accomplished. I’m not feeling sorry at all.”

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