The Kepler Space Telescope, the celebrated discoverer of worlds around distant stars, may have found its last planet. NASA announced Wednesday that the telescope, which to date has cost $600 million to build and operate, has lost the ability to point accurately.
It's not dead, but by going wobbly, it can't do the precision observations necessary for spotting signs of "exoplanets." Kepler is 40 million miles from Earth -- too far 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, NASA's head of science, 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 the telescope signaled Sunday 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, engineers discovered Tuesday 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, the Kepler team 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 -- may be lurking in that data, said William Borucki, Kepler's lead scientist and the driving force for the telescope.
"I don't think I'd be a pessimist here," Mr. 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 years. ... I'm just elated with what we've accomplished. I'm not feeling sorry at all."health - science