K2: Scientists cheer as Kepler’s second chance gets NASA go-ahead

It’s official: NASA has given the Kepler spacecraft’s mission makeover the go-ahead, turning it from a pure planet-hunting endeavor to an exploratory venture to study a wide range of celestial objects.

The new mission, called K2, would repurpose the hobbled space telescope in a clever way: by using the sun as a necessary “third wheel” to help steer the spacecraft. Under K2’s marching orders, Kepler would look at all manner of phenomena, including exoplanets, supernovae, galaxy clusters and still-forming stars.

“We’re absolutely thrilled,” said Kepler project manager Charlie Sobeck at NASA Ames Research Center in Mountain View, Calif. “We thought we had a very exciting mission, and it’s gratifying to see that the review committee agreed with us. ”

Since its launch in 2009, the planet-hunting Kepler spacecraft stared at roughly 150,000 stars in a single patch of sky, looking for repeated tiny dips in their brightness that would signal a passing planet blocking their light. To do this, the space telescope needed a highly tuned precision-pointing capability, which required at least three reaction wheels to hold it very still. But two of its four wheels broke, leaving it one wheel short.

Scientists thought that was the end for the crippled spacecraft. UC Berkeley astronomer Geoffrey Marcy even penned a mournful poem after Kepler’s apparent demise. But engineers at Ball Aerospace soon realized that they could use the pressure from the sun’s light particles (known as photons) to push on the spacecraft in just the right way, essentially acting as that missing “third wheel.”

It’s not perfect, but it gets the job done, Kepler project scientist Steve Howell told The Times recently. And although the spacecraft can no longer stare at the same field for years on end, it can now look at a variety of interesting objects that are sure to draw the gaze of many scientists.

“When this concept was first described to our science team … I was expecting to see nothing but downturned faces,” Sobeck said. Instead, “one of the astrophysicists ran me down in the hallway and said, ‘This is the mission you guys should have flown right from the beginning.’”

Sobeck says the mission has an estimated 2 1/2 years of fuel left, but it’s possible the team could stretch that even further as it learns to steer the spacecraft efficiently in its new mode.