Spacecraft will hunt for planets

Telescope plan rejected 4 times before approval

Jim Erickson, Rocky Mountain News

Monday, January 29, 2007

BOULDER - William Borucki wasn't sure he'd live to see his dream mission, the planet-hunting Kepler telescope, make it into space.

The planetary scientist's proposal was rejected four times by NASA. Then other delays and budget cuts threatened to scuttle the $500 million effort before it reached the launch pad.

But persistence is paying off for Borucki, 68. The Kepler space telescope is under construction at Ball Aerospace & Technologies in Boulder, with launch set for November 2008.

Borucki said Sunday he persevered because the question Kep-ler will answer is just too important to be ignored or deferred.

"Ultimately, what we're asking is, 'What's the place of mankind in the universe?' " he said at a workshop hosted by the NASA-funded Center for Astrobiology at the University of Colorado.

"The question of whether there are other habitable planets out there, and how frequent they are, is a first step in understanding the extent of life in the universe," said Borucki, who works at NASA's Ames Research Center in California.

"It's an important problem, and I want to be part of its solution."

Kepler will search for Earth- size planets within the "habitable zone," the region around a star where temperatures allow liquid water to persist. Since all known life forms require liquid water, such planets are probably the best place to look for life beyond our solar system.

If Earth-size planets in the habitable zone are common, Kepler may find 50 or 60 of them during its four-year mission. If they're rare, Kepler may not find any.

But even a goose egg would be a monumental result, Borucki said.

"If we find a lot in the habitable zone, life is probably ubiquitous," he said. "If we find zero, then we're probably alone."

Wobble is indicator

NASA's Kepler spacecraft, about 15 feet tall and 6 feet wide, won't be able to determine if the planets harbor life. That task will fall to future missions.

Since 1995 more than 200 planets have been discovered outside our solar system. Most of these so-called "extrasolar" planets are Jupiter-size, and some are closer to their parent star than Mercury is to the sun.

The Jupiter-size planets exert a gravitational tug on the parent star. That tug makes the star wobble slightly, revealing the presence of the unseen planet.

The vast majority of extrasolar planets have been discovered by looking for that wobble.

A handful of Jupiter-size planets also have been found using the transit technique that Kepler will employ.

But Kepler will be the first mission capable of detecting the slight dimming of an Earth- size planet passing in front of its star, said Jack Lissauer of Ames, a member of the Kepler team.

The amount of dimming caused by the transit of an Earth-size planet is comparable to a gnat flying in front of the car headlight, said Edna De Vore of California's SETI Institute.

Plan repeatedly rejected

It took years for Borucki to convince NASA officials that Kepler's goal was technically feasible. First proposed in 1992, the idea didn't win approval until December 2001. Engineers at Boulder's Ball Aerospace then faced two formidable challenges, said Monte Henderson, the company's program manager for Kepler.

The first was to create an ultra- stable telescope that could lock onto the same spot in space for four straight years.

"This is a staring mission," Henderson said. "The stability requirements on Kepler are far beyond anything that exists today, so we are developing a new stability and guidance system that doesn't exist anywhere in the world."

The second challenge was handling the flood of data Kepler will collect. The craft will carry the largest starlight-gathering mirror and the largest digital camera ever to fly in deep space.

Overall, Kepler - named for a German astronomer and mathematician - is about as complex as Deep Impact, the Ball-built NASA craft that smashed into a comet in 2005, Henderson said.

ericksonj@RockyMountainNews.com or 303-954-5129