The tech behind NASA's Kepler spacecraft

By Leonard David

updated 3:05 p.m. ET March 4, 2009

BOULDER, Colo. - NASA's sharp-shooting Kepler spacecraft is ready to take its place this week in the pantheon of planetary detection technologies.

It wasn't long ago when a question mark loomed over astronomers pondering whether other planets existed beyond our little family of solar system worlds. Today, nearly 330 exoplanets have been discovered in the past 15 years — most of which are gas giants with characteristics similar to Jupiter and Neptune.

It's a little out of the astronomical limelight, but there are those that see planet hunting as a "space race" ... a worldwide competition to find other Earths circling their respective stars.

In early February, it was announced that the French Convection Rotation and Planetary Transits spacecraft had discovered the smallest exoplanet yet, and with a surface to walk on to boot, albeit blazingly boot-melting hot.

COROT-exo-7b is the tiniest terrestrial planet ever detected outside the Solar System and orbits a sun-like star.

"CoRoT is an excellent mission...a complimentary mission to Kepler," explained William Borucki, Kepler's science principal investigator at NASA's Ames Research Center at Moffett Field, Calif.

Those using CoRoT have found that many of the stars they've surveyed are more variable than expected, Borucki noted in a February 19 NASA press briefing on Kepler.

"So it's going to be harder for us to find some of these planets. That's one of the reasons they haven't found as many planets as they had hoped for at this time," Borucki said. Still, the CoRoT team remained confident that their spacecraft will find many more planets, he added.

Show time for Kepler
Now it's show time for NASA's Kepler, which is set for a late-night liftoff on Friday, March 6.

It is billed as the first mission with the ability to find planets like Earth — rocky planets that orbit sun-like stars in a warm and cozy zone where liquid water could be sustained on the surface. Liquid water is viewed as crucial for the formation of life.

"The CoRoT mission continues to provide surprises with its latest discovery of a hot super Earth with a 21-hour orbit. The Kepler mission looks forward to the challenge of being the first to find an Earth-size planet in the habitable zone of another star," Borucki advised SPACE.com.

There are a host of differences between the two spacecraft.

The CoRoT mission, along with its planet finding skills, is also designed to detect the subtle variation in a star's light, caused by sound waves rippling across the surface. By doing this, CoRoT will gain a detailed insight into the internal conditions of the star. This technique is known as asteroseismology.

Slideshow   Month in Space Get fresh perspectives on the Crab Nebula, the Milky Way and other wonders in November's roundup of out-of-this-world imagery. more photos

For the $600 million Kepler, there is one goal: finding Earth-size planets in the habitable zone of sun-like stars.

CoRoT launched in December 2006 and in the last two years has led to the discovery of six giant planets and the recent claim of a terrestrial planet in a 21-hour orbit with a diameter about 1.7 times that of the Earth.

More discoveries of hot terrestrial size planets larger than the Earth are expected in the coming years. However, because of CoRoT's small aperture and because it can only look at a star field for five months before turning to another, it is not expected to discover Earth-size planets in the habitable zone.

Kepler, meanwhile, is specifically designed to discover dozens of Earth-size planets in the habitable zone and hundreds near the habitable zone.

A comparison of Kepler to CoRoT shows that Kepler has a 95-centimeter aperture, a field of view of 100 square degrees, 42 detectors, and monitors a field of view long enough to find planets with periods as long as 1.5 years.

For CoRoT, it has a 27-centimeter aperture, a field of view of four square degrees, and two detectors for planet finding, and monitors a single field of view long enough to find planets with periods no longer than 2.5 months.

MORE FROM SPACE

Space Section Front

Astronauts land with families on their mind Cosmic Log: Signs of Mars life? ... and more Powerful laser simulates stellar jet Solar tsunamis are real, NASA says Rocket man fails to fly from Morocco to Spain Is case finally closed on 1965 UFO mystery? New dad-in-space: Focusing on shuttle job easy Space telescope to probe sun’s atmosphere Space agencies argue over delayed launch   Month in space: Powerful pictures Space Section Front   Add Space headlines to your news reader: