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Dec. 21, 2001

Michael Mewhinney

NASA Ames Research Center, Moffett Field, Calif.

Phone: 650/604-3937 or 650/604-9000




NASA has selected the Kepler Mission, a project based at Ames Research Center, Moffett Field, Calif., as one of the next two new NASA Discovery missions.

Scheduled for launch in 2006, the Kepler Mission will use a unique spaceborne telescope specifically designed to search for Earth-like planets around stars beyond our solar system.

"The Kepler Mission will, for the first time, enable humans to search our galaxy for Earth-size or even smaller planets," said principal investigator William Borucki of Ames. "With this cutting-edge capability, Kepler may help us answer one of the most enduring questions humans have asked throughout history: are there others like us in the universe?"

To date, about 80 extra-solar planets have been discovered. However, these are all gaseous-giant planets similar to Jupiter, which are probably composed mostly of hydrogen and helium and unlikely to harbor life. None of the planet detection methods used so far has the capability of finding Earth-size planets - those that are 30 to 600 times less massive than Jupiter. None of the giants discovered to date has liquid water or even a solid surface.

The Kepler Mission is different from previous ways of looking for planets; it will look for the ‘transit’ signature of planets. A transit occurs each time a planet crosses the line-of-sight between the planet's parent star that it is orbiting and the observer. When this happens, the planet blocks some of the light from its star, resulting in a periodic dimming. This periodic signature is used to detect the planet and to determine its size and its orbit.

Three transits of a star, all with a consistent period, brightness change and duration, provide a robust method of detection and planet confirmation. The measured orbit of the planet and the known properties of the parent star are used to determine if each planet discovered is in the habitable zone, that is, at the distance from its star where liquid water could exist on the surface of the planet.

The Kepler Mission will hunt for planets using a specialized one-meter diameter telescope called a photometer to measure the small changes in brightness caused by the transits.

The key technology at the heart of the photometer is a set of charged coupled devices (CCDs) that measures the brightness of hundreds of thousands of stars at the same time. CCDs are the silicon light-sensitive chips that are used in today’s TV cameras, camcorders and digital cameras. Kepler must monitor many thousands of stars simultaneously, since the chance of any one planet being aligned along the line-of-sight is only about 1/2 of a percent.

"From monitoring 100,000 stars similar to our sun for four years, the Kepler team expects to find many hundreds of terrestrial-type planets," said David Koch of NASA Ames, the mission's deputy principal investigator.

The Kepler Mission will continuously view an amount of sky about equal to the size of a human hand held at arm's length or about equal in area to two ‘scoops’ of the sky made with the Big Dipper constellation. In comparison, the Hubble Space Telescope can view only the amount of sky equal to a grain of sand held at arms length, and then only for about a half-hour at a time.

"One of Ames' most important efforts is our work in the field of astrobiology - the study of life in the universe. Kepler's goal of finding planets that might harbor life represents a major step in advancing astrobiology research," said Dr. Harry McDonald, Ames’ Center Director.

"The Kepler mission represents a cornerstone in our effort to search for evidence of life in the universe, and will pave the way for future more complex space projects. I am very proud of the years of work invested by the Kepler team leading to this selection," said Scott Hubbard, Ames' Deputy Director for Research.

The industrial partner for development of the hardware is Ball Aerospace & Technologies Corp., Boulder, Colo. Kepler's selection involves a delayed start of development of up to one year due to funding constraints in the Discovery program.

NASA selected the two missions from 26 proposals made in early 2001. The missions must stay within the Discovery Program's development cost cap of about $299 million.

The Discovery Program emphasizes lower-cost, highly focused scientific missions. The past Discovery missions are NEAR Shoemaker, Mars Pathfinder and Lunar Prospector, all of which successfully completed their missions. Stardust and Genesis are in space; both have begun collecting science data, although Stardust has not yet arrived at its target comet. CONTOUR is scheduled to launch next summer, Deep Impact in January 2004 and MESSENGER in March 2004. ASPERA-3 and NetLander are Discovery Missions-of-Opportunity that are under development.

Details about the Kepler Mission are available at:

Kepler images are available at:

More information about the Discovery Program is available at:

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