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Quick Facts: Kepler – More Info

The Kepler spacecraft searches for planets in the habitable zone, which is the region around a star where the temperature permits water to be liquid on the surface of a planet. Liquid water is considered essential for the existence of life.

Kepler hunts for planets using a specialized one-meter diameter telescope (3.3 feet) called a photometer. The photometer continuously measures the precise brightness of more than 100,000 stars, waiting for the stars to “wink” when orbiting planets pass in front of them.

These events, called “transits” occur each time a planet crosses the line-of-sight between the planets parent star and the Kepler telescope. When this happens, the planet blocks some of the light from the star, resulting in the periodic dimming. This periodic signature is used to detect the planet and to determine its size and orbit.

By monitoring a large number of stars, Kepler permits astronomers to estimate the total number of Earth-size planets orbiting in the habitable zone around stars in our galaxy and by extrapolation, to the entire universe.

Additional Quick Facts

Delta II Fuel: Nine strap-on solid rocket motors. The first stage uses kerosene and liquid oxygen. The second stage uses hydrazine and nitrogen tetroxide.
Orbital Period: 371 days
Spacecraft Dimensions: 2.7 meters (9ft) diameter, 4.7 meters (15.3 ft) high
Weight: 1052.4 kg (2,320.1 lbs) at launch
Weight Breakdown:

  • Spacecraft- 562.7 kg (1240.5 lbs)
  • Photometer- 478 kg (1043.9 lbs)
  • Hydrazine Propellant- 11.7 kg (25.8 lbs)

Photometer: The sole Kepler instrument is a photometer—a Schmidt-type telescope consisting of a .95-meter (37-inch) aperture and a 1.4-meter (55-inch) primary mirror. This configuration allows for a 105 square degree field of view. Kepler’s photometer has a field of view 33,000 times greater than the Hubble Space Telescope. The photometer features a focal plane array with more than 95 million pixels. The focal plane array is the largest camera NASA has ever flown in space.

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  • Bill Possel
    Laboratory for Atmospheric and Space Physics

    303-492-6867
  • Jim Scott
    University of Colorado

    (303) 492-3114
  • Roz Brown
    Ball Aerospace & Technologies Corp.
    Boulder, Colo.
    Spacecraft

    (303) 533-6059