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Kepler/K2 mission graphic

Phase: Operating

Launch Date: March 06, 2009

Mission Project Home Page -

Program(s):Discovery, Exoplanet Exploration

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The Kepler Mission, a NASA Discovery mission, was designed to survey a region of the Milky Way Galaxy and monitor ~160,000 stars to detect and characterize hundreds of Earth-size and smaller planets in or nearby the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet’s surface. The scientific objectives of the Kepler Mission was to explore the structure and diversity of planetary systems to:

  • Determine the percentage of terrestrial and larger planets that are in or near the habitable zone of a wide variety of stars
  • Determine the distribution of sizes and shapes of the orbits of these planets
  • Estimate how many planets there are in the multiple-star systems
  • Determine the variety of orbit sizes and planet reflectivities, sizes, masses and densities of short-period giant planets
  • Identify additional members of each discovered planetary system using other techniques
  • Determine the properties of those starts that harbor planetary systems

The loss of a second of the four reaction wheels on board the Kepler spacecraft in May 2013 brought an end to the primary Kepler science mission.

Developed over the months following this failure, the K2 mission represents a new concept for spacecraft operations. The K2 mission entails a series of sequential observing "Campaigns" of fields distributed around the ecliptic plane.

Operating in the ecliptic plane minimizes the torque exerted on the spacecraft by solar wind pressure, reducing pointing drift to where spacecraft attitude can effectively be controlled through a combination of thrusters and the two remaining reaction wheels. Each ecliptic Campaign is limited by Sun angle constraints to a duration of approximately 80 days. All K2 targets are proposed by the science community through the Guest Observer Program. The K2 mission welcomes all proposals including, but not exclusive to, exoplanet, stellar, extragalactic and solar system science.

Science Highlights

  • Kepler-10b: A rocky planet (January 2011)
  • Kepler-16b: A planet with two suns (September 2011)
  • Kepler-22b: Habitable zone planet around a sun-like star (December 2011)
  • Kepler-20e & f: Earth-size planets (December 2011)
  • Kepler-42b, c & d: Three smallest planets (January 2012)
  • Kepler-62e & f: Super-Earth-size planets in the habitable zone (April 2013)
  • Kepler-90: Star with seven transiting planets (November 2013)
  • Kepler-186f: Earth-size planet in the habitable zone of its star (April 2014)

Last updated: March 7, 2016

Related Links
  • PlanetQuest -
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