Kepler (spacecraft) facts for kids

Kids Encyclopedia Facts
Kepler in orbit
Artist's impression of the Kepler telescope
Mission type Space telescope
Operator NASA / LASP
Mission duration Planned: 3.5 years
Final: 9 years, 7 months, 23 days
Spacecraft properties
Manufacturer Ball Aerospace & Technologies
Launch mass 1,052.4 kg (2,320 lb)
Dry mass 1,040.7 kg (2,294 lb)
Payload mass 478 kg (1,054 lb)
Dimensions 4.7 m × 2.7 m (15.4 ft × 8.9 ft)
Power 1100 watts
Start of mission
Launch date March 7, 2009, 03:49:57 (2009-03-07UTC03:49:57) UTC
Rocket Delta II (7925-10L)
Launch site Cape Canaveral SLC-17B
Contractor United Launch Alliance
Entered service May 12, 2009, 09:01 UTC
End of mission
Deactivated November 15, 2018 (2018-11-15)
Orbital parameters
Reference system Heliocentric
Regime Earth-trailing
Semi-major axis 1.0133 AU
Eccentricity 0.036116
Perihelion 0.97671 AU
Aphelion 1.0499 AU
Inclination 0.44747 degrees
Period 372.57 days
Argument of perihelion 294.04 degrees
Mean anomaly 311.67 degrees
Mean motion 0.96626 deg/day
Epoch January 1, 2018 (J2000: 2458119.5)
Main telescope
Type Schmidt
Diameter 0.95 m (3.1 ft)
Collecting area 0.708 m2 (7.62 sq ft)
Wavelengths 430–890 nm

Kepler Logo.png

Discovery program
← Dawn

Kepler space telescope is a retired space telescope launched by NASA to discover Earth-size planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched on March 7, 2009, into an Earth-trailing heliocentric orbit. The principal investigator was William J. Borucki. After nine years of operation, the telescope's reaction control system fuel was depleted, and NASA announced its retirement on October 30, 2018.

Designed to survey a portion of Earth's region of the Milky Way to discover Earth-size exoplanets in or near habitable zones and estimate how many of the billions of stars in the Milky Way have such planets, Kepler's sole scientific instrument is a photometer that continually monitored the brightness of approx 150,000 main sequence stars in a fixed field of view. These data are transmitted to Earth, then analyzed to detect periodic dimming caused by exoplanets that cross in front of their host star. Only planets whose orbits are seen edge-on from Earth can be detected. During its over nine and a half years of service, Kepler observed 530,506 stars and detected 2,662 planets.


Aerial View of the NASA Ames Research Center - GPN-2000-001560
Aerial view of the NASA Ames Research Center, Mountain View, California

Kepler space telescope was part of NASA's Discovery Program of relatively low-cost science missions. The telescope's construction and initial operation were managed by NASA's Jet Propulsion Laboratory, with Ball Aerospace responsible for developing the Kepler flight system. The Ames Research Center is responsible for the ground system development, mission operations since December 2009, and scientific data analysis.

The initial planned lifetime was 3.5 years, but greater-than-expected noise in the data, from both the stars and the spacecraft, meant additional time was needed to fulfill all mission goals. Initially, in 2012, the mission was expected to be extended until 2016, but on July 14, 2012, one of the spacecraft's four reaction wheels used for pointing the spacecraft stopped turning, and completing the mission would only be possible if all other reaction wheels remained reliable. Then, on May 11, 2013, a second reaction wheel failed, disabling the collection of science data and threatening the continuation of the mission.

Kepler-62f with 62e as Morning Star
Artist's concept depicts NASA's Kepler mission's smallest habitable zone planet, seen in the foreground is Kepler-62f, a super-Earth-size planet

On August 15, 2013, NASA announced that they had given up trying to fix the two failed reaction wheels. This meant the current mission needed to be modified, but it did not necessarily mean the end of planet hunting. NASA had asked the space science community to propose alternative mission plans. On November 18, 2013, the K2 "Second Light" proposal was reported. This would include utilizing the disabled Kepler in a way that could detect habitable planets around smaller, dimmer red dwarfs. On May 16, 2014, NASA announced the approval of the K2 extension.

Histogram of exoplanet discoveries

By January 2015, Kepler and its follow-up observations had found 1,013 confirmed exoplanets in about 440 star systems, along with a further 3,199 unconfirmed planet candidates. Four planets have been confirmed through Kepler's K2 mission. In November 2013, astronomers estimated, based on Kepler space mission data, that there could be as many as 40 billion rocky Earth-size exoplanets orbiting in the habitable zones of Sun-like stars and red dwarfs within the Milky Way. It is estimated that 11 billion of these planets may be orbiting Sun-like stars. The nearest such planet may be 3.7 parsecs (12 ly) away, according to the scientists.

Kepler-452b artist concept
Artist's concept of one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun

On January 6, 2015, NASA announced the 1,000th confirmed exoplanet discovered by the Kepler space telescope. Four of the newly confirmed exoplanets were found to orbit within habitable zones of their related stars: three of the four, Kepler-438b, Kepler-442b and Kepler-452b, are almost Earth-size and likely rocky; the fourth, Kepler-440b, is a super-Earth. On May 10, 2016, NASA verified 1,284 new exoplanets found by Kepler, the single largest finding of planets to date.

Keplers supernova
Multiwavelength X-ray, infrared, and optical compilation image of Kepler's supernova remnant SN 1604

Kepler data has also helped scientists observe and understand supernovae; measurements were collected every half-hour so the light curves were especially useful for studying these types of astronomical events.

On October 30, 2018, after the spacecraft ran out of fuel, NASA announced that the telescope would be retired. The telescope was shut down the same day, bringing an end to its nine-year service. Kepler observed 530,506 stars and discovered 2,662 exoplanets over its lifetime. A newer NASA mission, TESS, launched in 2018, is continuing the search for exoplanets.


Kepler orbit
Kepler's orbit, the telescope's solar array was adjusted at solstices and equinoxes

Kepler was operated out of Boulder, Colorado, by the Laboratory for Atmospheric and Space Physics (LASP) under contract to Ball Aerospace & Technologies. The spacecraft's solar array was rotated to face the Sun at the solstices and equinoxes, so as to optimize the amount of sunlight falling on the solar array and to keep the heat radiator pointing towards deep space.

Together, LASP and Ball Aerospace controlled the spacecraft from a mission operations center located on the research campus of the University of Colorado. LASP performs essential mission planning and the initial collection and distribution of the science data. The mission's initial life-cycle cost was estimated at US$600 million, including funding for 3.5 years of operation. In 2012, NASA announced that the Kepler mission would be funded until 2016 at a cost of about $20 million per year.

Ignition of Kepler's Delta II 7925-10L
Ignition of a Delta II 7925-10L rocket with the the Kepler space telescope on Board

Objectives and methods

The scientific objective of Kepler is to explore the structure and diversity of planetary systems. This spacecraft observes a large sample of stars to achieve several key goals:

  • To determine how many Earth-size and larger planets there are in or near the habitable zone (often called "Goldilocks planets") of a wide variety of spectral types of stars.
  • To determine the range of size and shape of the orbits of these planets.
  • To estimate how many planets there are in multiple-star systems.
  • To determine the range of orbit size, brightness, size, mass and density of short-period giant planets.
  • To identify additional members of each discovered planetary system using other techniques.
  • Determine the properties of those stars that harbor planetary systems.

Images for kids

Kepler (spacecraft) Facts for Kids. Kiddle Encyclopedia.