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| telescope_wavelength = 430–890 nm〔 | trans_bandwidth = X band up: 7.8 bps-2 kbps〔 X band down: 10 bps-16 kbps〔 Ka band down: Up to 4.3 Mbps〔 | insignia = Kepler Logo.png }} ''Kepler'' is a space observatory launched by NASA to discover Earth-like planets orbiting other stars. The spacecraft, named after the Renaissance astronomer Johannes Kepler, was launched on March 7, 2009.〔(【引用サイトリンク】title=Kepler Launch )〕 Designed to survey a portion of our region of the Milky Way to discover dozens of Earth-size extrasolar planets in or near the habitable zone and estimate how many of the billions of stars in the Milky Way have such planets,〔(【引用サイトリンク】url=http://kepler.nasa.gov/Mission/QuickGuide/ )〕 ''Kepler'' sole instrument is a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view.〔(【引用サイトリンク】url=http://aas.org/node/651 ) – click the itinerary builder to get to the abstract of "Kepler Planet Detection Mission: Introduction and First Results".〕 This data is transmitted to Earth, then analyzed to detect periodic dimming caused by extrasolar planets that cross in front of their host star. ''Kepler'' is part of NASA's Discovery Program of relatively low-cost, focused primary 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,〔("NASA Extends Planet-Hunting Kepler Mission Through 2016" ). Space.com. April 4, 2012. Retrieved May 2, 2012.〕 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〔(NASA - Kepler Mission Manager Update (May 21, 2013) )〕 and threatening the continuation of the mission. 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 "potentially including an exoplanet search, using the remaining two good reaction wheels and thrusters".〔(【引用サイトリンク】title=NASA Ends Attempts to Fully Recover Kepler Spacecraft, Potential New Missions Considered )〕 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. , ''Kepler'' and its follow-up observations had found 1,013 confirmed exoplanets in about 440 stellar systems, along with a further 3,199 unconfirmed planet candidates.〔(【引用サイトリンク】url=http://exoplanetarchive.ipac.caltech.edu/cgi-bin/ExoTables/nph-exotbls?dataset=cumulative )〕 Four planets have been confirmed through ''Kepler'' K2 mission. In November 2013, astronomers reported, based on ''Kepler'' space mission data, that there could be as many as 40 billion Earth-sized planets 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 away, according to the scientists.〔〔 On January 6, 2015, NASA announced the 1000th 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 near-Earth-size and likely rocky; the fourth, Kepler-440b, is a super-Earth. ==Spacecraft== The spacecraft has a mass of and contains a primary mirror feeding an aperture of – at the time of its launch this was the largest mirror on any telescope outside Earth orbit. The spacecraft has a 115 deg2 (about 12-degree diameter) field of view (FOV), roughly equivalent to the size of one's fist held at arm's length. Of this, 105 deg2 is of science quality, with less than 11% vignetting. The photometer has a soft focus to provide excellent photometry, rather than sharp images. The mission goal is a combined differential photometric precision (CDPP) of 20 ppm for a ''m''(V)=12 solar-like star for a 6.5-hour integration, though the observations so far have fallen short of this objective (see mission status). An Earth-like transit produces a brightness change of 84 ppm and lasts for thirteen hours when it crosses the center of the star. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Kepler (spacecraft)」の詳細全文を読む スポンサード リンク
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