Kepler (space telescope)

Kepler
NSSDC ID	2009-011A
Client	NASA
Launcher	Delta II 7925-10L D-339
construction
Takeoff mass	1039 kg
Course of the mission
Start date	March 7, 2009, 03:50 UTC
launch pad	Cape Canaveral LC-17B
End date	October 30, 2018

Artist's representation: Kepler in space
Shown are the earth and the moon on the right edge of the picture and a fictitious star surrounded by a planet in the constellation Swan in the top left .

The Kepler - space telescope of NASA , which was launched in March 2009 in order to extrasolar planets to search (exoplanets), was in operation until October 30, 2018. Named the project after the German was astronomer Johannes Kepler , the beginning of the 17th century. Century recognized the laws of planetary orbits.

In mid-May 2013, NASA announced that Kepler could no longer be aligned with the previous precision due to two defective reaction wheels . On August 15, 2013, the main mission was suspended, but Kepler was able to continue searching for exoplanets with a modified mission ( called K2 ). The scientific observations were stopped on October 30, 2018 due to lack of fuel, and on November 15, 2018 the telescope was finally shut down.

The main mission

An illustration of the area of ​​our Milky Way Galaxy that has been observed

The telescope observed a fixed section of the starry sky with approx. 190,000 stars in the constellation Swan in order to discover extrasolar planets using the transit method . The special objective of the project was to discover comparatively small planets (like our earth or smaller) and thus potentially habitable extrasolar planets. At the same time, it provided basic data on variable stars in order to be able to draw conclusions about the processes taking place inside. Kepler's mission was initially scheduled for three and a half years. In November 2012 it should be extended by up to four years. After the failure of two reaction wheels in May 2013, the observation method had to be changed and the secondary mission K2 followed with other scientific goals in order to be able to continue using the telescope scientifically.

Orbit

Kepler's orbit

In order to be able to carry out the observations as undisturbed as possible, the telescope was not brought into orbit around the earth. Instead, Kepler is in a solar orbit whose orbital period (372.5 days) and eccentricity differ somewhat from that of Earth. The probe follows the earth and moves further and further away from it over the years. This made it possible to monitor the observation region without periodic obscuration by the earth and with minimal interference.

technical description

The telescope, which weighs 1039 kilograms and is almost five meters high, uses a photometer to measure the brightness of stars in order to determine fluctuations in brightness that indicate the passage of a planet between the star and the space telescope. Kepler observed over 100,000 star systems in a certain area simultaneously over a period of several years.

The optics of the Kepler photometer are designed as a Schmidt telescope . The diameter of the Schmidt plate is 0.95 m and that of the main mirror 1.4 m. The focus is on an arrangement of 42 CCD sensors that were able to monitor a field of 105  square degrees , which roughly corresponds to the palm of the hand with an outstretched arm. Each CCD sensor has a size of 50 mm × 25 mm with a resolution of 2200 × 1024  pixels , so that the camera has a total of 95 megapixels. To increase the photometric accuracy, the optics were slightly defocused , and a band pass for wavelengths from 430–890 nm is also built in.

The transmission of the observation data to the ground station took place in the Ka-band with up to 4.33125 Mbps. The X-band with 7.8125 bps to 2 kbps for the uplink and 10 bps to 16 kbps for the downlink was used to control the satellite . In October 2018, Kepler was approx. 150 million km from the earth and the signals took approx. 500 seconds for one direction.

Search for earth-like planets

Representation of the probability of transit
(= star radius / planetary orbit radius)

Ignition of the engines of Kepler's Delta II 10L rocket

When passing through an extrasolar planet the size of the earth, a darkening of the order of 0.1 ‰ was expected on the space telescope (for earth and sun 0.084 ‰). This takes place with a central passage in front of the image of the star for a period of around half a day (for earth and sun 13 hours). If the passage is not central, the darkening time is shorter. If the same change in brightness was repeated twice in this star and the two intervals were the same and other causes for the signal (such as double stars) could be excluded, a planet on a fixed orbit was assumed to be the cause and was considered to be discovered. The orbit and size of the planet can be determined from the orbit and the change in brightness according to Kepler's laws . Due to the correspondingly determined distance of the discovered exoplanet to its sun and the luminosity of this sun (determined according to luminosity class and spectral class ), the temperature on the planet and thus its possible habitability can be approximately calculated. Due to the different orbital inclinations of the planets against our line of sight, however, only a fraction of Earth-like planets can be observed from our direction. The probability that such a transit can be observed from Earth is simply the quotient of the radius of the star and the planet's orbit, in the case of the Earth and the Sun, 0.465%.

course

The launch of the 600 million-dollar telescope took place on March 7, 2009 at 3:49:57 UTC as the payload of a Delta II 7925-10L carrier rocket from Launch Complex 17B of the Cape Canaveral AFS . It was the 339th launch of a Delta missile. After extensive testing and calibration of the sensors, the telescope started work two months later.

In January 2010 the first five planets discovered by Kepler were announced ( Kepler-4b to 8b, see also Kepler-6 , Kepler-7 ). Kepler 1b to 3b had already been discovered using terrestrial observation methods before the probe was launched. All of them are planets that orbit their stars at distances of less than 0.1 astronomical units and which have a significantly higher surface temperature than any planet in our solar system. In June 2010, the data of 306 of the 706 exoplanet candidates identified by then were published. The discovery of transits of cooler, potentially more Earth-like planets takes a longer observation phase because of their longer orbital period and was only expected for a later phase of the Kepler mission.

In January 2011 it was announced that Kepler had discovered the smallest rock planet known to date outside of our solar system: Kepler-10b . It was tracked down through observation from May 2009 to January 2010. Kepler-10b has 4.6 times the mass and 1.4 times the size of Earth and orbits its central star every 0.84 days. It is about 20 times closer to it than Mercury is to the sun. Later, the smallest known rock planet, Kepler-37b, was discovered, even smaller than Mercury and only slightly larger than the Earth's moon .

On February 2, 2011, NASA reported that 1235 planet candidates had been identified since the start of the mission. Five of them are almost as big as the earth and in the habitable zone. A total of 54 were discovered in the habitable zone and 68 almost earth-sized planet candidates. 288 super-earths , 662 the size of Neptune, 165 the size of Jupiter and 19 larger than Jupiter were identified as further planetary candidates .

On December 5, 2011, NASA confirmed the first planet within the habitable zone of a sun-like star. Kepler-22b is the first of 54 candidates published on February 2, 2011 within the habitable zone that has been officially confirmed. For this, Kepler had to have observed at least 3 rounds in front of his home star. Overall, the number of planet candidates has increased to 2326, of which 207 are about the size of the earth. Furthermore, 680 " super-earths ", 1181 Neptune-like, 203 Jupiter-like and 55 planets larger than Jupiter have been observed.

In July 2012, the only redundant one of the four reaction wheels that control and stabilize the position of the telescope in space failed. At the beginning of January 2013, there were increased coefficients of friction on another reaction wheel, the failure of which would no longer have been manageable. As a result, on January 17, 2013, Kepler was put into a safety mode ("wheel rest safe mode") for a planned duration of ten days, in the hope that the lubricant would redistribute itself in the stationary bearings by diffusion. The restart took place as planned and without any problems between January 27 and 29, 2013.

On May 11, 2013, a second reaction wheel failed, as announced on May 21, 2013. It was initially assumed that Kepler would have to switch to a worse stabilized mode, but could still collect data.

On August 15, 2013, NASA issued a press release announcing the final cessation of the original Kepler mission. However, a study was commissioned to examine the scientific operation with the two remaining reaction wheels in combination with the control nozzles.

On November 25, 2013, NASA announced that it had found a way to make the telescope operational again despite the failure of the two reaction wheels. The two remaining motors should work against the pressure of the sun's photons and thus stabilize Kepler.

On February 26, 2014, NASA published 715 new planetary finds (including some in the habitable zone) that could be derived from the old data. These finds all belong to systems with several planets and were not verified, as is usually the case, through follow-up observations with earth-based telescopes, but rather through statistical analyzes, taking into account the accumulation of data pointing to planets at the respective central stars.

On April 17, 2014 NASA announced the discovery of the Earth-like planet Kepler-186f , which is located in the habitable zone of its central star.

With Kepler-452b , the discovery of a planet with about 1.6 times the radius of the earth in the habitable zone of a sun-like star was announced on July 23, 2015 . The planet could be a rock planet. The star in the constellation Swan is approximately 1,400 light-years away from the Sun and, at around 6 billion years, a third older than it.

K2 mission

The alignment of the telescope during the K2 mission (text in English)

After the failure of two of the four reaction wheels, a new plan was developed for how the telescope could continue to operate. To do this, it had to be brought into a position in which the radiation pressure from the sun would not rotate the telescope. This only allowed observations along the ecliptic , and the telescope was aimed at a new region of the sky every 75 days. The search for exoplanets continued, and the study of star clusters , young and old stars as well as active galaxies and supernovae was one of the telescope's new tasks.

In December 2014, NASA announced the first discovery of an exoplanet (HIP 116454b) as part of the K2 mission; this discovery is based on data collected while testing the new observation methods in February 2014.

Since Neptune was in the observation area, Kepler was able to observe the planet for over 70 days from November 2014 to January 2015.

In February 2015, a list of 36 exoplanet candidates identified with the K2 mission was published, for which a study published at the end of March 2015 confirmed 18 exoplanet discoveries through statistical analyzes (one of them in the habitable zone of its central star, a bright red dwarf of the spectral class M2) and 6 rejected as false positives . The orbital times of the confirmed exoplanets are between 5 and 33 days, according to the observation possibilities of the K2 mission.

The constellation Aquarius, Kepler's last image. The black stripes are camera errors

On April 8, 2016, NASA announced that Kepler had put himself into emergency operation. In this mode, the positioning was controlled exclusively via position control nozzles and thus consumes significantly more fuel. The telescope tries to maintain communication with the Deep Space Network . On April 10, the telescope could be brought back into a stable condition, and on April 22, regular operation as part of the K2 mission could be resumed.

From the end of April to the beginning of July 2016, Kepler was oriented towards the galactic center as part of the K2 mission and took part in an observation campaign to find microlensing events, in which large earth-based telescopes were also used.

The financing of the K2 mission was extended to the end in June 2016 due to a lack of fuel, including the termination procedures at the end. This was expected for 2018. In September and October 2018 problems arose with the exact alignment of Kepler, which was interpreted as an indication of the end of fuel supplies. The data from the 19th campaign could be received in full by October 15th. On October 30, 2018, NASA announced that it had run out of fuel. Before it was shut down in mid-November, the space telescope took its last photo on September 25, 2018. Various star systems of the Aquarius constellation can be seen on it. Kepler will now remain in solar orbit indefinitely.

List of important discoveries

system	planet	publication	comment
Kepler-4	Kepler-4b	January 2010	first discoveries of the Kepler mission
Kepler-6	Kepler-6b	January 2010	first discoveries of the Kepler mission
Kepler-7	Kepler-7b	January 2010	Unusually low density planet
Kepler-10	Kepler-10b	January 2011	smallest rock (exo) planet known to date
Kepler-11	Kepler-11b - g	February 2011	Star with at least 6 exoplanets; triple transit in August 2010
Kepler-16	Kepler-16b	September 2011	first observed transit in a binary star system
Kepler-22	Kepler-22b	December 2011	first planet within the habitable zone
Kepler 37	Kepler-37b	February 2013	smallest known (as of August 2017) exoplanet, about the size of the Earth's moon
Kepler-62	Kepler-62e , f	April 2013	two earth-like planets in the habitable zone
Kepler-69	Kepler-69c	April 2013	an earth-like planet in the habitable zone
Kepler-90	Kepler-90b - h	October 2013	Star with the most exoplanets discovered by then (see also entry "Kepler-90i" December 2017)
Kepler-186	Kepler-186f	April 2014	an earth-like planet in the habitable zone
Kepler-10	Kepler-10c	June 2014	First identification of a planet as a mega-earth (based on follow-up observations of the planet discovered with Kepler in 2011 with HARPS-N )
Kepler-438	Kepler-438b	January 2015	probably an earth-like planet in the habitable zone
Kepler 442	Kepler-442b	January 2015	probably an earth-like planet in the habitable zone
Kepler 444	Kepler-444b - f	January 2015	System with five planets only barely Earth-sized; Central star with 11.2 ± 1.0 billion years one of the oldest known with planets
Kepler-452	Kepler-452b	July 2015	first approximately Earth-sized exoplanet in the habitable zone around a sun-like ( spectral class G2) central star
Kepler-1625	Kepler-1625b	May 2016	May be orbited by an exomoon .
Kepler-90	Kepler-90i	December 2017	first description of an eighth planet in a system outside the solar system

See also

• COROT (space telescope)
• Space interferometry mission

Web links

Commons : Kepler Mission  - collection of pictures, videos and audio files

• Official NASA website of the Kepler mission (accessed June 3, 2014)
• NASA - Current Missions - Kepler Mission (accessed June 3, 2014)
• Kepler Planet Candidate Data Explorer (accessed June 3, 2014)
• Spektrum .de: Eight Insights We Owe to Kepler October 31, 2018

Individual evidence

1. ↑ Manfred Lindinger: Is NASA losing its planet hunter? In: FAZ.net . May 16, 2013, accessed December 16, 2014 . 
2. ↑ ^{a b} Kepler Mission Manager Update. NASA, May 15, 2013, accessed May 16, 2013 . 
3. ^ ^{A b} NASA Ends Attempts to Fully Recover Kepler Spacecraft, Potential New Missions Considered. NASA (Ames Research Center), August 15, 2013, accessed December 20, 2014 . 
4. ↑ ^{a b} Kepler Mission Manager Update: K2 Has Been Approved! NASA, May 16, 2014, accessed May 18, 2014 . 
5. ↑ heise online: NASA telescope Kepler finally shut down. Accessed November 19, 2018 (German). 
6. ^ The Kepler Field Of View. NASA, January 11, 2013, accessed February 16, 2013 . 
7. ↑ A thousand new worlds? (PDF) Stars and Space 5/2012, pp. 24–25
8. ↑ Detection of Transiting Planet Candidates in Kepler Mission Data (PDF; 1.2 MB)
9. ↑ ^{a b} NASA's Kepler Completes Prime Mission, Begins Extended Mission. NASA, November 14, 2012, accessed February 16, 2013 . 
10. ↑ NASA - Kepler Overview (English)
11. ^ NASA - Characteristics of Transits
12. ↑ NASA - Kepler Launch (English)
13. ↑ ^{a b c d} NASA’s Kepler Space Telescope Discovers Its First Five Exoplanets. NASA, January 4, 2010, accessed December 21, 2014 . 
14. ↑ Borucki et al .: Characteristics of Kepler Planetary Candidates based on the first Data Set: The Majority are found to be Neptune-size and smaller , arxiv : 1006.2799v1 .
15. ↑ Stefan Deiters: First rocky planet discovered. astronews.com, January 11, 2011, accessed February 16, 2013 . 
16. ↑ NASA Finds Earth-size Planet Candidates in Habitable Zone, Six Planet System nasa.gov, February 2, 2011
17. ^ Kepler Planet Hunter Finds 1,200 Possibilities New York Times, February 2, 2011 (accessed February 3, 2011)
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19. ^ Kepler Mission Manager Update. NASA, January 17, 2013, accessed January 29, 2013 . 
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23. ^ Jack J. Lissauer et al .: Validation of Kepler's Multiple Planet Candidates. II: Refined Statistical Framework and Descriptions of Systems of Special Interest . Ed .: NASA / Astrophysical Journal. February 25, 2014, arxiv : 1402.6352 (English, nasa.gov [PDF; accessed December 21, 2014]).
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27. ↑ http://www.nasa.gov/keplerbriefing0723
28. ↑ http://orf.at/stories/2291118/ NASA discovers “cousin” of the earth. 1,400 light years away. orf.at July 23, 2015. Accessed July 24, 2015.
29. ↑ G.Á.Bakos et al .: HAT-P-54b: A hot jupiter transiting a 0.64 Msun star in field 0 of the K2 mission . April 17, 2014, arxiv : 1404.4417 (English, an exoplanet that was discovered with earth-based instruments before the start of the mission and its importance for comparative measurements planned with the K2 mission is described. ).
30. ↑ NASA's Kepler Reborn, Makes First Exoplanet Find of New Mission. NASA, December 18, 2014, accessed December 19, 2014 . 
31. ↑ Martin Holland: NASA: Rescued Kepler Space Telescope finds exoplanets again. heise.de, December 19, 2014, accessed on December 19, 2014 . 
32. ↑ Michele Johnson: VIDEO: Kepler Observes Neptune Dance with Its Moons . In: NASA . May 14, 2015 ( nasa.gov [accessed August 5, 2017]).
33. ^ Daniel Foreman-Mackey, Benjamin T. Montet, David W. Hogg, Timothy D. Morton, Dun Wang, Bernhard Schölkopf: A systematic search for transiting planets in the K2 data . February 16, 2015, arxiv : 1502.04715 .
34. ↑ Benjamin T. Montet, Timothy D. Morton, Daniel Foreman-Mackey, John Asher Johnson, David W. Hogg, Brendan P. Bowler, David W. Latham, Allyson Bieryla, Andrew W. Mann: Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 18 Systems, Including a Planet Receiving Earth-like Insolation . March 26, 2015, arxiv : 1503.07866 .
35. ↑ Michele Johnson: Kepler is Back in Business Collecting Science Data for the K2 Mission! In: NASA. Retrieved April 25, 2016 . 
36. ↑ http://www.nasa.gov/feature/mission-manager-update-kepler-spacecraft-in-emergency-mode
37. ↑ Kepler Planet-Hunting Spacecraft Bounces Back After Glitch - See more at: http://www.space.com/32534-nasa-kepler-exoplanet-spacecraft-recovers-glitch.html. April 11, 2016, Retrieved April 12, 2016 . 
38. ^ Kepler Recovered and Returned to the K2 Mission. NASA, April 22, 2016, accessed April 25, 2016 . 
39. ^ Searching for Far Out and Wandering Worlds. NASA, April 7, 2016, accessed April 25, 2016 . 
40. ↑ Knicole Colon: K2 mission officially extended through end of mission . In: Kepler & K2 . June 9, 2016 ( nasa.gov [accessed April 22, 2017]).
41. ↑ Michele Johnson: Kepler Spacecraft Updates . In: NASA . August 7, 2018 ( nasa.gov [accessed October 27, 2018]).
42. ↑ NASA Retires Kepler Space Telescope, Passes Planet-Hunting Torch . October 30, 2018 (English, nasa.gov [accessed October 31, 2018]).
43. ↑ Kepler's Final Image Shows A Galaxy Full Of Possibilities nasa.gov, Retrieved February 8, 2019
44. ↑ NASA's Kepler Mission Discovers Its First Rocky Planet. NASA, January 10, 2011, accessed December 21, 2014 . 
45. ↑ NASA Finds Earth-size Planet Candidates in Habitable Zone, Six Planet System. NASA, February 2, 2011, accessed December 21, 2014 . 
46. ↑ NASA's Kepler Mission Discovers a World Orbiting Two Stars. NASA, September 15, 2011, accessed December 21, 2014 . 
47. ↑ Discovery: Kepler-37b, a planet only slightly larger than the Moon. NASA (Ames Research Center), February 20, 2013, accessed December 19, 2014 . 
48. ↑ ^{a b} NASA's Kepler Discovers Its Smallest 'Habitable Zone' Planets to Date. NASA, April 18, 2013, accessed December 21, 2014 . 
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50. ↑ Xavier Dumusque et al .: The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet . May 30, 2014, arxiv : 1405.7881 (English).
51. ↑ Martin Holland: Exoplanet: Researchers discover a new type of planet with "Mega Earth". heise.de, June 2, 2014, accessed December 19, 2014 . 
52. ^ Francois Fressin et al .: Kepler-10c, a 2.2-Earth radius transiting planet in a multiple system . May 23, 2011, arxiv : 1105.4647 (English).
53. ↑ ^{a b} Guillermo Torres et al .: Validation of Twelve Small Kepler Transiting Planets in the Habitable Zone . January 7, 2015, arxiv : 1501.01101 (English).
54. ↑ ^{a b} Nadja Podbregar: Eight potentially life-friendly super-earths discovered. Image of Science, January 6, 2015, accessed February 11, 2015 . 
55. ↑ Tiago L. et al .: Campante An ancient extra-solar system with five sub-Earth-size planets . In: Astrophysical Journal . January 26, 2015, arxiv : 1501.06227 (English).
56. ↑ Methuselah Solar System discovered. scinexx .de, January 28, 2015, accessed on January 28, 2015 . 
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58. ↑ T. Morton et al .: False positive probabilities for all Kepler Objects of Interest: 1284 newly validated planets and 428 likely false positives
59. ↑ Alex Teachey, David M. Kipping, Allan R. Schmitt: HEK VI: On the Dearth of Galilean analogue in Kepler and the Exomoon Candidate Kepler 1625b I . In: AAS journals . 1707, 2017. arxiv : 1707.08563 . bibcode : 2017arXiv170708563T .
60. ↑ Christopher J. Shallue, Andrew Vanderburg: Identifying Exoplanets with Deep Learning: A Five Planet Resonant Chain around Kepler-80 and an Eighth Planet around Kepler-90. (PDF) In: Astronomical Journal (accepted for publication). December 13, 2017. Retrieved December 17, 2017 . arxiv : 1712.05044