View source for Terrestrial Planet Finder

{{short description|NASA concept study of an array of space telescopes}}
[[File:Terrestrial Planet Finder PIA04499.jpg|thumb|200px|Terrestrial Planet Finder – Infrared interferometer concept]]
[[File:Coronagraph starburst.jpg|thumb|200px|A simulated view of the coronagraph for Terrestrial Planet Finder. (Courtesy NASA/JPL-Caltech)]]

The '''Terrestrial Planet Finder''' ('''TPF''') was a proposed project by [[NASA]] to construct a system of [[space telescope]]s for [[Methods of detecting extrasolar planets|detecting]] [[exoplanet|extrasolar]] [[terrestrial planet]]s. TPF was postponed several times and finally cancelled in 2011.<ref name=Mullen>{{cite web |last1=Mullen |first1=Leslie |title=Rage Against the Dying of the Light |url=http://www.astrobio.net/exclusive/4005/rage-against-the-dying-of-the-light |date=2 June 2011 |work=Astrobiology Magazine |access-date=2011-06-07 |archive-url=https://web.archive.org/web/20110604121537/http://www.astrobio.net/exclusive/4005/rage-against-the-dying-of-the-light |archive-date=2011-06-04 |url-status=usurped}}</ref><ref name="NYT-20140512">{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Finder of New Worlds |url=https://www.nytimes.com/2014/05/13/science/finder-of-new-worlds.html |date=12 May 2013 |work=[[The New York Times]] |access-date=13 May 2014 }}</ref> There were two telescope systems under consideration, the '''TPF-I''', which had several small telescopes, and '''TPF-C''', which used one large telescope.

==History==
In May 2002, NASA chose two TPF mission architecture concepts for further study and technology development. Each would use a different means to achieve the same goal—to block the light from a parent [[star]] in order to see its much smaller, dimmer planets. The technological challenge of imaging planets near their much brighter star has been likened to finding a [[firefly]] near the beam of a distant [[searchlight]]. Additional goals of the mission would include the characterization of the surfaces and [[Celestial body atmosphere|atmosphere]]s of newfound planets, and looking for the chemical signatures of life. 
 
The two planned architectures were:
*[[Infrared]] [[astronomical interferometer]] ('''TPF-I'''): Multiple small telescopes on a fixed structure or on separated spacecraft floating in precision formation would simulate a much larger, very powerful telescope. The interferometer would use a technique called [[nulling interferometry|nulling]] to reduce the starlight by a factor of one million, thus enabling the detection of the very dim infrared emission from the planets.
*Visible Light [[Coronagraph]] ('''TPF-C'''): A large optical telescope, with a mirror three to four times bigger and at least 100 times more precise than the [[Hubble Space Telescope]], would collect starlight and the very dim reflected light from the planets. The telescope would have special optics to reduce the starlight by a factor of one billion, thus enabling astronomers to detect faint planets.

NASA and [[Jet Propulsion Laboratory]] (JPL) were to issue calls for proposals seeking input on the development and demonstration of technologies to implement the two architectures, and on scientific research relevant to planet finding. Launch of TPF-C had been anticipated to occur around 2014, and TPF-I possibly by 2020.

According to NASA's 2007 budget documentation, released on February 6, 2006,<ref>{{cite web|date=2006-02-06|url=http://www.planetary.org/about/press/releases/2006/0206_Planetary_Society_Charges.html|title=NASA budget statement|publisher=[[Planetary Society]]|access-date=2006-07-17|archive-date=16 June 2006|archive-url=https://web.archive.org/web/20060616122446/http://planetary.org/about/press/releases/2006/0206_Planetary_Society_Charges.html|url-status=dead}}</ref> the project was deferred indefinitely.<ref>{{Cite web |url=http://www.nasa.gov/pdf/142458main_FY07_budget_full.pdf |title=NASA President's FY 2007 Budget Request |access-date=11 July 2006 |archive-date=28 February 2021 |archive-url=https://web.archive.org/web/20210228042519/https://www.nasa.gov/pdf/142458main_FY07_budget_full.pdf |url-status=dead }}</ref>

In June 2006, a [[United States House of Representatives|House of Representatives]] subcommittee voted to provide funding for the TPF along with the long-sought mission to [[Europa (moon)|Europa]], a moon of Jupiter that might harbor [[extraterrestrial life]].<ref>{{cite web| date=2006-06-14| url=http://www.planetary.org/about/press/releases/2006/0614_House_Subcommittee_Helps_Save_Our.html| title=House subcommittee helps save our science| publisher=Planetary Society| access-date=2006-07-17| archive-date=20 September 2006| archive-url=https://web.archive.org/web/20060920115939/http://www.planetary.org/about/press/releases/2006/0614_House_Subcommittee_Helps_Save_Our.html| url-status=dead}}</ref> Congressional spending limits under House Resolution 20 passed on January 31, 2007, by the [[United States House of Representatives]] and February 14 by the [[U.S. Senate]] postponed the program indefinitely. Actual funding has not materialized, and TPF remains a concept.<ref>{{cite web
| title = New Technique Will Photograph Earth-Like Planets
| author = Charles Q. Choi
| url = http://www.space.com/businesstechnology/070418_tech_wednesday.html
| publisher = Space.com
| date = 2007-04-18
| access-date = 2007-05-02}}</ref> In June 2011, the TPF (and [[Space Interferometry Mission|SIM]]) programs were reported as "cancelled".<ref name=Mullen/>

== Top 10 target stars ==
{| class="wikitable" style="text-align:center; margin-left:auto; margin-right:auto;"
|-
! Rank<ref>{{cite web |title=TPF-C Top 100 |url=http://sco.stsci.edu/tpf_top100/index.php |archive-url=https://web.archive.org/web/20051212170833/http://sco.stsci.edu/tpf_top100/index.php |archive-date=12 December 2005 |url-status=dead}}</ref>
! Target star
! [[Constellation]]
! Distance<br>([[light-year]]s)
! [[Stellar classification|Spectral type]]
|-
| align="center"| 1
| align="center"| [[Alpha Centauri A]]
| align="center"| [[Centaurus]]
| align="center"| 4.3
| align="center"| G2V
|-
|align="center"| 2
|align="center"| [[Alpha Centauri B]]
|align="center"| [[Centaurus]]
|align="center"| 4.3
|align="center"| K1V
|-
|align="center"| 3
|align="center"| [[Tau Ceti]]
|align="center"| [[Cetus (constellation)|Cetus]]
|align="center"| 12
|align="center"| G8V
|-
|align="center"| 4
|align="center"| [[Eta Cassiopeiae]]
|align="center"| [[Cassiopeia (constellation)|Cassiopeia]]
|align="center"| 19
|align="center"| G3V
|-
|align="center"| 5
|align="center"| [[Beta Hydri]]
|align="center"| [[Hydrus]]
|align="center"| 24
|align="center"| G2IV
|-
|align="center"| 6
|align="center"| [[Delta Pavonis]]
|align="center"| [[Pavo (constellation)|Pavo]]
|align="center"| 20
|align="center"| G8V
|-
|align="center"| 7
|align="center"| {{Bayer|Pi|3|Orionis}}
|align="center"| [[Orion (constellation)|Orion]]
|align="center"| 26
|align="center"| F6V
|-
|align="center"| 8
|align="center"| [[Gamma Leporis]]
|align="center"| [[Lepus (constellation)|Lepus]]
|align="center"| 29
|align="center"| F7V
|-
|align="center"| 9
|align="center"| [[Epsilon Eridani]]
|align="center"| [[Eridanus (constellation)|Eridanus]]
|align="center"| 10
|align="center"| K2V
|-
|align="center"| 10
|align="center"| [[40 Eridani]]
|align="center"| [[Eridanus (constellation)|Eridanus]]
|align="center"| 16
|align="center"| K1V
|}

==See also==
* {{annotated link|Automated Planet Finder}}
* {{annotated link|CoRoT}} 
* {{annotated link|Darwin (spacecraft)|Darwin}}
* {{annotated link|High Accuracy Radial Velocity Planet Searcher}}
* {{annotated link|James Webb Space Telescope}}
* {{annotated link|Kepler space telescope}}
* {{annotated link|List of NASA cancellations}}
* {{annotated link|Navigator Program}}
* {{annotated link|Space Interferometry Mission}}

==References==
{{Reflist}}

== External links ==
{{Commons category|Terrestrial Planet Finder}}
*[https://spaceref.com/uncategorized/canceling-nasas-terrestrial-planet-finder-the-white-houses-increasingly-nearsighted-vision-for-space-exploration/ Canceling NASA's Terrestrial Planet Finder: The White House's Increasingly Nearsighted "Vision" For Space Exploration]
*[https://web.archive.org/web/20070118234857/http://planetary.org/programs/projects/sos/20061122.html Congressional Inaction Leaves Science Still Devastated]. Planetary Society (2006-11-26).
*[https://web.archive.org/web/20070715214042/http://planetquest.jpl.nasa.gov/TPF/TPFIswgReport2007.pdf Current status of TPF development work (March 2007)]
*[http://www.tno.nl/content.cfm?&context=markten&content=case&laag1=191&item_id=600&Taal=2 Interferometric Nulling at TNO]
*[https://web.archive.org/web/20041204111102/http://origins.jpl.nasa.gov/missions/missions.html#pi Planet Imager (PI)]

{{Space observatories}}
{{Exoplanet search projects}}
{{Exoplanet}}
{{Astrobiology}}

[[Category:Cancelled spacecraft]]
[[Category:Space telescopes]]
[[Category:Exoplanet search projects]]
[[Category:Astronomy projects]]
[[Category:Cancelled astrobiology space missions]]
[[Category:Projects disestablished in 2011]]