Terrestrial Planet Finder
The Terrestrial Planet Finder (TPF) was a proposed project by NASA to construct a system of telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled in 2011. There were actually two telescope systems under consideration, the TPF-I, which had several small telescopes, and TPF-C, which used one large telescope.
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. That technology challenge has been likened to finding a firefly near the beam of a distant searchlight. Additional goals of the mission would include characterizing the surfaces and atmospheres of newfound planets, and looking for the chemical signatures of life. In May 2004, both architectures were approved. Congressional spending limits under House Resolution 20 passed on 31 January 2007, by the United States House of Representatives and 14 February by the U.S. Senate have postponed the program indefinitely.
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 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 6 February 2006, the project was deferred indefinitely. In June 2006, a House of Representatives subcommittee voted to provide funding for the TPF along with the long-sought mission to Europa, a moon of Jupiter that might harbor extraterrestrial life. However, as of June 2008[update], actual funding has not materialized, and TPF remains without a launch date. More recently, in June 2011, the TPF (and SIM) programs have been reported as "cancelled".
Top 10 target stars 
|Rank ||Target star||Constellation||Distance
|1||Alpha Centauri A||Centaurus||4.3||G2V|
|2||Alpha Centauri B||Centaurus||4.3||K1V|
See also 
- Kepler (spacecraft)
- High Accuracy Radial Velocity Planet Searcher
- Space Interferometry Mission
- Darwin (spacecraft)
- Automated Planet Finder
- Mullen, Leslie (2 June 2011). "Rage Against the Dying of the Light". Astrobiology Magazine. Retrieved 2011-06-07.
- "NASA budget statement". Planetary Society. 2006-02-06. Retrieved 2006-07-17.
- NASA President's FY 2007 Budget Request
- "House subcommittee helps save our science". Planetary Society. 2006-06-14. Retrieved 2006-07-17.
- Charles Q. Choi (2007-04-18). "New Technique Will Photograph Earth-Like Planets". Space.com. Retrieved 2007-05-02.
- TPF C's Top Target Stars Space Telescope Science Institute
|Wikimedia Commons has media related to: Terrestrial Planet Finder|
- NASA PlanetQuest: Terrestrial Planet Finder
- Terrestrial Planet Finder Mission Profile by NASA's Solar System Exploration
- Canceling NASA's Terrestrial Planet Finder: The White House's Increasingly Nearsighted "Vision" For Space Exploration
- Congressional Inaction Leaves Science Still Devastated. Planetary Society (2006-11-26).
- Current status of TPF development work (March 2007)
- Interferometric Nulling at TNO