Terrestrial Planet Finder

Terrestrial Planet Finder - Infrared interferometer concept

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 telescopes in space 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.

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. 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.

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.

In May 2004, both architectures were approved.

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 April 2007, actual funding has not materialized, and TPF remains without a launch date.

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.

More recently, in June 2011, the TPF (and SIM) programs have been reported as "cancelled".

Top 10 target stars

Rank	Target star	Constellation	Distance (light-years)	Spectral type
1	Alpha Centauri A	Centaurus	4.3	G2V
2	Alpha Centauri B	Centaurus	4.3	K1V
3	Tau Ceti	Cetus	12	G8V
4	Eta Cassiopeiae	Cassiopeia	19	G3V
5	Beta Hydri	Hydrus	24	G2IV
6	Delta Pavonis	Pavo	20	G8V
7	Pi3 Orionis	Orion	26	F6V
8	Gamma Leporis	Lepus	29	F7V
9	Epsilon Eridani	Eridanus	10	K2V
10	40 Eridani	Eridanus	16	K1V

See also

• Kepler (spacecraft)
• High Accuracy Radial Velocity Planet Searcher, Ground based, in operation since 2013
• COROT, French space based exoplanet finder in operation from 2007 to 2012
• Space Interferometry Mission, a NASA proposal. Technology developed but spacecraft not funded.
• Darwin (spacecraft), an ESA proposal similar to TPF
• Automated Planet Finder, at Lick Observatory, operating from 2013

External links

• 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