The Terrestrial Planet Finder (TPF) was a proposed project by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

to construct a system of

space telescope A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launched ...

s for detecting

extrasolar An ''extrasolar object'' ({{ety, la, extra, outside or beyond, , solaris, of the Sun) is an astronomical object that exists outside the Solar System. It is not applied to stars, or any other celestial object that is larger than a star or the Sol ...

terrestrial planet A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, Ve ...

s. TPF was postponed several times and finally cancelled in 2011. 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 A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

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 The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production ...

near the beam of a distant

searchlight A searchlight (or spotlight) is an apparatus that combines an extremely bright source (traditionally a carbon arc lamp) with a mirrored parabolic reflector to project a powerful beam of light of approximately parallel rays in a particular direc ...

. Additional goals of the mission would include the characterization of the surfaces and

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

s of newfound planets, and looking for the chemical signatures of life. The two planned architectures were: *

Infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

astronomical interferometer An astronomical interferometer or telescope array is a set of separate telescopes, mirror segments, or radio telescope antenna (radio), antennas that work together as a single telescope to provide higher resolution images of astronomical objects ...

(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 A coronagraph is a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star's bright glare – can be resolved. Most coronagraphs are intended to view ...

(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 The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

, 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 The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...

(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 House of Representatives is the name of legislative bodies in many countries and sub-national entitles. In many countries, the House of Representatives is the lower house of a bicameral legislature, with the corresponding upper house often c ...

subcommittee voted to provide funding for the TPF along with the long-sought mission to

Europa Europa may refer to: Places * Europe * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Cliff ...

, a moon of Jupiter that might harbor

extraterrestrial life Extraterrestrial life, colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might ...

. Congressional spending limits under House Resolution 20 passed on 31 January 2007, by the

United States House of Representatives The United States House of Representatives, often referred to as the House of Representatives, the U.S. House, or simply the House, is the Lower house, lower chamber of the United States Congress, with the United States Senate, Senate being ...

and 14 February by the

U.S. Senate The United States Senate is the upper chamber of the United States Congress, with the House of Representatives being the lower chamber. Together they compose the national bicameral legislature of the United States. The composition and powe ...

postponed the program indefinitely. Actual funding has not materialized, and TPF remains a concept. In June 2011, the TPF (and SIM) programs were reported as "cancelled".

Top 10 target stars

References

External links

Canceling NASA's Terrestrial Planet Finder: The White House's Increasingly Nearsighted "Vision" For Space Exploration
Planetary Society (2006-11-26).
Current status of TPF development work (March 2007)Interferometric Nulling at TNO
{{Astrobiology Cancelled spacecraft Space telescopes Exoplanet search projects Astronomy projects Cancelled astrobiology space missions Projects disestablished in 2011

History

Top 10 target stars

See also

References

External links