The Terrestrial Planet Finder (TPF) is a plan by NASA for a telescope system that would be capable of detecting extrasolar terrestrial planets.

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 brilliant searchlight from far away. 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.

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 utilize 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 10 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 the faint planets.

NASA and JPL were supposed 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 is anticipated to occur around 2014, and TPF-I may launch by 2020.

According to NASA's 2007 budget documentation, released on 2006-02-06, the project was deferred indefinitely NASA President's FY 2007 Budget Request. In June 2006 funding for the TPF was provided along with the long-sought mission to Europa, a moon of Jupiter that may harbor extraterrestrial life .

The European Space Agency, ESA, is considering a similar mission, called Darwin.

See also

• Great Observatories program
• Aurelia (planet)
• Darwin (ESA)
• New Worlds Imager

Top 100 TPF target stars

References