What is the Terrestrial Planet Finder?

The Terrestrial Planet Finder (TPF) is a NASA project, currently in a conceptual stage due to budgetary constraints instituted on the agency by the U.S. Congress (Cowing, 2006). It consists of two approaches, both of which have been approved for development after reviewing more than 60 competing designs (TPF, 2004). One has been dubbed the TPF Coronograph, a visible light telescope at least three times as big as the HST, as well as more precise, equipped with special optics to reduce the incoming starlight by the factor of one million, thus allowing to capture the dimmer, reflected light from terrestrial planets in the vicinity of a star (NASA JPL, 2006). The other approach is the TPF Infrared Astronomical Interferometer, representing a number of small infrared telescopes, positioned in a precisely fixed structure in space (ideally in high Earth orbit), connected with one another so as to create a very large infrared telescope. The aim of this formation also will be to reduce the starlight to a point where the dim light from the planets orbiting the observed stars becomes seen (NASA JPL, 2006).

Both telescopes were planned to be constructed and launched by the middle of the next decade, with a specific intent of looking for terrestrial planets. Once such a planet is found, its distance from its parent star will be calculated to determine how hot the planet is, with the results being double-checked through the broad-spectrum examination of the planet's light emissions. Cool planets are expected to be brighter at the long wavelength end of their spectrum, while hot planets would be brighter at the short wavelength end of their spectrum (TPF, 2004). The planet's luminosity also will allow to determine its size, with these findings contributing to the eventual conclusion on the chances of the planet containing the atmospheric ingredients capable of producing and sustaining Earth-like life forms. For example, if a planet is too small, it might not be able to sustain atmosphere thick enough to produce Earth-like life. On the other hand, if the planet is too massive, its atmosphere will be too thick, and the force of gravity on it will be unbearable for a human being. Studying the absorption spectrum of the observed planets will provide further evidence of the presence of specific atmospheric elements. The most excitement probably will be generated by the discovery of ozone in a planet's atmosphere because, if it is anything like Earth, it would signify the presence of life. The TPF observations also will assist scientists in studying the history and techniques of planetary formations.

The goals of the TPF project are not purely scientific, however. In the long run, its findings may help determine the likelihood of organizing exploratory expeditions to those planets (if any are found) that most closely resemble Earth in their atmospheric and surface composition. The idea is to implement the apparent vision of the current White House administration that in 2004 announced that the efforts of space exploration, including manned space missions, would be renewed in the nearest future (Cowing, 2006).

References

Cowing, K. (2006). Canceling NASA's Terrestrial Planet Finder: The White House's increasingly nearsighted "vision" for space exploration. NASA Watch (February 6). Online at http://www.spaceref.com/news/viewnews.html?id=1092

NASA Jet Propulsion Laboratory (JPL). (2006). What is TPF? PlanetQuest. Online at http://planetquest.jpl.nasa.gov/TPF/tpf_what_is.cfm

Terrestrial Planet Finder (TPF). (2004). Earth-like planets. Online at http://www.terrestrial-planet-finder.com/