In order to evaluate and develop mission concepts for a search for Terrestrial Exoplanets, the European Space Agency has prepared a list of potential target systems. In this paper we present the criteria for selecting potential target stars suitable for the search for Earth like planets. We also establish the habitable zone for the stellar systems. Planets found within these zones would be potentially able to host complex life forms. The Darwin target star catalogue was created from the Hipparcos catalogue by examining the information on distance, spectral classification, multiplicity and stellar variability. Additional information on the targets stars including spectral type, metallicity, X-ray luminosity, rotation and Strömgren photometry from several other catalogues are included to determine the target star sample. Design constraints of the mission are added to derive a final target star catalogue of 262 target stars excluding and 447 target stars including M stars for the Darwin mission. We also discuss the completeness of sample for different classes of stars.

The direct detection of Earth-like exoplanets orbiting nearby stars and the characterization of such planetsparticularly, their evolution, their atmospheres, and their ability to host life-constitute a significant problem. The quest for other worlds as abodes of life has been one of mankind's great questions for several millennia. For instance, as stated by Epicurus *300 BC: ''Other worlds, with plants and other living things, some of them similar and some of them different from ours, must exist.'' Demokritos from Abdera (460-370 BC), the man who invented the concept of indivisible small parts-atoms-also held the belief that other worlds exist around the stars and that some of these worlds may be inhabited by life-forms. The idea of the plurality of worlds and of life on them has since been held by scientists like Johannes Kepler and William Herschel, among many others. Here, one must also mention Giordano Bruno. Born in 1548, Bruno studied in France and came into contact with the teachings of Nicolas Copernicus. He wrote the book De l'Infinito, Universo e Mondi in 1584, in which he claimed that the Universe was infinite, that it contained an infinite amount of worlds like Earth, and that these worlds were inhabited by intelligent beings. At the time, this was extremely controversial, and eventually Bruno was arrested by the church and burned at the stake in Rome in 1600, as a heretic, for promoting this and other equally confrontational issues (though it is unclear exactly which idea was the one that ultimately brought him to his end).In all the aforementioned cases, the opinions and results were arrived at through reasoning-not by experiment. We have only recently acquired the technological capability to observe planets orbiting stars other than

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Abstract. The European Space Agency's Darwin and NASA's Terrestrial Planet Finder (TPF) are among the most challenging space science missions ever considered. Their principal objective is to detect Earth-like planets around nearby stars and to characterize their atmospheres. Darwin and TPF-I are currently conceived as nulling interferometers with free-flying telescopes. Within the frame of the Darwin program, the ESA and the European Southern Observatory (ESO), supported by European industries and scientific institutes, have performed two parallel Phase A studies of a ground-based nulling interferometry experiment (GENIE) at the site of ESO's Very Large Telescope Interferometer (VLTI) in Paranal, Chile. GENIE will demonstrate several key technologies required for the Darwin mission. Its science objectives include the detection and characterization of dust disks and low-mass companions around nearby stars. These studies have established detailed instrumental designs, in which GENIE will operate in the L' band around 3.8 microns as a single Bracewell nulling or constructive interferometer, using either two Auxiliary or two Unit Telescopes. The studies were supported by detailed numerical simulations which indicated the possibility of detection and low-resolution spectroscopy in nulling mode of extra-solar giant planets (EGPs) with atmospheric temperatures down to 700 K, provided that a proper calibration of instrumental effects is applied. Detection of circumstellar exo-zodiacal (EZ) dust clouds is possible down to 0.5 mJy, with interesting prospects for the characterization of planet-forming disks.

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