Aas 05-424 Study on the Station Keeping Maintenance for the Tpf Mission

In 1995, Mayor and Queloz [5] detected for the first time a planet orbiting a nearby star (15.4 parsecs). Since then, the interest in the detection of extra-solar planets, in order to learn about the origin, evolution and composition of planetary systems, has been grown and at this moment more than 150 extra-solar planets have been found. Almost all of them have been discovered using indirect methods, mainly with the Doppler effect, with which it is possible to measure very small periodic changes in the velocity of the star, due to the orbiting planet gravitational force. However, direct imaging together with the spectroscopic analysis of the light coming from the planet, is the only way to obtain information about its nature and, eventually, to detect features which could indicate that the planet supported or could support life (this planets are referred in the literature as terrestrial or Earth-like planets). Leaving aside the high resolution required for the detection of an Earth-like planet at a distance of 15 parsecs, the main problem for direct imaging is that planets are associated with a much brighter source of light. The contrast ratio between a Jupiter-like planet and its parent star can be of the order of 10, depending on the wavelength. One possible procedure to reduce this ratio, as well as the star diffraction pattern, is the use of nulling interferometry. Some experiments, such as the one conducted by Hinz et al. [4] to detect light from nearby sources as close as 0.2 arcsec around Betelgeuse after cancelling the light coming from the star, have already shown the viability and power of this procedure for the purpose under consideration.