A European Space Agency mission planned for launch in 2024 to look for planetary systems around other stars, with particular emphasis on Earth-sized planets in the habitable zone around stars like the Sun. From a position at the L2 Lagrangian point it will use thirty-four 120-mm telescopes to scan up to a million nearby stars for signs of planetary transits. It will also investigate seismic activity in the host stars to help determine their mass, diameter, and age.
http://sci.esa.int/plato/ Official mission page at the European Space Agency.