Searching for exosolar planets with the COROT space mission

The space mission COROT (to be launched in 2002) will continuously monitor the flux of a number of stars during 150 days periods with a very high photometric accuracy. One of its objectives is the detection of extra-solar planets by looking for their transits in front of the disk of several tens thousand stars. COROT accommodates a 25 cm telescope with low straylight, and 4 2048×2048 CCDs, 2 of which monitoring 5000 to 12000 stars simultaneously up to m_v= 16.5. The stability and noise performances should make easy the detection of Jupiter-like planets and possible the detection of Earth-like planets with radius 1.5R_⊕. Under study is a dispersive system that will allow to retrieve some chromatic information : this could be essential to discriminate actual transit events against stellar fluctuations that would mimic a transit and to identify properly the events occurring in binary stars. The mission, the instrument and the results of simulations are presented, together with a discussion on the number of expected events : the multiple ones with a short orbital period signature, or the single or double events identified by their (a)chromatic signature. The later ones may lead to the discovery of planets in the habitable zone.