Visible spectroscopy of terrestrial exoplanets with SEE-COAST

While more than 450 exoplanets have been discovered, mid-infrared photometry and near-infrared (NIR) low-resolution spectroscopy were obtained for a few transiting gazeous planets. Nevertheless, the transit method is limited to close-in planets (≲0.1 AU). To study the chemical composition and structure of the atmosphere of wide-separated planets (≳1 AU), direct imaging is requested. To date, 12 planet candidates were detected by this method. In a near future (2011-2014), ground-based instruments (SPHERE, GPI, HiCIAO) and the James Webb Space Telescope (JWST) will survey a large sample of gazeous planets around young and M-dwarf stars in the solar neighborhood. To characterize terrestrial planets, extremely good and stable conditions as in space are required. Our team propose the SEE-COAST mission, a 1.5-m space telescope, that aims at visible spectro-polarimetry of mature giant and massive terrestrial planets. Here we briefly recall the principle of this mission and its objectives. We detailed the image analysis used to retrieve the planet spectra and we present the performance of SEE-COAST obtained by numerical simulations.