Many planets have been detected so far but very few around nearby stars that could allow characterization of their atmosphere thanks to their proximity. There are known exoplanets around less than 8.3% of the FGK stars of the Solar neighborhood (d<20 pc) and the vast majority of them are giant planets. Within the ESA Cosmic Vision 2015-2025 plan, the scientific goal of the NEAT (Nearby Earth Astrometric Telescope) mission is to detect and characterize planetary systems around these nearby stars in an exhaustive way down to 1 Earth-mass in the habitable zone. This survey would provide the actual planetary masses, the full characterization of the orbits including their inclination, for all the components of the planetary system down to the Earth-mass limit. NEAT will continue the work performed by Hipparcos and Gaia by reaching a precision that is improved by two orders of magnitude on pointed targets compared to Gaia. We present the free-flyer concept that has been submitted to the 2010 ESA call for M3 missions with two satellites flying in formation 40m apart.
