"Detection and characterization of extrasolar low-mass planets are currently limited by several astrophysical and instrumental effects. New exoplanet-hunter instruments, with improved capabilities, are foreseen at the horizon 2016 - 2017. To find other Earths, new state-of-the-art instruments must be followed by the state-of-the-art of data analysis software that takes into account for the astrophysical limitations. Currently, the main astrophysical limitations to the detection and the precise characterization of exoplanets are the precise characterization of the host star and the existence of false-positive scenarios (such as diluted binaries or stellar activity which are able to mimic extrasolar planets. The objective of this proposal is double. First, implement into the PASTIS software (a state-of-the-art of data-analysis software, co-developed by the candidate) tools to both characterize the planet-host star and to model stellar jitter. This will be done with the help of world-leading experts present at the host institution. The second objective is to validate new small and low-mass planets among the CoRoT, Kepler and HARPS data, using the improved PASTIS software. These developments and detections will be a milestone for the detection capabilities and analysis of data currently collected at the host institution and for the search of exo-Earths with future facilities, in which Europe always played a pioneer role."