SAXO, the eXtreme Adaptive Optics System of SPHERE: overview and calibration procedure

The direct imaging of exoplanet is a challenging goal of todays astronomy. The light transmitted by exoplanet atmosphere is of a great interest as it may witness for life sign. SPHERE is a second generation instrument for the VLT, dedicated to exoplanet imaging, detection, and characterisation. SPHERE is a global project of an European consortium of 11 institutes from 5 countries. We present here the state of the art of the AIT of the Adaptive Optics part of the instrument. In addition we present fine calibration procedures dedicated to eXtreme Adaptive Optics systems. First we emphasized on vibration and turbulence identification for optimization of the control law. Then, we describe a procedure able to measure and compensate for NCPA with a coronagraphic system.