STEP mission: high-precision space astrometry to search for terrestrial exoplanets

Search for Terrestrial Exo-Planest (hereafter STEP) mission is a latest advanced research project in Chinese Strategic Pioneer Program (SPP) on Space Science. STEP aims at the nearby earth-alike planets detection, comprehensive research on the planetary system and some astrometry research with 1 micro-arcsecond precision in the space, which will get the fruitful achievements in the exo-planetary and astrometry research fields. STEP will take the Space Astrometry technique in the optical band. The FOV is 0.44 degree, based on 1.2 m primary and focus length is 50 m. The special metrology technique will be taken to reach 0.5 ∼ 1 uas astrometry precision, which will be ideal for terrestrial exo-planets detection