Current Progress on Second Astrometric Satellite(Gaia) Project

The scientific goals of the second astrometric satellite(Gaia) are briefly described. Gaia will be launched in March 2013.The current progress of this project is presented in this paper,especially the basic principle of observational data processing method is given.The difference between Gaia and Hipparcos data processing is also pointed out.In order to attain the accuracy with micro-arcsecond in proper motion some systematic errors such as secular aberration drift,effects of the low-frequency gravitational wave,the Universe expansion anisotropy,the weak microlensing and the microlensing noise should be considered.The construction of Gaia optical reference frame,including the selection of quasars and the attainable accuracy,is mentioned. As for the link between Gaia reference and the radio reference frame ICRF-2,which is adopted by IAU at the 27 th IAU general assembly,the core drift and detection of luminosity in long-term as accident errors should be considered.Finally,through the collaboration with some countries some research subjects,which can be carried out on ground based observations with current instruments and 65 m radio telescope to be built at Shanghai Astronomical Observatory in China,are suggested to support Gaia observations.