Title: Relativistic Astrometry - History, principles, and modeling overview 

Speaker: Alberto Vecchiato (Turin astronomical observatory, Italy) 

Time & Place: Wednesday, 2:30pm, April 30th, 3rd floor middle conference room 

Abstract: 

　　Modern astrometric techniques can attain accuracies far beyond the capabilities of the classical astrometric models, based on Newtonian physics and Euclidean geometry. For this reason, during the last three decades, several attempts have been made to provide models able to meet these accuracies. Such models have to be formulated within a relativistic framework. The historical evolution of the classical astrometric models will be quickly followed, interpreting it with a vectorial formalism and under the principles of the Newtonian gravitation and dynamics. This will allow to present the steps needed to write a relativistically consistent model of the basic astrometric observable in similar fashion, highlighting the analogies and the differences of the two. Thereafter it will be given an overview of the different models presently available, with particular attention at those prepared for the Gaia mission, and finally, the results of the currently ongoing comparison attempts will be briefly shown.