Time: 16:00 h
Author: Lennart Lindegren
The second release of Gaia data, scheduled for April 2018, will give positions, parallaxes, proper motions, and photometric data for more than 1 billion stars. The astrometric solution is a core part of the Gaia data processing, which connects the several hundred billion measurements into a consistent dataset covering the whole celestial sphere. This is a challenging task in several respects: size, complexity, required numerical accuracy, and the need to model both known and unknown effects at microarcsec level. This talk gives an overview of the methods used and some examples of the difficulties encountered and how they are overcome. Although the astrometric solution was implemented and tested well before the launch of Gaia in 2013, it is still in a vigorous state of development as a result of the confrontation with real data.