Relativistic Modellingof Positional Observationswith Microarcsecond Accuracy

Abstract

The problem of relativistic modelling of GAIA observations isreviewed. Basic principles of the relativistic model and its overallstructure are described in detail. All relativistic effects which mayamount to 1 μas are revealed and discussed. It is argued thatrelativistic definitions of astrometric parameters (position,parallax, proper motion, radial velocity, etc.) consistent with anaccuracy of 1 μas should be considered only within a well-definedalgorithm of relativistic reduction of observational data.