Talk abstract details

The ESA mission Gaia gives the opportunity to reach the micro-arcsecond accuracy in the measurement of angles between stellar sources. Data exploitation for such a space astrometry mission requires a fully relativistic treatment of the stellar light propagation, namely the development of a highly precise sphere reconstruction within the framework of relativistic astrometry. In fact, the order of accuracy of one micro-arcsecond implies taking into account the general relativistic effects due the dynamical gravitational fields encountered by the light while propagating from the star to the observer. Contributing to ameliorate such a development and building a data reduction procedure in a fully general relativistic context is the purpose of the so called RAMOD project. The inverse ray tracing mathematical problem, which is at the basis of the RAMOD modelling, has been tackled by finding the proper reference frames of the satellite with respect to a local barycentric observer and an underlying global barycentric coordinate system (i.e. BCRS). It reconstructs the light trajectory in a curved space-time, which allows to link the astrometric observables to the relativistic effects associated to the stellar kinematical properties and distances as seen from inside the gravitational field of our Solar System. In order to single out these effects and as a tool for the comparison with other astrometrics models, we write the proper observed direction as function of the so called relativistic astrometric parameters within the post-Minkowskian formalism. Finally, these parameters provide a first look into the contents that the next astrometric catalogues will have to list after Gaia.