The Transformation between the Terrestrial and Celestial Reference Systems: Needs and Potential of GPS and Galileo
Capitaine, N.¹; Wallace, P. T.^2
1Observatoire de Paris/SYRTE; ²SST Department, STFC Rutherford Appleton Laboratory

The transformation between the International terrestrial reference system (ITRS) and the Geocentric celestial reference system (GCRS) is an essential part of the models to be used in the reduction of GNSS observations and scientific exploitation. Those observations can also be used for improving the models. This paper will first report on the recent high accuracy models that have been adopted at an international level (IAU/IUGG) for expressing the relevant quantities for the ITRS to GCRS transformation. The paper will then present simplified forms of the expressions that can be useful for reducing the computational time of the parameters depending on the required precision. It will finally discuss the potential contribution of GPS and Galileo to improvements of the models.