Towards a Rigorous Combination of Space Geodetic Techniques

The IERS with all its different components and products, ranging from the definition and realization of the reference frames (ITRF and ICRF), over EOPs and global geophysical fluid data all the way to conventions, is in a unique position to contribute in an essential way to the integration and combination efforts that are necessary to cope with the next generation of scientific missions and challenges. Concentrating on its core products first, the IERS should strive for a rigorous combination of ITRF, EOPs, and ICRF. A scheme for such a combination to obtain a much more consistent and accurate set of IERS products is presented and discussed. The vision of a rigorous combination goes, however, far beyond the combination of ITRF, EOPs, and ICRF, and includes all three pillars of space geodesy, i.e. geometry, Earth rotation, and the gravity field. The interaction of the two pillars “geometry” and “Earth rotation”, where the IERS is playing a major role, with the third pillar “gravity” and with the global geophysical fluids is therefore discussed as well. It shows that, on the long run, a rigorous combination of all common parameter types and all three pillars of space geodesy has to be achieved. The project of an Integrated Global Geodetic Observing System (IGGOS) proposed by the IAG might be the framework for such an ambitious undertaking.