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Andreas Iddink
Type of contribution: oral

Assessment of CRF Solutions from Session-wise Normal Equation Systems

Andreas Iddink, IGG University of Bonn Thomas Artz, IGG University of Bonn Sebastian Halsig, IGG University of Bonn Axel Nothnagel, IGG University of Bonn

The International Celestial Reference Frame (ICRF) is one of the fundamental products of the International VLBI Service for Geodesy and Astrometry (IVS). Until now, two realizations were computed and the next one is under construction. Today, some of the IVS Analysis Centers routinely produce solutions as session-wise normal equation systems also including radio source positions. For this reason, a rigorous combination using datum-free normal equation systems is also feasible for the ICRF. At the same time, the methodology permits the combination of single session X/S-band analysis results with that of Ka/X- band to provide an enhanced frequency coverage. However, various peculiarities have to be considered for the final CRF determination. In this presentation, we analyze various combined CRF catalogs from input of different analysis centers solely based on the official SINEX files submitted to the IVS. The combination process differs by the considered time spans as well as by the included session types and network geometries. The individual catalogs are compared and validated among themselves as well as to the ICRF2 by means of Helmert transformations. The quality is also assessed by looking at the resulting time series of Earth orientation parameters. In this context, the impact of the additional data, which became available after the ICRF2 was published, is examined and discussed as well.