[G01-2] Celestial reference frame and VLBI

[G01-2-04] Ray-traced delays and global reference frames with geodetic VLBI

David Mayer, Hana Krasna, Daniel Landskron, ^○Johannes Boehm (Technische Universitaet Wien, Vienna, Austria)

Geodetic Very Long Baseline Interferometry (VLBI) observations have been carried out since 1979 with a total number of more than 10 million group delays as of 2017. We use operational and re-analysis data of the European Centre for Medium-range Weather Forecasts (ECMWF) with a temporal resolution of six hours and a spatial resolution of one degree to determine ray-traced delays for every single VLBI observation as well as to determine horizontal tropospheric north and east gradients for all sites every six hours. We then use those tropospheric delays in the analysis of all VLBI observations to estimate terrestrial and celestial reference frames and to compare the results against those from standard analysis setups. In particular, we assess the influence of refined tropospheric models on the declination of source coordinates, on station heights, and on baseline length repeatabilities.