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D. Mayer, J. Böhm:
"VLBI Celestial Reference Frames and Assessment with Gaia";
Talk: 27th IUGG General Assembly, Montreal, Canada; 2019-07-08 - 2019-07-18; in: "IUGG 2019 Abstracts Book", (2019), 1 pages.

For decades, the accuracy of celestial references frame derived from Very Long Baseline Interferometry (VLBI) observations was out of reach for techniques operating in the optical part of the electromagnetic spectrum. This has changed with the Gaia satellite mission by ESA, which was launched in 2013 with the aim of mapping a billion stars with an unprecedented accuracy. We investigate the influence of different modeling and analysis strategies on the celestial reference frame estimated from nearly 40 years of VLBI observations in X/S-band. Systematic changes in the VLBI reference frame are assessed with the help of the Gaia reference frame from DR2. The state of the art technique used for comparing astrometric catalogs, the so-called Vector Spherical Harmonic (VSH) decomposition, was utilized. First, it was found that the correction of galactic aberration removes most of the deformation of degree 1 between the VLBI and the Gaia reference frame. Second, the D3-parameter, which is directly connected to the source declination, was found to be affected by many models and estimation choices. This indicates that this parameter is rather unstable, which has to do with the weak VLBI observing network in the Southern Hemisphere. Third, it was found that using ray-tracing to calculate a priori tropospheric delays succeeds in reducing the most significant VSH parameter (the a20 parameter) between these reference frames.

VLBI, Gaia, Celestial Reference Frame

https://publik.tuwien.ac.at/files/publik_280931.pdf