Turbulence investigations from local VLBI interferometer and short range GNSS observations for improved modelling of atmospheric refraction variations

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Simultaneous Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite System (GNSS) observations in a small local network will be employed to investigate the variability of atmospheric refraction giving insights into real turbulence behaviour and providing the basis for refraction model improvements. This will be achieved with the new triple of VLBI radio telescopes at Wettzell and a local GNSS network to be set up on and around the Wettzell premises. Mitigating technique-specific error contributions, the remaining differences in arrival time and interferometer or carrier phase can be attributed to variations in atmospheric refraction which will then be related to turbulence theory. In this project we will employ a geodetic observing cluster which will be the first and so far only integrated instrument in the world allowing the investigation of a variety of short-time discretisations of radio fre-quency refraction effects. The results of the project will be an enhanced quantification of local atmos-pheric refraction variations in space and time addressing and realizing a variety of interpretations and model improvements. Since atmospheric refraction is the limiting factor of any further improvements in accuracy, our results will serve to advance the quality of all kinds of space-geodetic observations at radio frequencies for precise positioning and monitoring Earth rotation.