WVR calibration applied to European VLBI observing sessions

Abstract

From a conceptual point of view water vapour radiometers (WVRs) are ideal instruments for a direct determination of the water vapour content in the atmosphere above a space geodetic observing site. For various reasons the application of WVRs for a direct correction of geodetic Very Long Baseline Interferometry (VLBI) observations for the wet component of atmospheric refraction has not been brought to a stage where it could be employed routinely. The installation of a new type of WVR at the 100 m Effelsberg radio telescope in Germany opens up new possibilities for a direct correction of the VLBI observations using line-ofsight WVR observations. The WVR has been in operation during two geodetic VLBI sessions of a purely European network. In addition, some WVR data at Onsala have been revisited to embark on a project which aims at applying wet delay corrections from WVRs to VLBI sessions of the European geodetic VLBI network for the Effelsberg, Madrid, Onsala and Wettzell sites. In this paper we present the analysis and results of a few examples of Effelsberg and Onsala observing sessions. © Springer-Verlag Berlin Heidelberg 2007.