Guy Bomford Prize Lecture 2011 Atmospheric Effects in Space Geodesy

The atmosphere is surrounding the solid Earth and the oceans, and with its variations at time scales from seconds to decades it opens up a wide field of challenging and fascinating tasks in space geodesy. The investigation of these atmospheric effects and the analysis of geodetic Very Long Baseline Interferometry (VLBI) observations have dominated my research in the past decade. Geodetic VLBI with its very simple geometric concept, the unbelievable observations of extragalactic radio sources billions of light years away, its fundamental advantages of linking the terrestrial and the celestial reference frame or providing the full set of Earth orientation parameters, is still as exciting to me as in 2000 when I first got in touch with this technique at the first General Meeting of the International VLBI Service for Geodesy and Astrometry in Kötzting, Germany. Moreover, VLBI with its high accuracy of single observations has always enabled me to test new models of atmospheric effects, like those for signal propagation, loading, or thermal deformation. I am eagerly looking forward to the new generation of VLBI observations (VLBI2010) that will allow the determination of positions with an accuracy of close to 1 mm in near real-time. And I am aware that this will pose new requirements on the models of atmospheric effects that are needed to correct the observations.