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Tobias Nilsson
Type of contribution: oral

Antenna axis offsets estimated in VLBI data analysis

Tobias Nilsson, GFZ German Research Centre for Geosciences Maria Karbon, GFZ German Research Centre for Geosciences Julian Mora-Diaz, GFZ German Research Centre for Geosciences Virginia Raposo-Pulido, GFZ German Research Centre for Geosciences Benedikt Soja, GFZ German Research Centre for Geosciences Robert Heinkelmann, GFZ German Research Centre for Geosciences Harald Schuh, GFZ German Research Centre for Geosciences

The reference point of a VLBI antenna is defined as the intersection of the two axes of rotation. However, for many VLBI telescopes these two axes do not intersect, but have an offset relative to each other. These axis offsets amount to several meters for some telescopes. Since the axis offsets affect the derived results they have to be corrected in the VLBI data analysis. There are two ways of obtaining the axis offset: either by measuring it in a local survey or estimating it in a VLBI global solution. In this work we investigate with which precision the axis offsets can be obtained from the VLBI data analysis. This is done by estimating axis offsets in global solutions and comparing them with the results of local surveys. We also study the impact of several analysis options, like the modelling of the atmospheric delays and loading effects, on the axis offset estimates. In addition, we investigate how well changes in the axis offsets, caused by e.g. antenna repairs, can be detected.