Journal of Geodesy

, Volume 88, Issue 12, pp 1145–1161 | Cite as

A complete VLBI delay model for deforming radio telescopes: the Effelsberg case

  • T. ArtzEmail author
  • A. Springer
  • A. Nothnagel
Original Article


Deformations of radio telescopes used in geodetic and astrometric very long baseline interferometry (VLBI) observations belong to the class of systematic error sources which require correction in data analysis. In this paper we present a model for all path length variations in the geometrical optics of radio telescopes which are due to gravitational deformation. The Effelsberg 100 m radio telescope of the Max Planck Institute for Radio Astronomy, Bonn, Germany, has been surveyed by various terrestrial methods. Thus, all necessary information that is needed to model the path length variations is available. Additionally, a ray tracing program has been developed which uses as input the parameters of the measured deformations to produce an independent check of the theoretical model. In this program as well as in the theoretical model, the illumination function plays an important role because it serves as the weighting function for the individual path lengths depending on the distance from the optical axis. For the Effelsberg telescope, the biggest contribution to the total path length variations is the bending of the main beam located along the elevation axis which partly carries the weight of the paraboloid at its vertex. The difference in total path length is almost \(-\)100 mm when comparing observations at 90\(^\circ \) and at 0\(^\circ \) elevation angle. The impact of the path length corrections is validated in a global VLBI analysis. The application of the correction model leads to a change in the vertical position of \(+120\) mm. This is more than the maximum path length, but the effect can be explained by the shape of the correction function.


VLBI Signal path variation Antenna deformation  Delay correction Ray tracing Terrestrial reference frames 



The investigations described in this publication make extensive use of observations acquired with the Effelsberg 100 m radio telescope of the Max Planck Institute for Radio Astronomy in Bonn, Germany. We thank the IVS for providing the VLBI observation data.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Institute of Geodesy and GeoinformationUniversity of BonnBonnGermany

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