Innovative approach for modelling gravity-induced signal path variations of VLBI radio telescopes (Dataset)

Gravitationally induced deformations of the receiving unit of radio telescopes used for Very Long Baseline Interferometry (VLBI) distort the observations and bias deduced products. As these deformations act systematically and are individual for each radio telescope, the International VLBI Service for Geodesy and Astrometry (IVS) calls for gravitational deformation investigations to correct VLBI data on the observation level. The most commonly used approach for modelling signal path variations was developed in 1988 during investigations at the 26 m VLBI radio telescope in Fairbanks (Alaska). This approach considers only homologous deformations of the receiving unit and takes into account three main deformation patterns affecting the signal path. For this reason, the measuring and modelling effort can be greatly simplified because the original spatial problem is reduced to a two-dimensional problem. However, more recent investigations refute the assumption of homogeneous deformations, and the receiver unit can be affected by arbitrary deformation patterns. Hence, identification and modelling as well as considering all parameterisable deformations in a corresponding correction function require specific and more complex analysing approaches. Based on Zernike polynomials an innovative approach for modelling signal path variations is presented in this contribution. In contrast to the conventional approach, the proposed approach models the entire receiving unit spatially, and is not restricted to a homologous deformation pattern. This new approach has been successfully exercised on the 26 m legacy VLBI radio telescope at the Mount Pleasant Radio Observatory Hobart (Tasmania). Despite the large dimensions of the legacy VLBI radio telescope, the detected deformations are unexpectedly small, and lead to signal path variations of less than 2 mm. The results of the investigation were derived from this dataset, which was obtained as part of a measurement campaign in February 2024.