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L. Kern, M. Schartner, B. Soja, A. Nothnagel, J. Böhm:
"VLBI Intensive sessions: the selection of baselines for UT1 estimation";
Talk: 25th Meeting of the European VLBI Group for Geodesy and Astrometry, Cyberspace; 2021-03-14 - 2021-03-18.

VLBI Intensives are one hour single baseline sessions dedicated to derive the parameter UT1-UTC with a short latency. Thus far, the optimal geometry was understood to include a long east-west extension to ensure an accurate estimation of UT1-UTC. In this presentation, we show that the selection of baselines for VLBI Intensives is not as simple as that. In the case of this study, Monte-Carlo simulations for a global 10° grid of artificial station locations were performed and the suitability of the individual baselines based on the formal error of dUT1 was analysed. Concerning the global grid, the antennas were located at latitudes of -80° to 80° and longitudes of 0° to 180° and are assumed to have the same properties as the WETTZ13S telescope. Nine of 323 stations are selected as reference stations, which are all located at longitude 0° on the northern hemisphere. Based on monthly schedules, 2898 possible baselines between the reference stations and other artificial stations are individually investigated over one year to minimize potential seasonal variations. Therefore, it is possible to derive a global picture of the suitability of baselines for dUT1 estimation. The findings show optimal geometries concerning VLBI Intensive sessions, which confirm that the IVS-INT1 baseline is among the best ones available. Moreover, we show that certain north-south baselines are also sensitive to dUT1 depending on their orientation with respect to the Earth rotation axis. Furthermore, we highlight that east-west baselines located on the equator are not suitable for the estimation of dUT1. Additionally, it has been shown that extremely long baselines are problematic due to the highly restricted mutual visibility.

https://publik.tuwien.ac.at/files/publik_295799.pdf