Assessment of performance of first VGOS operational sessions scheduled with source centric approach

VGOS operational sessions scheduled with source-centric approach in 2025 Krásná Hana, TU Wien, Vienna, Austria Schartner, Matthias, ETH Zurich, Zurich, Switzerland Charlot, Patrick, Laboratoire d’astrophysique de Bordeaux, Pessac, France Jacobs, Christopher, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA Very Long Baseline Interferometry Global Observing System (VGOS) has been in its operational phase since 2019. In our previous studies (Krásná et al., 2025, A&A 693; Krásná et al., EVGA2025) we demonstrate the high potential of VGOS sessions for geodetic and astrometric products. At the same time, possibilities for improvement in the scheduling and analysis strategies of the sessions have been identified, keeping in mind the unique VLBI characteristics as a bridge between geodesy, astrometry and astronomy. Based on our proposal, the International VLBI Service (IVS) has been testing an updated source-centric scheduling approach (Schartner et al., 2023, JGeod 97) in operational 24-h VGOS sessions once per month since July 2025. In this contribution, we assess the performance of available source-centric VGOS sessions (VS) and compare the precision and accuracy of derived geodetic parameters against those from established operational VGOS sessions (VO). Furthermore, we provide an overview of the performance and characteristics of VS versus VO sessions with a focus on the anticipated benefits for the maintenance of the celestial reference frame. In addition, we approach the sensitivity of VGOS solutions to critical analysis parameters such as observation cut-off elevation angle, elevation-dependent weighting schemes, and the temporal resolution for zenith wet delay and tropospheric gradient estimates.