Global VLBI solutions: advancing the realization of reference frames IAA2025

• Autores: Urunova, R. M.
• Año de publicación: 2025
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Ciencias Astronómicas; VLBI global solutions; Celestial and terrestrial reference frames; Helmert transformation
• Institución: Universidad Nacional de La Plata

The realization of celestial and terrestrial reference frames requires processing extensive VLBI data. At the Institute of Applied Astronomy, we use the QUASAR software to compute global solutions refining source and station coordinates. We processed 6,605 sessions from 1979 to 2024, including sessions from the VLBI Global Observing System, which, to the best of our knowledge, have been considered for the first time in a global solution. The a priori catalogs used are ICRF3 for celestial sources and ITRF2020-u2023 for terrestrial stations. To define the orientation of the terrestrial reference frame and compute Helmert transformation parameters, a dedicated set of reference stations was carefully selected. These stations serve to enforce the no-net-rotation and nonet-translation conditions. The selected stations are required to exhibit longterm stability and continuity in their coordinate time series, with no significant jumps or discontinuities. To ensure these criteria are met, we developed a specialized algorithm for detecting coordinate jumps. Based on its output, corrections were introduced into the a priori ITRF2020-u2023 catalog for affected time intervals. The final terrestrial reference frame, IAA2025-TRF, consists of 161 stations, including 31 stations where coordinate discontinuities were identified and corrected. We also analyzed how the accuracy of the Helmert transformation parameters depends on the weighting and transformation parameters choices. For the celestial reference frame, we selected 295 defining sources from ICRF3, enforcing no-net-translation. Other sources may exhibit coordinate jumps, necessitating detection and correction. Currently, such sources are artificially treated as two independent sources. The resulting IAA2025-CRF catalog includes 4,638 sources.
Facultad de Ciencias Astronómicas y Geofísicas