The Full Reprocessing Effort for the ITRF2020-u2025 Update by the IVS

The International VLBI Service for Geodesy and Astrometry (IVS) provides a unique and fundamental contribution to the determination of the International Terrestrial Reference Frame (ITRF), most notably as a primary technique for defining the frame's scale. While the last comprehensive reprocessing of the VLBI data archive was conducted for the ITRF2020 submission, subsequent updates (u2023 and u2024) were limited to the addition of recent years.

For the ITRF2020-u2025 update, the IVS has undertaken a full reprocessing of the entire history of VLBI observing sessions. This decision was motivated by the identification of critical issues within the data archive: station naming inconsistencies and systematic errors in ionospheric corrections, which required the re-creation of some of the databases. Furthermore, the reprocessing incorporated several refined station-specific models, including newly determined gravitational deformation models and updated antenna axis offsets.

A major highlight of this reprocessing effort is the expansion of the included frequency bands to K-band (24 GHz). While previous ITRF submissions relied solely on legacy S/X-band and broadband VLBI Global Observing System (VGOS) sessions, this update integrates approximately 200 K-band VLBI sessions for the first time, comparable to the total number of VGOS sessions. Nevertheless, the legacy S/X-band network remains the dominant backbone of the contribution, encompassing about 7,600 sessions.

This contribution presents preliminary results of the IVS-combined solution, generated by the IVS Combination Center from individual Analysis Center contributions. We evaluate the quality of the resulting geodetic parameters, with a primary focus on the stability of station coordinates, terrestrial scale realisation, and the precision of EOP.