Exploring reasons for the ITRF2020 VLBI scale drift

Paper in proceeding, 2023

Since the release of the new realisation of the International Terrestrial Reference System, ITRF2020, one of the focuses of the IVS community is to understand the cause of the drift in the VLBI scale factor time series after 2013.75 that is detected by the ITRF team.
In this work, we consider the official IVS combined solution, i.e. the IVS contribution to the ITRF2020 realisation, and calculate scale factors using the CATREF software with the single-technique combination strategy that was used to process the ITRF2020.
The investigation of time series of Up components of specific IVS stations with the statistical tool BEAST reveals offsets and trends changes that are not taken into account in the ITRF2020.
These changes are significant for five IVS stations: NYALES20, WETTZELL, ONSALA60, TSUKUB32, and MATERA.
Adding discontinuities for these five IVS stations significantly decreases the VLBI scale drift.