| Popis: |
In 2022 and at the beginning of 2023, the three latest realizations of the International Terrestrial Reference System (ITRS) became available: ITRF2020, JTRF2020, and DTRF2020. Among others, the data contribution by the International VLBI Service for Geodesy and Astrometry (IVS) to these reference frames contains new models for the gravitational deformation of six VLBI antennas. In particular, these models affect the estimated heights of the corresponding antennas. In 2023, the IVS Analysis Centers (AC) reprocessed their session series from 1979 to the present. The corresponding series of the AC at DGFI-TUM is "dgf2023a". The main changes w.r.t. to the previous series "dgf2020a", which served as input data for the ITRS 2020 realizations, are a) the usage of ITRF2020 as a priori reference frame, and b) the corrections for the gravitational deformation of another seven antennas. Thereby, the choice of stations used for the no-net-translation and no-net-rotation conditions is a crucial issue. Furthermore, the additional deformation models will likely influence the scale parameter of similarity transformations between VLBI single-session solutions and the ITRS realizations. Three of the respective seven antennas belong to the next generation VLBI Global Observing System (VGOS). In this presentation, we examine the effects of the above mentioned novelties in solution "dgf2023a". In particular, we take a look at the similarity transformations, i.e., the time series of datum parameters, and we put special emphasis on the scale parameter. Above all, a drift in the VLBI scale was observed for sessions after about 2013.75 during the computation of the ITRF2020. Not least to investigate this finding, we also apply the other two ITRS 2020 realizations, JTRF2020 and DTRF2020, as a priori reference frames. |
