Consistency assessment of EOP estimated by different VLBI correlators

The VLBI technique provides an extremely precise measurement of the geometric relationship between the receiving radio observatory and the celestial target. It utilizes methods of recording the signals at each antenna. These recordings are physically brought together and played back into a processing device, known as a correlator, which combines the signals in such a way that delivers the fundamental observables of geodetic VLBI, the time delays between signals arriving at the individual antennas as a function of time. Nowadays, numerous correlator software and strategies are employed which may result in inconsistencies on the geodetic products. In this study, we empirically assess the consistency between the different correlators by analyzing the R1/R4 VLBI sessions from 2002 to 2022 to reflect the impact on the EOP estimates. To compare the different pairs of EOP time series estimates, we calculated the Weighted Mean (WM) of the differences and the Weighted Root Mean Square (WRMS) differences between each of them. Besides, we empirically evaluate the consistency, systematics, and deviations of the IAU 2006/2000A precession-nutation model using several CPO time series derived from the different correlators, providing a new set of empirical corrections to the precession offsets and rates, and to the amplitudes included in the nutation models. Finally, we study the impact on the estimation of new free core nutation (FCN) models. This research was supported partially by Generalitat Valenciana (SEJIGENT/2021/001) and the European Union—NextGenerationEU (ZAMBRANO 21-04); and also by Spanish Projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033/) and  PROMETEO/2021/030 funded by Generalitat Valenciana.