The USNO IVS VLBI Analysis Center regularly makes global VLBI solutions to study the Celestial Reference Frame (CRF), the Terrestrial Reference Frame (TRF), and the set of 5 Earth Orientation Parameters (EOPs) that connect the TRF and the CRF. Global solutions are made by performing a least-squares analysis using thousands of individual 24-hr VLBI sessions. The USNO currently uses up to ~6700 such sessions, recorded between 1980 and the present. These solutions can determine terrestrial site positions and velocities, the celestial coordinates of thousands of compact extragalactic radio sources, and the EOP’s during each VLBI session.
The Analysis Center makes quarterly global solutions to solve for the CRF, the TRF, and EOPs. The current quarterly global solution can be found here.
The analysis center also occasionally makes special solutions for things such as: updates to the ICRF3 at S/X and K-bands, astronomical source time series, VLBA-only solutions, solutions to tie in new stations, VGOS broadband solutions, and more.