Tidal effects in VLBI analyzed with a Kalman filter

State-of-the-art Very Long Baseline Interferometry (VLBI) analysis determines relative positions of radio telescopes with an accuracy of a few millimeters. Within the next years the system aims towards the 1mm. For achieving this accuracy it is essential to have adequate models for describing periodic deformations of the Earth’s surface which can reach up to tens of centimeters, as the crustal deformation fully impacts on the local displacement vector between the antennas. The largest variation in the station coordinates is caused by lunisolar tidal forces, ocean tidal loading, and atmospheric pressure loading. Thus, VLBI is the perfect instrument to validate these displacement models.

For this study we will use our newly developed Kalman filter for the analysis of VLBI data, and compare its results to the classical least squares (LSM) approach. We expect, due to the nature of the Kalman filter, better results in the high-frequency spectra, as the filter can resolve the parameters on observation level, whereas the LSM approach needs usually a much lower temporal resolution of one hour up to one day. The temporal variation of the displacement effects will be shown for the VLBI antennas during the continuous VLBI campaigns called CONT, as well as their impact on the EOP. We will also test the models recommended in the IERS conventions 2010 w.r.t. more recently published models.