Update on VLBI Data Analysis at ESA/ESOC

ESA’s Navigation Support O ce is providing the geodetic reference for ESA missions mainly based on the processing of the satellite-geodetic techniques GNSS, SLR and DORIS. Since 2016 the Navigation Support O ce is extending its expertise to include VLBI processing and analysis. This e↵ort will establish ESA’s capability to determine the absolute orientation of the Earth and therewith enable the Navigation Support O ce to provide a fully independent set of Earth orientation parameters for ESA missions. ESOC’s software package NAPEOS will become capable of combining all four geodetic techniques on the observation level and thus supporting GGOS, the Global Geodetic Observing System. The VLBI delay model is now fully implemented following the IERS 2010 standards. With the current implementation in NAPEOS observation residuals of the level of 2-3 cm are reached. This result is expected and can be further improved by applying a better clock model and allowing for VLBI parameter estimation. The paper discusses briefly the current status and future plans of the VLBI implementation in NAPEOS and shows example residuals. The question as to which space-time coordinate systems to use for the various parameters of the VLBI delay model is addressed as well.