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Abstract:
This work introduces a new observation type, i.e., Very Long Baseline Interferometry (VLBI) on the next-generation Global Navigation Satellite System (GNSS). To determine the results from the new observation type, we combined the VLBI observations to quasars and one medium-Earth orbit (MEO) satellite with GNSS observations to 24 MEO satellites (Galileo-like) in a simulated environment. Here, one satellite is commonly observed between the two techniques, and this satellite is the co-location site in space (called space tie). In addition to the VLBI transmitter, the next-generation GNSS is characterized by optical inter-satellite links (ISL). The ISL enables all the MEO satellites to be linked within one orbital plane. There are previous studies that indicate improvement in parameters like geocentre coordinates, earth rotation parameters, etc. We combined by integrating the common parameters such as Kepler elements on the Normal-equation level. One of the objectives of this study is to access the quality of datum transferred from the GNSS network to the VLBI network. To evaluate this, we imposed datum conditions in the form of no-net rotation constraints only on 40 GNSS stations, and VLBI stations were datum-free. After analyzing the results for an initial period of ten days and no systematic effects in the simulations, we found that datum can be transferred to the VLBI network and realized on the mm level. Furthermore, UT1-UTC information is transferred from the VLBI observations to the combined solution, enabling us to determine UT1-UTC from the combination of next-generation GNSS and VLBI using space ties.
