Impact of the Inclination of Genesis on the VLBI Terrestrial Reference Frame

The Genesis mission of the European Space Agency (ESA) has been approved and is scheduled for launch in 2028. The satellite will serve as a dynamic space observatory, being equipped with the instruments of all four space-geodetic techniques referenced to each other with high precision. A unique feature of Genesis is a dedicated Very Long Baseline Interferometry (VLBI) transmitter, which allows the connection of geodetic VLBI stations to the instruments of the satellite techniques. One of the main objectives of the Genesis mission is the improvement of the Terrestrial Reference Frame (TRF), in terms of accuracy and stability. The satellite is currently planned to operate in a polar orbit with an inclination of 97° and an altitude of 6000 km. However, there are discussions about reducing the inclination of Genesis to 60°. This raises the question of which inclination would be more suitable, considering factors such as observational coverage and the accuracy of the TRF determination. This simulation study investigates the determination of a TRF based on VLBI observations to Genesis only for two different theoretical satellite orbits of Genesis, with inclination angles of 97° and 60°. To this end, a Genesis TRF is derived using 24-hour VLBI sessions on a weekly basis, encompassing observations to Genesis and quasars, scheduled over a two-year period. These investigations are conducted for a network comprising currently operational VGOS stations and an extended version of this network incorporating potential future VGOS stations. In this setup, the station coordinates are estimated solely from Genesis observations, allowing for the determination of these coordinates within the Genesis frame. This approach enables the comparison between the station coordinates in the dynamic Genesis frame and in the kinematic quasar frame, thereby providing information on a frame tie between these frames on a per-station basis.