Deriving a TRF from VLBI observations to Genesis - what is the impact of the inclination?

Abstract

The European Space Agency’s (ESA) Genesis mission has been approved and is scheduled for launch in 2028. Designed as a dynamic space observatory, the satellite will integrate instruments from all four space-geodetic techniques precisely referenced to each other. A distinctive feature of the Genesis mission is its dedicated Very Long Baseline Interferometry (VLBI) transmitter. One of the primary goals of the mission is to enhance the accuracy and stability of the Terrestrial Reference Frame (TRF). There have been discussions on the inclination of the satellite, i.e., whether the satellite should orbit the Earth in a polar orbit or with an inclination of 60°. The different inclinations will have an impact on the observation coverage and the observation geometries and, ultimately, on the accuracy of the VLBI station coordinates as derived from observations to the Genesis satellite. This simulation study explores these questions by analyzing the results of estimating station coordinates based on VLBI observations to Genesis using different theoretical satellite orbits. The study is carried out for two VGOS station networks - a network consisting of currently operational VGOS stations and an extended version of this network, including potential future VGOS stations. Based on this study setup, a Genesis TRF is derived from weekly VLBI sessions over a two-year period in order to identify the preferred inclination of the satellite for determining station coordinates in the Genesis frame.