Simulation of errors related to the VLBI transmitter on Genesis and their impact on the terrestrial reference frame

Mission Genesis of the European Space Agency has been approved for launch in 2028. Its primary goal is the enhancement of the terrestrial reference frame by establishing a space tie on the Genesis satellite between all space geodetic techniques used for the determination of the frame. The satellite will be equipped with a dedicated Very Long Baseline Interferometry (VLBI) transmitter for geodesy. In this work, simulation studies with a global 20-station VLBI network are carried out to assess the impact of errors related to the VLBI transmitter on the terrestrial reference frame, more precisely on station coordinates derived from VLBI observations to Genesis. Our findings indicate that the calibration of the position of the VLBI transmitter on Genesis is critical for the success of the mission. Errors in the position at the one-centimeter-level will cause station coordinate errors of several millimeters. In particular, the tangential and cross-track components do have a significant influence. The precision of the VLBI group delays, however, is not as critical. Simulating white noise for the group delays of 40 ps does still yield station coordinate accuracies at the millimeter level, if estimated in a global solution from weekly 24-h sessions over five years. Considering the investigated aspects, the simulations confirm that the VLBI-related goals of Genesis can be achieved, if stringent requirements with the VLBI transmitter are fulfilled.