Potential of UT1 - UTC determination with VLBI transmitters onboard future Galileo satellites

Abstract

Future Galileo satellites may include novel geodetic instruments such as an onboard VLBI transmitter. Currently, due to the insensitivity of GNSS observations to UT1-UTC, this information needs to be inserted into the orbit determination procedure from external sources obtained from VLBI observations. In addition to GNSS observations, measurements from an onboard VLBI transmitter on Galileo satellites, acquired by VLBI stations jointly with quasar observations, would enable for a direct transfer of the UT1-UTC information to the Galileo constellation. Such observations will also have implications on reference frame determination by combination of techniques exploiting co-located GNSS and VLBI transmitters in space. This study evaluates the determination of absolute orientation of the orbits of GNSS satellites and the performance of retrieval of UT1-UTC using VLBI observations of future Galileo satellites.