Simulated VLBI Satellite Tracking of the GNSS Constellation: Observing Strategies

Very Long Baseline Interferometry (VLBI) observations to satellite targets is a promising technique to improve future realizations of terrestrial reference frames (TRF). The high number of available satellites of Global Navigation Satellite Systems (GNSS) provides an attractive existing infrastructure that could be utilized for such observations. The Vienna VLBI Software (VieVS) was extended for the possibilities of scheduling, simulating, and processing VLBI observations to GNSS satellites, allowing to give information on expected accuracies of derived station coordinates. Assuming the GNSS signals to be measured with a precision of 30 ps, we find weekly station position repeatabilities at the centimeter level or better for simulated observations to satellite targets only. Adequate scheduling strategies have to be applied, e.g. in terms of a fast switching between the observed satellites. Even better solutions of about 5mm in mean 3D position rms after one day are achieved when integrating the satellite observations into standard VLBI sessions to extragalactic radio sources. Further, this combined approach allows the determination of a frame tie between the satellite system and the VLBI system in terms of relative Earth rotation parameters and a scale with a precision of about 1–2mm at the Earth’s surface.