Fully automated VLBI analysis with c5++ for ultra-rapid determination of UT1

VLBI is the only space-geodetic technique which gives direct access to the Earth's phase of rotation, i.e. universal time UT1. Beside multi-baseline sessions, regular single baseline VLBI experiments are scheduled in order to provide estimates of UT1 for the international space community. Although the turn-around time of such sessions is usually much shorter and results are available within one day after the data were recorded, lower latency of UT1 results is still requested. Based on the experience gained over the last two years, an automated analysis procedure was established. The main goal was to realize fully unattended operation and robust estimation of UT1. Our new analysis software, named c5++, is capable of interfacing directly with the correlator output, carries out all processing stages without human interaction and provides the results for the scientific community or dedicated space applications. Moreover, the concept of ultra-rapid VLBI sessions can be extended to include further well-distributed stations, in order to obtain the polar motion parameters with the same latency and provide an up-to-date complete set of Earth orientation parameters for navigation of space and satellite missions.