Experimental Study on VLBI Time Transfer Based on GEO Satellite Observation

With precise orbits of GEO satellites, the precise time transfer between stations can be realized by VLBI observations of GEO satellite. This can be a new time transfer method independent of GNSS co-view, and can obtain same or even higher time transfer accuracy.In this paper, a VLBI time transfer method based on GEO satellite observation is proposed. The time transfer measurement model is established, and the major systematic errors and correction methods are studied. The precise orbits of GEO satelltes which are critical for VLBI measurement model, are determined by GNSS and by the method of Orbit Determination Transfer Tracking (ODTT). The VLBI time transfer experiment was carried out by observing Beidou GEO satellite using Jilin and Sanya stations of the National Time Service Center (NTSC) VLBI network. The GNSS PPP time transfer results are used as a standard for evaluation. The results show that the consistency between VLBI time transfer and GNSS PPP time transfer is consistent within 2 nanoseconds.Here, we present the preliminary experimental results. Further improvements include: Selection of setellites with larger bandwidth to improve the time transfer accuracy; the correction of satellite antenna phase center to satellite center of mass; the geometric tide correction of stations and other error sources should be investigated in the future.