Objectives  The very long baseline interferometry(VLBI) global observing system (VGOS) is a new generation of geodetic VLBI system which is equipped with broadband receiver and fast slewing antenna in order to achieve very high accuracy for measuring station coordinates, source positions as well as Earth rotation. Within the framework of the international VLBI service (IVS) for geodesy and astrometry, the first UT1 observing session was conducted using the VGOS stations at Kokee in USA and Wettzell in Germany, with a goal to validate VGOS data processing pipeline and estimate UT1 parameters.

  Methods  The raw data were correlated at Shanghai VLBI correlator, followed by post-correlation processing and data analysis. The UT1 measurement results were derived and compared using VGOS database files produced from Shanghai correlator and the other correlator. Moreover, VGOS results were compared with those from the parallel UT1 session, which was conducted in the same time span using co-located legacy S/X-band stations.

  Results  The UT1 estimation results obtained from Shanghai correlator output agree very well with those from the other correlator. The UT1 formal error obtained from VGOS observations is about 7 μs, approximately 2 times lower than the UT1 formal error obtained from the parallel legacy S/X-band observations.

  Conclusions  VGOS system has the capability to obtain better UT1 measurement results than the legacy S/X-band system. The data processing pipeline established at Shanghai VLBI correlator has been validated and laid a foundation for regular VGOS data correlation in the near future.