Progress of VLBI observations of the 40-m Radio Telescope of the National Time Service Center

The Haoping 40-m radio telescope (HPRT) of the National Time Service Center (NTSC) was built in 2014 and is mainly used for navigation satellite observations and pulsar observations. Since the first successful acquisition of L-band Very Long Baseline Interferometry (VLBI) radio source fringes in 2022, more than ten VLBI observations have been made so far. The stations involved in the observations include the Haoping 40-m radio telescope (Haoping), the Tianma 65-m radio telescope (Tianma), the Nanshan 26-m radio telescope (Urumqi), the Guizhou 500-m radio telescope (FAST), the Jilin 13-m radio telescope (Jilin), the Effelsberg 100-m radio telescope (Effelsberg), the Onsala 25-m radio telescope (Onsala), and the Chiang Mai 40-m radio telescope (Chiang Mai). This paper presents details on the main specifications of the HPRT, as well as the design of the VLBI experiment, the observation process, the data processing. It also discusses the analysis of the fringe results involving HPRT, and obtains very good fringe results by using Distributed FX Correlator (DiFX). It shows that HPRT has the mature ability to participate in VLBI observations and to perform certain data processing tasks, and it will play a greater role in the future domestic and international joint VLBI observations.