Ongoing Operation and Perspectives of Simple Vlbi Networks of Geostationary Satellites Monitoring

The report is dedicated to introducingthe operation and prospects of further development ofsimple VLBI networks which were created in Ukraine,Latvia, and China for monitoring the orbital informationof geostationary satellites. The Ukrainian-Latvian networkconsists of five stations located in Mykolaiv, Kharkiv,Mukacheve, Ventspils, and Rivne, and it operates since2015. The Chinese network consists of three stations lo-cated in Shanghai, Duyun, and Urumqi, and it formallycarried out a network observation from June 2019.The networks have identical hardware and software. Themain principle of the operation of the networks learnedfrom the VLBI is correlation analysis of broadband noise-like signals of satellite television DVB-S, which are emittedby satellites and synchronously received by the stations ofthe networks. Single-frequency GPS receivers are used forthe synchronizing of network stations. Time difference ofarrival (TDOA) between the signals paths from the identicalTV satellite to different stations is obtained via using corre-lation analysis. These values of TDOA are used to deter-mine orbital elements of the tracked satellites which aregiven in the report. Notably, the cost of one set of stationequipment does not exceed $2000, and the current operat-ing costs are about $50 per day.The prospects of further development of the simpleVLBI networks include a) the possibility of continuousindependent non-invasive high-precision determination ofthe position of arbitrary active satellites (especially im-portant in the case of their co-location), b) the possibilityto fully automate targeting and operation, c) the possibilityof using accumulated observational data to solve scientificgeophysical and astronomical tasks, d) relatively fewfunds necessary for the modernization and operation ofthe networks.