Comparison and quality assessment of differential total electron content obtained from VGOS and CODE GIM

Very Long Baseline Interferometry (VLBI) observing in the radio frequency range is sensitive to the Total Electron Content (TEC) of the ionosphere. VGOS network can contribute with data to ionosphere observations and modelling. The new generation of geodetic VLBI - VLBI Global Observing System (VGOS) is a growing and developing network of radio telescope systems performing regular observations coordinated by the International VLBI Service (IVS). We analyze the data quality of VGOS ionosphere product – differential total electron content (dTEC). The CODE Global Ionospheric Maps (GIM) were used as a reference to perform VGOS dTEC assessment. A bias presented between VGOS and CODE data was investigated and VGOS dTEC systematic errors were detected and characterised. The comparison also revealed shortcomings of CODE GIM for example in Kokee Park station located in Hawaii. VGOS observation can be valuable in such locations where GNSS data are not as dense as compared to the continental stations.