Quantitative analysis of the tropospheric delay difference using empirical mapping functions on VLBI stations

Tropospheric delay is a major error source for the high-accuracy Very Long Baseline Interferometry (VLBI) technique due to rapid water vapor variations. The Niell mapping function (NMF) and Global Mapping Function (GMF) are extensively applied to convert zenith tropospheric delay to slant delays for real-time deep-space VLBI operations. In this study, we quantitatively evaluate the performance of different empirical Mapping Functions for VLBI signal correction, with Vienna Mapping Function 3 (VM