Modelling Very Long Baseline Interferometry (VLBI) observations

Abstract

The main objective of this study is to provide in detail the theoretical basis of the Very Long Baseline Interferometry (VLBI) delay model, mainly according to the International Earth Rotation and Reference Systems Service (IERS) Conventions 2010. This goes along with introducing the concept of continuous piece‒wise linear offset (CPWLO) functions for estimating sub‒daily geodetic parameters at pre‒defined epochs, e.g. at Universal Time (UT) integer hours or at integer fractions or multiples of integer hours. The geodetic parameters can be simultaneously and accurately estimated from VLBI observations in sub‒daily resolution if enough observations within each estimation interval are carried out from homogenously distributed Earth‒fixed VLBI antennas to space‒fixed radio sources. After providing the basic VLBI model of the geometric delay including clock synchronization and tropospheric effects, the partial derivatives of VLBI observation equation with respect to the most important geodetic parameters are given and some typical VLBI results are shown.