Importance of the Hartebeesthoek Radio Astronomy Observatory for the VLBI network

The Hartebeesthoek Radio Astronomy Observatory (HartRAO) is the only very long baseline interferometry (VLBI) station in Africa, its importance to the current and future network is discussed in the presented analysis. In order to quantify the contribution of the HartRAO station to VLBI products, different approaches (e.g. comparison of number of observations to sources, formal errors of EOP and baseline length repeatabilities) are analysed. Two datasets were used, CONT08 and IVS-R1 sessions from the years 2011 and 2012. The results suggest that the station is of high importance to the current and future global VLBI network. In particular, HartRAO is crucial for maintaining the ICRF on the Southern Hemisphere; it is also one of the most important stations for the estimation of polar motion and nutation (e.g. when HartRAO is excluded from different networks the formal error of nutation increases by about 50 %). The quality of the station coordinates of remote southern stations such as TIGOCONC is also heavily dependent on HartRAO.