IRIS-S: Extending geodetic Very Long Baseline Interferometry observations to the southern hemisphere


  • W. E. Carter,

  • D. S. Robertson,

  • A. Nothnagel,

  • G. D. Nicolson,

  • H. Schuh,

  • J. Campbell


High-accuracy geodetic very long baseline interferometry measurements between the African, Eurasian, and North American plates have been analyzed to determine the terrestrial coordinates of the Hartebeesthoek observatory to better than 10 cm, to determine the celestial coordinates of eight southern hemisphere radio sources with milliarc second (mas) accuracy, and to derive quasi-independent polar motion, UTl, and nutation time series. Comparison of the Earth orientation time series with ongoing International Radio interferometric Surveying project values shows agreement at about the 1 mas of arc level in polar motion and nutation and 0.1 ms of time in UTl. Given the independence of the observing sessions and the unlikeliness of common systematic error sources, this level of agreement serves to bound the total errors in both measurement series.