Requirements for Earth Rotation Parameters

Abstract

AbstractObservations of Earth orientation parameters (polar motion and Universal Time) have reached a level of accuracy which challenges the definition of the reference systems which these observations seek to relate. Observational accuracies of better than in polar motion and in Universal Time are now routinely available. Urgent requirements therefore exist now for the IAU to take a fresh look at the concepts and definitions of the reference systems as well as reference frames. Of particular concern are the definitons of the equinox, the terrestrial reference pole, the zero of longitude and sidereal time.