Concepts and methods of the Central Bureau of the International Earth Rotation Service

Foreword The International Earth Rotation Service (IERS) was organized by the International Union of Geodesy and Geophysics and the International Astronomical Union. It started operation on 1988 January 1. Its responsabilities and activities are described in the Geodesist's Handbook (1988). The Central Bureau ofIERS is operated by a scientific team established in cooperation by Observatoire de Paris, Institut Géographique National and Bureau des Longitudes. This team was selected in 1987 on the basis of the present document which describes in some detail the concepts and methods for establishing and maintaining celestial and terrestrial reference frames for Earth orientation monitoring (polar motion, universal time, precession/nutation). The work of the Central Bureau is based on these concepts and methods, not withstanding future evolution made possible by the improvements in observations and theories.