Positioning the terrestrial ephemeris origin in the international terrestrial reference frame

Resolution B1.8 adopted by the XXIV General Assembly of the International Astronomical Union (Manchester, August 2000) recommends the use of the Non-Rotating Origin (Guinot 1979) on the moving equator both in the International Celestial Reference System (ICRS) and in the International Terrestrial Reference System (ITRS). The Non-Rotating Origin (NRO) in the ITRS is designated the Terrestrial Ephemeris Origin (TEO). Resolution B1.8 is to be implemented on 1 January 2003 by the International Earth Rotation Service (IERS) which is required to provide the position of the TEO in the ITRS. This paper is devoted to the calculation of this position. Because the TEO depends on the polar motion, which is poorly modeled, its position has been derived from observational data. This has been compared to an analytical model based on a simplified representation of polar motion. We propose then a numerical expression for the displacement of the TEO to be used in the new coordinate transformation from the Celestial Reference System to the Terrestrial Reference System according to the resolution.