Nearly diurnal structure of polar motion analysing Lageos SLR data.

Since more accurate and precise measurements are available in space geodetic techniques, there is a growing interest for the scientific community in studying the short periodic fluctuation of the Earth’s rotation axis. In particular subtle nearly diurnal variations of the orientation of the rotation axis, as viewed from the Earth, reflect dynamical properties of the deep interior of the Earth. Recently Very Long Baseline Interferometry (VLBI) data analysis sets a stringent upper limit to the nearly diurnal wobble whose amplitude is well below the milliarc second (mas) level [Herring et al., 1991].