The response of the Earth to the (nearly) diurnal torques applied by the Sun and the Moon provides a means for studying the characteristics of the Earth and the interactions of the Earth's mantle with its fluid parts (fluid-outer core, atmosphere and oceans). The PIs will study these problems through the use of very-long-baseline (VLBI) measurements of the motions of the Earth's rotation axis in space - the nutations of the Earth, addressing issues concerning the accuracy with which the nutation series coefficients can be determined from VLBI data, and at the interpretation of the differences between the observed coefficients and those computed from theoretical models of the response of the Earth to the nearly diurnal torques.
