Diurnal and semidiurnal variations in Earth orientation determined from LAGEOS laser ranging

Abstract

Variations in universal time and polar motion due to ocean tides at nearly diurnal and nearly semidiurnal frequencies are determined from analysis of laser ranging to the LAGEOS satellite over the period from 1987 to 1992. The adjusted diurnal tides were K1, S1, P1, O1, and Q1, while the semidiurnal tides were K2, S2, M2, and N2. A formulation was used that explicitly separated prograde and retrograde terms in the polar motion in order to eliminate aliasing from the singularity of retrograde wobble with long period orbit error and nutation. The results are compared to other experimentally derived observations from very long baseline interferometry (VLBI) and with predictions from an ocean tide model. The results of this study agree well with those from the VLBI studies, typically at the 2–3 μs level in universal time and 30–50 microarc sec (μas) level in polar motion. The agreement with the predictions from the ocean tide model were roughly a factor of 3 worse for UT although better for polar motion, particularly in the diurnal band.