Earth tides and Lense-Thirring effect

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Abstract
The general relativistic Lense-Thirring effect can be measured by inspecting a suitable combination of the orbital residuals of the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II. The solid and ocean Earth tides affect the recovery of the parameter by means of which the gravitomagnetic force is accounted for in the combined residuals. Thus an extensive analysis of the perturbations induced on the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II by solid and ocean Earth tides is carried out. It involves only the l=2 terms for the solid tides and also the l=3,4 terms for the ocean tides. The perigee of LAGEOS II results to be very sensitive to the l=3 part of the ocean tidal spectrum, contrary to the nodes of LAGEOS and LAGEOS II. The uncertainty on the solid tidal perturbations, mainly due to the Love number k2, ranges from 0.4% to 1.5%, while the ocean tides are uncertain at a level of 5%-15%. The results obtained are used in assessing which zonal constituents, if not accounted for by the dynamical models employed in building up the orbital residuals, affect the combined residuals. The necessity of correctly predicting the orbital perturbations, and consequently updating the orbital determination models, turns out to be particularly stringent for the l=2 m=0 18.6-year tide and for the l=3 m=0 part of Sa and Ssa. It results that, if modeled at the level of accuracy worked out in the paper, the l=2,4 m=0 and also, to a lesser extent, the l=3 m=0 tides cancel out

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