Earth tides and Lense-Thirring effect

TL;DR

This paper analyzes how Earth tides influence the measurement of the Lense-Thirring effect using satellite orbital residuals, assessing tidal perturbations and their uncertainties to improve gravitomagnetic experiments.

Contribution

It provides a detailed analysis of solid and ocean tidal effects on satellite orbits, quantifies uncertainties, and evaluates their impact on detecting the Lense-Thirring effect.

Findings

Solid tidal perturbations uncertainty: 0.4%-1.5%.

Ocean tides uncertainty: 5%-15%.

Certain tidal constituents cancel out in the combined residuals.

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 these orbital elements by the solid and ocean Earth tides is carried out. It involves the l=2 terms for the solid tides and the l=2,3,4 terms for the ocean tides. The perigee of LAGEOS II turns out 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 in 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 5%-15% level. The obtained results are used in order to check in a preliminary way which tidal constituents the Lense-Thirring shift is sensitive to. In particular it is tested if the semisecular 18.6-year zonal tide really does not affect the combined residuals. It turns out 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 tidal perturbations cancel out.