A comment on "A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model", by I. Ciufolini et al

Abstract

Recently, Ciufolini et al. reported on a test of the general relativistic gravitomagnetic Lense-Thirring effect by analyzing about 3.5 years of laser ranging data to the LAGEOS, LAGEOS II, LARES geodetic satellites orbiting the Earth. By using the GRACE-based GGM05S Earth's global gravity model and a linear combination of the nodes $\Omega$ of the three satellites designed to remove the impact of errors in the first two even zonal harmonic coefficients $J_2,~J_4$ of the multipolar expansion of the Newtonian part of the Earth's gravitational potential, they claimed an overall accuracy of $5\%$ for the Lense-Thirring caused node motion. We show that the scatter in the nominal values of the uncancelled even zonals of degree $\ell = 6,~8,~10$ from some of the most recent global gravity models does not yet allow to reach unambiguously and univocally the expected $\approx 1\%$ level, being large up to $\lesssim 15\%~(\ell=6),~6\%~(\ell=8),~36\%~(\ell=10)$ for some pairs of models.