A critical analysis of a recent test of the Lense-Thirring effect with the LAGEOS satel- lites

In this paper we quantitatively discuss the impact of the current uncertainties in the even zonal harmonic coefficients Jl of the Newtonian part of the terrestrial gravitational potential on the measurement of the general relativistic Lense-Thirring effect using a suitable linear combination of the nodes Ω of the laser-ranged LAGEOS and LAGEOS II satellites. The 1-sigma systematic error due to the mismodelling in the Jl coefficients ranges from ∼ 4% for the EIGEN-GRACE02S gravity field model to ∼ 9% for the GGM02S model. Another important source of systematic error of gravitational origin is represented by the secular variations J̇l of the even zonal harmonics. While the relativistic and Jl signals are linear in time, the shift due to J̇l is quadratic. We quantitatively assess their impact on the measurement of the LenseThirring effect with numerical simulations obtaining a 10−20% 1-sigma total error over 11 years for EIGEN-GRACE02S. Ciufolini and Pavlis, in a test performed in 2004, claim a total error of 5% at 1-sigma level.