Will it be possible to measure intrinsic gravitomagnetism with Lunar Laser Ranging?

TL;DR

This paper investigates the feasibility of detecting Earth's intrinsic gravitomagnetic effects on the Moon's orbit using Lunar Laser Ranging, considering current measurement precision and systematic errors.

Contribution

It analyzes the potential to measure gravitomagnetic precessions of the Moon's orbit with LLR, accounting for current limitations and systematic uncertainties.

Findings

Lunar Laser Ranging can determine the lunar orbit at mm accuracy.

Lense-Thirring precession signals are below current detection thresholds.

Systematic errors from classical orbital perturbations dominate over relativistic signals.

Abstract

In this note we mainly explore the possibility of measuring the action of the intrinsic gravitomagnetic field of the rotating Earth on the orbital motion of the Moon with the Lunar Laser Ranging (LLR) technique. Expected improvements in it should push the precision in measuring the Earth-Moon range to the mm level; the present-day Root-Mean-Square (RMS) accuracy in reconstructing the radial component of the lunar orbit is about 2 cm; its harmonic terms can be determined at the mm level. The current uncertainty in measuring the lunar precession rates is about 10^-1 milliarcseconds per year. The Lense-Thirring secular, i.e. averaged over one orbital period, precessions of the node and the perigee of the Moon induced by the Earth's spin angular momentum amount to 10^-3 milliarcseconds per year yielding transverse and normal shifts of 10^-1-10^-2 cm yr^-1. In the radial direction there is only a short-period, i.e. non-averaged over one orbital revolution, oscillation with an amplitude of 10^-5 m. Major limitations come also from some systematic errors induced by orbital perturbations of classical origin like, e.g., the secular precessions induced by the Sun and the oblateness of the Moon whose mismodelled parts are several times larger than the Lense-Thirring signal. The present analysis holds also for the Lue-Starkman perigee precession due to the multidimensional braneworld model by Dvali, Gabadadze and Porrati (DGP); indeed, it amounts to about 5 X 10^-3 milliarcseconds per year.