Earth rotation parameter estimation from LLR and impact of non-tidal station loading

TL;DR

This study improves Earth rotation parameter estimates from LLR data, achieving higher precision and incorporating non-tidal loading effects, which marginally enhance the accuracy of the results.

Contribution

It introduces a refined method for estimating Earth rotation parameters from LLR data, including non-tidal loading corrections, leading to improved uncertainty levels.

Findings

Uncertainties of ERP estimates are less than 20 μs for ΔUT and 3 mas for pole offsets.

Inclusion of non-tidal loading effects marginally improves uncertainty by about 1%.

Enhanced precision in Earth rotation parameters from post-2000 LLR data.

Abstract

LLR measures the distance between observatories on Earth and retro-reflectors on Moon since 1969. In this paper, we estimate the Earth Rotation Parameters (ERP; terrestrial pole offsets, $x_p$ and $y_p$, and Earth rotation phase, $\Delta$UT) using LLR data. We estimate the values of $\Delta$UT, and the pole offsets separately. For the pole offsets, we estimate the values of $x_p$ and $y_p$ together and separately. Overall, the uncertainties of ERP from the new LLR data (after 2000.0) have significantly improved, staying less than 20 $\mu$s for $\Delta$UT, less than 2.5 mas for $x_p$, and less than 3 mas for $y_p$ for nights selected from subsets of the LLR time series which have 10 and 15 normal points obtained per night. Furthermore, we add the non-tidal loading effect provided by the IMLS, as observation level corrections of the LLR observatories in the analysis. This effect causes deformations of the Earth surface up to the centimetre level. Its addition in the Institute of Geodesy (IfE) LLR model, leads to a marginal improvement in the uncertainties (3-$\sigma$ values) of about 1% for both, $\Delta$UT and the pole offsets.