Non-Tidal Station Loading Impact at Lunar Laser Ranging Observatories

Abstract

The distance between the observatories on Earth and the retro-reflectors on the Moon has been regularly observed by the Lunar Laser Ranging (LLR) experiment since 1970. In this study, we add the effect of non-tidal station loading (NTSL) in the analysis of LLR data. The non-tidal loading datasets provided by the German Research Centre for Geosciences (GFZ) and the International Mass Loading Service (IMLS) are used in our study to correct the positions of the LLR observatories. The Earth surface deforms up to the centimetre level due to this effect. With its addition in the Institute of Geodesy (IfE) LLR model, we get an improvement in the uncertainty of the station coordinates at the sub-millimetre level, and an improvement in the LLR residuals of up to centimetre level. Additionally, we also looked at a change of the annual signal in the LLR post-fit residuals, as both NTSL datasets show a dominating signal with an annual period; however a conclusive change could not be observed.