Advanced Lunar Laser Ranging for Testing Relativity and Studying the Earth-Moon System

Abstract

Lunar Laser Ranging (LLR) measures the round-trip travel times of short laser pulses between Earth observatories and lunar retro-reflectors. This became possible for the first time after the landing of Apollo 11 on the Moon in 1969. The measurements are mainly carried out by six observatories at five retro-reflectors with an accuracy at millimetre level. The analysis of the LLR data contributes to the understanding of the Earth-Moon system and is a unique laboratory for the investigation of Einstein's theory of relativity. At Table Mountain Observatory of JPL, Differential LLR (DLLR) is planned for the future. DLLR measurement is the range difference between different lunar reflectors and a very high measurement accuracy (~ 30 µm) is expected. With the analysis of the DLLR data a significant improvement for lunar orientation, rotation, and interior is expected. Some results of LLR and DLLR are presented here.