Abstract
Since 1969, Lunar Laser Ranging (LLR) data have been collected by various observatories and analysed by different analysis groups. In the recent years, observations with bigger telescopes (APOLLO) and at infra-red wavelength (OCA) are carried out, resulting in a better distribution of precise LLR data over the lunar orbit and the observed retro-reflectors on the Moon. This is a great advantage for various investigations in the LLR analysis. The aim of this study is to evaluate the benefit of the new LLR data for the determination of relativistic parameters. Here, we show current results for relativistic parameters like a possible temporal variation of the gravitational constant G˙/G0=(−5.0±9.6)×10−15yr−1, the equivalence principle with Δmg/miEM=(−2.1±2.4)×10−14, and the PPN parameters β−1=(6.2±7.2)×10−5 and γ−1=(1.7±1.6)×10−4. The results show a significant improvement in the accuracy of the various parameters, mainly due to better coverage of the lunar orbit, better distribution of measurements over the lunar retro-reflectors, and last but not least, higher accuracy of the data. Within the estimated accuracies, no violation of Einstein’s theory is found and the results set improved limits for the different effects.
Highlights
It was 20 July 1969 when the astronauts of the Apollo 11 crew landed in the southern part of Mare Tranquillitatis on the Moon
Until 1973, four further reflectors were deployed on the lunar surface: two reflectors by the astronauts of the Apollo 14 and 15 missions, and two reflectors mounted on the unmanned Soviet Lunokhod rovers
The equivalence principle (EP) dates back to the 17th century when Galileo Galilei studied the acceleration of two bodies in free fall and found that in the same gravitational field it is independent of their shape, mass, and composition [32]
Summary
It was 20 July 1969 when the astronauts of the Apollo 11 crew landed in the southern part of Mare Tranquillitatis on the Moon They deployed the Apollo Lunar Surface Experiments Package, where the retro-reflector for Lunar Laser Ranging (LLR) is the last operating part of the experiment. For more than 50 years there has been continuous measuring of the distance between observatories on the Earth and retro-reflectors on the Moon. All that results in an improved coverage of the lunar orbit and is a big benefit in the analysis of the data and for the determination of various parameters. In Germany, from the early 1980s on, the software package LUNAR (LUNar laser ranging Analysis softwaRe) has been developed to study the Earth–Moon system and to determine several related model parameters [9,10,11,12]. In our recent study their effect can be addressed in detail
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