Contribution of Lunar Laser Ranging to Realise Geodetic Reference Systems

Abstract

Lunar Laser Ranging (LLR) has provided observations for more than 36 years. There is enormous science potential of LLR to further our understanding of the dynamics of the Earth-Moon system (e.g.Earth orientation parameters (EOP) or the secular increase of the Earth-Moon distance: 3.8 cm/year) and to determine relativistic quantities such as the equivalence principle or any time variation of the gravitational constant. Here, we discuss the potential of LLR to contribute to the realisation of various reference systems, i.e. the terrestrial and selenocentric frame, but also thedynamic realisation of the celestial reference system, where most benefit is obtained from the long-term stability of the lunar orbit. Because of the tight link budget, only a handful terrestrial laser ranging stations are capable to routinely carry out the distance measurements (at cm level of precision). Therefore, we propose a next-generation lunar ranging experiment. Lunar landers shall deploy laser ’beacons’pointing at Earth.We estimate that the received pulse strength froma50 mJ Laser is 3 orders of magnitude larger than at classical LLR. Such laser shots could be received by most existing Satellite Laser Ranging (SLR) stations and measurement accuracies at mm level can then be accomplished. The contribution to the realisations of the aforementioned geodetic reference systems could be further improved.If in addition radio transponders were deployed at the same locations, a strong tie to the kinematic VLBI system couldbe established.