Characteristics of Novel Differential Lunar Laser Ranging Compared to Classical Lunar Laser Ranging

Kurzfassung

A new lunar laser ranging (LLR) station of JPL at the Table Mountain Observatory can allow a novel way of lunar tracking: differential lunar laser ranging (DLLR). There, fast switching between two or more lunar reflectors would be possible in future to get DLLR observations by differencing two consecutive ranges. This new kind of observable will largely decrease the atmospheric and station-related errors, resulting in a very high accuracy of about 30 µm. Using such accurate data will give us the opportunity to obtain better knowledge of the interior and the rotation of the Moon. Additionally, DLLR is expected to improve other parameters of the Earth-Moon dynamics, including those relevant for relativity tests, for example, test of the equivalence principle and a possible time-variation of the gravitational constant G. Presently, our group works on the simulation of DLLR data and investigates its characteristics, like the sensitivity and the impact of different switching intervals by comparing with LLR. DLLR keeps the same sensitivities as LLR for some parameters (group A), for example, the lunar rotation parameters, while it becomes less sensitive to other parameters (group B), such as station positions and velocities, resulting from its cancelling effect on the station part. However, thanks to its excellent measurement accuracy, DLLR can still keep the estimated accuracies for group B at the same level as LLR and significantly enhance the estimation of group A. The correlation between stations and reflectors is increased by DLLR. Nevertheless, larger switching intervals (e.g., 15 min) will be helpful for their decorrelation. In future, we will combine DLLR with classical LLR data to benefit from both observations. In this presentation, we will show first simulation results on the specific characteristics and the benefit of DLLR.