Research On A New Technical Method For The Lunar Laser Ranging

Lunar Laser Ranging (LLR) is a great goal in the world and it represents the height of the single photon detection. The goal of this thesis is to study a new technical method of increasing returned photon numbers for the lunar laser ranging, and to try to increase the successful probability of the lunar laser ranging. The idea originates a new concept that is to introduce the real-time compensation technique of atmospheric tip-tilt on the LLR First, the status of the lunar laser ranging and its difficulties are introduced in the thesis. The difficulty of the LLR is that the returned photon numbers are too few. The LLR basically belongs to sub-single photon detection. All factors that affect tile returned photon numbers of the LLR are analyzed and discussed at current technique condition in this paper, and therefore I propose to consider the atmospheric turbulence effects and the energy distribution of the laser beam on the LLR. For this new idea, the basic statistic properties of the atmospheric turbulence and the electric field in the atmosphere, the effects of atmospheric turbulence on the laser beam propagation and on the laser ranging are analyzed. So I get a conclusion that the atmospheric turbulence has a significant influence on the laser beam propagation, especially on the LLR. Following above analysis, the classical laser ranging equation is modified, so it can be more near the true condition when it applies to the LLR and can guide the compensation that we want to do. For the distorted laser beam compensation on the LLR due to the atmospheric turbulence, I catch its key that the real-time compensation of the wavefront tilt is an important factor for increasing the returned photon numbers of the LLR. After combining the LLR and the laser ranging system of Yunnan Observatory, I propose a new technical method that is use a 2 small area near the retroreflector array on the moon surface as an extended source to detect and calculate the wavefront tilt, and then carry on the real-time tilt compensation for the laser beam on the LLR. After analysis and comparison several algorithms for calculation the wavefront tilt from a low contrast extended source, the absolute difference algorithm is the best one. Following are the details of the technical plan of the new method for the LLR, and are analysis and discussions on its theory and technique, then are the deductions for the theory foundations, compensation effects, feasibility and practice of the new technical method. The research of this thesis is only a beginning of a new technical method, and there are still many works need to do. I hope the results of the thesis have a significant meaning on developing the LLR theory and on practically increasing its successful probability.