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 for 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 the returned photon numbers of the LLR are analyzed and discussed at current technique condition, and therefore it is proposed 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.It is concluded that the atmospheric turbulence has the significant influence on the laser beam propagation, especially on the LLR. Following above analysis, the classical laser ranging equation is modified so that 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,It is found 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,a new technical method is proposed.A small area near the reflector array on the moon surface is used 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 of several algorithms for calculation of the wavefront tilt from a low contrast extended source, the absolute difference algorithm is the best one. The details of the technical plan to the new method for the LLR,its theory and technique are also discussed.