Research On Detecting And Computing Atmospheric Tip-tilt Real Time From The Extended Source Of Lunar Surface

Lunar Laser Ranging (LLR) is a great goal in the world and it represents the height of the single photo detection.The goal of this thesis is to study the best algorithm for computing the atmospheric Tip-Tilt real time from low contrast and extended source based on the theory that introduces the real-time compensation for atmospheric Tip-Tilt in LLR.First, the status of the lunar laser ranging and its difficult are introduced in the thesis. The difficulty of the LLR is that the returned photo numbers are too few, the LLR basically belongs to sub-single photo detection, and at the same time some ways which can improve on LLR are introduced. Then, the effects of the atmospheric turbulence on the laser beam propagation and on the laser ranging are analysed, the classifies and the characters are analysed when the laser beam propagates through the atmosphere and affected by the atmospheric turbulence. The two algorithms, absolute difference and cross correlation are compared in theory and in computing time based on the fact that the lunar surface is low contrast and extended source. Then the data of lunar surface are collected using 1.2m telescope of Yunnan Observatory.Programmes that established by C language for the two algorithms are first proved OK using sun data. Following above analysis, the atmospheric Tip-Tilts are computed real time with the two programmes from the lunar surface images near the Apollo 15 retro-reflectors, and the long exposure images with and without the Tip-Tilt are compared and the two algorithms are compared again with the data. Last, some ideas are bring forward to improve the job.This just the first try in LLR, the following work will be well done soon.