Research On The Distribution Characteristics Of Echo Photons In Laser Ranging

Satellite laser ranging(SLR)technology measures the distance from the ground station to the satellite through the accurate determination of laser pulse'round-trip time between the ground station and the satellite.With the progress of science and technology,this measurement technology is developed toward long distance(the moon and other deep space laser ranging)and large range(noncooperative target),etc.For non-cooperative target and deep space target ranging,the echo signal is very weak.So study the distribution characteristics of echo photons back to receiving system is of great significance to effectively detect the signal.For this purpose,the paper completed the following studies:First,basing on the laser ranging principle and considering various factors,such as atmospheric turbulence,beam pointing error and target distance,etc.laser ranging equation is deduced.Meanwhile,a software was developed with matlab to characterize the echo photons distribution.By setting relevant parameters of the laser,the launch and receiving telescope,the detector and so on,this software can estimate the number of echo photons and illustrate the relation curve.Second,in-depth study of the effect of atmospheric turbulence on ranging echo photons were carried out in this work.On the basis of the theory of optical transmission in the turbulent atmosphere,approximate analytical expressions of laser beam's extension and drift which are affected by the turbulence were obtained using the intermittent turbulence model She which resembles more the actual turbulence.Such expressions are meanwhile applicable to the Kolmogorov and intermittent turbulences.Based on this expression,the new range equation is obtained,and numerical calculations of the echo photon numbers for low and high orbit satellites and the Moon have been performed,as well as the analysis of the effects of the intermittent atmospheric turbulence on laser ranging echo photons.The result shows that the greater the intermittence of the turbulence,the more the echo photons in the laser ranging.And the highest ratio of the echo photon number in the case of intermittent turbulence to the case without turbulence is about 1/16?1/17 and 1/18,respectively.This study of the characteristics of the distribution of echo photons is based on the 1.2 m laser ranging system in Yunnan Observatories.The research result can provide important reference for designing ranging systems and evaluating the performance of the systems.