应用天文研究组知识库

卫星激光测距中，为满足不同距离目标的测距要求，需要调整激光光束的发散角。利用离焦式扩束系统改变两透镜间的距离调整发散角会产生离焦像差，影响激光光束的质量和系统的测距能力。因此，研究离焦像差对激光光束质量和系统测距能力的影响具有重要意义。首先，分析扩束系统对基模高斯光束的变换作用，得到发散角和离焦量的关系。其次，根据基模高斯光束的传播理论，得到离焦像差对光束能量密度空间分布的影响。最后，对于不同距离的卫星，计算有离焦像差和无离焦像差时激光测距系统接收的回波光子数。仿真结果表明，发散角和离焦量近似服从线性关系，离焦量变化1 mm,发散角变化1μmrad;离焦像差影响光束的能量密度分布，使光斑弥散；对于不同距离的卫星，在不同角放大率下无离焦像差时测距系统接收的回波光子数约为有离焦像差时的2倍，可以有效提高系统的测距能力。

In satellite laser ranging, in order to meet the ranging requirements of different range targets, it is necessary to adjust the divergence angle of laser beam. Usually, the defocused beam expander system is used to change the distance between two lenses and adjust the divergence angle, which will produce defocused aberration and affect the laser beam quality and the ranging ability of the system. Therefore, it is important to study the influence of defocusing aberration on laser beam quality and system ranging ability. Firstly, the transformation effect of the beam expander system on the fundamental mode Gaussian beam is analyzed, and the relationship between the angular magnification and the defocusing amount is obtained. Secondly, based on the propagation theory of fundamental mode Gaussian beam, the influence of defocusing aberration on the spatial distribution of beam energy density is obtained. Finally, for satellites with different distances, the number of photons received by the laser ranging system with and without defocusing aberrations is calculated. The simulation results show that the angular magnification and defocusing amount obey a linear relationship approximately, the defocusing amount changes 1 mm and the divergence angle changes 1 μmrad; The defocusing aberration affects the energy density distribution of the beam and makes the spot diffuse; For satellites with different distances, the number of photons received by the ranging system without defocusing aberrations at different angular magnification is about twice that of the system with defocusing aberrations, which can effectively improve the ranging capability of the system.