激光导引星产生与自适应光学波前探测校正中的基础问题研究

Laser Guide Star (LGS, namely synthetic beacon) is an artificial turbulence-probing source of Adaptive Optics (AO) for compensating for wave-front error of the faint object. In actual turbulence probing, the return light characteristics from LGS, the LGS spot elongation effect resulted from beacon-laser projection mode, and the anisoplanatic effect resulted from different optical-path experience between LGS and object are critical factors to restrict the limits of adaptive optics correction, which should be systematically investigated. Taking account of the LGS operational circumstance, the LGS projection mode, the LGS generation mechanism, and the LGS up- and downlink propagation and imaging, a synthesized numerical simulation model for characterization of atmosphere turbulence-induced wave-front detection and correction with LGS AO will be constructed and put forward in this program. With this model, the influence of LGS operational circumstance, LGS projection mode, LGS generation mechanism, and variation in LGS backscatter region distribution structure on the wave-front measurement accuracy will be fully discussed. The influence of anisoplanatic effect and LGS elongation effect on AO correction, and its corresponding suppression and optimization method will be investigated by numerical simulation. Furthermore, some related experiments will be carried out in our experimental platform, and an exploratory research could be carried out to expand the numerical model application in multiple artificial beacons simulation scene with large field of view. The implementation of this program wil be very useful for providing theoretical and technical support to the technical road-map selection and scheme design of AO systems in future anstronomy observing and laser propagating applications.

激光导引星（即人造信标）是自适应光学应对暗弱目标的湍流参考源。实际工作体制下的人造信标回光形态、光斑尺度扩展、大气非等晕效应等是影响与限制自适应光学目标校正效果的重要因素，有必要进行深入研究。本课题将构建配备人造信标工作体制、发射方式、产生机理、上行/下行大气传输与系统哈特曼成像探测的激光导引星自适应光学波前探测与校正性能分析数值仿真模型，深入研究并掌握实际人造信标工作体制、发射方式、相应散射介质时空分布结构变化等因素对AO波前探测的影响，研究大气非等晕效应对AO校正的影响，研究光斑拉长效应对AO波前探测校正的影响及其相应的抑制方法，并开展相关的自适应光学实验研究。在此基础上，对该模型在大视场多导星场景下的扩展应用进行探索性研究。本项目的实施，必将为未来天文观测、激光传输等外大气校正应用需求自适应光学的技术路线选择与技术方案设计提供重要理论与技术支撑。

激光导引星解决了自适应光学在应对暗弱科学目标实时大气波前探测与校正时的参考源问题，然而实际激光导引星工作体制下的非等晕效应、光斑尺度扩展效应等是影响与限制自适应光学校正效果的重要物理因素。本项目首先从激光导引星上行/下行链路大气传输、特定高度激光导引星产生、激光导引星哈特曼成像大气湍流波前探测、包含时间演化进程系综统计评估等四个方面入手，建立了激光导引星自适应光学波前探测与校正性能分析的数值仿真模型。通过数值仿真，深入研究了不同激光导引星工作体制下大气非等晕效应及其对自适应光学波前探测校正的影响；深入分析了旁轴发射钠激光导引星回光成像光斑形态及其对自适应光学波前探测校正的影响。在数值仿真研究的同时，基于实际的米级望远镜系统，重点开展了基于同步时序探测的钠激光导引星大气角度非等晕效应测量、大气中间层内相对钠原子密度分布规律反演、旁轴发射激光导引星回光成像光斑形态及其对自适应光学波前探测影响的相关实验研究工作，获得了一定条件下实验测量与理论分析相互吻合的有益结果。通过本项目的研究，为我国未来外大气校正应用自适应光学系统的技术路线选择与方案设计提供了基础支撑。