我国的太极计划以及ESA（European Space Agency, 欧洲航天局）的LISA（Laser Interferometer Space Antenna, 空间激光干涉天线）计划为最具代表性的空间引力波探测计划，拟采用激光干涉的测量方法实现0.1mHz-1Hz频段的引力波探测。在卫星发射到既定轨道后，需首先完成百万公里量级星间激光链路的构建，使用于科学测量的QPD（Quadrant Photodiode, 四象限探测器）能够接收到连续的激光信号，为此需引入激光捕获系统将激光指向偏差压制到1μrad。为避免引力波信号淹没于激光抖动噪声之中，完成激光捕获后还需进行激光精密指向过程，将激光指向抖动进一步压制到10nrad/√Hz@(0.1mHz-1Hz)。

  空间引力波探测激光捕获-指向过程具有超远距离及超高精度捕获的特点，拟采用三级捕获探测器的方案，通过STR（Star Tracker, 恒星敏感器）、CCD（Charge-Coupled Device, 电荷耦合器件）/CMOS（Complementary Metal Oxide Semiconductor, 互补金属氧化物半导体）捕获相机、QPD逐级压制激光指向偏差。目前对全过程的模拟结果初步验证了上述方案的可行性，但作为太极计划不可或缺的关键技术，在应对空间实际工况时，激光捕获-指向系统中尚有较多的关键科学与技术问题仍需解决。为分析激光捕获-指向系统在轨可行性，本论文解决的主要科学与技术问题如下：（1）如何提出激光捕获-指向过程各阶段采用的器件及技术指标？（2）激光捕获阶段的核心方法学是：通过计算地面校正的参考光斑与捕获相机上接收到的入射激光光斑间的位置偏差，反演相应方向激光指向偏差，因此光斑中心定位精度直接决定了激光捕获精度。光束传播百万公里量级距离后，用于激光捕获的光强仅有100pW量级，如何在100pW量级弱接受光强情况下实现激光光斑实时、高精度定位？（3）激光精密指向阶段拟采用DWS（Differential Wavefront Sensing, 差分波前传感）技术进行角度的高精度测量。同样由于光束远距离传播，进入接受口径内的光束具有高斯平顶光束的性质，因此实际空间探测中DWS信号是由本地的高斯光束和远处传来的高斯平顶光束干涉产生。在空间实际干涉情况下DWS技术有怎样的表现？为满足太极计划激光精密指向阶段精度要求，DWS技术应用的边界条件为何？

  目前对空间引力波探测激光捕获系统的研究仍停留在方案模拟阶段，为充分验证激光捕获系统原理与方法学可行性，本论文设计并构建了激光捕获地面模拟实验系统。实验系统从捕获光路、捕获精度和捕获扫描过程三个方面对太极计划实际激光捕获过程进行了模拟，并通过DWS信号读出捕获后激光角度残余偏差。论文分析了地面实验中，光束非平顶特性对激光捕获实验结果的影响，提出了改进的实验方案，从原理方法学上验证了太极计划激光捕获方案的可行性，为太极计划激光捕获系统设计提供了理论及实验基础。

  太极计划激光捕获方案拟采用CCD/CMOS捕获相机进行光斑中心定位，但捕获相机本身有严重的发热问题，对干涉仪测量精度会产生较大影响。激光捕获完成后需将系统静置两周左右的时间才能开始进行引力波信号探测，这会大大浪费科学测量时间。为避免上述问题，本论文提出了一种高速、高精度的QPD捕获方案。通过仿真验证了该方法可在70s内实现1μrad的捕获精度，可作为未来空间引力波探测激光捕获备选方案。

The Chinese proposed Taiji program and the ESA (European Space Agency) proposed LISA (Laser Interferometer Space Antenna) program are the most representative space-based gravitational wave detection missions. Laser interference measurement method is planned to be used in the programs for realizing gravitational wave detection within the frequency band of 0.1mHz-1Hz. After launching to the established orbit, the inter-satellite laser link should be constructed first. Otherwise, the QPD (Quadrant Photodiode) detectors, which are used in scientific measurement, cannot receive continuous laser signal. Therefore, it is necessary to introduce a laser acquisition system to suppress the laser pointing deviation to 1μrad. On the other hand, in order to avoid submerging the gravitational wave signal in the laser jitter noise, the laser pointing process should also be carried out for further suppressing the laser pointing jitter to 10nrad/√Hz@(0.1mHz-1Hz) after the laser acquisition process.

  The laser acquisition-pointing process of space gravitational wave detection has the properties of ultra-long distance and ultra-high precision acquisition. The acquisition-pointing system is proposed to adopt a scheme of three-stage sensors. The STR (Star Tracker), the acquisition camera of CCD (Charge-Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) and the QPD are used in turn for suppressing the laser pointing deviation. At present, the simulation results of the whole process have preliminarily verified the feasibility of the above scheme. However, as an indispensable technology of the Taiji program, there are still many key scientific and technical problems to be solved in the laser acquisition pointing system in response to the actual space conditions. In order to analyze the in-orbit feasibility of the laser acquisition-pointing system, the main scientific and technical problems to be solved in this paper are as follows: (1) How to put forward the parameters of the devices and the technical indicators in each stage of laser acquisition-pointing process? (2) The core methodology of laser acquisition stage is: by calculating the position deviation between the reference spot corrected on the ground and the incident laser spot received by the acquisition camera, the laser pointing deviation in the corresponding direction can be derived. As a result, the laser spot center positioning precision directly determines the laser acquisition precision. After the transmitting beam propagating a distance of a million kilometers magnitude, only 100pW laser intensity can be used for laser acquisition. So, how to realize the real-time and high-precision positioning of laser spot under the condition of 100pW weak receiving light intensity? (3) DWS (differential wavefront sensing) technology is proposed to be used for high precision angular measurement in laser pointing stage. Similarly, due to the laser beam long-distance propagation, the beam entering the receiving aperture has the properties of a flat top beam, so the DWS signal in actual condition is generated by the interference signal of the local Gaussian beam and the remote flat top beam. How does the DWS technique perform with the actual interference condition? What are the boundary conditions of DWS technology for meeting the requirement of the laser pointing precision?

  At present, the researches on laser acquisition system of space gravitational wave detection missions is still in the stage of scheme simulation. In this thesis, a laser acquisition simulation experiment system is designed and constructed to realize methodological demonstration of the acquisition scheme. The experiment system simulates the actual acquisition process from three aspects: acquisition optical path, acquisition precision and acquisition scanning process. After the acquisition simulation, the residual angular deviation is read out by the DWS signal. The influence of the non-flat top characteristics of the beam to the experimental system is also analyzed. To reduce the influence, an improved experimental scheme is proposed. The experiment system realizes methodological demonstration of the acquisition scheme. The results offer the experimental foundation and theoretical basis for the acquisition system of the Taiji program.

  The current acquisition scheme of the Taiji program plans to use CCD or CMOS acquisition camera to position the laser spot center. However, the serious heating problem of CCD/CMOS camera will greatly influence the precision of the laser interferometer, which is used to detect the gravitational wave signal. Only by turning off the whole system for two weeks after the acquisition process can the interferometer work properly, which is a great waste of the time of scientific measurement. In order to avoid the above problem, a high speed, high precision QPD acquisition scheme is introduced in this thesis. The simulation results show that the acquisition accuracy of 1μrad can be achieved within 70s, which can be used as an alternative laser acquisition scheme for future space gravitational wave detection.