Overview: Gravitational waves are spacetime oscillations radiated outward by accelerating mass objects. Significant astronomical events in the universe, such as the merging of massive black holes, emit stronger gravitational waves. Detecting gravitational waves allows for a deeper study of the laws governing celestial bodies and the origins of the universe, making accurate detection crucial. Gravitational wave detection technology utilizes Michelson interferometers to convert the extremely faint spacetime fluctuations caused by gravitational waves into measurable changes in optical path length. Recently, ground-based large Michelson interferometers have achieved direct detection of high-frequency gravitational waves. However, the detection of low-frequency gravitational waves, which is equally important, is not feasible on the ground due to arm length and ground noise issues. This necessitates the construction of ultra-large Michelson interferometers in space for low-frequency gravitational wave detection. Spaceborne gravitational wave detection telescopes play a vital role in collimating bidirectional beams in ultra-long interferometric optical paths in space. The extremely subtle changes in optical path caused by gravitational waves impose high demands for pm-level optical path length stability and below 10^?10 level backscattered light in these telescopes. The ultra-high level index requirements exceed the precision limits of current ground testing techniques for telescopes. To ensure that spaceborne telescopes maintain their ultra-high design performance in the orbital environment, developing testing and evaluation techniques for these key indicators is a crucial prerequisite for the success of the space gravitational wave detection program. This paper provides an overview of the development of spaceborne gravitational wave detection telescopes, both domestically and internationally. It focuses on the current status and some test results of optical path length stability and backscattered light testing of telescopes under development, as well as further testing plans, providing a reference for the testing and evaluation of Chinese space gravitational wave detection space-borne telescopes.

Overview: Since the groundbreaking discovery of gravitational waves, the scientific community has fervently pursued the exploration of low-frequency gravitational waves to glean deeper insights into the cosmos. The inherent limitations of ground-based conditions, however, pose formidable challenges for detectors in capturing gravitational waves below the 1 Hz threshold. Consequently, the imperative has shifted toward the deployment of space-based gravitational wave detectors as the paramount solution for effective low-frequency gravitational wave detection. At the crux of space-based gravitational wave detection lies the pivotal role of spaceborne telescopes. Given the expansive transmission distances spanning magnitudes of 10⁹ m between celestial constellations, the demand for nanoradian-level precision in telescope pointing accuracy becomes non-negotiable. The concomitant necessity for high-precision measurements and calibration emerges as a prerequisite for achieving the exacting standards of pointing accuracy in spaceborne telescopes dedicated to gravitational wave detection. To ameliorate the deleterious effects of pointing deviations on gravitational wave detection, this study strategically optimizes key parameters, including microlens structures, detector selection, and algorithmic frameworks, thereby achieving a breakthrough in high-precision pointing deviation measurements. Leveraging a low-density microlens array with extended sub-aperture focal lengths enhances the spatial scale of the light spot within each sub-aperture. This, coupled with detectors boasting a high signal-to-noise ratio, synergistically elevates the pointing detection accuracy of each discrete lens. Moreover, the paper introduces an innovative, Hartmann principle-based methodology for high-precision pointing deviation measurements, deploying a spatially reused paradigm across multiple sub-apertures. By aggregating measurement results from diverse sub-apertures, the approach effectively mitigates the influence of assorted random errors on measurement accuracy, thereby markedly enhancing the precision of pointing deviation measurements. Illustrating the efficacy of these methodologies, the paper exemplifies their application within the ambit of the "Tianqin Plan" for space-based gravitational wave detection. Employing numerical simulations and factoring in the design parameters of the Hartmann sensor, the study performs a meticulous analysis of pointing deviation measurement accuracy. Comparative analysis between single sub-aperture and sub-aperture correlation reuse technologies reveals a compelling enhancement in measurement accuracy, approximating a sevenfold improvement with the latter. The pointing deviation measurement accuracy achieved through sub-aperture correlation reuse technology is quantified at approximately 18.81 nanoradians. Considering the optical magnification inherent in spaceborne telescopes, estimated at around 30 times, the resultant pointing deviation measurement accuracy reaches an impressive 0.62 nanoradians. This design precision significantly surpasses the stipulated 1 nanoradian accuracy requirement for ground-based gravitational wave pointing deviation measurements. As a prudential measure, the proposed design incorporates a substantial margin to accommodate potential accuracy diminution attributable to external perturbations during empirical testing.

针对大口径太阳望远镜系统运行过程中由于静态位置失配误差、风载弯沉等准静态位置失配误差以及热变形等非失配误差引起的波前像差导致成像质量下降的问题，在对太阳望远镜系统波前像差时空分频的基础上，提出采用次镜刚体位移对太阳望远镜低时空频率波前像差校正的方法，建立起次镜刚体位移与像差校正量的关系，并通过数值仿真及实验验证了采用次镜刚体位移对上述来源像差的校正能力。数值仿真和实验结果表明：次镜刚体位移能够对望远镜系统运行过程中的低时空频率波前像差进行有效校正，其中，对位置失配误差校正后像差RMS值低于原值的9%，对非失配误差校正后像差RMS值低于原值的40%，对多源混合误差校正后像差RMS值低于原值的15%。

干涉图像区域分割属于重要的干涉图像预处理步骤，目的是从干涉图像中提取出有效数据区域。干涉图像区域分割广泛存在于各种数字波面干涉仪的实验测试和数据处理中，对于精确波前复原以及相位解包裹可靠实施具有重要影响。介绍了3类常见干涉图像的区域分割技术，包括单帧干涉图、同步移相干涉图和横向剪切干涉图，并系统总结了相关研究进展、展望了该领域研究趋势。

三维成像技术在自动驾驶、航空任务、**领域等都有着广泛的应用，不同技术体制的成像系统有不同的优点，其中基于多像素光子计数器(Multi-Pixel Photon Counter, MPPC)的三维成像技术由于其成像速度快、对极弱光敏感等优势具有广阔的发展潜力。然而，由于MPPC阵列发展不成熟，基于MPPC阵列的弱光三维成像探测水平受到限制。利用日本滨松公司研发的具有32×32规模的MPPC阵列S15013系列二维光子计数图像传感器，开发了一套三维成像系统，传感器的每个像素由12个单光子雪崩二极管并联而成，其总探测像素达到1 K以上。基于该系统，分析了阈值电压、镜头光阑等参数条件对三维成像探测结果的影响，对系统探测灵敏度和精度进行了测试，并针对37 m远模拟目标开展了三维成像探测试验。试验结果表明：在回波光子数约1.98 (光子/像素)的暗弱条件下，目标区域测距精度达到0.268 m，三维结构特征明显，达到了接近单光子成像的探测水平。