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.

The empirical findings from this study confirm the superiority of reinforcement learning in formulating effective stray light suppression measures for space gravitational wave detection telescope systems. The approach not only achieves superior suppression outcomes but also introduces an efficient, flexible, and innovative solution to the challenges of stray light in space gravitational wave detection and other high-precision optical systems.

星载测风干涉仪采用临边观测模式测量大气气辉谱线的多普勒频移来实现大气风场探测，干涉仪有效覆盖性会受到探测目标源及卫星平台模式的限制，在卫星任务规划前端对观测数据进行分析，判断其是否满足科学目标，对风场数据应用具有重要意义。首先，建立了临边观测几何模型，对卫星运行期间仪器的临边切点分布情况进行仿真；其次，探讨了影响仪器有效观测的主要因素，并以昼气辉探测为例，分析在不同时段下，太阳入射角与干涉仪有效时空覆盖性之间的关系；最后使用分离变量法研究卫星轨道参数对测风干涉仪有效覆盖性的影响，并评估不同轨道参数下的干涉仪对欧亚大陆的覆盖百分比。结果表明：1）影响仪器有效观测的因素主要为太阳天顶角和太阳散射角，太阳入射角影响切点纬度覆盖范围和切点地方时；2）卫星轨道倾角和轨道高度共同决定仪器有效覆盖效率，且轨道倾角为欧亚大陆覆盖百分比的主要影响因素，当轨道倾角在60°~80°之间时，覆盖百分比可达到百分百。文中为星载干涉仪的后续设计及性能评估提供了观测几何框架，实现了载荷观测覆盖效能的定量分析，且该模型具备泛用于其他各类大气光学遥感载荷观测模式分析的能力。

在空间引力波探测的超长臂干涉测量过程中，杂散光问题长期以来受到广泛关注。一方面，本地干涉仪发出的激光通过望远镜时会产生后向相干杂散光。另一方面，在轨情况下，来自空间的环境辐射入射到航天器还会产生前向非相干杂散光。一直以来，前向非相干杂散光受到的关注较少，然而却是空间引力波望远镜设计必须要考虑的因素。因此，本文对空间引力波探测望远镜在轨情况下产生的杂散光进行测量与抑制。首先，根据太极计划三星卫星编队的轨道数据对全年太阳角进行计算，对1064 nm波段附近的太阳辐射进行评估，推导了遮光罩投影函数，最终给出遮光罩设计指标。然后，对望远镜进行光学与机械建模，并对关键光学元件进行散射测量。最后，根据入射太阳光能量对到达望远镜出瞳的杂散光进行计算。结果表明：当入射光与光轴夹角为60°时，出瞳处的杂散辐射可达到3.9×10⁻¹² W，对应点源透射比为8.7×10⁻⁹，满足空间引力波探测超低杂散光的需求。

随着航天红外技术向高定量化、高集成化方向的发展，传统基于CPU或DSP的黑体测控温系统无法满足高集成化和高精度的需要。针对上述问题，设计了基于FPGA的星载黑体高精度集成温控系统。该系统以FPGA为核心控制单元进行温度采集和控制，实现多功能高速并行处理。黑体测温模块采用三线制惠斯通电桥减小导线电阻影响，然后在信号调理部分采用集成运算放大器组成的三级有源滤波和放大实现了对电气输出的低噪声放大。与传统仪用放大器加无源滤波的信号调理方式相比，该方法具有更强的干扰抑制能力。同时，对铂电阻阻值与温度的非线性误差以及测温系统电路误差，提出了基于多项式模型及最小二乘理论的分级拟合校正方法，进一步提高了测温精度。控温模块采用新型模糊控制和增量式PID（FIPID）结合减小过冲，加快收敛速度。基于精密标准电阻的实测结果表明该系统测温精度在247~375 K范围内为0.035 K，比校正前精度0.383 K提高了90.9%。控温仿真实验表明与PID控温相比，FIPID的过冲为零，而PID算法有12.4%的过冲，且收敛速度提高了64%。地面热真空和在轨实际控温实验表明在256~367 K范围内实测控温精度为0.039 K，该方法已成功应用于某型号空间红外相机，且满足在轨高精度定标要求。该系统具有测控温精度高、动态范围大、易于集成化的优点，可推广应用于星上其他高精度主动温控。