Overview: The space gravitational wave detection telescope is one of the core payloads of the gravitational wave detection satellite, simultaneously expanding and contracting the transmitted beam. Optical path stability is one of the core indices for the telescope, closely related to its structural stability. To meet the ultra-high path stability and structural stability requirements posed by the gravitational wave detection mission, it is essential to study the structural deformation measurement of the telescope. Currently, there are still several shortcomings in the research of multi-degree-of-freedom deformation measurement methods for gravitational wave detection telescopes, such as inaccurate selection of measurement points, inability to decouple multi-degree-of-freedom coupling, and unclear identification of error sources in multi-degree-of-freedom measurement. This paper deeply investigates the high-precision measurement of structural deformation of space-borne telescopes designed for space gravitational wave detection. It preliminarily establishes a framework and method system for measuring the structural deformation of space-borne telescopes, theoretically describing the measurement principle of the method. The feasibility of this method applied to space gravitational wave detection is verified through simulation analysis and error decomposition. The paper focuses on resolving the issue of decoupling multiple degrees of freedom, establishing a mathematical model using analytical methods, and conducting preliminary validation using Zemax. Finally, noise analysis of the measurement system is carried out, with experimental testing of the main noise components in the measurement system, validating the correctness of the theoretical noise model proposed in this paper. The experimental results show that near 1 Hz, the displacement noise background of the single-link interferometer is 100 pm/Hz^1/2. At 1 mHz in the low-frequency range, the displacement noise background reaches 10 nm/Hz^1/2. The noise level of the measurement system below 1 mHz is mainly limited by environmental temperature noise, while above 10 mHz, it is primarily constrained by laser frequency noise, phase acquisition background noise, and vibration noise. During the development phase of the space gravitational wave detection telescope, the research on this measurement method is expected to fulfill the telescope's multi-degree-of-freedom deformation measurement needs. It also provides data feedback for telescope design and offers guidance for the study of the telescope's optical path stability.

Taking the LISA system as a reference, the phase noise of the inter-satellite transmission needs to be less than 1 pm. Research has shown that the defocus and the astigmatism are the main aberrations affecting jitter noise at a distance of 2.5×10⁹ m. There is a deviation between the phase stationary point and the origin position. To minimize the phase noise, the telescope angle needs to be adjusted. The gravitational wave detection at the phase stationary point can effectively reduce the phase noise and the requirements of the telescope exit pupil wavefront RMS. The large defocus and small coma can make the phase stationary point close to the optical axis and increase the received laser power.

Overview: In order to achieve the measurement of gravitational wave signals in the millihertz frequency band, the space-based gravitational wave detection projects such as LISA, TianQin, and Taiji projects, which are based on laser interference systems, require the hardware noise floor of the interferometers to be lower than the interstellar weak light shot noise limit. This imposes stringent engineering specifications on the optical-mechanical design and the corresponding interferometer payload. This paper approaches the issue from the perspective of detection mode selection and derives the expressions of readout noise and stray light noise in the interference signal under the single detector mode and the balanced mode. Furthermore, a detailed discussion is provided on the weak-light interference process of the scientific interferometer. The results demonstrate that the balanced mode is capable of suppressing the interference phase noise caused by laser power fluctuations and backscattered stray light across multiple orders of magnitude. However, the suppression capability is constrained by the unequal splitting property of the beam combiner. To address this, a relative gain factor is introduced to compensate for the unequal splitting property of the beam combiner. Further analysis reveals that electronic gain compensation can only eliminate the impact of unequal splitting on one of the two noises rather than both simultaneously. Therefore, a balance must be struck in selecting gain compensation between the suppression of laser power fluctuation noise and stray light noise. Even with this consideration, the balanced mode still offers significant noise suppression capabilities at a magnitude difference, thus potentially reducing the engineering requirements for laser power fluctuations and telescope backscattered stray light.

为了降低探测器的噪声与暗电流，使光谱仪的CMOS探测器能获得更准确的光谱曲线，设计了探测器温度控制系统。本系统核心采用基于现场可编程逻辑门阵列（FPGA）的增量式比例-积分-微分（PID）控制算法。在传统控制算法的基础上，增加了抗积分饱和控制，并且在PID算法的前端增加了对目标值的过渡过程。该系统在实现探测器温度变化速率可控的同时，也解决了超调过大的问题。多次整机环境实验结果表明：在轨环境温度条件下，40 °C温差范围内该系统可以控制探测器以指定温变速率（4.5±0.05） °C/min达到任意温度；并且可在该温度下稳定工作；温度变化范围为±0.1 °C。相比于传统模拟PID控制方法，其具有灵活度高，稳定性强等优点。当制冷到−10 °C时，探测器的噪声得到了有效抑制。

成功设计了一款天文应用的640×512短波红外焦平面读出电路。由于红外天文观测具有极低背景辐射、光子通量低的特点，为了实现探测器的高信噪比，需要降低器件的暗电流和电路噪声。电路采用有效的功耗管理策略，在保证电路正常工作的前提下尽可能地降低电路功耗以减小电路辉光对器件暗电流的影响。同时，研究非破坏性读出的数字功能，实现了超长的积分时间和信号的多帧累积,并作为一种斜坡采样的策略有效地降低读出噪声。短波HgCdTe焦平面的测试结果符合理论设计预期，开启电路非破坏性读出功能，设置6000 s的积分时间，当电路功耗调低至14.04 mW时暗电流为0.9 e-·pixel⁻¹·s⁻¹。读出噪声在两档增益下分别为50 e-（10 fF）和27 e-（5 fF），非线性度低于0.1%。