Research on mK-level thermal control design and environmental test verification for a space-borne gravitational-wave telescope

• Design and fabricate an off-axis four-mirror gravitational-wave telescope • Large aperture telescope with a primary mirror up to 300mm • Use real-size telescope thermal prototype as the experimental subject • Establish a test system capable of simulating the complex space environment • Design and implement a multi-stage active–passive thermal-control system • Limiting temperature fluctuations of the telescope key locations to mK level Gravitational wave telescopes impose extremely stringent requirements on thermal stability. The key optical elements are required to maintain temperature control accuracy at the millikelvin (mK) level to suppress the impact of thermal noise on optical measurements. In this work, an off-axis four-mirror gravitational wave detection telescope was tested which had the primary mirror aperture up to 300mm. A multi-stage thermal suppression system was developed for the gravitational wave detection telescope by integrating multiple active and passive thermal control techniques. A high-precision temperature measurement and control scheme was established, and the system’s performance was experimentally evaluated under cryogenic vacuum conditions in a space environment simulation facility. The results demonstrate that the proposed multi-stage thermal suppression system could maintain the temperature fluctuation of key elements in the telescope within ±3.0mK over a continuous 2.2h period. In the center point of the primary mirror back surface, it achieved a temperature stability of ±1.6mK. These results proved the effectiveness of the high-stability multistage heat suppression techniques and high-precision temperature measurement/control method, providing a potential choice for the thermal design of future space-based gravitational wave detectors.