Thermal control of primary mirror of Space Solar Telescope

The space-based Lyman-alpha Solar Telescope (LST) developed by China will conduct in-depth observation and research on solar activity and internal dynamics of the sun. Thermal control of the primary mirror is the core of the LST and ensures normal and efficient operation of the LST primary mirror. The primary mirror directly receives solar energy. Its element is produced from fused silica, and the multilayer coatings have high heat absorption. The primary mirror is connected with the front of the piezoelectric actuator for high-frequency image stabilization. According to these characteristics, we study the thermal properties of the primary mirror by attaching a high-thermal-conductivity graphite membrane to its back and connecting the annular bracket. We conduct a thermal equilibrium test and finite element network simulation in high-temperature mode, and their results differ by < 1 degrees C. High- and low-temperature simulations of the primary mirror in orbital operation show that it meets the thermal control target of < 40 degrees C. Therefore, applying a graphite membrane to the LST primary mirror well meets the needs of thermal control. This provides a theoretical basis for improving the reliability and thermal optimization of the primary mirror.