Design and simulation of a thermostatic cover for the edge sensor of segmented mirror telescope

Compared to the large monolithic primary mirror, an array of smaller segmented primary mirror is considered as a more feasible solution for both ground and space telescopes with large aperture. Active optics is the key technology to ensure the imaging quality of a segmented mirror, in which edge sensors are used to monitor and provide feedback on the relative position information of the sub mirrors for the surface maintenance of the segmented mirror. The edge sensor needs to maintain a nanoscale measurement accuracy under conditions of large temperature span and long observation period, which is the most demanding and challenging core device in active optics technology. In this paper, a thermostatic cover is designed to remain a relatively stable working environment for the edge sensor. When the external temperature environment changes, if there is no thermostatic cover, the edge sensor working area longitudinal temperature difference changes more than 3°C, in the conditions of a thermostatic cover, the longitudinal temperature difference is not more than 0.3°C; transverse temperature difference is nearly zero. FEA model of fluid-solid heat transformation is built to simulate and analyze the thermal conducting characteristics of the system with sub mirror, the edge sensor, and thermostatic cover. Simulation results show that the thermostatic cover can effectively reduce the temperature influence of the external environment.