Design of the active cooling focal plane component for the space astronomy telescope

Abstract

The detecting CCD of a space astronomical telescope needs to be cooled to -75℃ to suppress the dark current for faint target detecting in the universe, and coplanarly spliced with two fine guidance sensor(FGS) which needs to be cooled to -40°C for the stability as long time observation. Two one stage thermos-electric cooler(TEC) was connected to actively cool the detector to ensure the working temperature and the temperature control accuracy, the Structural of the actively cooling detector assembly and the focal plane component were presented and the power dissipation of the TEC was calculated. In order to ensure the coplanarity of the focal plane component on the working temperature, the finite element method was used to analyze the thermal distribution on the detector surface and the thermal deformation of the supporting structure of the FGS with different materials. The analysis results showed that the lowest cooling temperature of the detecting CCD is -75°C, the temperature control accuracy was better than 1°C, and the coplanar error of the detection CCD and the fine guidance sensors did not exceed 20μm. The thermal equilibrium test showed that the lowest cooling temperature was -74.9°C~-75.1°C for the detecting CCD, The temperature control accuracy was 0.1°C. The thermal optical test showed that the defocus of the FGS was 4μm after focusing, which verified the thermal and structural design performance of the focal plane component.