Design and implementation of cooling system for focal plane assembly of observation camera in astronomical satellite

Abstract

In order to observe dim astronomical objects, the imaging sensor of the Astronomical Observation Camera (AOC) in the satellite needs to work at −65°C to suppress its dark current noise. To achieve the low temperature environment, a cooling system on Thermoelectric Cooler (TEC) was designed. The cooling system adopted a Single Chip Microprocessor as its control computing platform and its software used self-adaptive digital PID control algorithm was developed. The data of the real-time temperatures, captured by the acquiring circuits from the temperature sensors which were mounted at the back surface of the imaging sensor, were used to be the input of the self-adaptive digital PID control algorithm, and the output calculated by the algorithm was applied to adjusted the control current of the driver circuit for the TEC, and then the temperature of Focal Plane Assembly (FPA) was cooled down or warmed up to satisfy the working requirements. Experimental results show that the designed system can control the temperature gradient of the FPA less than 1°C and reach its normal working temperature −65°C quickly. Its control accuracy is ±2°C. The practical experiment results displayed the imaging performance of the FPA was stable and the designed cooling system suppressed the dark current noise effectively to get high Signal-to-Noise Ratio images, and the designed cooling system worked stable.