As an important measurement method of atmospheric parameters, atmospheric edge radiation has important scientific and application value. In recent years, with the rapid development of LEO satellite constellation technology, infrared camera, as one of the important means of edge detection to obtain data, is developing towards miniaturization and multispectral. Due to the limited internal space of the miniaturized infrared camera, the optical mechanical system has no independent refrigeration, and the complex internal thermal field is easy to affect the sensitivity of the camera. Therefore, it is necessary to study the influence of miniaturization on the sensitivity of infrared camera. Aiming at the miniaturized multispectral infrared camera developed by ourselves, this paper analyzes the problems existing in the internal thermal field of the camera through modeling and simulation, and puts forward the improvement scheme of thermal design. The sensitivity measurement tests at room temperature and low temperature are designed to verify the influence of internal thermal field on the sensitivity of the camera, and a method to improve the sensitivity of the camera by reducing the temperature of internal optical mechanical system is proposed. The test results and simulation analysis confirm each other, which lays a foundation for further improving the sensitivity of miniaturized infrared camera.

Firstly, this paper introduces the structure, internal heat source and thermal control difficulties of infrared camera. According to the internal structure of the infrared camera, the heat conduction model is established, the steady-state and transient finite element numerical calculations are carried out for the internal heat balance process of the infrared camera, the temperature distribution and changes at the key positions in the heat balance process of the camera are determined, and a targeted thermal structure optimization scheme is proposed from the perspective of strengthening the heat conduction between the structural surfaces and optimizing the structural layout to reduce heat accumulation. Based on the thermal simulation calculation, the sensitivity measurement test at room temperature is designed to confirm the influence of the internal thermal field of the infrared camera on the sensitivity, and a method to improve the sensitivity of the camera by strengthening the heat dissipation capacity of the bottom plate is proposed. In addition, in designing the low-temperature sensitivity measurement test in vacuum environment, the influence of the thermal radiation on the test measurement accuracy of the outer surface of the infrared camera is considered. The actual emission radiation of the target blackbody in the test is calculated and corrected by the finite difference method, which guides the design of the low-temperature sensitivity measurement test. In the low temperature sensitivity measurement experiment, a pixel by pixel data inversion processing method is established. Through the pixel by pixel extraction processing of the gray image obtained from the experiment, the accuracy of sensitivity measurement and infrared detection data inversion is improved. The test results further confirmed the influence of the internal thermal field of the camera on the sensitivity. The enhancement of the sensitivity brought by strengthening the heat dissipation is very obvious, which lays a good foundation for further optimizing the internal thermal design of the camera and improving the performance of the camera.

Combined with the thermal simulation analysis and sensitivity measurement test results of the infrared camera, this paper explores the influence of the internal thermal field of the miniaturized infrared camera on the sensitivity, and puts forward the optimization scheme of the internal thermal structure of the infrared camera. The sensitivity measurement tests at room temperature and low temperature are designed, and the method of reducing the internal temperature of the infrared camera by controlling the temperature of the bottom plate is proposed to improve the sensitivity of the infrared camera. It lays a foundation for the self-developed infrared camera to detect the atmospheric background radiation near the orbit.