Modeling and analysis of out-of-field stray radiation of space infrared detection system

When space infrared detection system is detecting weak targets in low Earth orbit, the complex and intense out-of-field stray radiation from Earth, Sun and Moon is several orders of magnitude higher than the target energy, which has a serious impact on detection. Therefore, modeling and analysis of out-of-field stray radiation are needed. In this paper, the observation hemisphere at the entrance of the system is divided into regional grids, and then the stray radiation model in any time and space is established according to the detection geometry, combining the characteristics of the stray radiation from different sources. Taking the long-wave infrared spectrum of a detection system as an example, the energy of stray radiation reaching the focal plane is calculated, and the stray radiation is analyzed in typical space and time state. The out of-field stray radiation accounted for 39.1% of the total radiation, and the out-of-field stray radiation from the incident off axis angle less than 20° accounted for 95.3% of the total radiation. When the observation hemisphere is illuminated by the Sun, the maximum out-of-field stray radiation from the Earth's surface region and the Earth's atmosphere region increases by 16.7% and 10.9%, respectively. The out-of-field stray radiation model established in this study can be used as the support and basis for the design of stray radiation suppression in space infrared detection systems.