Infrared imaging characteristics of space-based targets based on bidirectional reflection distribution function

A modeling method of infrared imaging characteristics of a space-based target was presented. Background radiation environment of a space-based target was analyzed and the background radiation mainly consists of direct radiation of the sun, thermal radiation and reflected radiation of the earth. The target surface was divided into regions based on geometrical shape and surface material characteristics and a surface equation of each region was built based on its body coordinate system. Each region was divided into meshes supposing that each mesh is a micro-plane. A bidirectional reflection distribution function (BRDF) model considering the characteristics of surface Gauss statistics and self-shadow was introduced to describe reflected infrared of each mesh of the target surface. The emitted infrared radiation of each mesh of the target surface was described according to its thermal equilibrium temperature. Then a mathematical model on infrared radiation imaging characteristics of the space-based target was built in terms of the given infrared detector. The relative positions of the space-based target, the background radiation sources and the detector are determined by orbital parameters based on coordinate conversion. Visual surfaces of the target to observation system were determined by vector coordinate method. Simulation of optical imaging characteristics of the target in orbit was achieved according to its given geometrical dimensions and physical parameters. The results show the method is feasible and robust for infrared characteristics of the space-based target when single reflection is considered and its surface is regular and can be described in a surface equation. It can provide a facility to real-time analysis of infrared imaging characteristics of the space-based targets.