Bidirectional Reflectance Distribution Function (BRDF) measurements, modeling and applications in space-agile Tx/Rx common aperture system

Abstract

The Tx/Rx common aperture system not only needs to suppress out-of-field stray light, but also needs to suppress the influence of optical surface backscatter on detectivity. Backscatter generated by optical surfaces is often the dominant source of stray radiation that causes T/R isolation problems, and the black surfaces chosen for baffles also play a significant role in stray light suppression. Four commonly used optomechanical structure surfaces scattering BRDF data are measured, emulated and used. CFRP is selected as the baffle material, for the processing performance, cost performance and thermal control difficulty. A comparison is made between theoretical and experimental results for clean and particle contaminated ultra-smooth optical surface (CL= 800) scattering BRDF data. With the help of Mie theory and measured BRDF, the study improved the fitting accuracy of the Harvey-Shack model for the contaminated micro roughness surface. The Harvey-Shack model modeling coefficients of the particle contaminated micro-roughness surface are b = 0.12, l = 0.08, and s=-2.2. The scattering radiation introduced by particulates reduces the T/R isolation of the space-agile Tx/Rx common aperture system by 3.74 dB. Measurement results of particulates reducing the T/R isolation by 4.05 dB, verified the accuracy of particle contaminated surface BRDF modeling.