Influence of LOS angle on aero-optics imaging deviation

Abstract

When the airborne optical system works in the atmosphere, the image received in the optical system is deviation due to the change of gas flow field outside the optical head cover. This paper studies the effect of target line-of-sight(LOS)angle on aero-optics imaging deviation. We modeled and meshed a typical blunt-nosed high-speed vehicle by GAMBIT software. The CFD calculation was carried out by using the integrated RANS solver in FLUENT software. A reverse ray tracing method and a trace stop criterion were developed for optical calculation. The light propagation path was divided into three segments: the inside of the aircraft, the non-uniform flow field outside the aircraft, and the freestream of the atmosphere. Then we studied the influence in a wide range of LOS angles from 5° to 85°. The results show that as the LOS angle increases, the non-uniform flow field density distribution on the light propagation path becomes more and more flat, the corresponding refractive index becomes smaller, and the aero-optics imaging deviation is also reduced gradually.