Optical Performance Anal Ysis of Standard Missile Blockiy a Seeker

The flight environment of the Standard Missile, Block IV A interceptor involves high speeds that place severe aerodynamic and aero-thermalloads on the missile optical window and sensor. The supersonic flow over the missile produces aero-optical effects that can degrade IR seeker performance. This report summarizes an analysis of aero-optical aberrations due to shock front and shear layer density gradients. Computational Fluid Dynamics (CFD) models, which incorporate turbulence due to coolant spray, are used to compute the density and refractive index distribution about the IR dome. This data is then used in a ray-tracing program to determine boresite error and astigmatic lensing. These results compare favorably with computational results derived from general fluid mechanical approximations. Conclusions are drawn which indicate that boresite error may hinder seeker-targeting performance when looking in a forward direction or for low altitude intercepts.