Adaptively Cooled Wavefront Error Correction for Enhanced Hypersonic KV IR Seeker Windows

Strategic missile defense will directly benefit from increasing the operational infrared bandwidth from just a 3mm-5.5mm capability to a 1mm - 12mm capability. Increased seeker spectral bandwidth will enable improvements in detection range, acquisition performance, discrimination of unresolved objects, and aimpoint selection in the presence of a target plume. The mission outlined requiring an operational system to function effectively in the atmosphere at velocities ranging between 5 km/s to 8 km/s (25km < alt < 45km) dictates that an innovative approach involving thin film cooling and real time dynamic wavefront error correction is needed. Issues related to the adverse conditions experienced during hypersonic flight virtually eliminate all candidate infrared materials currently available for potential deployment. Any candidate material must be robust enough to withstand the aerothermal heating environment (thermal shock), be chemically robust, possess a high cut-off temperature and be broadband. Both GaP and GaAs have relatively high cut-off temperatures , greater thermal shock characteristics than either ALON or sapphire, and are broadband performers. The operational environment requires that any infrared window material be actively cooled and that mission performance be optimized with a real time dynamic wavefront error correction capability to minimize or eliminate the wavefront distortion due to inhomogeneous window deformation and dn/dT.