MMJkA A1AA 92-2752 An Integrated Radiance Throughput Model for Hypersonic Interceptor Seeker Performance Evaluation

Hypersonic endoatmospheric interceptors are presently under serious consideration for strategic and theater missile defenses. On board infrared seekers are planned for terminal guidance. It is desirable to perform seeker trade studies determining such things as expected S/N, tracking performance and optimum wavelength of operation. The dynamics of the interceptor/target trajectories combine with atmospheric interaction at both vehicles to degrade the infrared signal of the target. Because of this degradation, computation of this signal at the seeker focal plane and, consequently, performance of the seeker trade studies are made very difficult. These computations are usually performed piecemeal, fora limited number of trajectory points, and for very specific seeker configurations. An integrated radiance throughput model is under development that encompasses the trajectory dynamics and the atmospheric interactions. The model is intended for medium fidelity performance analysis to enable overall systems performance evaluations and trades. Performance of proposed window materials under a variety of aerothermal environments isan example of a typical trade space. Various existing codes are utilized integrally within the model, or are used to generate lookup tables for parameters over the range of trajectory and atmospheric variables. These include: the Optical Signature Code and the SIRRM Code for target signatures and bow shock radiance. The LOWTRAN 7 Code is used integrally to calculate atmospheric transmission and background. S/N and tracking performance will be estimated using a simple detector module. The model is described, and initial results are given that illustrate atmospheric transmission and window performance effects. CO m n2d5 33 ^n-i^S m —1 ^TJZ^ r^0