Aerodyne has recently developed an "IRST Engagement Model" under contract for Lockheed Aeronautical Systems Company [LASC]. The model's purpose is to simulate the performance of an IRST system in long-range air-to-air detection and tracking engagements. The hallmark of the model is its end-to-end first-principles modeling of all major elements which determine specific performance. The target aircraft IR signature, the atmospheric cloud and sky background, and associated atmospheric effects are modeled at high fidelity, thereby producing an input image matched to the specific IRST under study. A detailed deterministic model of the IRST accounts for optical and sensor effects, signal processing, and track association typical of first-generation IRSTs. These model elements are coupled together along with a dynamic target and observer [IRST] trajectories model so that an analyst can specify air-to-air engagements at various velocities, ranges, and viewing angles. The analyst can study the effects of varying IRST algorithms, sensor characteristics, optical bandpass, cloud background levels, atmospheric effects, and target performance characteristics as well as varying the target aircraft itself. This computer model was designed for portability and growth.