The US Air Force and Navy are cooperating in a program to increase their capabilities for installed systems avionics test. Complete aircraft will be suspended in very large, shielded, anechoic test chambers. Hardware-in-the- loop and man-in-the-loop tests will be conducted by simulating combat mission scenarios in which aircraft systems will be stimulated as they would be on an actual mission. Current installed systems test facilities are limited to RF threats. The improvements will include radar target generation; communication, navigation, and identification stimulation; and, an infrared scene stimulator (IRSS). The iRSS must generate a realistic, real-time simulation of the IR environment including complex backgrounds, multiple dynamic targets, IR countermeasures, and atmospheric effects. Current computer image generators can create highly detailed, geo-specific, real-time visual imagery. However, high-fidelity, detailed, flexible IR predictions including source phenomenology and atmospheric effects typically require several seconds to several hours per frame. Further, IR predictions require significantly more geo-specific data than is widely available for large gaming areas. The goal of IRSS development, therefore, is to integrate two well-developed technologies: real-time image generation and IR prediction. In this paper, potential solutions and necessary compromises will be discussed and evaluated.