INCORPORATION OF A TIME-DEPENDENT THERMODYNAMIC MODEL AND A RADIATION PROPAGATION MODEL INTO INFRARED 3-DIMENSIONAL SYNTHETIC IMAGE GENERATION

A model is presented for generation of synthetic images representing what an airborne or satellite thermal infrared imaging sensor would record. The scene and the atmosphere are modeled spectrally with final bandwidth determined by integration over the spectral bandwidth of the sensor (the model will function from 0.25 to 20-mu-m). The scene is created using a computer-aided-design package to create objects, assign attributes to facets, and assemble the scene. Object temperatures are computed using a thermodynamic model incorporating 24-h worth of meteorological history, as well as pixel specific solar load (i.e., self-shadowing is fully supported). The radiance reaching the sensor is computed using a ray tracer and atmospheric propagation models that vary with wavelength and slant range. Objects can be modeled as specular or diffuse with emissivities (reflectivities) dependent on look angle and wavelength. The resulting images mimic the phenomenology commonly observed by high-resolution thermal infrared sensors to a point where the model can be used as a research tool to evaluate the limitations in our understanding of the thermal infrared imaging process.