The paper will discuss a simulation code developed at Aerodyne Research, Inc. to reflect the major sources of clutter that are of concern to staring and scanning sensors at resolutions where discrete objects, e.g. buildings are not resolved. The Aerodyne Infrared Earth (AERIE) code uses topographic features to model terrain, typically from DMA data, but with a statistical overlay of the critical underlying surface properties (reflectance, emittance, and thermal factors) to simulate the resulting texture in the scene. Reflectance and emittance from broken cloud decks are also included, as are effects of cloud and terrain shadows, and atmospheric transmittance and radiance. The AFGL LOWTRAN6 model is included as a subroutine. The code is based on first principles radiometric models that preserve the integrity of the resulting simulations as various scenario properties (sun angle, spectral band, etc.) are varied. The paper will discuss the basic models utilized for the simulation of the various scene components and the various "engineering level" approximations that are incorporated to reduce the computational complexity of the simulation.