Modeling microphysical influences on optical turbulence

Abstract

ABSTRACT Optical turbulence is important because it can significa ntly degrade the performan ce of electro-optical and infrared sensors, such as free-space la ser communications and infrared imaging systems. Changes in the refractive index of air along the transmission path of an optical system in free space can influence traveling light waves temporally and spatially causing blurring, scintillation, and bean wander. If left uncompensated, these effects could cause fades and surges in transmitted signals and result in high bit errors in communicated data. An earlier paper discussed the growing need for increasingly accurate and re liable numerical models to predict optical turbulence conditions, especially in complex (non-uniform) signal propagation environments. He nce, we present a finite-difference computer model to predict the microphysical (microclimate) influences on optical turbulence ( C n2) around the ARL A_LOT Facility and its surroundings, e.g. , forests and multiple buildings. Our multi-dimensional prototypical model begins to address optical turbulence conditions along more complex optical lines-of-site and account for inhomogeneities in C n2 brought about by horizontal changes in la ndscape, wind flow, temperature, and humidity. We anticipate that this kind of computational research will be an important vehicle for investigating C n2 and related laser-optic propagation effects in complex areas. Keywords: Refractive index structure constant, computer model, buildings, forests, free-space laser communications