SPIE Journal Paper | 17 August 2023
KEYWORDS: Transmittance, Visibility, Aerosols, Atmospheric modeling, Infrared radiation, Electro optical modeling, Data modeling, Data transmission, Electro optics, Mid-IR
Electro-optical and infrared propagation within the troposphere is strongly determined by the atmospheric path along the line-of-sight. The industry standard program moderate resolution transmittance (MODTRAN) model can be used to approximate path transmittance and radiance from the ultraviolet to the infrared. To understand the variability in the path effects (transmittance/radiance), one must accurately represent the environment in which they are operating. One significant knowledge gap is a universal and consistent means to inform the aerosol component of the atmospheric modeling within MODTRAN. The aerosol component can be highly variable, which can result in significant changes to the overall path transmittance and radiance depending on aerosol size and type. A fusion of European Centre for Medium Range Weather Forecasts Re-Analysis 5 atmospheric profile data and statistical draws from the global NOAA-ISD visibility archives are presented to construct regionally specific atmospheric inputs to MODTRAN. Using a 6 km horizontal path geometry, a year’s worth of hourly (8760 times) data is modeled to determine the path transmittance. The results are aggregated via empirical cumulative distribution functions of the path transmittance. We determine the type of day one is operating within by defining a bad day as the 10th percentile low transmission, an average day as the 50th percentile, and a good day as the 90th percentile high transmission. Using the percentile atmospheres determined by transmittance, one can analyze expected performance levels from current sensor systems, e.g., if a detection threshold is met on the 50th percentile day, one can expect this threshold to be met 50% of the time. In addition, the specific atmospheres (visibility, pressure, temperature, humidity, rain, etc.), which were determined to result in the 10th, 50th, or 90th percentile day, can be analyzed to build synthetic scenes, construct modeling environments, and ultimately drive design and system trades to optimize performance from the visible to the longwave infrared.
