High-Altitude Cloud Effects on Airborne Electro-Optical Sensor Performance

Abstract

A modeling approach is proposed to predict the impact of high-altitude clouds on the detection performance of an airborne electro-optical surveillance sensor. The sensor is dedicated to target detection, and it may be disturbed by cloud presence along the line of sight. The targets are supposed to be dim artificial sources in the atmosphere or stars, and the viewing conditions lead to lines of sight close to horizontal paths. The model is suitable to determine sensor performance for various locations in the earth?s atmosphere and for different seasons. It is based on cloud statistics data determined by the inversion of NOAA satellite observations. Computations of clear line-of-sight probabilities are based on geometric and statistical approaches, and the major hypothesis used here is that all clouds can be considered opaque. Seasonal and diurnal/nocturnal cloud cover variations strongly change the probability of a clear line of sight for a fixed viewing geometry, and the maximal range without clouds that can be reached for a fixed viewing angle and a fixed observer altitude has large temporal variations. These results can be used to reduce the sensor?s field of view to a line of sight having a sufficiently high probability of being cloud free.