Modeling Issues in the Prediction of the Modulation Transfer Function of a Brownout Cloud

A methodology is presented for the prediction of the Modulation Transfer Function of a brownout cloud. The methodology is based upon Radiative Transfer Theory, a heuristic approach that involves the computation of the scattering and absorption of incident light by a volume element in which many sediment particles reside. The MTF predictions are shown to be sensitive to the particulate composition of the brownout cloud and the limitations of the imaging system. The relationship between cloud density and visual degradation appears to be nonlinear, indicating that visibility will abruptly decrease when the cloud (or some region within the cloud) reaches a critical density. This characteristic could be a contributing factor to the rapidity of the brownout problem that has been anecdotally reported. A separate study is presented in which MTF measurements from controlled experiments are compared with predictions. Key challenges in predicting the MTF of a brownout cloud are identified.