Rapid Multiple-Scattering Radiative Transfer Algorithm for Target Acquisition Weapons Software

Scene simulations are increasingly used for electro-optical sensor design, performance evaluation, and data analysis over a wide range of environment and engagement conditions. For Army ground-to-ground scenarios, Target Acquisition Weapons Software (TAWS) is used to determine target-to-background contrast for optical bandpasses over many lines-of-sight (LOS's). This quantity is highly dependent on single scattering and multiple scattering (MS) of solar flux. The present delta-Eddington MS method used in TAWS is insufficiently accurate for the battlespace-critical horizontal and near-horizontal LOS's. A more accurate radiative transfer (RT) method with little or no sacrifice in computational speed is needed. Spectral Sciences, Inc. (SSI) proposes to develop a fast and highly accurate RT capability based on scattering methods used in MODTRAN(TM), together with SSI's state-of-the-art correlated-k algorithm, kURT, to compute in-band contrast radiances. The result will be a general atmospheric RT software package with unprecedented fidelity and speed. Re-use of MS calculations will provide an overall speed comparable to the current TAWS or better. Phase I will demonstrate the approach using prototype code elements. In Phase II the software package will be fully developed and integrated into TAWS.