Oblique In-Scene Atmospheric Compensation

This research introduces a novel oblique longwave infrared (LWIR) atmospheric compensation (AC) technique for hyperspectral imagery, oblique in-scene AC (OISAC). Current AC algorithms have been developed for nadir-viewing geometries, which assume that every pixel in the scene is affected by the atmosphere in nearly the same manner. However, this assumption is violated in oblique imaging conditions where the transmission and path radiance vary continuously as a function of object-sensor range, negatively impacting current algorithms’ ability to compensate for the atmosphere. The technique presented here leverages the changing viewing conditions to improve rather than hinder AC performance. An initial analysis of OISAC’s ability to perform AC for both synthetic and measured hyperspectral images suggests improved performance in oblique-viewing conditions compared with standard techniques. OISAC is an extension of ISAC, a technique that has been used extensively for LWIR AC applications for over 20 years. OISAC has been developed to incorporate the range dependence of atmospheric transmission and path radiance in identification of the atmospheric state. Similar to the full implementation of ISAC, OISAC requires the existence of near-blackbody-like materials over the 11.73- $\mu \text{m}$ water band.