Surface Reflectance in MODTRAN

Multi-spectral and hyperspectral remote-sensing technologies have been developed over the last thirty years for a variety of applications. These technologies cover the entire optical spectrum, ranging from visible to NIR (VNIR), SWIR, MWIR, and LWIR light. The most mature sensor technology currently covers the VNIR–SWIR portion of the optical spectrum, which is known as the reflective region. Operations within this spectral range rely on solar illumination of the scene and are limited to daytime hours to avoid photon starvation. For operation during nighttime hours and for special targets such as gaseous effluents, operation in the MWIR–LWIR bands, which are known as the emissive region, is required. Operation at these latter wavelengths is based on sensing thermally emitted radiation from the scene and is not constrained by solar illumination.