Reflectance characteristics of reference materials used in lidar hard target calibration

Lidar hard target calibration is discussed, emphasizing the transfer target methodology. Characteristics of example calibration target surfaces are described in light of the four reflectance mechanisms: specular, diffuse, retroreflection, and off-specular reflectance. This ideal transfer target is one which can be described as entirely diffusely reflecting, i.e., Lambertian. Correction for retroreflection is required when using the flowers of sulfur transfer target at CO(2) laser wavelengths. Corrections for specular and retroreflection for the integrating sphere are negligible; however, the off-specular reflectance of rough metal surfaces used in the integrating spheres is only qualitatively compared with the diffuse reflectance of flowers of sulfur.