Radiometer-Based Estimation of the Atmospheric Optical Thickness

Atmospheric optical thickness affects the quality of satellite imagery, especially over urban areas where aerosol concentrations (sulphates, soot, mineral dust, etc.) are high. Optical thickness is usually provided by photometer or Lidar ground station measurements and introduced in empirical atmospheric correction models. However, Lidar wavelengths do not correspond in number and value to those used by satellite sensors, and therefore they introduce drawbacks in atmospheric correction methods. In this paper, a methodology developed for estimating atmospheric optical thickness by the use of satellite images and ground radiometer (GER 1500) is described. Lidar measurements of the optical thickness at two wavelengths, 355 nm and 532 nm, served for validation purposes. Within this framework, two major issues are investigated. The first concerns the most appropriate target in an urban environment that yields the most accurate atmospheric optical thickness value. The second deals with the appropriate surrounding area of the target. Evaluation of results showed that using the methodology developed, targets of olive leaves within a black artificial area produce the most accurate atmospheric optical thickness.