Spectral and Atmospheric Characterization of a Site at Atacama Desert for Earth Observation Sensor Calibration

The application of Earth observation sensor data in quantitative approaches calls on the conversion of original digital numbers to radiometric quantities such as radiance or reflectance. This conversion depends on the sensor absolute calibration. One of the postlaunch methods adopted to calibrate orbital sensors is the reflectance-based approach. According to this method, a reference surface with specifics characteristics is required. The main objective of this work is to evaluate the suitability of a specific surface located at Atacama Desert in Chile to be used as a reference surface for calibration of Earth observation sensor purposes. A field campaign was carried out from August 19 to 22, 2014, when radiometric measurements were performed to spectrally characterize the reference surface and to evaluate the atmospheric characteristics of the study area. The average reference surface reflectance factor in the spectral region from 350 to 2500 nm ranged from 0.1 to 0.3, and its spatial uniformity was within 2%-4%. The amount of atmospheric aerosols was low, with an aerosol optical depth at 550 nm between 0.08 and 0.11 during the fieldwork period. The climate is hyperarid, and the water column abundance was lower than 0.43 g/cm². The results demonstrated that a reference surface at Atacama Desert could be effectively used for calibration of either airborne or orbital electrooptical sensors, providing an excellent surface in South America.