Temporal stability of Tuz Gölü and atacama desert reference surfaces for absolute calibration of orbital sensors

Abstract

The vicarious absolute calibration of electro-optical sensors dedicated to the Earth observation includes the definition of a reference surface from which radiometric measurements taken from the ground are compared to the effective radiance measured by the sensor in orbit. In order to facilitate the surface ra- diometric characterization process and consequently the sensor radiometric calibration, it is desirable that the surface presents, besides additional characteristics, temporal reflectance stability. This study aimed to evaluate the temporal stability of two potential reference surfaces for radiometric calibration of orbital electro-optical sensors located at: Tuz Gölü Salar in Turkey and Atacama Desert in Chile. Therefore, a temporal analysis of the radiometric properties of these two surfaces using cloud free images of TM/Landsat 5 sensor, acquired from 2003 to 2011, was performed. It was concluded, based on statistical criteria, that both reference surfaces do not presented temporal stability. Nevertheless, both surfaces may still be used for sensor calibration purposes if they were submitted to further spectral characterization with higher frequency and/or if the surfaces were considered stable “enough” within a certain limit of variation in reflectance. Taking that into account, according to the results of this work, it can be stated that Tuz Gölü surface reflectance has temporal stability within a range of 3-14% and the Atacama Desert better than 6%. © 2015 Sociedade Brasileira de Geofísica.