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The multiangular calibration is used to estimate the sensitivity changes in the different points of the wide field of view of an optical instrument equipped with linear or array detectors. The baseline method consists in having the instrument looking at a spatially uniform landscape. For a wide field of view instrument, continuous uniform landscape does not exist, so we propose a new method using several desert sites to simulate a spatially known landscape.

Desert areas are already good candidates for the assessment of multitemporal calibration of optical satellite sensors. This requires that the sites be well characterised in terms of directional variations of their Top Of Atmosphere reflectances, to account for variations in the solar or viewing configurations between each measurement. A ground campaign has been done to evaluate the bidirectional reflectances of different sites which are then used as reference. POLDER instrument is the first instrument using these references for the multiangular calibration.

First, this paper describes the multiangular calibration method used on POLDER based on the knowledge of these desert sites. The site selection criteria and the method developed to localise these desert sites are remembered. Then the results are presented in different spectral bands and the performances of this calibration estimated.