Retrieval of temporal profiles of reflectances from simulated and real NOAA-AVHRR data over heterogeneous landscapes

To carry out functioning and dynamic vegetation studies, a temporal analysi s is needed. So far, only data provided by the National Oceanic and Atmosph eric Administration (NOAA) satellites with Advanced Very High Resolution Ra diometer (AVHRR) sensors offer the required temporal resolution, but their spatial resolution is coarse (1.1km). But, in many situations, the vegetati on cover is heterogeneous and the 1.1km AVHRR pixel contains several types of land use radiometrically different and is, in fact, a mixed pixel. Thus, the reflectance and consequently deduced parameters (NDVI, LAI, etc.) meas ured by AVHRR is actually average value and does not represent a value for each vegetation class present in the pixel. The objective is to extract the reflectance of each vegetation class from the mixed pixel using NOAA-AVHRR data and SPOT-HRV data simultaneously which give the proportions of each t ype of vegetation inside the mixed pixel through a classification map. The paper presents a method for radiometrically unmixing coarse resolution signals through the inversion of linear mixture modelling on heterogeneous regions of natural vegetation (Bidi-Bahn) in Burkina-Faso and in Niger (Hap ex site). In a first step, simulated coarse resolution data (NOAA-AVHRR) ob tained from the degradation of SPOT images are used to assess the method. I n a second step, real NOAA-AVHRR data are used and some elements of validat ion are given by comparing the results to airborne reflectance measurements .