Operational value-adding to AVHRR data over Europe: methods, results, and prospects

The German Remote Sensing Data Center (DFD) of the German Aerospace Center (DLR) has been operating a ground segment for High Resolution Picture Transmission (HRPT) data acquisition, archiving, and distribution since the early 1980s. The station's visibility covers all of Europe. DFD started with the generation of thematic level-3 AVHRR value-added products consisting of Multichannel Sea Surface Temperatures (MCSST) and Normalized Difference Vegetation Indices (NDVI) in March 1993 [8], Additionally, calibrated and registered 5-channel image subsets in two areas have been generated for supporting user-specific applications since 1994 [8]. The status of the current level-3 product generation chain as well as corresponding processing algorithms are presented. Perspectives are introduced to improve the existing products in terms of channel 1 and 2 radiometric optimization by implementing an atmospheric correction scheme, as well as to correct the solar channels for anisotropic reflectance with respect to different surfaces. As AVHRR data proved to be one of the major sources to derive global information on different land-oriented parameters, special emphasis is given in this paper on methods to extract land cover, the fraction of Absorbed Photosynthetic Active Radiation (fAPAR), and Leaf Area Index (LAI) with respect to operational use. Furthermore, different algorithms were discussed to derive Land Surface Temperatures (LST) by estimating surface emissivity based on NDVI time synthesis. First results over Germany are shown, problems addressed, and outlines for operational usage are given. (C) Elsevier, Paris.