PIRRENE : a multidisciplinary research program about field radiometry L. Poutier 1* , X. Briottet 1 , G. Serrot 1 , C.Miesch 1 , L. Coret 1 , A. Malaplate 1 , F. Lemaître 1 , G. Dedieu 2 , V. Demarez 2 , Y. Kerr 2 , G. Marty 2 ,F. Lavenu 2 ,JC. Calvet 3 , N. Fritz 3 , M.P. Stoll 4 , F. Nerry 4 1 Office National d’Etudes et de Recherches Aérospatiales, 2 av. E. Belin, BP 4025, 31055 Toulouse Cedex4, France 2 Centre d'Etudes Spatiales de la Biosphère, 18 av. E. Belin, BP2801, 31401 Toulouse Cedex4, France 3 Centre National de Recherches Météorologiques, 42 av. G. Coriolis, 31057 Toulouse Cedex 1, France 4 Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection, Bd Brant, 67400 Illkirch, France * laurent.poutier@onecert.fr 1. Introduction Pirrene is a French acronym for “Programme Interdisciplinaire de Recherche sur la Radiométrie en Environnement Extérieur”(Interdisciplinary research program on radiometry in an outdoors environment). The program includes a set of theoretical and experimental activities on optical radiometry, ranging from ultraviolet to thermal infrared. This program was set up in partnership by four French laboratories : the Toulouse-based Office National d'Etudes et de Recherches Aérospatiales (ONERA), the Centre d'Etudes Spatiales de la Biosphère (CESBIO), the Centre National de Recherches Météorologiques (CNRM), and the Laboratoire des Sciences de l'Image, de l'Informatique et de la Télédétection (LSIIT), based in Strasbourg. All of these organizations carry out field experiments related to radiometry and all of the data acquired are gathered so as to produce a coherent and fully annotated data set with a complet description of the test site. All of the data can then be processed to develop and validate new radiometric measurement protocols and the associated processing. This paper describes the objective of the PIRRENE program, then presents the test site with both its facilities and instrumentation. The major activities are finally briefly reported. 2. Objectives and applications The main objective of PIRRENE consists in the development of new measurement approaches to estimate the physical and optical properties of a given scene in its general aspects together with a characterization of the atmosphere which govern radiative transfers. The measurement includes the physical properties and related spectral characteristics, ranging from ultraviolet to thermal infrared, the (bi)directional dependence, the heterogeneity of the materials and the associated scaling and environmental effects. Correlatively, the analysis, the understanding and the modeling of the involved physical phenomena fall beyond the PIRRENE scientific goal. The goals of PIRRENE are : - the collection of a coherent and self sufficient set of thermo-optical properties in order to improve the physical knowledge of the test site and thus create a fully characterized reference area. All ground measurements are stored in a common data base shared by the four partners. The data base also contains airborne and spaceborne data of the site. Part of these data sets are available to the scientific community via the web site http://wwwe.onecert.fr/pirrene. - the validation of algorithms. These algorithms include direct models, in which case the thermo-optical properties are used as reference inputs, and also inverse algorithms. In this latter case the numerical outputs are compared to the reference measurements. - the in-flight performance evaluation of airborne and spaceborne instruments. The performance assessment concerns both instrument quality (in terms of radiometry and spatial resolution), and the validation of scientific products derived from remote-sensing acquisitions. 3. The test site and its instrumentation. PIRRENE test site is located 30 km south west of Toulouse, France, at the ONERA’s Fauga-Mauzac Center (43° 23' 02'' N, 01° 17' 28''E, 188 m in altitude). Its extension is about 700 x 1000m and it is mainly covered by