1. a Soil and Irrigation Department (EEAD-CSIC Associated Unit) , Agrifood Research and Technology Centre of Aragon (C.I.T.A.) , Zaragoza, Spain
2. b Laboratoire Dynamique Terrestre et Planetaire (UMR 5562)-Université de Toulouse-C.N.R.S. , Toulouse, France
3. c Centre National Etudes Spatiales (C.N.E.S.) , Toulouse, France