In situ soil moisture observations for the CAL/VAL of SMOS: the SMOSMANIA network - Jean-Christophe Calvet; Noureddine Fritz; Françis Froissard; David Suquia; Alain Petitpa; Bruno Piguet (IEEE International Geoscience & Remote Sensing Symposium, IGARSS 2007, July 23-28, 2007, Barcelona, Spain, Proceedings, 2007)