C. De Nardi, CNES-French Space Agency, Toulouse, France; R. Desplats, CNES - French Space Agency, Toulouse, France; P. Perdu, CNES-French Space Agency, 31401 Toulouse Cedex 9, France; F. Beaudoin, IBM; J. L. Gauffier, Institut National des Sciences Aplliquées (INSA), Toulouse, France