1. Department of Aerospace Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
2. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA
3. Centre National de la Recherche Scientifique, ICARE Laboratory, 1c Avenue de la Recherche Scientifique, 45071 Orléans, France
4. Department of Aeronautics and Astronautics, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwano-ha, Kashiwa, Chiba 277-8561, Japan