1. Space Sciences Laboratory; University of California at Berkeley; Berkeley California 94720 USA
2. Hawai‘i Institute of Geophysics and Planetology; University of Hawai‘i at Mānoa; Honolulu Hawai‘i 96822 USA
3. Department of Astronomy; University of Washington; Seattle Washington 98195 USA
4. Advanced Light Source; Lawrence Berkeley National Laboratory; Berkeley California 94720 USA
5. Institut des Sciences de la Terre; Observatoire des Sciences de l'Univers de Grenoble; Grenoble France