[1] AUSTRALIAN NATL UNIV, MT STROMLO & SIDING SPRING OBSERV, WESTON, ACT 2611, AUSTRALIA
[2] UNIV WISCONSIN, DEPT ASTRON, MADISON, WI 53706 USA
[3] UNIV MICHIGAN, DEPT ATMOSPHER OCEAN & SPACE SCI, ANN ARBOR, MI 48109 USA
[4] SPACE TELESCOPE SCI INST, BALTIMORE, MD 21218 USA
[5] ESA, DEPT SPACE SCI, DIV ASTROPHYS, BALTIMORE, MD 21218 USA
[6] CALTECH, JET PROP LAB, PASADENA, CA 91109 USA
[7] JOHNS HOPKINS UNIV, DEPT ASTRON, BALTIMORE, MD 21218 USA
[8] ARIZONA STATE UNIV, DEPT PHYS & ASTRON, TEMPE, AZ 85287 USA
[9] CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA 91125 USA