1. Advanced Space Propulsion Laboratory, NASA Johnson Space Center, Houston, Texas 77058, U.S.A., ,
2. Marshall Space Flight Center, Huntsville, Alabama, U.S.A.
3. The University of Texas at Austin, Austin, Texas, U.S.A.
4. University of Houston, Houston, Texas, U.S.A.
5. Australian National University, Canberra, Australia
6. Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.
7. Los Alamos National Laboratory, Los Alamos, New Mexico, U.S.A.