1. NASA Goddard Space Flight Center, Greenbelt, Maryland, United States
2. Northwestern University, Department of Physics and Astronomy, Evanston, Illinois, United States
3. Center for Astrophysics Harvard and Smithsonian, Cambridge, Massachusetts, United States
4. National Institute of Standards and Technology, Boulder, Colorado, United States
5. Lawrence Livermore National Laboratory, Livermore, California, United States
6. MIT Kavli Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
7. University of Wisconsin, Department of Physics, Madison, Wisconsin, United States
8. University of Florida, Department of Physics, Gainesville, Florida, United States