1. Department of Atmospheric, Oceanic and Space Sciences; University of Michigan; Ann Arbor Michigan USA
2. School of Earth and Atmospheric Sciences; Georgia Institute of Technology; Atlanta Georgia USA
3. Johns Hopkins University Applied Physics Laboratory; Baltimore Maryland USA
4. Geophysical Institute; University of Alaska Fairbanks; Fairbanks Alaska USA
5. Department of Electrical and Computer Engineering; University of Alaska Fairbanks; Fairbanks Alaska USA
6. Center for Geospace Studies; SRI International; Menlo Park California USA