1. Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA
2. Applied Physics Laboratory, University of Washington, Seattle, Washington 98105, USA
3. BAE Systems, Burlington, Massachusetts 01803, USA
4. BAE Systems, Merrimack, New Hampshire 03054, USA
5. Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093, USA