1. Bradley Department of Electrical and Computer Engineering Virginia Tech Blacksburg Virginia USA
2. Now at Department of Physical Sciences Embry-Riddle Aeronautical University Daytona Beach Florida USA
3. The Johns Hopkins University Applied Physics Laboratory Laurel Maryland USA
4. Istituto Nazionale di Geofisica e Vulcanologia Rome Italy
5. SpacEarth Technology Rome Italy
6. Department of Electronic and Electrical Engineering University of Bath Bath UK
7. Merrimack College North Andover Massachusetts USA