1. Microwaves and Radar Institute, German Aerospace Center, Weßling, Germany
2. NASA Postdoctoral Program, Biospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
3. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
4. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA