1. School of Engineering University of Newcastle Newcastle NSW Australia
2. Now at Department of Geosciences Virginia Tech Blacksburg VA USA
3. Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA
4. NASA Goddard Space Flight Center Geodesy and Geophysics Laboratory Greenbelt MD USA
5. GFZ German Research Centre for Geosciences, Department 1: Geodesy and Remote Sensing Potsdam Germany