1. Institute of Environmental Physics; University of Bremen; Bremen Germany
2. Institute of Space and Atmospheric Studies, Department of Physics and Physics Engineering; University of Saskatchewan; Saskatoon, Saskatchewan Canada
3. Remote Sensing Laboratories, Department of Geography; University of Zurich; Zurich Switzerland
4. NASA Goddard Space Flight Center; Greenbelt Maryland USA
5. Physics Department; University of Osnabrück; Osnabrück Germany