1. Department of Space Physics Institute of Atmospheric Physics of the Czech Academy of Sciences Prague Czechia
2. Faculty of Mathematics and Physics Charles University Prague Czechia
3. University Groningen Kapteyn Astronomical Institute Groningen The Netherlands
4. ASTRON Dwingeloo The Netherlands
5. Department of Meteorology Institute of Atmospheric Physics of the Czech Academy of Sciences Prague Czechia
6. Department of Physics and Astronomy Space Science Center (EOS) University of New Hampshire Durham NH USA