1. National Observatory of Athens, Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing 1 , Athens 15236, Greece
2. California Institute of Technology 2 , Pasadena, California 91125, USA
3. Lunar and Planetary Laboratory, University of Arizona 3 , Tucson, Arizona 85721, USA
4. NASA/Goddard Space Flight Center 4 , Greenbelt, Maryland 20771, USA
5. Department of Physics and Astronomy, University of Delaware 5 , Newark, Delaware 19716, USA
6. Department of Astrophysical Sciences, Princeton University 6 , Princeton, New Jersey 08544, USA
7. Universidad de Alcalá 7 , Alcalá de Henares 28805, Spain
8. Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel 8 , Kiel 24118, Germany
9. Johns Hopkins University, Applied Physics Laboratory 9 , Laurel, Maryland 20723, USA