1. Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam, the Netherlands
2. Institute of Space Sciences (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, E-08193 Barcelona, Spain
3. Institut d’Estudis Espacials de Catalunya (IEEC), E-08034 Barcelona, Spain
4. INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, Milano, via E. Bassini 15, I-20133 Milano, Italy
5. INAF – Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius (CA), Italy
6. INAF – Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone (RM), Italy
7. Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
8. Departament de Física Aplicada, Universitat d’Alacant, Ap. Correus 99, E-03080 Alacant, Spain