1. Space Instrumentation Group, Department of Automatic Control and Systems Engineering; University of Sheffield; Sheffield UK
2. Blackett Laboratory; Imperial College of Science, Technology and Medicine; London UK
3. Laboratoire de Physique et Chimie de l'Environnement, CNRS; Orleans France
4. Consiglio Nazionale delle Richerche; Frascati Italy
5. Swedish Institute of Space Physics-Uppsala; Uppsala Sweden