[1] Univ Politecn Catalunya, Dept Fis Aplicada, Castelldefels 08860, Spain
[2] Inst Estudis Espacials Catalunya, Barcelona 08034, Spain
[3] CSIC, Inst Ciencies Espai, Fac Ciencies, Bellaterra 08193, Spain
[4] Natl Univ La Plata, Fac Ciencias Astron & Geofis, RA-1900 La Plata, Argentina
[5] Consejo Nacl Invest Cient & Tecn, Inst Astrofis La Plata, RA-1033 Buenos Aires, DF, Argentina