[1] INAF Ist Astrofis & Planetol Spaziali, Via Fosso del Cavaliere 100, I-00133 Rome, Italy
[2] CSIC, IAA Inst Astrofis Andalucia, Glorieta Astron S-N, Granada 18008, Spain
[3] MPIfR Max Planck Inst Radio Astron, Hugel 69, D-53121 Bonn, Germany
[4] Aalto Univ, Metsahovi Radio Observ, Metsahovintie 114, Kylmala 02540, Finland
[5] Aalto Univ, Dept Elect & Nanoengn, PL 15500, Aalto 00076, Finland
[6] Russian Acad Sci, Lebedev Phys Inst, Leninsky Prospekt 53, Moscow 119991, Russia
[7] Moscow Inst Phys & Technol, Inst Sky Per 9, Dolgoprudnyi 141700, Moscow Region, Russia
[8] Univ Valencia, Dept Astron & Astrofis, C Dr Moliner 50, Valencia 46100, Spain
[9] Univ Valencia, Observ Astron, C Catedrat Jose Beltran 2, Valencia 46980, Spain
[10] Tech Univ Berlin, Inst Geodasie & Geoinformat Tech, Fak 6, Sekr KAI 2-2,Kaiserin Augusta Allee 104-106, D-10553 Berlin, Germany
[11] GFZ German Res Ctr Geosci, D-14473 Potsdam, Germany
[12] CSIRO Astron & Space Sci, POB 76, Epping, NSW 1710, Australia
[13] JIVE Joint Inst VLBI ERIC, Oude Hoogeveensedijk 4, NL-7991 PD Dwingekoo, Netherlands
[14] Delft Univ Technol, Dept Astrodynam & Space Missions, Kluyverweg 1, NL-2629 HS Delft, Netherlands
[15] Crimean Astrophys Observ, Nauchny 298409, Crimea, Russia
[16] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[17] Moscow MV Lomonosov State Univ, Sternberg Astron Inst, Univ Skii Pr 13, Moscow 119992, Russia