The Helioseismic and Magnetic Imager (HMI) on SDO: Full Vector Magnetography with a Filtergraph Polarimeter Graham, J. D. ; Norton, A. ; López Ariste, A. ; Lites, B. ; Socas-Navarro, H. ; Tomczyk, S. Abstract Publication: Solar Polarization Pub Date: 2003 Bibcode: 2003ASPC..307..131G