Magnetic field vector retrieval with HMI
  The Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), will begin data acquisition in 2008. It will provide the first full disk, high temporal cadence observations of the full Stokes vector with a 0.5 arc sec pixel size. This will allow for a continuous monitoring of the Solar magnetic field vector. HMI data will advance our understanding of the small and large-scale magnetic field evolution, its relation to the solar and global dynamic processes, coronal field extrapolations, flux emergence, magnetic helicity and the nature of the polar magnetic fields. We summarize HMI's expected operation modes, focusing on the polarization cross-talk induced by the solar oscillations and how this affects the magnetic field vector determinations. 
J.M. Borrero, S. Tomczyk, A. Norton, T. Darnell, J. Schou, P.   Scherrer, R. Bush, Y. Lui