  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.
