Estimation of the Stokes Parameters

The Stokes parameters $I$, $Q$ and $U$ are all measures of intensity, and together provide a useful description of the polarization of the object being studied. Since $I$, $Q$ and $U$ all have the same units, this description is generally easier to use than the more obvious description given by the degree of polarization and the orientation of the plane of polarization. The mathematical connection between the Stokes parameters and the sky-subtracted intensities is described here. The output from this stage of the reduction process is a Stokes vector (i.e. a set of $I$, $Q$ and $U$ values) for each measured pixel on the sky.