EVLA Memo 177 Polarimetric calibration and dynamic range issues

This memo considers some dynamic range issues resulting from limitations in the polarimetric calibration solutions used in typical observations. Whereas we focus on “traditional” radio interferometric telescopes such as the VLA, ATCA or ALMA, the analysis approach can be used for other interferometer arrays. The memo is mostly concerned with the principles: rather than addressing real data, this memo focuses on analysis. The discussion generally applies to any feed system, including linearly or circularly polarized feeds and arrays of heterogeneous (i.e. dissimilar) feeds. Generally we consider the calibration information available from an observation of a point source calibrator at a single frequency at the field center at a single instant in time. However the added constraints provided by parallactic rotation are also considered. We will consider the effect when this calibration information is applied to the data of a target source. For brevity, we will assume that the Stokes total intensity of the calibrator source is 1 Jy, and that the target source is also 1 Jy.