Modeling the instrumental contribution of a radio telescope to astronomical polarization measurements: the Mueller matrix approach

The challenge in radioastronomical polarimetry is the accurate measurement of a weak polarized signal embedded in a (usually) much stronger unpolarized signal. The imperfection of the telescope, such as its cross-polarization, sidelobes, beam squint, and beam squash, alters the polarization state of the incoming radiation and converts unpolarized signal to apparently polarized signal [1]. From an astronomer’s perspective, the radio telescope causes the Stokes parameters of the incoming signal to leak into one another. Such leakage can jeopardize the reliability of an observation [2, 3].