Mueller matrix parameters for radio telescopes and their observational determination

Modern digital cross-correlators permit the simultaneous measurement of all four Stokes parameters. However, the results must be calibrated to correct for the polarization transfer function of the receiving system. The transf er function for any device can be expressed by its Mueller matrix. We expre ss the matrix elements in terms of fundamental system parameters that descr ibe the voltage transfer functions (known as the Jones matrix) of the vario us system devices in physical terms and thus provide a means for comparing with engineering calculations and investigating the effects of design chang es. We describe how to determine these parameters with astronomical observa tions. We illustrate the method by applying it to some of the receivers at the Arecibo Observatory.