Solving for closure errors due to polarization leakage in radio interferometry of unpolarized sources

Abstract

Mechanical and electronic imperfections can result into polarization leakage in individual antennas of a radio interferometer. Such leakages manifest themselves as closure errors even in co-polar visibility measurements of unpolarized sources. This paper describes and tests a method for the study of polarization leakage for radio interferometric telescopes using only the nominally co-polar visibilities for unpolarized calibrators. Interpretation of the resulting closure phases on the Poincar e sphere is presented. Since unpolarized sources are used, the actual solutions for leakage parameters is subject to a degeneracy which is discussed. This however, does not aect the correction of closure errors in our scheme.