Understanding radio polarimetry. II. Instrumental calibration of an interferometer array
Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
2 Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping, N.S.W. 2121, Australia
Send offprint request to: J.D. Bregman
Accepted: 22 October 1995
In a companion paper, a mathematical formalism to describe the polarimetric response of a radio interferometer was presented. Some of the instrumental parameters, however, are either unknown or poorly known. Here we consider the determination of these parameters both by a traditional radio-interferometry instrumental approach as well as by using optical polarimetry principles. In doing so, we establish links between the two fields. We show that some degrees of freedom cannot be solved for with various calibration or self-calibration schemes. These degrees of freedom are identified with instrumental parameters and physical source properties. The number of unsolvable degrees of freedom is reduced for a long synthesis with alt-az antennas. We also consider the effect of errors in the assumed instrumental parameters on the resultant calibrated data. The polarimetric calibration procedure for some telescopes is reviewed in the context of this analysis.
Key words: methods: analytical / methods: data analysis / techniques: interferometers / techniques: polarimeters
© European Southern Observatory (ESO), 1996