Intrinsic cross-polarization ratio maps from all-sky observations with the SKA-Low prototype station Aperture Array Verification System 2

The low-frequency radio telescope of the Square Kilometre Array (SKA-Low), currently under construction in the remote Murchison shire in Western Australia’s outback, will observe the sky between 50 and 350 MHz with unprecedented sensitivity and stringent requirements for polarization accuracy. We investigate the instrumental polarization purity of a SKA-Low prototype station by means of the intrinsic cross-polarization ratio (IXR) figure of merit. We derive all-sky experimental IXR maps using data from the Aperture Array Verification System 2. The results are presented at three frequencies within the SKA-Low bandwidth (110, 160, and 230 MHz) with a quantitative comparison between observed and simulated all-sky IXR maps. Our findings show good agreement in IXR map distributions and promising consistency in their radial profiles, meeting SKA-Low’s IXR specification overall. We offer an empirical approach to verifying SKA-Low’s polarization performance using all-sky observations from individual stations and will potentially support the telescope’s early science commissioning phase.