Towards a uniform evaluation of the science quality of SKA technology options: Polarimetrie aspects

We discuss how to evaluate SKA technology options with regard to science output quality. In this work we will focus on polarimetry. We review the SKA specification for polarimetry and assess these requirements. In particular we will use as a illustrative case study a comparison of two dish types combined with two different feeds. The dish types we consider are optimized axi-symmetric prime-focus and offset Gregorian reflector systems; and the two feeds are the Eleven-feed (wideband) and a choked horn (octave band). To evaluate the imaging performance we employ end-to-end simulations in which given sky models are, in software, passed through a model of the telescope design according to its corresponding radio interferometrical measurement equation to produce simulated visibilities. The simulated visibilities are then used to generate simulated sky images. These simulated sky images are then compared to the input sky models and various figures-of-merit for the imaging performance are computed. A difficulty is the vast parameter space for observing modes and configurations that exists even when the technology is fixed. However one can fixed certain standard benchmark observation modes that can be applied across the board to the various technology options. The importance of standardized, end-to-end simulations, such as the one presented here, is that they address the high-level science output from SKA as a whole rather than low-level specifications of its individual parts.