Understanding the impact of beamshapes on radio interferometer imaging performance

Primary beam shapes are emerging as a vital consideration both in the calibration of the new generation of radio interferometers, and in the design of future instruments such as the SKA. However, their impact on interferometer performance is far from obvious, especially since calibration techniques addressing these effects are still in their relative infancy. We present the results of recent work aimed at developing a comprehensive interferometric simulations methodology which can be used to quantify the impact of beamshapes on radio interferometer sensitivity. We show the results of applying this methodology to a comparative study of several possible MeerKAT dish designs. In particular, two beamshape-related effects that have been virtually ignored in older (lower-sensitivity) telescopes are far sidelobe confusion noise (FSCN), and calibration artefacts due to pointing errors (PEs). These effects are quite subtle and often completely non-intuitive, so exploring them via simulations can lead to interesting new insights into radio telescope design.