Computing cost of sensitivity and survey speed for aperture array and phased array feed systems

Aperture array (AA) and phased array feed (PAF) systems are envisaged to play an important role in the Square Kilometre Array (SKA), because their multi-beaming capability can be used to improve survey speed and enhance observing flexibility. In this paper, we demonstrate that computing costs and I/O rates should be considered as an integral part of the overall system design. We do so by comparing the correlator and imaging computing requirements for the current SKA phase 1 (SKA₁) AA-low baseline design with those for an alternative design with the same survey speed and sensitivity. We also compare the correlator and imaging computing demands and survey speed for the proposed SKA₁ survey array (dishes with PAFs), the envisaged SKA₁ dish array (dishes with single pixel feeds (SPFs)) and an AA-mid alternative design for the 300-1000 MHz range. We conclude that the current SKA₁ baseline design may not be the optimal solution in view of computing requirements (hence operating costs) for given sensitivity and survey speed.