Amir Leshem and Stefan J. Wijnholds, "Imaging and Calibration for Aperture Array Radio Telescopes," IEEE International Conference on Acoustics, Speech and Signal Processing, Tutorial Lecture T14, Brisbane (Australia), 19-24 April 2015.

Calibration and imaging of a new generation of radio telescopes based on phased array technology poses a number of challenges: a low SNR per receiving element (typically < -20 dB), a large field-of-view (up to 4pi sr) and direction dependent propagation conditions and instrument response. Dealing with these effects requires advanced algorithms that need to work through huge data volumes, which limits the acceptable numerical complexity. In this tutorial, we give an overview of the current state of the art in radio astronomical imaging and (self-)calibration and discuss the limitations of these methods. We then discuss a selected number of routes that are currently being explored to overcome these limitations. The tutorial will provide a complete overview of state-of-the-art imaging techniques for synthetic-aperture arrays and will give the attendees a clear view of the main challenges in future radio-astronomical imaging research.
Several new radio telescopes based on phased-array technology have recently become operational. The large field of view provided by this technology should improve the surveying and transient detection capabilities of these instruments by more than an order of magnitude compared to more conventional dish arrays, but this large field of view also poses new signal processing challenges, that should be dealt with to fully exploit these capabilities. The commissioning of these instruments has stimulated a burst of research on signal processing techniques for aperture-array radio telescopes as demonstrated by the considerable amount of recent signal processing papers in the technical as well as the astronomical literature. Significant progress in this area is still needed to attain the science potential of these instruments and mature phased-array technology for radio astronomy in the context of the Square Kilometre Array (SKA). The SKA is a future radio telescope, with receivers to be placed in South Africa and Australia, that is envisaged to be over an order of magnitude more sensitive than any telescope built to date and for which detailed designs are currently being made.

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