Effectiveness of the Correlator Field of View Weighting Technique in Source Attenuation

The science requirements of next-generation radio telescope arrays present a new set of challenges to traditional imaging and data processing techniques. Instruments such as the MWA, SKA, and other arrays implementing large numbers of small diameter dishes have a naturally large field-of-view due to the small diameter of individual telescopes. In order to achieve high image fidelity and dynamic ranges, noise contributions from off-center sources must be reduced – a task traditionally requiring imaging of the full field-of-view. However, implementation of this subtraction requires unreasonable computational resources while also generating unmanageable volumes of data. One approach to this problem involves dynamic control over the field-of-view, implemented in software as a weighting function internal to the integration routine of the correlator. Using this technique one can effectively reduce the noise contribution levels from sources outside the region of interest, and in some cases dramatically reduce the volume of data exiting the correlator for post-processing. In this paper we focus on verifying the effectiveness of this technique, implemented through the MIT Array Performance Simulator (MAPS) using simulated data sets. Additionally, several dimensions of possible parameter space are explored in order to test limitations and determine design requirements of this approach, including the impact of variable levels of radio frequency interference (RFI) excision on image fidelity and off-center source signal rejection.