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30th of May 2018
ATNF Colloquium
LEAP calibration scheme and its application to MWA Phase II
by Maria Rioja (UWA/CASS)
Abstract: The ambitious scientific goals of the SKA require a matching capability to calibrate the systematic errors that contaminate the observed signals. I will present a scheme, LEAP, for correcting the direction-dependent ionospheric and instrumental phase effects at the low frequencies and with fields of view planned for SKA-Low, in the visibility domain.

It has been developed and fully characterised in the MWA parameter space using Phase 1 observations at 88 and 154 MHz observations under various weather conditions. These studies show that this method is suitable to measure and correct for temporal and direction-dependent spatial distortions on a wide range of scales: both larger and smaller than the array size. LEAP is an embarrassingly parallel process, as multiple directions can be processed independently and simultaneously, as it does not depend on a complete sky model.

I will also present recent results from a preliminary analysis of MWA Phase 2 observations. These support the expectations that higher order spatial ionospheric distortions and short timescale variations are more significant with longer baselines, that is they are detectable at higher frequencies and under a wider range of weathers. Such imaging defocusing artefacts can only be corrected for in the visibility domain, so a DD-correction scheme such as LEAP is imperative for MWA Phase II. Furthermore we expect LEAP to scale to the requirements of SKA-Low.

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