Marsfield Lecture Theatre

Maria Rioja

Maria Rioja Colloquium: LEAP calibration scheme and its application to MWA Phase II

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.