CosmoClub: Virginie Ollier (02/02/2017)

Date: February 2nd 2017

Speaker: Virginie Ollier (ENS Cachan/Supélec)

Title: Robust Calibration of Radio Interferometers in Non-Gaussian Environment [slides]


The development of new phased array systems in radio astronomy, as the low frequency array (LOFAR) and the square kilometre array (SKA), formed of a large number of small and flexible elementary antennas, has led to significant challenges. Among them, calibration is a crucial step in order to provide meaningful high dynamic range images and is commonly performed under the assumption of Gaussianity of the noise.
Nevertheless,  observations in the context of radio astronomy are known to be affected by the presence of outliers which are due to several causes, e.g., weak non-calibrator sources or man made radio frequency interferences. In order to take into account the outlier effects, the noise  can be assumed to follow a spherically invariant random distribution.
Based on this modeling, a robust calibration algorithm is exposed in this presentation. More precisely, this new scheme is based on the design of an iterative relaxed concentrated maximum likelihood estimation procedure and allows to obtain closed-form expressions for the unknown parameters with a reasonable computational cost.