Joint imaging and DDE calibration for RI.

A. Repetti, J. Birdi and Y. Wiaux.

3GC4 workshop , Port Alfred, South Africa, 24th October-4th November 2016.

In the context of radio-interferometry, the objective is to find an estimate of an unknown image of the sky from a degraded observation, acquired through an array of antennas. In the theoretical case of a perfectly calibrated array, it has been shown in the last years that solving the corresponding imaging problem thanks to iterative algorithms based on convex optimisation tools and using CS theory can be competitive with classical algorithms such as CLEAN. However, in practice, antenna-based gains are unknown and have to be modeled, during the calibration process. The latter aims to estimate the DIEs and DDEs (i.e. direction independent and dependent effects) related to each antenna of the interferometer. We propose to do so thanks to an iterative alternated minimisation algorithm based on non-convex optimisation, namely the block-coordinate forward-backward algorithm. Moreover, we generalize the proposed calibration method to joint calibration and imaging method, where the image and the DIEs/DDEs can be estimated together. In this context, the previous block-coordinate forward-backward algorithm is generalized, estimating alternatively the DIEs/DDEs, and the image while promoting its sparsity on a given dictionary, taking advantage of the CS theory.




Biomedical and Astronomical Signal Processing group
Institute of Sensors, Signals and Systems
Heriot-Watt University
Edinburgh EH14 4AS

mail: A.Repetti@hw.ac.uk