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New generation of radio interferometers are envisaged to produce highquality, high dynamic range Stokes images of the observed sky from thecorresponding under-sampled Fourier domain measurements. In practice, thesemeasurements are contaminated by the instrumental and atmospheric effects thatare well represented by Jones matrices, and are most often varying withobservation direction and time. These effects, usually unknown, act as alimiting factor in achieving the required imaging performance and thus, theircalibration is crucial. To address this issue, we develop a global algorithm,named Polca SARA, aiming to perform full polarization, direction-dependentcalibration and sparse imaging by employing a non-convex optimizationtechnique. In contrast with the existing approaches, the proposed method offersglobal convergence guarantees and flexibility to incorporate sophisticatedpriors to regularize the imaging as well as the calibration problem. Thus, weadapt a polarimetric imaging specific method, enforcing the physicalpolarization constraint along with a sparsity prior for the sought images. Weperform extensive simulation studies of the proposed algorithm. Whileindicating the superior performance of polarization constraint based imaging,the obtained results also highlight the importance of calibrating fordirection-dependent effects as well as for off-diagonal terms (denotingpolarization leakage) in the associated Jones matrices, without inclusion ofwhich the imaging quality deteriorates.

Polca SARA - Full polarization, direction-dependent calibration and sparse imaging for radio interferometry