Self Direction-Dependent Calibration For Wideband Radio-Interferometric Imaging

Radio-interferometric (RI) imaging can be formulated as
an inverse problem, where the objective is to estimate a sky intensity image from degraded undersampled Fourier measurements. Future radio telescopes aim at improving imaging resolution and sensitivity by orders of magnitude. At this precision level, the reconstruction quality will be limited by the unknown calibration kernels. Accurate calibration of the array during imaging is thus needed, leading to a blind deconvolution problem. Recently, we have proposed a non-convex optimisation method to perform joint calibration and imaging in the context of monochromatic imaging, assuming that the calibration kernels are smooth both in space and time. In the current work, we extend this approach to wideband imaging by further assuming spectral smoothness of the calibration kernels. The resulting problem is solved using an alternating forwardbackward scheme, benefiting from convergence guarantees.