Sparse interferometric Stokes imaging under the polarization constraint (Polarized SARA)

Birdi, Jasleen; Repetti, Audrey; Wiaux, Yves

doi:10.1093/mnras/sty1182

Cited by 23 publications

(26 citation statements)

References 81 publications

(118 reference statements)

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“…More precisely, inspired by the good performance of the sparsity averaging reweighted analysis (SARA) prior for Stokes I imaging in Carrillo et al (2013Carrillo et al ( , 2014 and for full Stokes imaging in Similarly, for the image update, J ∈ N forward-backward steps are executed, wherein depending on the chosen regularization, the proximity step is either evaluated using Algorithm 2 or Algorithm 3. Birdi et al (2018b), we employ this prior consisting in promoting average sparsity over a concatenation of Dirac basis and first eight Daubechies wavelet bases. It is coupled with a reweighting scheme, solving sequentially the ℓ 1 regularized problems (Candès et al 2008).…”

Section: A Brief Overview Of the Proposed Methodsmentioning

confidence: 99%

“…In practice, other sophisticated priors injecting additional information about the images of interest can also be taken into account in the regularization term, eg. polarization constraint in Birdi et al (2018b). In the current work, we consider both the cases without and with the enforcement of the polarization constraint.…”

Section: A Brief Overview Of the Proposed Methodsmentioning

confidence: 99%

“…Then, the application of this matrix on the Fourier transformed over-sampled images produce the measurements. When working in the absence of the DDEs, a direct correspondence of the measurement operator in equation ( 7) can be noticed with the measurement operator used for Stokes I imaging (Onose et al 2017;Pratley et al 2017) and more recently, for full Stokes imaging (Birdi et al 2018b).…”

Section: Imaging Problemmentioning

confidence: 96%

“…However, in presence of calibration errors, the imaging techniques should account for these terms within their models. Working in this direction, we can generalize the model proposed in Birdi et al (2018b) and employ it to solve inverse problem (6). The corresponding imaging strategy leverages the CS theory.…”

Section: Imaging Problemmentioning

confidence: 99%

“…This formulation has been introduced in in the particular case of joint Stokes I imaging and calibration. In order to incorporate various polarimetric imaging specific prior informations in the regularization function, Birdi et al (2018b) proposed to use a hybrid regularization term of the form…”

Section: Imaging Problemmentioning

confidence: 99%

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

Birdi,

Repetti,

Wiaux

2019

Preprint

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New generation of radio interferometers are envisaged to produce high quality, high dynamic range Stokes images of the observed sky from the corresponding under-sampled Fourier domain measurements. In practice, these measurements are contaminated by the instrumental and atmospheric effects that are well represented by Jones matrices, and are most often varying with observation direction and time. These effects, usually unknown, act as a limiting factor in achieving the required imaging performance and thus, their calibration is crucial. To address this issue, we develop a global algorithm, named Polca SARA, aiming to perform full polarization, direction-dependent calibration and sparse imaging by employing a non-convex optimization technique. In contrast with the existing approaches, the proposed method offers global convergence guarantees and flexibility to incorporate sophisticated priors to regularize the imaging as well as the calibration problem. Thus, we adapt a polarimetric imaging specific method, enforcing the physical polarization constraint along with a sparsity prior for the sought images. We perform extensive simulation studies of the proposed algorithm. While indicating the superior performance of polarization constraint based imaging, the obtained results also highlight the importance of calibrating for direction-dependent effects as well as for off-diagonal terms (denoting polarization leakage) in the associated Jones matrices, without inclusion of which the imaging quality deteriorates.

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Section: A Brief Overview Of the Proposed Methodsmentioning

confidence: 99%

Section: A Brief Overview Of the Proposed Methodsmentioning

confidence: 99%

Section: Imaging Problemmentioning

confidence: 96%

Section: Imaging Problemmentioning

confidence: 99%

Section: Imaging Problemmentioning

confidence: 99%

See 3 more Smart Citations

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

Birdi,

Repetti,

Wiaux

2019

Preprint

Self Cite

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RHAPSODIE: Reconstruction of High-contrAst Polarized SOurces and Deconvolution for cIrcumstellar Environments

Denneulin

Langlois

Thiébaut

et al. 2021

A&A

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Context. Polarimetric imaging is one of the most effective techniques for the high-contrast imaging and characterization of circumstellar environments. These environments can be characterized through direct-imaging polarimetry at near-infrared wavelengths. The Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE)/IRDIS instrument, installed on the Very Large Telescope (VLT) in its dual-beam polarimetric imaging (DPI) mode, offers the capability to acquire polarimetric images at high contrast and high angular resolution. However, dedicated image processing is needed to eliminate the contamination from the stellar light, instrumental polarization effects, and blurring from the instrumental point spread function. Aims. We aim to reconstruct and deconvolve the near-infrared polarization signal from circumstellar environments. Methods. We used observations of these environments obtained with the high-contrast imaging infrared polarimeter SPHERE-IRDIS at the VLT. We developed a new way to extract the polarimetric signal using an inverse approach method that benefits from the additional knowledge of the detected signal formation process. The method includes a weighted data fidelity term and smooth penalization, and it takes the instrumental polarization into account. Results. This method enables us to accurately measure the polarized intensity and angle of linear polarization of circumstellar disks by taking into account the noise statistics and the convolution by the instrumental point spread function. It has the capacity to use incomplete polarimetry cycles, which enhance the sensitivity of the observations. The method improves the overall performances in particular for instances of both low signal-to-noise (S/N) and small polarized flux compared to standard methods. Conclusions. By increasing the sensitivity and including deconvolution, our method will allow for more accurate studies of these disks morphology, especially in the innermost regions. It also will enable more accurate measurements of the angle of linear polarization at low S/N, which would lead to in-depth studies of dust properties. Finally, the method will enable more accurate measurements of the polarized intensity, which is critical for the construction of scattering phase functions.

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Bayesian radio interferometric imaging with direction-dependent calibration

Roth,

Arras,

Reinecke

et al. 2023

A&A

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Context. Radio interferometers measure frequency components of the sky brightness, modulated by the gains of the individual radio antennas. Due to atmospheric turbulence and variations in the operational conditions of the antennas, these gains fluctuate. Thereby the gains do not only depend on time, but also on the spatial direction on the sky. To recover high-quality radio maps, an accurate reconstruction of the direction and time-dependent individual antenna gains is required. Aims. This paper aims to improve the reconstruction of radio images, by introducing a novel joint imaging and calibration algorithm including direction-dependent antenna gains. Methods. Building on the resolve framework, we designed a Bayesian imaging and calibration algorithm utilizing the image domain gridding method for numerically efficient application of direction-dependent antenna gains. Furthermore, by approximating the posterior probability distribution with variational inference, our algorithm can provide reliable uncertainty maps. Results. We demonstrate the ability of the algorithm to recover high resolution high dynamic range radio maps from VLA data of the radio galaxy Cygnus A. We compare the quality of the recovered images with previous work relying on classically calibrated data. Furthermore, we compare the results with a compressed sensing algorithm also incorporating direction-dependent gains. Conclusions. Including direction-dependent effects in the calibration model significantly improves the dynamic range of the reconstructed images compared to reconstructions from classically calibrated data. Compared to the compressed sensing reconstruction, the resulting sky images have a higher resolution and show fewer artifacts. For utilizing the full potential of radio interferometric data, it is essential to consider the direction dependence of the antenna gains.

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Sparse interferometric Stokes imaging under the polarization constraint (Polarized SARA)

Cited by 23 publications

References 81 publications

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

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

RHAPSODIE: Reconstruction of High-contrAst Polarized SOurces and Deconvolution for cIrcumstellar Environments

Bayesian radio interferometric imaging with direction-dependent calibration

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