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
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Polca SARA - 全偏振、方向相关校准和无线电干涉测量的稀疏成像
DOI：
10.1093/mnras/stz3555
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发表时间：
2020
影响因子：
4.8
通讯作者：
Birdi J
中科院分区：
文献类型：
--
作者：
Birdi J
新一代的无线电干涉仪被设想从相应的欠采样傅立叶域测量中产生高质量，高动态范围的观测天空的斯托克斯图像。在实践中，这些测量结果受到仪器和大气效应的影响，这些影响由琼斯矩阵很好地表示，并且通常随观测方向和时间而变化。这些影响通常是未知的，是实现所需成像性能的限制因素，因此，它们的校准至关重要。为了解决这个问题，我们开发了一种名为Polca SARA的全局算法，旨在通过采用非凸优化技术进行全极化、方向相关校准和稀疏成像。与现有方法相比，该方法具有全局收敛性和灵活性，可以将复杂的先验因素纳入正则化成像和校准问题。因此，我们采用了一种偏振成像特定方法，对所寻找的图像进行物理偏振约束和稀疏性先验。我们对所提出的算法进行了广泛的仿真研究。结果表明，当与全Jones矩阵的方向依赖效应（包括其非对角线项（表示极化泄漏））的校准相结合时，基于偏振约束的成像具有优越的性能。该方法所选择的先验也能很好地处理一元模糊问题。
New generation of radio interferometers are envisaged to produce high quality, high dynamic range Stokes images of the observed sky from the corresponding undersampled 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. The results indicate the superior performance of polarization constraint based imaging when combined with the calibration of the direction-dependent effects for full Jones matrices, including their off-diagonal terms (denoting polarization leakage). The chosen priors in the proposed approach are also shown to handle the unitary ambiguity problem to a good extent.