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arXiv 1702.05009astro-ph.IM
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干涉成像中的W效应:从快速稀疏测量算子到超分辨率

The w-effect in interferometric imaging: from a fast sparse measurement operator to super-resolution

Arwa Dabbech, Laura Wolz, Luke Pratley, Jason D. McEwen, Yves Wiaux

摘要:

现代射电望远镜,如平方公里阵列(SKA),将在大视场范围内探测射电天空,这导致天空图像的大w调制。这种效应使测量的活力与仔细观察的图像之间的关系复杂化。在算法方面,它会产生大量的内存和计算时间需求。然而,就天空图像的重建质量而言,它可以是一种祝福。近年来,一些工作表明,大的w调制促进扩频效果。在压缩感知框架内,这种效应增加了要恢复的信号的感知基础和稀疏基础之间的不相干性,从而导致对天空图像的更好估计。在这篇文章中,我们重新审视了在现实环境中使用凸优化的w-投影方法,其中测量算子将傅立叶中的w-项与去网格化内核耦合在一起。我们通过自适应稀疏化程序提供测量算子傅里叶部分的稀疏且快速的模型。因此,存储器需求和计算成本被显著减轻,代价是在无线电干涉测量数据模型上引入误差。我们提出了第一次调查的稀疏变量的测量算子对图像重建质量的影响。最后,我们分析了与w调制的扩频效应相关的有趣的超分辨率潜力,并通过仿真展示了它。我们的C++代码可以在GitHub上在线获得。

英文摘要:

Modern radio telescopes, such as the Square Kilometre Array (SKA), will probe the radio sky over large fields-of-view, which results in large w-modulations of the sky image. This effect complicates the relationship between the measured visibilities and the image under scrutiny. In algorithmic terms, it gives rise to massive memory and computational time requirements. Yet, it can be a blessing in terms of reconstruction quality of the sky image. In recent years, several works have shown that large w-modulations promote the spread spectrum effect. Within the compressive sensing framework, this effect increases the incoherence between the sensing basis and the sparsity basis of the signal to be recovered, leading to better estimation of the sky image. In this article, we revisit the w-projection approach using convex optimisation in realistic settings, where the measurement operator couples the w-terms in Fourier and the de-gridding kernels. We provide sparse, thus fast, models of the Fourier part of the measurement operator through adaptive sparsification procedures. Consequently, memory requirements and computational cost are significantly alleviated, at the expense of introducing errors on the radio-interferometric data model. We present a first investigation of the impact of the sparse variants of the measurement operator on the image reconstruction quality. We finally analyse the interesting super-resolution potential associated with the spread spectrum effect of the w-modulation, and showcase it through simulations. Our C++ code is available online on GitHub.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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