Optimization and commissioning of the EPIC commensal radio transient imager for the long wavelength array
Optimization and commissioning of the EPIC commensal radio transient imager for the long wavelength array
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长波长阵列EPIC共生无线电瞬态成像仪的优化和调试
DOI：
10.1093/mnras/stad263
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发表时间：
2023
影响因子：
4.8
通讯作者：
Thyagarajan, Nithyanandan
中科院分区：
文献类型：
--
作者：
Krishnan, Harihanan;Beardsley, Adam P.;Bowman, Judd D.;Dowell, Jayce;Kolopanis, Matthew;Taylor, Greg;Thyagarajan, Nithyanandan
下一代孔径阵列预计将由数百至数千个天线元件组成，具有大量的数字信号处理功能，可处理数十至数百MHz的大工作带宽。传统上，FX解调器被用作干涉仪的主要信号处理单元。这些迭代器的计算成本与大型阵列的计算成本一样.另一种成像方法是在电场并行成像相关器（EPIC），最近部署在长波长阵列站在塞维利亚国家野生动物保护区（LWA-SV）在新墨西哥州。EPIC使用一种新颖的架构，产生电场或强度图像的天空中的角度分辨率的阵列与全部或部分偏振和全频谱分辨率的信道。通过消除中间互相关数据产品，与传统的FX或XF相关器相比，对于密集（但其他任意）阵列布局，计算成本可以显著降低。EPIC还可以通过直接产生用于科学分析的偏振图像产品来降低输出数据速率。我们已经优化了EPIC，现在已经在LWA-SV将其作为一个可扩展的全天空成像后端，可以在毫秒级时间尺度上检测和定位脉冲无线电发射源。在本文中，我们回顾了EPIC的体系结构，描述了提高性能的代码优化，并从调试观察中提出了初步验证。EPIC测量和同步波束形成的观测亮源之间的比较表明，光谱的时间结构，在很好的协议。
Next-generation aperture arrays are expected to consist of hundreds to thousands of antenna elements with substantial digital signal processing to handle large operating bandwidths of a few tens to hundreds of MHz. Conventionally, FX correlators are used as the primary signal processing unit of the interferometer. These correlators have computational costs that scale asfor large arrays. An alternative imaging approach is implemented in the E-field Parallel Imaging Correlator (EPIC) that was recently deployed on the Long Wavelength Array station at the Sevilleta National Wildlife Refuge (LWA-SV) in New Mexico. EPIC uses a novel architecture that produces electric field or intensity images of the sky at the angular resolution of the array with full or partial polarization and the full spectral resolution of the channelizer. By eliminating the intermediate cross-correlation data products, the computational costs can be significantly lowered in comparison to a conventional FX or XF correlator fromtofor dense (but otherwise arbitrary) array layouts. EPIC can also lower the output data rates by directly yielding polarimetric image products for science analysis. We have optimized EPIC and have now commissioned it at LWA-SV as a commensal all-sky imaging back-end that can potentially detect and localize sources of impulsive radio emission on millisecond timescales. In this article, we review the architecture of EPIC, describe code optimizations that improve performance, and present initial validations from commissioning observations. Comparisons between EPIC measurements and simultaneous beam-formed observations of bright sources show spectral-temporal structures in good agreement.