Electromagnetic modelling of the SKA-LOW AAVS2 prototype

Davidson, David; Bolli, Pietro; Bercigli, M.; Ninni, Paola Di; Monari, Jader; Perini, Federico; Sokołowski, M.; Tingay, Steven; Ung, D.; Virone, G.; Waterson, M.; Wayth, R. B.; Zerbi, F. M.

doi:10.23919/ursigass49373.2020.9232307

Cited by 14 publications

(20 citation statements)

References 9 publications

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“…5(c), left side]. This discrepancy may be due to mutual coupling from the antennas, 5,18 which is more prominent near the horizon and is not accounted for in our simulations. We also note that our simulated images do not include the station uv-coverage and that this can also cause slight differences between observed and simulated images, although a more quantitative comparison is left for the future.…”

Section: Observations and Data Processingmentioning

confidence: 89%

“…3.1, 4.1, and 4.2) by the primary beam response corresponding to the Sun position in the snapshot observation used for calibration, normalized to zenith. We assumed that all antennas have the same primary beam, the average embedded element pattern (EEP 5,18 ). Examples of primary beams at each frequency are reported in Appendix A (Fig.…”

Section: Observations and Data Processingmentioning

confidence: 99%

“…Since 2016, various full-size prototype SKA-Low stations have been deployed and tested at the MRO [e.g., Aperture Array Verification System 1 (AAVS1) 3 and Engineering Development Array 1 (EDA1) 4 ]. In this paper, we will focus on the latest prototype station built at MRO, the AAVS2 5,6 , deployed in 2019 and currently operational along with the comparator system EDA2 (see Ref. 7 submitted to this journal, for details).…”

Section: Introductionmentioning

confidence: 99%

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Characterization of the SKA1-Low prototype station Aperture Array Verification System 2

Macario

Pupillo

Bernardi

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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The low frequency component of the Square Kilometre Array (SKA1-Low) will be an aperture phased array located at the Murchison Radio-astronomy Observatory (MRO) site in Western Australia. It will be composed of 512 stations, each consisting of 256 log-periodic dual-polarized antennas, and will operate in the low frequency range (50 to 350 MHz) of the SKA bandwidth. The Aperture Array Verification System 2 (AAVS2), operational since late 2019, is the last full-size engineering prototype station deployed at the MRO site before the start of the SKA1-Low construction phase. The aim of this paper is to characterize the station performance through commissioning observations at six different frequencies (55, 70, 110, 160, 230, and 320 MHz) collected during its first year of activities. We describe the calibration procedure, present the resulting all-sky images and their analysis, and discuss the station calibratability and system stability. Using the difference imaging method, we also derive estimates of the SKA1-Low sensitivity for the same frequencies and compare them with those obtained through electromagnetic simulations across the entire telescope bandwidth, finding good agreement (within 13%). Moreover, our estimates exceed the SKA1-Low requirements at all considered frequencies by up to a factor of ∼2.3. Our results are very promising and allow for an initial validation of the AAVS2 prototype station performance, which is an important step toward the coming SKA1-Low telescope construction and science.

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Section: Observations and Data Processingmentioning

confidence: 89%

Section: Observations and Data Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Characterization of the SKA1-Low prototype station Aperture Array Verification System 2

Macario

Pupillo

Bernardi

et al. 2022

J. Astron. Telesc. Instrum. Syst.

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“…We have also tested flux density vs time (lightcurves) of two bright calibrators (Hydra A and Virgo A) and found that their flux variations were within 10% when they were above elevation and 50 for EDA2 and AAVS2 stations, respectively. The inaccuracy of flux density measurements at lower elevations stems mainly from the inaccuracy using a single dipole beam pattern for all station antennas, which may be significantly different from embedded elements patternsc especially for the AAVS2 station using more complex antenna and more affected by the mutual coupling effects (Davidson et al 2020b).…”

Section: Real-time All-sky Imagermentioning

confidence: 99%

“…For accurate flux calibration, the apparent flux density of the Sun was calculated by multiplying the flux density predicted by the Benz (2009) model by the response of the dipole beam pattern (Davidson et al 2020b) in the direction of the Sun. These beam patterns were simulated in FEKO electromagnetic simulation software.…”

Section: Flux Calibrationmentioning

confidence: 99%

A Southern-Hemisphere all-sky radio transient monitor for SKA-Low prototype stations

Sokołowski

Wayth

Price

et al. 2021

Publ. Astron. Soc. Aust.

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We present the first Southern-Hemisphere all-sky imager and radio-transient monitoring system implemented on two prototype stations of the low-frequency component of the Square Kilometre Array (SKA-Low). Since its deployment, the system has been used for real-time monitoring of the recorded commissioning data. Additionally, a transient searching algorithm has been executed on the resulting all-sky images. It uses a difference imaging technique to enable identification of a wide variety of transient classes, ranging from human-made radio-frequency interference to genuine astrophysical events. Observations at the frequency 159.375 MHz and higher in a single coarse channel ( $\approx$ 0.926 MHz) were made with 2 s time resolution, and multiple nights were analysed generating thousands of images. Despite having modest sensitivity ( $\sim$ few Jy beam–1), using a single coarse channel and 2-s imaging, the system was able to detect multiple bright transients from PSR B0950+08, proving that it can be used to detect bright transients of an astrophysical origin. The unusual, extreme activity of the pulsar PSR B0950+08 (maximum flux density $\sim$ 155 Jy beam–1) was initially detected in a ‘blind’ search in the 2020 April 10/11 data and later assigned to this specific pulsar. The limitations of our data, however, prevent us from making firm conclusions of the effect being due to a combination of refractive and diffractive scintillation or intrinsic emission mechanisms. The system can routinely collect data over many days without interruptions; the large amount of recorded data at 159.375 and 229.6875 MHz allowed us to determine a preliminary transient surface density upper limit of $1.32 \times 10^{-9} \text{deg}^{-2}$ for a timescale and limiting flux density of 2 s and 42 Jy, respectively. In the future, we plan to extend the observing bandwidth to tens of MHz and improve time resolution to tens of milliseconds in order to increase the sensitivity and enable detections of fast radio bursts below 300 MHz.

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Contemporary Array Analysis Using Embedded Element Patterns

Davidson¹,

Warnick²

2022

Antenna and Array Technologies for Future Wireless Ecosystems

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Electromagnetic modelling of the SKA-LOW AAVS2 prototype

Cited by 14 publications

References 9 publications

Characterization of the SKA1-Low prototype station Aperture Array Verification System 2

Characterization of the SKA1-Low prototype station Aperture Array Verification System 2

A Southern-Hemisphere all-sky radio transient monitor for SKA-Low prototype stations

Contemporary Array Analysis Using Embedded Element Patterns

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