We describe the design and performance of the Engineering Development Array (EDA), which is a low frequency radio telescope comprising 256 dual-polarisation dipole antennas working as a phased-array. The EDA was conceived of, developed, and deployed in just 18 months via re-use of Square Kilometre Array (SKA) precursor technology and expertise, specifically from the Murchison Widefield Array (MWA) radio telescope. Using drift scans and a model for the sky brightness temperature at low frequencies, we have derived the EDA's receiver temperature as a function of frequency. The EDA is shown to be sky-noise limited over most of the frequency range measured between 60 and 240 MHz. By using the EDA in interferometric mode with the MWA, we used calibrated visibilities to measure the absolute sensitivity of the array. The measured array sensitivity matches very well with a model based on the array layout and measured receiver temperature. The results demonstrate the practicality and feasibility of using MWA-style precursor technology for SKA-scale stations. The modular architecture of the EDA allows upgrades to the array to be rolled out in a staged approach. Future improvements to the EDA include replacing the second stage beamformer with a fully digital system, and to transition to using RF-over-fibre for the signal output from first stage beamformers.

Radio Astronomy

10.1017/pasa.2017.27

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Citations (16)

Proton-proton collisions at production thresholds

P. Moskal H.-H. Adam A. Budzanowski D. Grzonka L. Jarczyk

Recent results obtained by the COSY-11 collaboration concerning the production of eta and eta' mesons in the pp --> pp Meson reaction are presented. A comparison of the production amplitude for the pi(0), eta and eta' mesons at the same phase space volume allows to conclude that the proton-eta' interaction is in the order of, or smaller than, the proton-pi(0) one. A total cross section determined in a preliminary analysis of the data of elementary kaon and antikaon production via the pp-->ppK(+)K(-) reaction measured at excess energy of Q = 17 MeV is reported.

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MWA tied-array processing IV: A multi-pixel beamformer for pulsar surveys and ionospheric corrected localisation

Publications of the Astronomical Society of Australia (2022)

N. A. Swainston N. D. R. Bhat Ian S. Morrison S. J. McSweeney S. M. Ord

Abstract The Murchison Widefield Array (MWA) is a low-frequency aperture array capable of high-time and frequency resolution astronomy applications such as pulsar studies. The large field-of-view of the MWA (hundreds of square degrees) can also be exploited to attain fast survey speeds for all-sky pulsar search applications, but to maximise sensitivity requires forming thousands of tied-array beams from each voltage-capture observation. The necessity of using calibration solutions that are separated from the target observation both temporally and spatially makes pulsar observations vulnerable to uncorrected, frequency-dependent positional offsets due to the ionosphere. These offsets may be large enough to move the source away from the centre of the tied-array beam, incurring sensitivity drops of ${\sim}30{-}50\%$ in Phase II extended array configuration. We analyse these offsets in pulsar observations and develop a method for mitigating them, improving both the source position accuracy and the sensitivity. This analysis prompted the development of a multi-pixel beamforming functionality that can generate dozens of tied-array beams simultaneously, which runs a factor of ten times faster compared to the original single-pixel version. This enhancement makes it feasible to observe multiple pulsars within the vast field of view of the MWA and supports the ongoing large-scale pulsar survey efforts with the MWA. We explore the extent to which ionospheric offset correction will be necessary for the MWA Phase III and the low-frequency square kilometre array (SKA-low).

Field of view

10.1017/pasa.2022.14

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Pi of the sky: search for optical flashes of extragalactic origin

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2005)

Aleksander Burd M. Ćwiok H. Czyrkowski R. Dąbrowski W. Dominik

"Pi of the Sky" is a detector designed for search for optical flashes of the cosmic origin in the sky. Its primary goal is to look for optical afterglows associated with the gamma ray bursts (GRB), but it is capable to detect also other optical transients of extragalactic origin. The apparatus consists of two arrays of 16 cameras each, which allow for simultaneous observation of the whole sky. Due to on-line data analysis in the real time, it has self-triggering capability and can react to external triggers with negative time delay. The prototype with two cameras has been installed at Las Campanas (Chile) and is operational from July 2004. General idea of experiment, the apparatus and its performance will be presented. Physical results will be reviewed and perspectives for the future will be outlined.

10.1117/12.622860

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The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey—I. Survey design and processing pipeline

Publications of the Astronomical Society of Australia (2023)

N. D. R. Bhat N. A. Swainston S. J. McSweeney Mengyao Xue Bradley W. Meyers

Abstract We present an overview of the Southern-sky MWA Rapid Two-metre (SMART) pulsar survey that exploits the Murchison Widefield Array’s large field of view and voltage-capture system to survey the sky south of 30 $^{\circ}$ in declination for pulsars and fast transients in the 140–170 MHz band. The survey is enabled by the advent of the Phase II MWA’s compact configuration, which offers an enormous efficiency in beam-forming and processing costs, thereby making an all-sky survey of this magnitude tractable with the MWA. Even with the long dwell times employed for the survey (4800 s), data collection can be completed in $<$ 100 h of telescope time, while still retaining the ability to reach a limiting sensitivity of $\sim$ 2–3 mJy (at 150 MHz, near zenith), which is effectively 3–5 times deeper than the previous-generation low-frequency southern-sky pulsar survey, completed in the 1990s. Each observation is processed to generate $\sim$ 5000–8000 tied-array beams that tessellate the full $\sim 610\, {\textrm{deg}^{2}}$ field of view (at 155 MHz), which are then processed to search for pulsars. The voltage-capture recording of the survey also allows a multitude of post hoc processing options including the reprocessing of data for higher time resolution and even exploring image-based techniques for pulsar candidate identification. Due to the substantial computational cost in pulsar searches at low frequencies, the survey data processing is undertaken in multiple passes: in the first pass, a shallow survey is performed, where 10 min of each observation is processed, reaching about one-third of the full-search sensitivity. Here we present the system overview including details of ongoing processing and initial results. Further details including first pulsar discoveries and a census of low-frequency detections are presented in a companion paper. Future plans include deeper searches to reach the full sensitivity and acceleration searches to target binary and millisecond pulsars. Our simulation analysis forecasts $\sim$ 300 new pulsars upon the completion of full processing. The SMART survey will also generate a complete digital record of the low-frequency sky, which will serve as a valuable reference for future pulsar searches planned with the low-frequency Square Kilometre Array.

Zenith

LOFAR

Data Processing

10.1017/pasa.2023.17

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Citations (7)

GRB 110402A: early optical limit by "Pi of the sky".

GCN (2011)

M. Sokołowski T. Batsch A. Majcher A. Majczyna K. Nawrocki

Source

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Characterization of a Low-Frequency Radio Astronomy Prototype Array in Western Australia

IEEE Transactions on Antennas and Propagation (2015)

Adrian Sutinjo T. Colegate R. B. Wayth Peter J. Hall Eloy de Lera Acedo

We report characterization results for an engineering prototype of a next-generation low-frequency radio astronomy array. This prototype, which we refer to as the Aperture Array Verification System 0.5 (AAVS0.5), is a sparse pseudo-random array of 16 log-periodic antennas designed for 70-450 MHz. It is co-located with the Murchison Widefield Array (MWA) at the Murchison Radioastronomy Observatory (MRO) near the Australian Square Kilometre Array (SKA) core site. We characterize the AAVS0.5 using two methods: in-situ radio interferometry with astronomical sources and an engineering approach based on detailed full-wave simulation. In-situ measurement of the small prototype array is challenging due to the dominance of the Galactic noise and the relatively weaker calibration sources easily accessible in the southern sky. The MWA, with its 128 "tiles" and up to 3 km baselines, enabled in-situ measurement via radio interferometry. We present array sensitivity and beam pattern characterization results and compare to detailed full-wave simulation. We discuss areas where differences between the two methods exist and offer possibilities for improvement. Our work demonstrates the value of the dual astronomy-simulation approach in upcoming SKA design work.

Radio Astronomy

Virtual Observatory

Aperture synthesis

10.1109/tap.2015.2487504

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Citations (68)

Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts

Astronomy and Astrophysics (2011)

J. Abadie B. P. Abbott R. Abbott T. D. Abbott M. R. Abernathy

Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec 17 2009 to Jan 8 2010 and Sep 2 to Oct 20 2010), a low-latency analysis pipeline was used to identify GW event candidates and to reconstruct maps of possible sky locations. A catalog of nearby galaxies and Milky Way globular clusters was used to select the most promising sky positions to be imaged, and this directional information was delivered to EM observatories with time lags of about thirty minutes. A Monte Carlo simulation has been used to evaluate the low-latency GW pipeline's ability to reconstruct source positions correctly. Results. For signals near the detection threshold, our low-latency algorithms often localized simulated GW burst signals to tens of square degrees, while neutron star/neutron star inspirals and neutron star/black hole inspirals were localized to a few hundred square degrees. Localization precision improves for moderately stronger signals. The correct sky location of signals well above threshold and originating from nearby galaxies may be observed with ~50% or better probability with a few pointings of wide-field telescopes.

10.1051/0004-6361/201118219

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Citations (101)

The statistics of low frequency radio interference at the Murchison Radio-astronomy Observatory

M. Sokołowski R. B. Wayth Morgan Lewis

We characterize the low frequency radio-frequency interference (RFI) environment at the Murchison Radio-astronomy Observatory (MRO), the location selected for the low-frequency component of the Square Kilometre Array. Data were collected from the BIGHORNS instrument, located at the MRO, which records a contiguous bandwidth between 70 and 300 MHz, between November 2014 to March 2015 inclusive. The data were processed to identify RFI, and we describe a series of statistics in both the time and frequency domain, including modeling of the RFI occupancy and signal power as a series of distribution functions, with the goal of aiding future scientists and operation staff in observation planning.

Radio Astronomy

10.1109/gemccon.2015.7386856

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A High Time Resolution All-Sky Monitor for Fast Radio Bursts and Technosignatures

2022 3rd URSI Atlantic and Asia Pacific Radio Science Meeting (AT-AP-RASC) (2022)

M. Sokołowski Danny C. Price R. B. Wayth

Despite hundreds of Fast Radio Burst (FRB) detections at frequencies above 400 MHz, only a handful of FRBs have been observed at lower frequencies, hence the FRB rates at frequencies below 350 MHz remain highly uncertain. This paper describes our efforts to increase the observing bandwidth (to ∼40 MHz) and imaging time resolution (to ∼10 ms) of the Engineering Development Array 2 (EDA2), a prototype station of the low-frequency Square Kilometre Array (SKA-Low), which will increase its sensitivity to short, FRB-like, radio pulses by two orders of magnitude and convert it into a high-time resolution all-sky monitor for FRBs and signals from extraterrestrial intelligence (techno-signatures). Based on highly uncertain FRB rates at these frequencies and sensitivity of SKA-Low stations, we expect to detect up to hundreds of FRBs per year and firmly establish the FRB rates in this relatively under-explored parameter space.

Fast radio burst

Radio Astronomy

Ranging

Low resolution

10.23919/at-ap-rasc54737.2022.9814380

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Citations (1)