scholarly journals MWA tied-array processing I: Calibration and beamformation

2019 ◽  
Vol 36 ◽  
Author(s):  
S. M. Ord ◽  
S. E. Tremblay ◽  
S. J. McSweeney ◽  
N. D. R. Bhat ◽  
C. Sobey ◽  
...  
Keyword(s):  
Western Australia ◽  
Radio Astronomy ◽  
Low Frequency ◽  
Frequency Resolution ◽  
Science Program ◽  
Astronomy Observatory ◽  
Beam Formation ◽  
Imaging Telescope ◽  
Signal Path ◽  
Murchison Widefield Array

AbstractThe Murchison Widefield Array is a low-frequency Square Kilometre Array precursor located at the Murchison Radio-astronomy Observatory in Western Australia. Primarily designed as an imaging telescope, but with a flexible signal path, the capabilities of this telescope have recently been extended to include off-line incoherent and tied-array beam formation using recorded antenna voltages. This has provided the capability for high-time and frequency resolution observations, including a pulsar science program. This paper describes the algorithms and pipeline that we have developed to form the tied-array beam products from the summation of calibrated signals of the antenna elements, and presents example polarimetric profiles for PSRs J0437-4715 and J1900-2600 at 185 MHz.

scholarly journals Science with the Murchison Widefield Array

2013 ◽  
Vol 30 ◽  
Author(s):  
Judd D. Bowman ◽  
Iver Cairns ◽  
David L. Kaplan ◽  
Tara Murphy ◽  
Divya Oberoi ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Early Universe ◽  
Western Australia ◽  
Space Weather ◽  
Time Domain ◽  
Angular Resolution ◽  
Low Frequency ◽  
Performance Properties ◽  
Square Kilometre Array ◽  
Murchison Widefield Array

AbstractSignificant new opportunities for astrophysics and cosmology have been identified at low radio frequencies. The Murchison Widefield Array is the first telescope in the southern hemisphere designed specifically to explore the low-frequency astronomical sky between 80 and 300 MHz with arcminute angular resolution and high survey efficiency. The telescope will enable new advances along four key science themes, including searching for redshifted 21-cm emission from the EoR in the early Universe; Galactic and extragalactic all-sky southern hemisphere surveys; time-domain astrophysics; and solar, heliospheric, and ionospheric science and space weather. The Murchison Widefield Array is located in Western Australia at the site of the planned Square Kilometre Array (SKA) low-band telescope and is the only low-frequency SKA precursor facility. In this paper, we review the performance properties of the Murchison Widefield Array and describe its primary scientific objectives.

scholarly journals A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory

2020 ◽  
Vol 37 ◽  
Author(s):  
S. J. Tingay ◽  
M. Sokolowski ◽  
R. Wayth ◽  
D. Ung
Keyword(s):  
Radio Frequency ◽  
Radio Astronomy ◽  
Angular Resolution ◽  
Low Frequency ◽  
Earth Orbit ◽  
Radio Frequency Interference ◽  
Astronomy Observatory ◽  
Frequency Range ◽  
Radio Astronomy Observatory ◽  
Imaging Mode

Abstract We present the first survey of radio frequency interference (RFI) at the future site of the low frequency Square Kilometre Array (SKA), the Murchison Radio-astronomy Observatory (MRO), that both temporally and spatially resolves the RFI. The survey is conducted in a 1 MHz frequency range within the FM band, designed to encompass the closest and strongest FM transmitters to the MRO (located in Geraldton, approximately 300 km distant). Conducted over approximately three days using the second iteration of the Engineering Development Array in an all-sky imaging mode, we find a range of RFI signals. We are able to categorise the signals into: those received directly from the transmitters, from their horizon locations; reflections from aircraft (occupying approximately 13% of the observation duration); reflections from objects in Earth orbit; and reflections from meteor ionisation trails. In total, we analyse 33 994 images at 7.92 s time resolution in both polarisations with angular resolution of approximately 3.5 $^{\circ}$ , detecting approximately forty thousand RFI events. This detailed breakdown of RFI in the MRO environment will enable future detailed analyses of the likely impacts of RFI on key science at low radio frequencies with the SKA.

scholarly journals The High Time and Frequency Resolution Capabilities of the Murchison Widefield Array

2015 ◽  
Vol 32 ◽  
Author(s):  
S. E. Tremblay ◽  
S. M. Ord ◽  
N. D. R. Bhat ◽  
S. J. Tingay ◽  
B. Crosse ◽  
...  
Keyword(s):  
Radio Emission ◽  
Time Resolution ◽  
High Time ◽  
Frequency Resolution ◽  
High Time Resolution ◽  
Radio Bursts ◽  
Radio Telescopes ◽  
Initial Design ◽  
Imaging Telescope ◽  
Murchison Widefield Array

AbstractThe science cases for incorporating high time resolution capabilities into modern radio telescopes are as numerous as they are compelling. Science targets range from exotic sources such as pulsars, to our Sun, to recently detected possible extragalactic bursts of radio emission, the so-called fast radio bursts (FRBs). Originally conceived purely as an imaging telescope, the initial design of the Murchison Widefield Array (MWA) did not include the ability to access high time and frequency resolution voltage data. However, the flexibility of the MWA’s software correlator allowed an off-the-shelf solution for adding this capability. This paper describes the system that records the 100 μs and 10 kHz resolution voltage data from the MWA. Example science applications, where this capability is critical, are presented, as well as accompanying commissioning results from this mode to demonstrate verification.

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

2015 ◽  
Vol 63 (12) ◽  
pp. 5433-5442 ◽  
Author(s):  
A. T. Sutinjo ◽  
T. M. Colegate ◽  
R. B. Wayth ◽  
P. J. Hall ◽  
E. de Lera Acedo ◽  
...  
Keyword(s):  
Western Australia ◽  
Radio Astronomy ◽  
Low Frequency

scholarly journals The Low-Frequency Environment of the Murchison Widefield Array: Radio-Frequency Interference Analysis and Mitigation

2015 ◽  
Vol 32 ◽  
Author(s):  
A. R. Offringa ◽  
R. B. Wayth ◽  
N. Hurley-Walker ◽  
D. L. Kaplan ◽  
N. Barry ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Low Frequency ◽  
Digital Tv ◽  
Frequency Resolution ◽  
Interference Detection ◽  
Radio Frequency Interference ◽  
Receiver Design ◽  
Square Kilometre Array ◽  
Atmospheric Propagation ◽  
Murchison Widefield Array

AbstractThe Murchison Widefield Array is a new low-frequency interferometric radio telescope built in Western Australia at one of the locations of the future Square Kilometre Array. We describe the automated radio-frequency interference detection strategy implemented for the Murchison Widefield Array, which is based on the aoflagger platform, and present 72–231 MHz radio-frequency interference statistics from 10 observing nights. Radio-frequency interference detection removes 1.1% of the data. Radio-frequency interference from digital TV is observed 3% of the time due to occasional ionospheric or atmospheric propagation. After radio-frequency interference detection and excision, almost all data can be calibrated and imaged without further radio-frequency interference mitigation efforts, including observations within the FM and digital TV bands. The results are compared to a previously published Low-Frequency Array radio-frequency interference survey. The remote location of the Murchison Widefield Array results in a substantially cleaner radio-frequency interference environment compared to Low-Frequency Array’s radio environment, but adequate detection of radio-frequency interference is still required before data can be analysed. We include specific recommendations designed to make the Square Kilometre Array more robust to radio-frequency interference, including: the availability of sufficient computing power for radio-frequency interference detection; accounting for radio-frequency interference in the receiver design; a smooth band-pass response; and the capability of radio-frequency interference detection at high time and frequency resolution (second and kHz-scale respectively).

scholarly journals A Census of Southern Pulsars at 185 MHz

2017 ◽  
Vol 34 ◽  
Author(s):  
Mengyao Xue ◽  
N. D. R. Bhat ◽  
S. E. Tremblay ◽  
S. M. Ord ◽  
C. Sobey ◽  
...  
Keyword(s):  
Phase 1 ◽  
Low Frequency ◽  
Frequency Component ◽  
Frequency Resolution ◽  
Large Field ◽  
Initial Time ◽  
Wide Field ◽  
Processing Load ◽  
Square Kilometre Array ◽  
Murchison Widefield Array

AbstractThe Murchison Widefield Array, and its recently developed Voltage Capture System, facilitates extending the low-frequency range of pulsar observations at high-time and -frequency resolution in the Southern Hemisphere, providing further information about pulsars and the ISM. We present the results of an initial time-resolved census of known pulsars using the Murchison Widefield Array. To significantly reduce the processing load, we incoherently sum the detected powers from the 128 Murchison Widefield Array tiles, which yields ~10% of the attainable sensitivity of the coherent sum. This preserves the large field-of-view (~450 deg2 at 185 MHz), allowing multiple pulsars to be observed simultaneously. We developed a WIde-field Pulsar Pipeline that processes the data from each observation and automatically folds every known pulsar located within the beam. We have detected 50 pulsars to date, 6 of which are millisecond pulsars. This is consistent with our expectation, given the telescope sensitivity and the sky coverage of the processed data (~17 000 deg2). For 10 pulsars, we present the lowest frequency detections published. For a subset of the pulsars, we present multi-frequency pulse profiles by combining our data with published profiles from other telescopes. Since the Murchison Widefield Array is a low-frequency precursor to the Square Kilometre Array, we use our census results to forecast that a survey using the low-frequency component of the Square Kilometre Array Phase 1 can potentially detect around 9 400 pulsars.

The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

2019 ◽  
Vol 15 (S356) ◽  
pp. 375-375
Author(s):  
Sarah White
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Visual Inspection ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Relativistic Jets ◽  
The Galaxy ◽  
Murchison Widefield Array ◽  
Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

scholarly journals Estimation of the Noise Source Level of a Commercial Ship Using On-Board Pressure Sensors

2021 ◽  
Vol 11 (3) ◽  
pp. 1243
Author(s):  
Hongseok Jeong ◽  
Jeung-Hoon Lee ◽  
Yong-Hyun Kim ◽  
Hanshin Seol
Keyword(s):  
Noise Source ◽  
Pressure Sensors ◽  
Low Frequency ◽  
Frequency Resolution ◽  
Source Strength ◽  
Recording Time ◽  
Source Level ◽  
The One ◽  
Hydrophone Array ◽  
Good Agreement

The dominant underwater noise source of a ship is known to be propeller cavitation. Recently, attempts have been made to quantify the source strength using on-board pressure sensors near the propeller, as this has advantages over conventional noise measurement. In this study, a beamforming method was used to estimate the source strength of a cavitating propeller. The method was validated against a model-scale measurement in a cavitation tunnel, which showed good agreement between the measured and estimated source levels. The method was also applied to a full-scale measurement, in which the source level was measured using an external hydrophone array. The estimated source level using the hull pressure sensors showed good agreement with the measured one above 400 Hz, which shows potential for noise monitoring using on-board sensors. A parametric study was carried out to check the practicality of the method. From the results, it was shown that a sufficient recording time is required to obtain a consistent level at high frequencies. Changing the frequency resolution had little effect on the result, as long as enough data were provided for the one-third octave band conversion. The number of sensors affected the mid- to low-frequency data.

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