The Signal Processing Firmware for the Low Frequency Aperture Array

Publ. Astron. Soc. Aust.

et al. 2020

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.

Section: Observationsmentioning

confidence: 99%

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

Tingay

Sokołowski

Publ. Astron. Soc. Aust.

et al. 2020

“…The firmware for the Xilinx FPGAs is described in Comoretto et al (2017). It is implemented in VHSIC Hardware Description Language (VHDL) and is based on a highly modular structure that separates the technology-dependent part of the firmware, included in an input-output (IO) module, from the actual digital signal processing (DSP) design.…”

Section: Digital Signal Pathmentioning

confidence: 99%

The Aperture Array Verification System 1: System overview and early commissioning results

Benthem

Acedo

et al. 2021

A&A

The design and development process for the Square Kilometre Array (SKA) radio telescope's Low Frequency Aperture Array component was progressed during the SKA pre-construction phase by an international consortium, with the goal of meeting requirements for a critical design review. As part of the development process a full-sized prototype SKA Low 'station' was deployed -the Aperture Array Verification System 1 (AAVS1). We provide a system overview and describe the commissioning results of AAVS1, which is a low frequency radio telescope with 256 dual-polarisation log-periodic dipole antennas working as a phased array. A detailed system description is provided, including an in-depth overview of relevant sub-systems, ranging from hardware, firmware, software, calibration, and control sub-systems. Early commissioning results cover initial bootstrapping, array calibration, stability testing, beam-forming, and on-sky sensitivity validation. Lessons learned are presented, along with future developments.

“…Steam-processing firmware running on the TPM boards coarsely channelises the incoming voltage streams into 512 channels of width ≈0.926 MHz; this firmware is detailed in Comoretto et al (2017). The EDA2 and AAVS2 are connected by high-speed Ethernet to a software correlator running on commercial-off-theshelf computer hardware with both stations using exactly the same rack-mounted Dell servers each with two Intel Xeon Gold 6226 2.7 GHz, 192 GB RAM, 64 TB of SSD hard-drives in RAID5 for the data, two 240 GB solid-state drives in RAID1 for the operating system, NVIDIA Tesla V100 16GB GPU, and one Mellanox ConnectX-5 dual port 40/100 Gb Ethernet card.…”

Section: Ska-low Prototype Stationsmentioning

confidence: 99%

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

Sokołowski

Publ. Astron. Soc. Aust.

Price

et al. 2021

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.