SKA-Low’s route from first antenna to verified array

The first antenna on Country

SKA-Low’s first antenna was installed on Wajarri Yamaji Country in Western Australia’s Murchison region on March 7, 2024. Its design baseline comprises 131,072 two-metre antennas, complementing the dish-based SKA-Mid telescope in South Africa. SKAO director-general Philip Diamond and SKA-Low director Sarah Pearce described the scientific ambition as looking back towards the first stars and galaxies. The installation marked an early physical step in building the telescope in Australia.

Seven of the first ten field technicians were Wajarri Yamaji, entering a twelve-month training programme. Technician Lockie Ronan connected the work with his family’s Country and culture; Wajarri Enterprises chair Des Mongoo emphasised heritage protection and employment opportunities. SKAO’s projected comparison with the Netherlands’ LOFAR telescope was 25% better resolution, eight times the sensitivity and 135 times the survey speed. These were expectations for the developed instrument.

Civil works and long connections

Ventia began terrain-clearing works on part of SKA-Low’s southern spiral arm in 2023, with a milestone ceremony on September 6. The location was Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory. Trenching machinery was to install the AARNet fibre connection between the early antenna array and the science-processing computers in Perth. The work extended beyond antenna foundations into the communications infrastructure serving the telescope’s remote observing site.

Ventia’s approximately A$200 million, three-year contract, awarded in December 2022, covered power and fibre networks and the design and commissioning of central and remote processing facilities. Construction commencement ceremonies at the Australian and South African sites took place that December. The contractor worked with regional and Indigenous partners, including Wajarri participants. Its Australian infrastructure programme connected field locations distributed across the planned array, whose full design groups 256 antennas into each of 512 stations. The 2023 civil-works milestone preceded the installation of the first production antennas the following March.

Accommodation during remote construction

The remote construction workforce also needed accommodation and daily services. Ventia supplied a temporary fly camp when delivery of a planned 200-person construction village was delayed. The initial deployment was a 100-person camp, with accommodation, kitchen, dining, gym and recreation facilities serving up to 140 people. Those figures describe different aspects of the temporary arrangement and the intended replacement village, rather than a single completed bed count.

Ventia linked the camp’s delivery to bringing construction forward by a month, with the first meals served three days after camp construction finished. Its Living Services team also catered for roughly 100 council and government visitors from 15 countries following a site visit. Philip Diamond hosted the SKAO Council dinner, attended by Australian officials and Wajarri Yamaji Aboriginal Corporation representatives. Ventia national project director Peter Green praised the teams’ work on the camp and the event. The site lies about 700 kilometres north of Perth.

Manufacturing thousands of repeatable antennas

SIRIO Antenne’s production work in Italy translates the antenna design into manufactured components. By April 2025, SKAO put SIRIO’s contracted production at 78,520 antennas over approximately two and a half years. SIRIO had participated in the project since 2017, working with the Italian National Institute for Astrophysics, CNR-IEIIT and international design partners.

The company added two production buildings, increasing its facility space by 35%, and acquired measurement and testing equipment for quality control. Staff received training for new production lines and machinery, including laser welding. The planned workforce increase at peak production was 30%. Each antenna has four aluminium arms; meeting a requirement of more than 3,000 antennas a month implied finishing an arm every 42 seconds. SKAO also linked the design collaboration to SIRIO’s development of a commercial 698–2700 MHz antenna, which subsequently won a French electrical-network supplier’s tender. The manufacturer had been owned and run by the same family for about fifty years.

Industrialising the signal-processing electronics

Elemaster announced a €45 million contract in December 2023 to design and build SKA-Low’s signal-processing subsystem. Industrialisation began from baseline designs supplied by the Italian National Institute for Astrophysics. The company’s named collaborators included Sanitas EG, EES and CR&C. This was an electronics-development and supply commitment for the low-frequency telescope, with specialised hardware intended to process signals from its extensive antenna array.

SKA-Low’s antennas have no moving parts. Digital processing enables observations in different directions by combining their signals. Elemaster’s software-enabled circuitry was intended to digitise, correlate, combine and help interpret the received radio signals before further processing hundreds of kilometres away. The computing design provided for simultaneous processing across approximately 65,000 radio frequencies. SKA-Low digitisation project manager Jacque Stoddart emphasised the demands created by antennas separated across distances of up to 74 kilometres and the capacity required of their long-range connections. The contract concerned a system to be built, rather than a completed telescope’s measured data flow. Elemaster put the planned antenna array’s collecting area above 400,000 square metres.

Testing signal processing with packets

A. B. Bolin and colleagues developed an automated testing framework for the correlator and beamformer, presented at URSI GASS in August 2023. Their design used Alveo FPGA processing cards, 100-gigabit Ethernet links and programmable P4 switches. Processing was divided into discrete frequency-band workloads, allowing an individual FPGA generally to perform end-to-end work for a defined combination of bandwidth and stations. Four firmware personalities handled different real-time processing operations. Test packets represented FPGA inputs and their expected outputs.

Customisable Network Interface Card firmware ran on an Alveo card to stream and capture real-time test data. GitLab pipelines drove tests at CSIRO’s Marsfield prototype integration facility, which combined a Kubernetes cluster, P4 switch and FPGA server. Reserving cards for manual debugging kept them available alongside automated jobs. Pipeline inheritance allowed shared build and test tasks to be specified once. The testing framework checked:

• Firmware correctness and regressions.
• Real-time packet streaming and capture at up to 100 gigabits per second.
• Integration with control software.

Calibration and operational state

The Monitoring, Control and Calibration Subsystem, described by E. L. Arandjelovic and colleagues in a 2025 engineering paper, manages receiver electronics, diagnostic data and resource health. Its hierarchy uses Tango devices deployed through Kubernetes. Eighteen device types and more than 100 deployed devices per station describe different levels of that software structure. Station electronics include sixteen tile-processing modules, while the field power-and-signal system includes twenty-four local smartboxes.

Calibration gathers antenna signals, forms correlations and compares the resulting data with a sky model that includes diffuse emission and the Sun. Solutions are stored with observing-condition metadata and selected when preparing observations. Device health can be OK, degraded, failed or unknown, with thresholds governing how component states affect their parent systems. The authors identified treatment of switched-off components with unknown health as an outstanding design question. They also profiled polling and deployment overheads while preparing the software for larger arrays. Calibration solutions were saved in HDF5 files, with a database recording their metadata and repository paths.

A complete station observes the sky

In August 2024, SKAO released an image and a twenty-four-hour observing sequence from a single complete SKA-Low station. Its 256 antennas had been integrated with the computing systems needed for observations. The sequence followed the Milky Way across the sky, with Centaurus A, M87 and the Sun among the identified radio sources. This was a station-level observation made roughly five months after the first antenna installation.

By that announcement, antennas had been assembled and installed at four of the planned 512 stations, taking the installed total beyond 1,000. Physical assembly and computer integration were both part of completing a station. SKAO characterised the sequence as demonstrating stable operation and an image that needed relatively little processing. These early observations used a small part of the design baseline. CSIRO and SKAO were jointly building and preparing to operate the Australian telescope on the traditional lands of the Wajarri Yamaji. The Sun appeared during the day, while the Milky Way rose and passed overhead during the night.

Four stations combine their observations

On March 17, 2025, SKAO released a different image, this time combining observations from the first four connected stations. Their 1,024 antennas covered baselines shorter than six kilometres. A seven-hour observation produced an image spanning about 25 square degrees, containing approximately 85 bright galaxies. The radio emission came from galaxies containing supermassive black holes. The antenna count was less than one percent of the telescope’s full design, and the image represented an early interferometric configuration.

Lead commissioning scientist George Heald expressed satisfaction with the image quality from that early array. SKAO accompanied the result with simulations of future sensitivity as more stations were added. Its projected galaxy counts rose into the thousands for intermediate stages and towards hundreds of thousands for deep surveys with the full telescope. Those illustrations represented expected future capability. The 85 galaxies in the released image were the observed result; the much larger simulated populations belonged to later instrument configurations and observing programmes.

Verification of the first array assembly

In August 2025, the first four-station array completed its final verification-testing phase and was officially delivered as SKA-Low’s first array assembly. The milestone covered an operational configuration of 1,024 antennas. SKAO described the result as demonstrating that the architecture and supply chain for the initial system were working. Construction of additional stations continued while the first group went through testing.

Array, verification and integration lead engineer Lucio Tirone identified the working elements: four stations, synchronisation and timing, a correlator and beamformer, science and non-science data networks, and a computing cluster at the Pawsey Supercomputing Research Centre. Integration, verification and commissioning procedures had been established, with operational procedures being formed. The result followed the March image and concerned the tested initial array. SKAO’s construction approach adds equipment and capabilities in stages, with components supplied by its international partners and CSIRO participating in the Australian telescope’s delivery. The first construction milestone was reached less than three years after on-site construction began.

A partnership to run the village

A joint venture between Ventia and Wajarri Enterprises Limited received the contract to manage Nyingari Ngurra, the construction accommodation village. The five-year contract was awarded directly by SKAO to the partnership. By 2024, more than half of the village’s employees were Wajarri Yamaji. The village’s name means Zebra Finch Home, referring to a bird native to the area. The partnership followed a community-engagement workshop held in Geraldton in 2023.

Ventia Living Services general manager Gary Bradford described commitments to ongoing training, personal development and local procurement, alongside employment. The partnership’s stated objective included spending 20% of the project budget with local businesses, including Indigenous and non-Indigenous suppliers. That was a procurement target, with a different denominator from the share of village staff. Ventia’s TRECCA Indigenous-engagement team and Wajarri Enterprises co-designed the venture’s branding using Wajarri language and traditional colours. Its four-member board included two Ventia representatives. These arrangements concerned the services supporting the construction workforce, alongside the technical installation contracts.

A shielded processing facility opens

Ngurra-Maga, the SKA-Low Central Processing Facility building, officially opened on June 24, 2026. The Wajarri name means Home of the Head. Western Australia’s governor Christopher Dawson opened the building with Wajarri Yamaji Elders Jennylyn Hamlett and Des Mongoo. The facility was designed to house on-site signal processing and computing, connected by fibre to the antenna field and to further processing capacity in Perth.

Radio-frequency shielding forms part of the building’s design because electronics can introduce interference into sensitive observations. Aurecon, CSIRO, SKAO, Ventia and specialist partners contributed to the facility and wider infrastructure programme. Ventia’s infrastructure scope included central and remote processing facilities, power distribution and more than 1,000 kilometres of fibre. Data volumes approaching a terabit per second were a full-operation design expectation. The building’s opening was a dated infrastructure milestone within the continuing phased telescope project, alongside the earlier antenna installation and array-verification events. The processing building sits within a protected radio-quiet environment, alongside the telescope’s exceptionally sensitive receiving equipment.

Models test the measurement problem

Lister Staveley-Smith examined SKA-Low’s spectral response in 2025. Reflections, mutual coupling between antennas and the ground screen make station response vary with frequency and pointing direction. He used impulse-response methods to model those effects efficiently, alongside electromagnetic calculations. Mock observations combined sky emission, instrumental response, noise and an injected Cosmic Dawn signal. The tested observing and reduction methods failed to recover that artificial all-sky feature.

The experiment concerned individual-station autocorrelation measurements; detecting the all-sky Cosmic Dawn signal in that mode is not an SKA science goal. Staveley-Smith nevertheless identified gain and beam variations relevant to designing interferometric spectral-line experiments. His modelling used simplifying assumptions for the ground plane and polarisation, and identified further work on interactions between stations. Possible mitigation included weighting antennas to suppress distant sidelobes, with associated trade-offs. Some reductions produced low residuals while removing the injected signal entirely. These were modelling results and research recommendations, alongside the separate observations and engineering-verification milestones achieved by the early array.