6 minute read
SKA-Mid construction highlights
from Contact 16
BY TRACY CHEETHAM, SKA-MID SITE CONSTRUCTION DIRECTOR
The windless, crisp winter morning of 4 July 2024 enabled the successful “big lift” of our first SKAO-procured dish on the SKA-Mid telescope site.
There was great jubilation and celebration from teams following a live feed in the Science Operations Centre in Cape Town and in our Global Headquarters in the UK, with everyone glued to the screens as we saw the dish structure successfully being lifted onto its pedestal in its new home in the Karoo. Congratulations to our dish structure contractor CETC54, and all the teams across the Observatory on this wonderful achievement.
The lift was followed by the installation of the subreflector, feed indexer and fibre connections. Next, the surface accuracy will be measured and the main reflector, sub-reflector and feed indexer will be aligned, while work continues to install network switches, receivers and digitisers, and to undertake final integration and commissioning of the whole dish system.
Assembly of the second and third dishes is well underway with the fourth dish recently delivered to site. A further three dish structures have now arrived in South Africa, and four more have completed factory acceptance testing in China and are being prepared for shipment.
Once assembled and commissioned, the first four dishes comprise the first milestone for SKA-Mid construction, known as Array Assembly 0.5 (AA0.5) which is due for completion mid-2025. The AA0.5 dishes are pre-production dishes which will be tested and verified to confirm that they meet the design requirements before CETC54 can proceed with full-scale production.
Land access
Our collaboration partner SARAO has successfully concluded the eight-year land programme which included the acquisition of 135,000 hectares of land by the National Research Foundation, which forms the core of the SKA-Mid telescope. This area is now called the Meerkat National Park (named after the animal, not the telescope), managed by SANParks, the body responsible for managing all of South Africa’s national parks. All the land servitudes required for SKA-Mid’s three spiral arms have also been secured.
Around 450 km of road works (including new roads and upgrades) are required for SKA-Mid, and 650 km of underground and overhead power and fibre are needed to connect to the SKA-Mid dishes.
Within the core area, close to half the roads have now been cleared and road beds prepared, while excavation work continues for the power and fibre trenching, with micro-duct cabling underway to supply power and fibre to the first 30 dishes.
In the spiral arms, construction of new roads has begun, as has preparatory work for power and fibre connections. Beyond the core, it is more cost effective to have overhead power lines, and there has been good progress on the construction of the steel overhead monopole structures from 5 km to 30 km into each spiral arm. The design of the overhead structure includes special earthing, bonding and lightning protection characteristics to avoid “sparking” on the power line which causes interference with the radio telescope.
Piling for the dish antenna foundations in the core is now 70% complete, and the first concrete pours are underway for all the antenna foundations for the next stage of delivery, Array Assembly 1 (AA1), which comprises an additional four dishes added to the AA0.5 milestone.
Signal chain success
Back at our system Integration Test Facility (ITF) at the Science Operations Centre in Cape Town, teams have put together a full signal from the digitiser through to the science data processor. They successfully generated a source signal in the ITF with the “sky simulator”, with system analysts confirming the integrity of the captured signal. This shows not only that the signal chain is working as planned, but also that components produced in many different countries can be successfully integrated into a single functioning system.
The team can now also control and monitor the test system by integrating monitoring and control software, which enables the control of the telescope from a single point. With more hardware and software products being delivered and integrated in the ITF system, the team is now focused on achieving system stability in preparation for starting formal ITF verification.
In September, a team from the SKAO and collaboration partners inspected and tested 517 km of new optical fibre provided by Liquid Intelligent Technologies linking Beaufort West to Cape Town. The route is part of the data transmission link that will eventually carry data at a rate of up to 20 Tb/s (a million times faster than a typical 20 Mb/s household broadband connection speed) from the telescope to the data processing facility in Cape Town.
Putting HSE values into practice
As we continue to embed a safety culture, the SKA-Mid team recently obtained its ISO45001 accreditation, an international standard demonstrating that we have a structured system to identify and manage risks related to employee safety, prevent workplace accidents and comply with legal requirements. We have also introduced monthly contractor health, safety and environmental awards.
The site’s internal low-frequency communication network is now operational, giving teams the ability to communicate with hand-held and fixed communication devices which is critical from a health, safety, and security perspective. The network includes a world-first 26-GHz microwave link operating at a distance of 83.6 km; no previous 26-GHz link has operated at a distance over 50 km anywhere on Earth! Using these higher, microwave frequencies enables communication without interfering with the radio frequencies used by the telescopes on site.
Environmental walkthroughs of the infrastructure routing continue at the SKA-Mid site in compliance with our environmental management plan. These walkthroughs identify protected flora and fauna and determine whether species need to be protected or relocated or whether infrastructure must be rerouted.
Local community participation
Our local workforce continues to grow on site, reflecting our commitment to ensuring local community participation and stimulating the local economy. More than 273 local community members are now employed by our main infrastructure contractor Power Adenco from Carnarvon, VanWyksvlei, Williston and Brandvlei to work on site; 22% are women, and 62% are between 18 and 35 years old.
Power Adenco has also appointed 11 small, medium and micro enterprises (SMMEs) from the four towns for various construction works to date. Community meetings were held in the towns in July to provide feedback on progress related to local employment and contracting opportunities.
Ten local community members have completed their National Qualification Framework (NQF) learnerships in construction supervision. Two of the graduates have successfully obtained construction work packages as SMMEs and the remainder have been appointed by Power Adenco as construction supervisors, so we extend our congratulations to them all.
We are well on our way now to AA0.5!
