The SKA Observatory’s growing telescope array in South Africa, SKA-Mid, has achieved “first fringes” when signals received by two or more antennas are successfully combined.
In the first true test that all the SKAO’s systems are working together, and that the SKA-Mid telescope is alive as a scientific instrument, the facility has achieved ‘first fringes’, a milestone that demonstrates it is now operating as an interferometer.
Two of SKA-Mid’s 15m-diameter dishes were used together to achieve the result, observing a radio galaxy estimated to be around 2.6 billion light years away.
SKA-Mid, like its counterpart SKA-Low in Australia, is an array where many individual antennas are connected by optical fibre to act like one much larger telescope, equivalent in size to the distance between its furthest antennas. “Fringes” are obtained when signals received by two or more antennas are combined successfully.
“Having each dish observe the sky individually is an achievement but having them operate in concert as one telescope is a much bigger technical challenge, and our teams have now achieved that milestone,” said SKAO Director-General Prof. Philip Diamond.
The radio galaxy observed by SKA-Mid’s two dishes has been well studied so researchers knew what the signal should look like, and that’s what was observed with this first fringes result. It confirms that SKA-Mid’s hardware and software systems are working as designed.
“That includes seeing that: the dishes can track across the sky in a coordinated way under the control of the telescope manager software, the receivers are being cooled to the required temperature of minus 250°C, the synchronisation and timing system is accurately timing signals from the different dishes to a billionth of a second, and the correlator is correctly processing and aligning the data,” explained Dr Betsey Adams, SKA-Mid Commissioning Scientist.
SKA-Mid now has seven dish structures assembled on site in South Africa’s Northern Cape. When complete the telescope will comprise 197 dishes, including the integration of the existing MeerKAT radio telescope built and operated by the South African Radio Astronomy Observatory (SARAO).
Hardware and software for the SKA telescopes is being developed across the Observatory’s partner states. In Switzerland:
- Cosylab, a leading provider of control systems for some of the world’s most complex projects including the particle accelerator at CERN in Geneva, has contributed to the SKA telescopes’ Observatory Management Control software
- The Neuchatel division of Safran Electronics & Defense, formally the Neuchatel Observatory, has delivered state-of-the-art atomic clocks, called hydrogen MASERS to both the South Africa and Australia sites
- MECHA AG, a mechanical engineering company based in Bern is producing 2000 fine machined mechanical parts required to build the 133 SKA Mid Band horn antennas, designed to pick up radio waves from space
- And Herisau based HUBER & SUHNER has been awarded a multi-year sub-contract by antenna manufacturer, Sirio Antenne, to supply electronic components for SKA-Low in Australia.
“Achieving ‘first fringes’ at SKA-Mid in South Africa is a great start to the new year, and contributes to the excitement that continues to build as to what we will be able to see and discover once the entire telescope is online towards the end of the decade,” said EPFL Professor Jean-Paul Kneib, the Swiss Scientific Delegate to the SKAO. “In Switzerland, we can be proud that our research across nine institutions, and our industrial expertise, is contributing to this global project pushing the boundaries of science.”
In Australia, the SKA-Low telescope continues to grow at pace. Around 70 antenna stations, each comprising 256 antennas, have now been installed at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory on Wajarri Yamaji Country in Western Australia.
Last year its first image was released, using an early version of the telescope comprising four connected stations – 1,024 antennas – or less than 1% of the complete telescope.
As work continues to commission stations and integrate them into the array, planning is underway for the start of science verification activities with SKA-Low in 2027, when the first data will be released to the community for test observations.
Current members of the SKACH Consortium are:
École Polytechnique Fédérale de Lausanne (EPFL),
Eidgenössische Technische Hochschule Zürich (ETH Zurich),
Fachhochschule Nordwestschweiz (FHNW),
Universität Zürich (UZH),
Zürcher Hochschule für Angewandte Wissenschaften (ZHAW),
Universität Basel (UniBas),
Université de Genève (UniGE),