Looking Back in Time with the World’s Largest Radio Telescope
Constructing the Square Kilometre Array in South Africa and Australia
The Square Kilometre Array (SKA) is a proposed international radio telescope project. Rather than being a single telescope, the SKA is a collection of different antennas working together, known as an array, which would have a total collecting area of over 1 km². The size of the array would make the SKA 50 times more powerful than other radio instruments, allowing it to detect very weak radio signals emitted in the first billion years of the Universe.
This will allow the SKA to explore questions about the evolution of galaxies, the nature of dark energy, the source of giant magnetic fields in space, and the formation of the first stars and black holes. The versatility and sensitivity of the SKA also give this project the potential to make unexpected discoveries. The telescope will produce around 160 terabytes (equivalent to 35,000 DVDs) per second, so the SKA project is collaborating with companies such as IBM to create advances in Big Data science.
A radio telescope consists of the antenna, receiver (which incorporates an amplifier to boost weak signals) and a data recorder. Spreading the array over a large area improves the resolution, meaning that it will be able to discern extremely fine details. The SKA will be constructed in two phases to allow for technological evolution, and will build on the experience gained from pathfinders and precursors that already use similar technology.
The SKA is currently in its final pre-construction phase. The SKA Organisation, a private, non-profit company made up of 13 member countries, is transitioning into the intergovernmental organisation of the SKA Observatory, with seven countries signing the SKA Observatory Convention in 2019. Construction of SKA1 is expected to begin towards the end of 2020. The total cost for the construction of SKA1 has been capped at 674 million euros, and the funding contribution from each member is still the subject of negotiations.
The different antenna designs consist of dipole antennas, which receive very low frequencies similar to FM radio signals, and parabolic antennas (dishes), which operate at higher frequencies similar to mobile phone signals. The dishes will mainly be located in South Africa and its eight partner countries, whereas the dipoles will be sited in Australia.
The two countries had originally put forward competing bids, along with China and Argentina, but the SKA Organisation decided that both locations could provide benefits to the project. Although a dual-site approach would incur greater costs, the precursors and related infrastructure in both sites offered scientific advantages. The Australian site at Boolardy Station, about 500 km north of Perth, and the South African site of the Karoo in the Northern Cape are both isolated enough to experience very little radio interference from television broadcasts and phone networks. High frequency radio waves can be absorbed by moisture in the atmosphere, so it is also vital that the observatory is in a dry location.
Both sites have encountered threats from proposed mining activity, particularly electromagnetic interference due to heavy industrial equipment and radio communication equipment. One of the proposed African remote stations was excluded from the project due to flooding, despite the SKA Site Selection Committee stating that all remote stations would be able to implement solutions to mitigate floods.
The choice of the Karoo in South Africa as the location for the SKA has caused controversy, as the SKA organisation failed to quantify their promises of local economic development, causing them to struggle with the expectations of the poorest residents, who are primarily people of colour. For example, although SKA provided a high-school teacher for Carnarvon, they have not done so in other towns. As well as this, the richer, mainly white community of sheep farmers have concerns about the local economy following the Astronomy Geographic Advantage Act of 2007, which allows the government to acquire land for the project within certain areas. The advocacy group “Save the Karoo” believes that the project will increase unemployment in an area where it is already around 32%.
The Australian SKA Pathfinder telescope will be built on land that traditionally belongs to the Wajarri Yamatji tribe. The tribe has received 13.5 million US dollars in exchange for the use of their land for radio astronomy following the 2009 Indigenous Land Use Agreement, but a new agreement must be negotiated between the tribe and the government for the SKA project.
This demonstrates the complexity of establishing the radio quiet zone required for such an enormous radio astronomy project, which has the potential to unlock the answers to some of the Universe’s biggest questions.
References:
- In South Africa, Opposition Flares against Giant SKA Radio Telescope — Sarah Wild, Nature
- Africa and Australasia to share Square Kilometre Array — Jonathon Amos, BBC
- SKA FAQ
- Co-hosting the Square Kilometre Array — Australian Government
- Mining plans pose threat to South African astronomy site — Linda Nordling, Nature
