Natural gas exploration is causing a headache for South Africa's bid to host the Square Kilometre Array. Credit: SPDO/Swinburne Productions

South Africa's commitment to hosting the world's most sensitive radio-telescope array is being tested by a request from oil giant Shell to drill for natural gas in the remote region that would house the facility.

South Africa is competing with Australia to be the home of the €1.5-billion (US$2.1-billion) Square Kilometre Array (SKA), a collection of around 3,000 antennas with a total collecting area of 1 km2.

The SKA will capture radio signals from just after the Big Bang, a time before stars formed. Because these signals are quite faint, the array needs to be in a remote location, free from radio interference — making the remote Karoo highlands near Carnarvon, some 500 kilometres northeast of Cape Town, a good potential location. The region is already home to the Southern African Large Telescope (SALT), the Southern Hemisphere's biggest single optical telescope, for similar reasons.

But Shell has applied to explore 90,000 km2 of the Karoo to search for natural gas trapped in shale rock. Its search area runs close to the proposed site for the SKA as well as near to Sutherland, which is home to SALT. The company plans to use a controversial mining technique called hydraulic fracturing, or fracking, to extract the gas. This involves pumping water and chemicals into drilled wells, increasing the underground pressure so as to fracture the rock and release the gas.

News of the bid has sparked worries about the effects the mining operation could have on the SKA. "We are concerned. Our international partners are starting to ask where this is going and how it will impact the SKA," Val Munsami, deputy director-general for research, development and innovation at the Department for Science and Technology, told a 16 March parliamentary hearing on the SKA bid in Cape Town.

The big worry for the SKA is radio-frequency interference, says Adrian Tiplady, site-characterization manager at SKA South Africa. "The primary risk is electromagnetic interference generated from heavy industrial equipment, such as that associated with mining equipment, and any radio communication equipment associated with the mining activity," he says. "Seismic activity would also have an impact, but only within a closer proximity."

SALT could also be adversely affected. The telescope needs clear skies to operate, but the dust from roads and drill sites and vibrations from the mining could dull its images. It also uses extremely sensitive seismic meters to monitor the settings of the mirrors.

In theory, South Africa's Astronomy Geographic Advantage (AGA) Act of 2007 protects the core SKA site and the immediate area around SALT from activities that could interfere with astronomy, such as radio activity or mining. But this is the first time that the law has been tested in a situation in which lucrative mining contracts are at stake.

Shell has made some concessions to the astronomical activities in the Karoo. In its draft environmental-management plan, published on 1 March, the company promises to adhere to the AGA Act, which it says instructs developers to leave a 3-km buffer around core astronomy areas.

But Tiplady believes that Shell's plan "completely misinterprets" the act. "They have confused SALT and the SKA, thinking that the requirements are the same for both facilities. They are not, as SALT is an optical telescope, and the SKA is a radio-astronomy telescope," he says. "Any mineral exploitation will require a detailed analysis, and very detailed impact assessment on radio astronomy and the SKA before proceeding."

Shell has already attracted adverse publicity over its attitude to astronomy in the Karoo. Earlier this month, Bonang Mohale, chairman of Shell South Africa, told the South African Press Association that Shell was in regular contact with South Africa's science minister, Naledi Pandor, over its intentions in the Karoo, adding that it would have "no impact" on the SKA.

But in a statement to the press, Pandor hastily denied any contact, saying that she "never had any communication from Shell in this regard, and has never met Mr Mohale to discuss the proposed project".

The South African SKA team will sit down with Shell to discuss the restricted areas later this month. The Petroleum Agency of South Africa has to make its decision on whether to let Shell go ahead with exploratory drilling by August at the latest.

Meanwhile, Australia's bid faces trouble of its own from the mining industry. Last year the Australian Communications and Media Authority published plans to increase the radio quiet zone surrounding the country's SKA site in Western Australia. But according to media reports, mining companies in the area oppose plans to block the issue of new low-bandwidth radio licences within 100km of the SKA site. Mining companies need such licenses to direct equipment operators and issue blast and safety warnings, among other things.

The Sunday Times newspaper also reported on 1 January that the extended radio restrictions could jeopardise the AU$4.4 billion ($4.4bn) Oakajee Port and Rail Project — a gargantuan railroad and harbour construction to transport ore and other goods from the mining areas in midwest Western Australia onto ships.

The South Africans hope the strict enforcement of their law will give them an edge over the competition. "If we succeed, it will look very good for us," says Tiplady. The international committee overseeing the SKA is expected to make a final decision on where the array will be built in 2012.