Towards an African Network of Radio Telescopes

Towards an African Network of Radio Telescopes
When completed the SKA project will be the largest radio telescope in the world

AFRICANGLOBE – South African scientists, with government backing, are working on a project to recycle disused telecommunications dishes spread out over a number of African countries in order to create an African network of radio telescopes.

In June last year, the board of the African Renaissance Fund, which is located in South Africa’s Department of International Relations and Cooperation, approved R120-million in funding for the initial work to construct a network of radio telescopes in Africa’s nine Square Kilometre Array (SKA) partner countries.

The Department of Science and Technology has been working with its counterparts in South Africa’s eight SKA partner countries – Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia – since 2009 on ways to fund an African-owned network of radio telescopes.

The African VLBI Network project, which is being driven by SKA South Africa and the Hartebeesthoek Radio Astronomy Observatory (HartRAO) near Johannesburg, aims both to fill a major gap in the global VLBI network and, by boosting engineering and science skills development across the continent, to pave the way for the arrival of the SKA.

Very long baseline interferometry (VLBI) is an astronomical technique that uses widely separated radio telescopes in unison to simulate a single telescope hundreds or thousands of kilometres in diameter, producing the clearest, highest resolution images of some of the most distant objects in the universe.

The greater the distance between the telescopes, the greater the resolution of the images produced in this way. Africa’s large north-south geographical spread would therefore make for a powerful VLBI network.

The costs of setting up such a network, however, seemed prohibitive – until HartRAO’s Mike Gaylard came up with the idea of converting satellite dishes, rendered obsolete by the arrival of fibreoptic telecommunications cables, into radio astronomy antennae.

According to SKA South Africa, there are at least 26 satellite ground segment dishes, possibly more, spread out over Africa which could become a part of the new VLBI network.

Where countries do not have existing antennae suitable for conversion, converted dishes from other parts of Africa could be “transplanted”. In some cases, new dishes will be built.

The 26-metre radio telescope at HartRAO in South Africa is currently the only VLBI-capable instrument currently operational in Africa. However, work has begun on converting a 32-metre satellite communications antenna at Kuntunse in Ghana, which was donated to the country’s science ministry by telecoms company Vodafone Ghana.

If this succeeds, it will provide a model for similar dish conversions in other SKA partner countries.

In the meantime, a training programme is being developed in South Africa to equip members from each of the partner countries with the requisite technical and scientific skills.

The idea is to have a new generation of African radio astronomers in place when the Square Kilometre Array (SKA) is completed in the mid-2020s.

“We want to make very sure that Africa delivers the best possible instrument, and that African engineers and scientists can maintain and support it,” SKA South Africa’s Anita Loots told scientific journal Nature in August.

Tom Muxlow, of the Jodrell Bank Centre for Astrophysics near Manchester in the UK, was quoted in the same Nature article as saying that the African VLBI Network also stood to benefit global VLBI science, significantly enhancing the work carried out by VLBI networks in the US and Europe.

“The addition of a dedicated array of African antennas observing the equatorial sky, by itself or in combination with global arrays, has the potential for a truly transformational step in imaging quality,” Muxlow said.