11 February 2008
Time is on South Africa’s side in its bid to host the giant Square Kilometre Array (SKA) telescope project – expected to cost some €1.5-billion – according to South African astronomer Professor Phil Charles.
Speaking to BuaNews, Charles, who is director of the South African Astronomical Observatory, explained that the technology needed to cater for the bandwidth, computer processing power and data storage requirements of the SKA project does not as yet exist.
Once finished, the SKA is likely to be the largest and most sensitive radio telescope ever, consisting of thousands of dishes between 10 and 15 metres in diameter.
Currently, South African and Australia are the only remaining candidates to host the telescope. A final decision on the host site is expected by 2010, and construction is expected to start by 2014.
Charles told BuaNews that he believed the required technology – demanded by the combination of the spatial and temporal resolution of the SKA telescope – would be available in between five to eight years.
Charles calculated this on the basis of what is known as Moore’s Law, the theory arising from the current rate of technological innovation that assumes that raw processing power and hard disk capacity will double every two years.
In the meantime,he said, South Africa needs large investments in bandwidth capacity to bridge the digital divide and, more specifically, for a high-speed academic internet backbone.
Plans are in the pipeline for an African equivalent of the European GÉANT2 network, which currently provides an academic backbone through Europe of 10 gigabits per second – at least 1 000 times faster than what is currently available in South Africa.
Already, the Southern African Large Telescope (SALT) that was inaugurated in November 2005 is working around limitations in data transmission by using a dedicated 1.5-million bits per second data line between Sutherland, where the telescope is located, and Cape Town.
This “uncalibrated” data is then reduced through processing to a point where SALT’s partnership scientists can access it over the internet from the United States, Europe and elsewhere.
However, Charles argues that better bandwidth ias needed as, without it, the pathfinder radio telescope arrays being constructed by South Africa (and Australia) in preparation for the SKA will have a limited capability.
From the initial four regions of the world that expressed an interest, South Africa and Australia have been short-listed as potential hosts for the SKA, mainly because scientists examining the various bids found that the ionospheric background in the Earth’s atmosphere was less apparent in the southern hemisphere.
Charles explained that the ionospheric background in the Earth’s atmosphere – the upper part of the Earth’s atmosphere that is affected by radiation from the sun to the point where it impacts on the propagation of radio signals – was not uniform over the whole planet.
“The quietest parts [of the earth’s atmosphere] are actually southern Africa and Australia,” said Charles. “You can see this background during the day, and there are times when it just sort of flows from south America up across north Africa and across China and, during the most sensitive observations, that would limit the sensitivity of the proposed SKA telescope.”
Charles points out that the southern hemisphere already has more large telescopes than the northern hemisphere because of its competitive edge over the north, in part because the galactic centre goes directly overhead in the southern hemisphere, giving astronomers in the south “the best view of the centre of our own galaxy”.
In the south, South Africa has a further competitive edge because world-class research requires access to dark, clear skies at regions preferably above 1 500 metres above sea level, and for this only Chile and South Africa qualify because of the lower altitudes of Australian optical observatories.
Already, Chile is home to the European Southern Observatory, which has four eight-metre telescopes situated in the country.
South Africa was favoured for the SALT telescope, which is situated in a quiet part of the Karoo – in Sutherland – that is largely free from human interference in the form of night lights, television signals, cellphone signals and other waves, all of which cause radio interference.
South Africa moved to strengthen this advantage last year by passing the Astronomy Geographic Advantage Bill, which seeks to preserve and protect areas within South Africa that are uniquely suited to optical and radio astronomy.
In the meantime, work goes on at the South African Astronomical Observatory in Observatory, Cape Town, and in Sutherland, while work has begun on the SKA “demo model”, the world-class MeerKAT telescope whose 12-metre dishes will be spaced over 10 kilometres in the Karoo.
Should South Africa win the SKA bid, there will be antennae scattered all over the southern African region, with the main site in the northern Cape. It will have an effective data collecting area of one million square metres, making it the most powerful radio telescope on Earth, Charles said in the South African science magazine Quest last year.
South Africa needs the project, said Charles, and not just for studying the skies. “Astronomy is a fantastic way of inspiring young people into science,” he said. “[It is also] one of the most superb ways of actually teaching people basic physics and mathematics.”
The country, he said, “desperately needs a scientifically, technically literate workforce if it is truly going to make the transformation that we hope for”.