Aiming for the stars
SA is bidding against Australia for front seats to the Big Bang with the Square Kilometre Array (SKA), a giant radio telescope. But with its massive bandwidth and power requirements, do we have what it takes to host this astronomical beast?
Around the middle of 2012, SA will finally find out if it is to be the host of one of the most ambitious projects in the history of astronomy. At time of writing, the other country in the running is Australia. One of the two will host the Square Kilometre Array (SKA) - a massive radio telescope that will make the host country central to 21st-century astronomy.
The SKA will tackle the biggest of questions we face, relating to the universe and how it all began. With 3 000 receptors linked together and a total collecting area of 1 000 square metres, the SKA will have 50 times the sensitivity and 10 000 times the survey speed of the best current-day radio telescopes.
We say SA will host the SKA, but the physical pieces of the instrument will be spread across eight African countries, with SA as the lead, competing against Australia and New Zealand.
Both potential hosts have submitted their final bidding documents. In November 2011, an international site selection group made a final recommendation on the best site and the SKA board will announce its decision in 2012.
Reading electromagnetic 'background' radiation, radio telescopes allow us to determine what is happening throughout the universe. The more data we can gather and analyse, the more we can determine. And the SKA will allow us to see more than ever before.
Says Adrian Tiplady, the local SKA team's Radio Frequency Interference (RFI) and Site Characterisation manager: “SKA is the global astronomical community's initiative to build the biggest and best radio telescope ever made. When it comes to radio astronomy, the bigger you build the telescope, the more sensitive it is and the weaker the signals you can detect.
“Some of these signals have been travelling across the universe for billions of years. By detecting these signals, you get a view of what the universe looked like billions of years ago,” he adds.
“In much the same way, when you look at the sun, you are looking at it as it was eight minutes ago because of the time it takes the light to reach Earth.”
Astronomers hope that the SKA will provide insight into the formation and evolution of the first stars and galaxies, the role of cosmic magnetism, the nature of gravity, and possible life beyond Earth.
“The problem with building one big dish is that you aren't able to move it around, so the solution is to break it up into lots of smaller dishes,” says Tiplady. “These smaller dishes will be distributed across southern Africa.”
The problem with building one big dish is that you aren't able to move it around, so the solution is to break it up into lots of smaller dishes.Adrian Tiplady, SA SKA team
To achieve both high-sensitivity and high-resolution images of the radio sky, the antennas of the SKA will be densely distributed in the central region of the array and then logarithmically positioned in groups along five spiral arms - with each group becoming more widely spaced further away from the centre.
Three antenna types - high-frequency dishes and mid- and low-frequency aperture arrays - will be used to provide continuous frequency coverage from 70MHz to 10GHz. By combining the signals from all the antennas, this will create a telescope with a collecting area equivalent to a dish with an area of about one square kilometre (hence the name).
The telescope's core will be located in a radio reserve in the Northern Cape province. The Astronomy Geographic Advantage Act of 2007 protects this area against future radio interference. Numerous remote stations of around 24 antennae each will be spread out as far as 3 000km from the core of the SKA throughout Namibia, Botswana, Madagascar, Mozambique and Zambia. Stations in Ghana, Kenya and Mauritius will provide extended distances of up to 5 000km from the core.
“We are basically designing the SKA for technology that will be available at the time of construction,” explains Tiplady.
“For example, we are looking into developing a supercomputer that will need to be around 100 times more powerful than any supercomputer that exists today.”
...we are looking into developing a supercomputer that will need to be around 100 times more powerful than any supercomputer that exists today.Adrian Tiplady, SA SKA team
According to Tiplady, IBM has already shown interest in the project and has indicated that the construction of such a supercomputer is possible. In addition, the Centre for High Performance Computing (CHPC), at the Council for Scientific and Industrial Research (CSIR), is currently upgrading its computing power in anticipation of the SKA.
If the SKA is as powerful as astronomers hope it will be, supercomputers will indeed be the only viable way to process the massive amounts of information it will generate. Director of the International Centre for Radio Astronomy Research in Western Australia, Peter Quinn, expects the SKA to generate 10 petabits of data to be distributed to computing facilities, storage and researchers every second.
This immediately raises the question of whether SA has the capacity to handle the data. All the information generated by the SKA will be processed at a computing site near Carnarvon in the Northern Cape. Tiplady says the project will operate its own private network, but it will also make use of existing fibre-optic infrastructure.
“The proliferation of fibre-optic networks throughout Africa and new undersea cables are having a huge impact on bandwidth on the continent,” he says. “We are speaking to various operators about connectivity and there are many options available to us. Given the emphasis on connectivity across Africa, I believe it will be even easier to secure the necessary bandwidth by the time the SKA needs to be built.”
The SKA will also be severely power-hungry. Tiplady says that based on the current SKA model, the requirement would be around 105MW of power - which is equivalent to what most medium-sized towns need. The majority of the power will be used up by the SKA supercomputer and a piece of hardware called the correlator. The local SKA team says it will most likely use power from the grid, but will consider making use of renewable energy if the technology has matured by the time SKA is in operation.
Apart from the physical and technical requirements, the development of knowledge and expertise is a fundamental part of the local project. The SKA's precursor, the Karoo Array Telescope or MeerKAT, is providing the ideal training ground for this purpose.
The MeerKAT is SA's first interferometer for radio astronomy, a telescope consisting of many linked dishes that all contribute towards the production of high-resolution images. The construction of the MeerKAT is helping drive the development of new skills within the local astronomical community and on the rest of the continent.
Once completed, the 64-dish MeerKAT will be the southern hemisphere's largest radio telescope and one of the world's biggest and most powerful telescopes. The first seven dishes - known as KAT-7 - of the MeerKAT were completed by December 2010 and are now being commissioned. According to reports, KAT-7 has already delivered images of the Centaurus A galaxy, 14 million light years away.
If all goes according to plan and we succeed in our bid, this is just a small indication of what we could potentially achieve with the SKA.
First published in the February 2012 issue of ITWeb Brainstorm magazine.