Ask an Expert

Why do we need such a big telescope? What will it look like? How will it be built? How will it handle the data?

The Square Kilometre Array Telescope (SKA) will delve further into the Universe than ever before, produce more data about the cosmos than modern-day computers can handle, and shift the focus of radio astronomy from the 'dish' to silicon.

In essence, what we are seeing is the evolution of telescopes away from the concrete and steel that forms the antennas and into the world of supercomputing, says Professor Brian Boyle, CSIRO's SKA director.

"The supercomputer is as much a part of the telescope as is the antenna.

"In the 1960s you built really big dishes to take all the data, now you put all your effort into the silicon brains behind it," Boyle says.

An array telescope is composed of lots of different antennas connected to a supercomputer via a super-fast fibre optic network.

"So in the SKA's case we're talking 3000 antennas over a minimum distance of 3000 kilometres.

"All that data is transported from the SKA at speeds of 400 terabits per second across the continent — that's about ten times greater than global internet traffic today.

"Then it's processed by a super computer capable of doing one million, million, million operations per second — about one hundred times faster than the world's fastest super computer today," says Boyle.

Scientists hope that by delving deeper into space than ever before they will be able to investigate fundamental questions about the universe, such as the evolution of galaxies, dark energy and cosmic magnetism, and probe the earliest stars and black holes.

^ to top

What will the telescope look like?

Australia's bid for the telescope (see box below) will see 3000 antennas spread across Australia and New Zealand.

"The distance between the telescopes gives you the resolution the telescopes can see.

"The bigger the baseline the more fine detail you can see. So the baseline is 3000 kilometres at wavelengths we're talking about here you get to see features about 10 times better than the Hubble Space Telescope, says Boyle.

The Australasian bid covers a distance of 5000 kilometres on an east-west axis.

"East to west follows the rotation of the Earth — that allows us to do higher quality imaging over a larger area of sky," says Boyle.

The SKA will use three kinds of antennas:

Parabolic dishes around 12–15 metres in diameter, which collect data in frequencies of 1–20 gigahertz. These dishes can be rotated and will collect data on gravity, cosmic magnetism and life in the universe.

Sparse (low frequency) aperture arrays, which look a bit like TV/radio antenna, are fixed antenna that collect data in frequencies of 70–300 megahertz. They will be used to research the earliest stars to evolve in the Universe.

Dense (mid frequency) aperture arrays, which are touching dipole arrays lying on, or under, the ground. These antennas collect data in the 300 megahertz to 1 gigahertz range and will be used to study the evolution of the cosmos.

When it is finished, half the 3000 antennas will be concentrated within a 5 kilometre zone centred on the Murchison Radio Astronomy Observatory, a remote location in Western Australia. Seventy-five per cent of the antennas will be located in clumps within 180 kilometres of this central point, then another 25 stations will reach out across the continent and into New Zealand.

^ to top

Building big

The project is big, ambitious, and will grow in stages, says Boyle.

"The scale is so immense and the technological challenges are so immense that part of the strategy around mitigating the technical risk is to build this in stages," he says.

As time goes on the project would expand in distance and allow astronomers to see deeper into space, says Boyle.

"We will be moving into different areas of astronomy from wide field survey of astronomy to really deep field stuff," he says.

If Australia wins the bid, Boyle says the plan is to roll the first 300 antennas stretched over 100 kilometres by the end of this decade, and roll the rest out in the early part of the next decade. It is due to be fully operational by 2024.

The first stage of the project, building a telescope known as the Australian SKA Pathfinder, has already begun and will be completed regardless of whether or not Australia wins the bid for the complete telescope.

"The Australian SKA Pathfinder is a one percent scale of the SKA," says Boyle.

"It's 36 dishes stretched over six kilometres in distance. But at the same time we're putting all the infrastructure in place such as the roads and the fibre, the central control buildings, the support buildings and the power station that would at least initially help support the deployment of the full SKA," says Boyle.

The Australian SKA Pathfinder will also use a new type of radio camera, known as a phased array feed.

"Radio telescopes have essentially used a '1-pixel camera' in the past so they've got a very, very narrow area of sky that they can see," says Boyle.

"We're now moving to having a 100 pixel camera so all of a sudden we have instantaneously increased the field of view of the telescope by a factor of a hundred."

"When SKA is equipped with these technologies, because of its collecting area it will be able to look much deeper into space," he says.

^ to top

Crunching data

It's estimated that the fully operational SKA will produce enough data to fill 15 million 64 gigabyte mp3 players every day.

"Today we don't have a supercomputer that will process the data from the SKA," says Boyle.

"As we build up the telescope we're building up the computer to support it.

"At the moment we have a petaflop computer — that's a thousand, million, million operations per second.

"That will be sufficient to process the data from the Australian SKA Pathfinder, but when we build the SKA we won't need a petaflop computer, we'll need an exaflop computer — a thousand times greater than its capacity," he says.

Boyle says the fastest computer today runs at 5 petaflops. But if Moore's Law, which says computer power doubles every 18 months, is correct we will have computers capable of delivering an exaflop towards the end of the decade.

"And the full SKA will be right at the leading edge of what's possible in computing technology."

Professor Brian Boyle was interviewed by Genelle Weule.