The Square Kilometre Array
The Square Kilometre Array is the world's biggest international project in radio astronomy. Phase 1 will consist of two separate arrays of antennas: 197 large dish antennas in the Karoo desert in South Africa, and over 131,000 low-frequency wire antennas (each like a large TV antenna), in the desert of Western Australia. Together these will cover the entire range of radio frequencies, from 50 MHz up to 25 GHz, with unprecedented sensitivity, resolution, and sky coverage. The SKA will transform our view of the Universe in a number of key science areas:
- Seeing how the structure of the first galaxies in the Universe emerged from the cosmic Dark Ages
- Searching for the signatures of life in the Universe: the formation of planets and the presence of organic and biological molecules
- Testing Einstein's theory of General Relativity by finding pulsars, nature's most accurate clocks, in locations of extreme gravity and distorted space-time.
- Understanding the magnetic fields that permeate the Universe.
Construction of the SKA Phase 1 begins in 2021 and is expected to be complete by 2027. Phase 2 would build out both arrays to the scale of thousands of dish antennas and over a million low-frequency antennas.
The SKA Organisation that runs the project has been set up under an international treaty, and is based in the UK at Jodrell Bank near Manchester. Phase 1 of the SKA and the first 10 years of operations will cost around €1.9 billion; the UK is contributing over £100 million.
Oxford and the SKA
Oxford scientists have been central to the design effort for the SKA since its inception, and are currently leading work packages in several areas:
- Non-Imaging Processing (pulsars and fast radio bursts)
- Real-time signal processing and calibration for the low-frequency array (SKA-Low)
- Design of the cryogenic receivers for the mid-frequency dish array (SKA-Mid)
- Software design for calibration and imaging that will run on the SKA's super-computers
We are also heavily involved in multiple science working groups, aiming to fully exploit our expertise gained by use of pathfinder and precursor arrays such as LOFAR and MeerKAT.
Pulsars and Fast Radio Bursts with the SKA
We are developing the capabilities of SKA for time-domain science in Pulsars and Fast Radio Transients. Our group lead this effort together with colleagues at the University of Manchester. The SKA surveys for pulsars will discover the Galactic pulsars beaming towards Earth, signifying a step change in pulsar science. Dedicated and commensal surveys for fast radio transients will have a large impact on the emerging science of Fast Radio Bursts and their potential as probes of intergalactic matter. The Pulsar Group specialize in the high-performance software necessary to conduct real-time searches for pulsars, including for the first time a real-time acceleration search for pulsars orbiting binary companions. We are pioneering an effort to standardize radio astronomical time-domain software with some strict principles in testing and variable typesetting. Our software prototypes are currently running on the world's most sensitive telescopes, including MeerKAT and LOFAR.
Digital systems for SKA-Low
The digital systems group has been developing the real-time digital signal processing for SKA-Low since 2009. Since then our systems have been installed on SKA-Low precursors and have been essential in consolidating the role of UK universities and industry within the SKA. Software and firmware developed within the Oxford-SKA group serves as a template for the industrial development of the SKA-Low's firmware code and real-time systems. We have played an active role in the design of the SKA-Low antennas as well as the monitoring and calibration system of the SKA and look forward to the construction of the SKA where our contribution will play a significant role.
Cryogenic receivers for SKA-Mid
We are designing the high-frequency, cryogenic (super-cooled) receivers that will provide most of the frequency coverage for the SKA-Mid dish array - between 1.6 and 25 GHz. Five different receivers are combined in to a single system that will be mounted at the focus of each of the dish antennas. The interior of the receiver box is cooled to 10 degrees above absolute zero, in a vacuum of one ten-billionth of atmospheric pressure, to reduce as much as possible the noise added by the electronics to the incredibly weak radio signals from the sky. The design of the receivers builds upon the extensive experience our group has in building sensitive instruments for measuring the cosmic microwave background radiation. We also work closely with industry partners to ensure that the final receiver design is optimised for mass production.
The SKA will generate a huge amount of raw data that has to be processed, calibrated, and then turned in to images and other data products that can be used by astronomers. Each SKA array will need a supercomputer capable of 100 Petaflops - equivalent to about 100 million personal computers. Writing the software for these computers is one of the biggest tasks in the whole project. This work is led in Oxford by our colleagues at the Oxford e-Research Centre, working together with astronomers in the Department of Physics.