The Square Kilometre Array Design Study

点击翻译按钮获取中文摘要

The 'Square Kilometre Array' (SKA) will be an international radio telescope with a collecting area of one million square metres - equivalent to about 200 football pitches / making SKA 200 times bigger than the University of Manchester's Lovell Telescope at Jodrell Bank. The four-year Square Kilometre Array Design Study, SKADS, brings together European and international astronomers to formulate and agree the most effective design. The final design will enable the SKA to probe the cosmos in unprecedented detail, answering fundamental questions about the Universe, such as 'what is dark energy?' and 'how did the structure we see in galaxies today actually form?' The SKA concept was first proposed to observe the characteristic radio emission from hydrogen gas. Measurements of the hydrogen signature will enable astronomers to locate and weigh a billion galaxies It will also test Einstein's General Theory of Relativity to the limit / and perhaps prove it wrong. It will add to the long list of fundamental discoveries made by radio astronomers including quasars, pulsars and the radiation from the Big Bang. The design will be complete by 2010 and building SKA with full operation in 2020. Another target for the SKA is pulsars; spinning remnants of stellar explosions which are the most accurate clocks in the universe. A million times the mass of the Earth but only the size of a large city, pulsars can spin around hundreds of times per second. With the SKA we will find a pulsar orbiting a black hole and, by watching how the clock rate varies, we can tell if Einstein had the last word on gravity or not. The scale of the instrument needed to fulfil these science goals is huge, a total of 1,000,000 square metres of collecting area spread across a continent, but the technology required to fulfil the potential of the instrument is in many ways more daunting. The SKADS effort is based on phased array receivers. When placed at the focus of conventional mass-produced radio 'dishes', these arrays operate like wide-angle radio cameras observing huge areas of sky. A separate, much larger, phased array at the centre of the SKA constantly scans the sky. Catalyst funding has been provided by the European Commission of 27% of the total of ¤38M funding over the next four years. The UK has invested £5.6M (¤8.3M) funding provided by PPARC. The UK's is contributing 30% of the SKADS programme. The UK is concentrating on sophisticated digital phased arrays and the distribution and analysis of the enormous volumes of data which the SKA will produce. The main technological design aim of UK SKADS is to produce a dual polarisation all-digital phased array 'tile' approximately 1m by 1m, so call '2-PAD'. This will represent the culmination of a number of fundamental system design studies into array antenna element design; very low cost semiconductors for the critical low noise amplifiers (LNAs) at the antenna and the very high speed analogue to digital converters (ADCs) which put the received signal into the digital domain; considerable research into very high speed digital processing techniques which are affordable in terms of cost and power and the reduction of interference both external and self-induced by the equipment. This development is expected to be the highest performance phased array tile for astronomical purposes available at the end of the project. The requirements and performance of a simulated SKA will be investigated when used for selected astronomical observations. The results will be key to deriving the target specification for the SKA and will be used extensively by the engineering groups. The communication and computing resources of a completed SKA will be simulated in order to find the optimal configurations. Techniques for distributing very accurate time signals will be worked upon and demonstrated. This is vital to a radio telescope using many receiving systems sometimes separated by thousands of kilometres.