Square Kilometre Array Design Study (Version 2 19/6/06)

“平方公里阵列”（SKA）将是一个国际射电望远镜，其收集面积为100万平方米——相当于大约200个足球场/使SKA比曼彻斯特大学在Jodrell Bank的洛弗尔望远镜大200倍。为期四年的平方公里阵列设计研究（SKADS）将欧洲和国际天文学家聚集在一起，制定并商定最有效的设计。最终的设计将使SKA能够以前所未有的细节探测宇宙，回答关于宇宙的基本问题，比如“什么是暗能量？”以及“我们今天在星系中看到的结构实际上是如何形成的？”SKA的概念最初是为了观测氢气的特征射电辐射而提出的。对氢特征的测量将使天文学家能够对10亿个星系进行定位和称重。它还将在极限上检验爱因斯坦的广义相对论，或许还能证明它是错误的。它将为射电天文学家的一长串基础发现增添新的内容，这些发现包括类星体、脉冲星和宇宙大爆炸的辐射。设计将于2010年完成，SKA将于2020年全面投入使用。SKA的另一个目标是脉冲星；恒星爆炸的旋转残余物是宇宙中最精确的时钟。脉冲星的质量是地球的100万倍，但只有一个大城市的大小，它每秒可以旋转数百次。通过SKA，我们将发现一颗脉冲星围绕黑洞运行，通过观察时钟速率的变化，我们可以判断爱因斯坦是否对引力有最后的看法。实现这些科学目标所需的仪器的规模是巨大的，在整个大陆上总共有100万平方米的收集面积，但实现仪器潜力所需的技术在许多方面更加令人生畏。SKADS的工作是基于相控阵接收器。当放置在传统的大规模生产的射电“碟形天线”的焦点上时，这些阵列就像广角射电摄像机一样运行，可以观测天空的大片区域。一个独立的，更大的，位于SKA中心的相控阵不断地扫描天空。欧盟委员会将在未来四年提供总额为3800万欧元的27%的催化剂资金。英国已经投入了由PPARC提供的560万英镑（830万欧元）资金。英国为SKADS项目贡献了30%的资金。英国正专注于复杂的数字相控阵，以及SKA将产生的海量数据的分布和分析。英国SKADS的主要技术设计目标是生产大约1米× 1米的双极化全数字相控阵“瓷砖”，因此称为“2-PAD”。这将代表阵列天线元件设计的一些基本系统设计研究的高潮；用于天线上的临界低噪声放大器（LNAs）的极低成本半导体和将接收到的信号转换为数字域的极高速模拟数字转换器（adc）；对非常高速的数字处理技术进行大量的研究，这些技术在成本和功率方面都是负担得起的，并且可以减少设备外部和自身引起的干扰。预计在项目结束时，这一发展将成为天文学用途中性能最高的相控阵瓦片。当用于选定的天文观测时，将研究模拟SKA的要求和性能。该结果将是推导SKA目标规范的关键，并将被工程小组广泛使用。为了找到最优配置，将对一个已建成的SKA的通信和计算资源进行模拟。将研究和演示分发非常精确的时间信号的技术。这对于使用许多接收系统的射电望远镜来说至关重要，这些接收系统有时相隔数千公里。

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.