Cluster Post-Launch Support 2008-2010

“星团任务”（Cluster Mission）是第一次用四艘航天器组成的编队来探索磁层。磁层是地球周围可以探测到地球磁场的空间区域。它是影响我们生活质量的许多航天器的运行环境，例如气象、电视和通信卫星，以及用于研究地球、太阳和太阳系以及宇宙的科学航天器。磁层有时对航天器来说是一个危险的环境，了解为什么会这样是集群项目的动机之一。最初的2年任务被延长，允许Cluster通过每年改变Cluster四面体的大小来研究一系列不同规模的现象。最近，群集多尺度任务正在进行中，其中3个航天器相隔约10,000公里。其中一艘和第四艘航天器之间的距离从40公里（太空等离子体术语）到1万公里不等。这项工作正在为拟议的跨尺度任务奠定基础（见www.cross-scale.org）。星系团多尺度任务的另一个令人兴奋的方面是，它将访问星系团以前未探索过的磁层区域，包括太阳风第一次与磁层相遇的地方，极光产生的地方，以及一些磁层亚风暴的起源。在所有这些地方，星系团的4艘设备齐全的航天器将提供新的数据，揭示等离子体的物理过程，这反过来将帮助我们了解磁层是如何工作的。等离子体电子和电流实验（PEACE）仪器可以每4秒测量空间等离子体中电子的三维速度分布，能量范围从几电子伏特到大约30千电子伏特。“和平”仪器在四个“群集二”航天器的每一个航天器上飞行，由两个传感器单元和一个数据处理单元组成。所有8个传感器和4个dpu在太空中运行了8年，尽管定期通过地球的辐射带。PEACE可以告诉我们航天器附近电子等离子体的密度和温度，它是否在流动，速度有多快，以及来自其他地方高能源的电子束是否在当地磁场的引导下经过航天器——这使PEACE具有了遥感能力。PEACE可以告诉我们电子携带的电流，这是很重要的，因为这种电流在整个磁层中传递力。四个PEACE仪器一起工作可以告诉我们，在电子等离子体中是否存在局部气流剪切（比如在靠近中部的河流中水流更快），甚至是漩涡和漩涡；等离子体内或等离子体边界上是否存在波，并能确定压力梯度。这是星系团的独特测量能力，因为对应的等离子体离子仪器不能在所有四个航天器上工作。它提供了爆炸能量释放过程的一瞥，这样一个磁重联的工作方式，这是非常重要的，因为这样的过程在太阳和整个宇宙中非常活跃。同样，PEACE也在帮助揭示无碰撞冲击是如何工作的。冲击也是可能在整个宇宙中发生的现象，它能够激发电子和离子产生非常大的能量。这笔拨款将使我们能够继续操作PEACE仪器，直到2009年底，并在数据处理，处理和管理以及维护最新仪器校准方面做必要的工作。所有这一切都是为了使我们能够向研究界提供科学上有用的数据。它还将帮助我们在欧洲空间局正在创建的群集活动档案的建设和填充方面发挥我们的作用。

The Cluster Mission, for the first time, is exploring the magnetosphere with a fleet of four spacecraft orbiting in a group. The magnetosphere is the region of space around the Earth in which the Earth's magnetic field can be detected. It is the operating environment for many spacecraft that affect our quality of life, such as weather, television and communications satellites, as well as scientific spacecraft used to study the Earth, the Sun and solar system, and the cosmos. The magnetosphere is occasionally a dangerous environment for spacecraft, and understanding why this is so is one of the motivations for the Cluster project. The original 2 year mission was extended to allow Cluster to investigate a range of phenomena with different scale sizes, by varying the size of the Cluster tetrahedron from year to year. More recently, the Cluster Multi-Scale Mission has been under way, in which 3 of the spacecraft are separated by ~10,000 km. The distance between one of these and the fourth spacecraft has been varied from a tiny 40 km (in space plasma terms) up to 10,000 km. This work is laying the foundations for the proposed Cross-Scale mission (see www.cross-scale.org). Another exciting aspect of the Cluster Multi-scale Mission is that it will visit regions of the magnetosphere which were previously unexplored by Cluster, including the places where the solar wind first meets the magnetosphere, where aurorae are generated and where some magnetospheric substorms originate. In all of these places, Cluster's 4 well instrumented spacecraft, will provide new data to reveal the plasma physical processes at work, which in turn will help us understand how the magnetosphere works. A Plasma Electron And Current Experiment (PEACE) instrument can measure the three dimensional velocity distribution of electrons in a space plasma, for an energy range from a few electronvolts to about 30 kiloelectronvolts, every 4 seconds. A PEACE instrument is flying on each of the four Cluster II spacecraft, and consists of two sensor units and a data processing unit. All 8 sensors and 4 DPUs are still working well, after 8 years in space, despite regular passages through the earth's radiation belts. PEACE can tell us about the density and temperature of the electron plasma near the spacecraft, whether it is flowing and how fast, and whether electron beams from energetic sources elsewhere are passing the spacecraft, guided by the local magnetic field - giving PEACE a remote sensing capability. PEACE can tell us about the electrical currents being carried by the electrons, which is important as such currents transmit forces throughout the magnetosphere. The four PEACE instruments working together can tell us whether there are local flow shears (as in a river where the water flows faster nearer the middle) or even eddies and vortices in the electron plasma; whether there are waves in the plasma or on plasma boundaries, and can determine pressure gradients. This is a unique measurement capability for Cluster, as the counterpart plasma ion instruments do not work on all four spacecraft. It is providing glimpses of the way that explosive energy release processes such a magnetic reconnection work, which is very important as such processes are very active on the Sun and throughout the cosmos. Similarly, PEACE is helping to reveal how collisionless shocks work. Shocks are also phenomena that likely occur throughout the cosmos, and which are capable of energising electrons and ions to very large energies. This grant will allow us to continue operating the PEACE instruments until late 2009 and to do essential work on data handling, processing and curation, and maintaining up-to-date instrument calibrations. All this is needed to enable us to make scientifically useful data available to the research community. It will also help us to play our part in constructing and populating the Cluster Active Archive being created by the European Space Agency.