2001年9月15日Cluster卫星对电流片的观测研究

2001年9月15日0430-0515 UT期间,Cluster卫星多次穿越磁尾电流片.由FGM、CIS等仪器获得了电流片磁场,粒子速度等数据变化情况,并得到了磁尾高速流的两次明显反转.本文采用GSM坐标系.利用求磁场空间梯度张量的方法获得了越尾电流,其电流密度的峰值为28nA/m2.并对电流片在垂直方向上的摆动和在晨昏方向的波动现象进行了分析.数据显示此时电流片为薄电流片并有一个变薄的趋势,其厚度大约为0.2-0.3 Re.磁场重联时地向流与尾向流均超过了1000 km/s,并测得了电流片的法线方向和运动速度,从而得到了磁尾电流片的结构和运动情况.      

Science Missions Using CubeSats

As the role of missions and experiments carried out in outer space becomes more and more essential in our understanding of many earthly problems, such as resource management, environmental problems, and disaster management, as well as space science questions, thanks to their lower cost and faster development process CubeSats can benefit humanity and therefore, young scientists and engineers have been motivated to research and develop new CubeSat missions. Not very long after their inception, CubeSats have evolved to become accepted platforms for scientific and commercial applications. The last couple of years showed that they are a feasible tool for conducting scientific experiments, not only in the Earth orbit but also in the interplanetary space. For many countries, a CubeSat mission could prompt the community and young teams around the world to build the national capacity to launch and operate national space missions. This paper presents an overview of the key scientific and engineering gateways opened up to the younger scientific community by the advent and adaptation of new technology into CubeSat missions. The role of cooperation and the opportunities for capacity-building and education are also explored. Thus, the present article also aims to provide useful recommendations to scientists, early-career researchers, engineers, students, and anyone who intends to explore the potential and opportunities offered by CubeSats and CubeSats-based missions.      

利用TDRS数据进行启动定轨

哥达德航天中心已研制出一种星载定轨系统的模型机,用于星上导航的研究与开发。该系统有两种形式,一种用于实验室研究,另一种用于地面验征,以便深入研究以微处理机为基础的自动定轨系统的可行性和实用性。本文描述了每个系统的数学模型和软件结构,并给出了计算精度和实时处理性能方面的实验室鉴定结果。     

先进的模块化跟踪器:一个实时的电视跟踪器

本文叙述先进的模块化跟踪器(AMT),一个可以实时跟踪诸如运载火箭、卫星等目标的电视跟踪器。AMT是美国空军菲力浦实验室为捕获、跟踪、瞄准(ATP)实验而自行开发的一个项目。它采用了DATACUBE公司并行流水式图象处理硬件和图象流软件。目前的AMT版本使用DATACUBE公司的 MAXVIDEO一20、MAXSCAN和MAX860板。AMT可同时对二个不同的视频输入进行行星、边缘和相关跟踪,并可实时进行输入图象的视频转换、实时直方图计算及图象的处理。AMT具有自动捕获跟踪目标,自动调节阈值和波门大小的能力,它可用于任何地基、空基和天基等需要自动跟踪的应用场合。     

任务操作中心——航天器地面数据系统关键部件的一体化

在以减少预算、限定系统开发时间和用户要求增加能力为特征的环境中,国家航空航天局开达德航天中心的任务操作处(MOD)在开发其航天地面数据系统方面提出了一个新的、高经济效益的新概念:任务操作中心(MOC)。按这种称为的方法,使用一种现代化的图形用户接口把关键部件集成为一个集航天器规划、监视、遥制为一体的综合系统。MOD目前正在构造多个MOC,其特点是采用通用的、可重复使用的和可扩展的系统结构,可支持X射线定时探测卫星(XTE)、热带降雨测量卫星(TRMM)和先进合成探测(ACE)卫星。 由于有了MOC方法,各种任务操作集合成整体,用户用一个系统即可完成实时健康和安全监视、实时遥控、实时姿态处理、航天器实时和预测性图形式监视、趋势分析、任务规划和调度、指令生成和管理、测控网调度、引导星选择;用专家系统进行航天器监视以及故障排除。MOD还准备按新的MOC管理机构构造测试和训练模拟器。 本文描述了MOC的概念,开发MOC系统中所使用的管理办法,使用的技术和构造MOC系统中对开发过程进行的改进,以及采用MOC法对用户和卫星工程带来的预期益处。     

无需热压罐的复合材料维修方案

修理罐的发明 很多复合材料结构的修理都能使用热补仪和真空产生的压力来完成,然而,也有很多修理根据结构维修手册(SRM)的要求需要使用高达344.7kPa的正压力才能完成.仅仅使用抽真空产生的压力已经无法达到SRM的要求.     

Influence of the Ionosphere on the Observation of the Mid-Latitude Pi2 Pulsations at the Global Scale

Results of our investigation showed that occurrence frequency of Pi2 over a 24 hour period undergoes seasonal variations in time coincidence with foF2. In the winter months, at sunrise and sunset (when foF2gradients are the largest) the observation probability of these oscillations is minimal. At periods of summer solstice when the F2-layer persists almost round the clock, no effect of Pi2 pulsation attenuation is observed at sunrise and sunset. The pulsation amplitudes behave in a similar manner. Results of this study suggest the conclusion that the propagation of signal from the Pi2 sourse into the mid-latitudes, and also the parameters of these pulsations are essentially affected by electron density in the ionospheric F2-layer.      

Sugar synthesis from a gas-phase formose reaction

Prebiotic possibilities for the synthesis of interstellar ribose through a protic variant of the formose reaction under gas-phase conditions were studied in the absence of any known catalyst. The ion-molecule reaction products, diose and triose, were sought by mass spectrometry, and relevant masses were observed. Ab initio calculations were used to evaluate protic formose mechanism possibilities. A bilateral theoretical and experimental effort yielded a physical model for glycoaldehyde generation whereby a hydronium cation can mediate formaldehyde dimerization followed by covalent bond formation leading to diose and water. These results advance the possibility that ion-molecule reactions between formaldehyde (CH(2)O) and H(3)O(+) lead to formose reaction products and inform us about potential sugar formation processes in interstellar space.     

Porphyrin as an ideal biomarker in the search for extraterrestrial life

A key issue in astrobiological research is identifying target molecules that are unambiguously biological in origin and can be easily detected and recognized. We suggest porphyrin derivatives as an ideal target, because these chromophores are global in distribution and found in virtually all living organisms on Earth, including microorganisms that may approximate the early evolution of life on Earth. We discuss the inherent qualities that make porphyrin ideally suited for astrobiological research and discuss methods for detecting porphyrin molecules in terrestrial sedimentary environments. We present preliminary data to support the use of ToFSIMS as a powerful technique in the identification of porphyrins.     

PAMIR—一种宽带相控阵SAR／MTI系统

在未来的各种监视侦察任务中，机载及星载成像雷达系统必须满足越来越严格的要求。下一代最高水平的合成孔径雷达(SAR)系统将具有高灵敏度地面动目标指示能力和多种复杂工作模式，其中包括高分辨率和远距离成像能力。只有通过运用可重构相控阵天线连同综合宽带系统设计以及多通道能力才能完成各种任务。在FGAN已经设想出一种新的X波段实验雷达，该雷达最终将被改进成拥有由16个自动可重构子孔径组成的电控相控阵，5个独立的接收通道和大约1．8GHz的总信号带宽。这种传感器叫做PAMIR(多功能相控阵成像雷达)。着重用实例说明远距离超高分辨率SAR成像。借助于地面动目标的逆SAR(ISAR)成像也能实现高分辨率。而且，通过空时自适应信号处理和超高3一D分辨率单向干涉SAR(IfSAR)，接收通道的数目将提供地面动目标指示(GMTI)。在一个接收通道和机械控制天线阵列的情况下，PAMIR在其现行发展阶段中是切实可行的。文章介绍了PAMIR的系统设计和预期能力，并提供了高分辨率SAR及ISAR成像的地面及机载实验结果。