Markov chain Monte Carlo methods for high dimensional inversion in remote sensing

Summary.  We discuss the inversion of the gas profiles (ozone, NO₃, NO₂, aerosols and neutral density) in the upper atmosphere from the spectral occultation measurements. The data are produced by the 'Global ozone monitoring of occultation of stars' instrument on board the Envisat satellite that was launched in March 2002. The instrument measures the attenuation of light spectra at various horizontal paths from about 100 km down to 10–20 km. The new feature is that these data allow the inversion of the gas concentration height profiles. A short introduction is given to the present operational data management procedure with examples of the first real data inversion. Several solution options for a more comprehensive statistical inversion are presented. A direct inversion leads to a non-linear model with hundreds of parameters to be estimated. The problem is solved with an adaptive single-step Markov chain Monte Carlo algorithm. Another approach is to divide the problem into several non-linear smaller dimensional problems, to run parallel adaptive Markov chain Monte Carlo chains for them and to solve the gas profiles in repetitive linear steps. The effect of grid size is discussed, and we present how the prior regularization takes the grid size into account in a way that effectively leads to a grid-independent inversion.     

宽带卫星通信和星际链路间激光通信的应用前景

提出了由于信息化社会、Ｉｎｔｅｒｎｅｔ、Ｉｎｔｒａｎｅｔ和多媒体技术的出现,从而要求卫星通信向多体制、多功能发展。文中着重分析了具有独特优点的激光通信在宽带卫星通信和星际链路中的现实商用前景。     

卫星光通信关键技术与演示系统光学天线

针对卫星间光通信链路需求,分析了卫星间激光通信系统关键技术分布。介绍具有自动跟瞄功能的激光通信系统光学天线构成方式,对主要性能参数进行了设计和计算。     

Television and the making of a transnational Alevi identity

ABSTRACT

Satellite broadcasting technologies contribute a great deal to interaction across national boundaries, and in this regard satellite television is significant in the construction of a transnational public sphere for the Alevi community in Turkey and abroad. This paper addresses the role of television in the making of that transnational Alevi identity. In particular, it focuses on the flow and the programme contents of Cem TV and Yol TV, two leading Alevi channels, to demonstrate how the transnational imagination of Alevi identity corresponds to different political understandings of Aleviness.     

小卫星项目的法律适用和发展趋势

具有高功能密度的小卫星项目蓬勃发展，大大增强了私营实体和非航天大国参与空间活动的能力，引发了规则修订的需求。国家应建立空间活动的分级、分类许可条件，放宽小卫星行业的准入要求，并根据小卫星项目的目的、成本、收益和风险来设定第三者责任保险要求，规范小卫星的登记实践。空间碎片减缓应作为小卫星项目许可条件之一，以切实履行国家的外空环境保护责任。应简化国际电信联盟卫星频率和轨道位置协调程序，建立适应小卫星轨道特性、运行寿命和业务类型的管理规则。     

GOES-8 X-ray sensor variance stabilization using the multiscale data-driven Haar–Fisz transform

Summary.  We consider the stochastic mechanisms behind the data that were collected by the solar X-ray sensor (XRS) on board the GOES-8 satellite. We discover and justify a non-trivial mean–variance relationship within the XRS data. Transforming such data so that their variance is stable and its distribution is taken closer to the Gaussian distribution is the aim of many techniques (e.g. Anscombe and Box–Cox). Recently, new techniques based on the Haar–Fisz transform have been introduced that use a multiscale method to transform and stabilize data with a known mean–variance relationship. In many practical cases, such as the XRS data, the variance of the data can be assumed to increase with the mean, but other characteristics of the distribution are unknown. We introduce a method, the data-driven Haar–Fisz transform, which uses the Haar–Fisz transform but also estimates the mean–variance relationship. For known noise distributions, the data-driven Haar–Fisz transform is shown to be competitive with the fixed Haar–Fisz methods. We show how our data-driven Haar–Fisz transform method denoises the XRS series where other existing methods fail.     

低轨卫星移动通信系统馈电链路切换方案

研究了无星际链路低轨卫星移动通信系统中的馈电链路的切换问题,提出了两种馈电切换方案-最短馈电链路切换方案和最长可视时间切换方案。结合两种已有的用户链路切换准则,在构造的非均匀分布全国话务密度模型上进行了系统仿真。仿真结果表明馈电链路切换方案对系统开销影响较大,选择最长可视时间馈电链路切换方案,可以减少切换带来的信令开销,提高服务质量,具有较高的参考和实用价值。     

卫星信道基带残留误码分布特性拟合与模拟

卫星通信信道的基带残留误码特性直接影响上层通信协议的性能。通过对卫星通信系统仿真,提取基带误码图案,将基带误码分布图案通过误码持续期发生概率密度分布、误码持续期长度概率密度分布来表征。在典型的卫星通信系统参数条件下,拟合表明经过有噪莱斯衰落信道的误码持续期发生概率接近广义极值分布;经过高斯噪声信道的误码持续期发生概率密度、误码持续期长度概率密度接近负二项式分布。在此基础上完成的卫星基带信道硬件模拟器能够为通信协议的测试提供方便、可信的信道基带特性模拟。     

“村村通”广电建设中存在的问题与对策研究

国家对基层广电事业提出了确保"村村通"长期通的新目标,但由于西部基层广电事业自身固有的问题以及在"村村通"建设中产生的新矛盾,完成艰巨任务存在很大困难.而且西部基层广电事业原有的资源条件和经营环境受挤严重,旧的发展方式力不从心,困局渐显.政府主导、行业直管、整合资源、纵深开发是西部基层广电事业改革发展,建立"村村通"长效机制的关键性策略.     

卫星遥感数据法庭可证据性法律问题研究

卫星遥感数据相比传统证据采集方式存在优越性,近些年也频繁地被国际和国内法庭争端当事方用作证据。法庭在是否采信的问题上立场不一,国际法院在涉及领土主权争端案件中对其较为排斥,国际刑事法院、欧盟法院和部分国家国内法院在涉及特定事项时态度较为肯定和积极。原因和卫星遥感数据本身的特质有关,在有着无可比拟优势的同时,其作为证据仍存在个人隐私权保护、知识产权保护、数据的可获得性以及专家证词真实性等问题。卫星遥感数据法庭可证据性问题集中体现了科技与法律之间相互促进和矛盾性,国际社会目前立法仍为空白,国际和地区实践处于分而治之的局面。