Rician衰落信道下Turbo码性能分析

文中研究了Rician信道下Turbo码的性能,并详细推导Turbo码在Rician信道下的误码率上界的表达 式,最后对Rician信道的主要参数对译码性能的影响作了仿真。     

Will space run out of space? The orbital debris problem and its mitigation

An appraisal of current and future risks from space debris is presented with the aid of calculations carried out by the MASTER model. The efficacy of various technical options -- such as fuel venting, de-orbiting and use of a graveyard orbit -- for counteracting the problem is discussed. The article then focuses on governmental and international cooperative measures and looks at the recent work done by subcommittees of the UN COPUOS.     

载人航天器的再入与回收

文中主要概述了美国载人飞船回收技术的发展,介绍了保证载人飞船安全返回着陆的方法、采用的回收控制技术、地面对再入返回段的测控支持、载人飞船的回收作业、载人飞船的应急返回和回收救援等技术问题。     

苏联(俄罗斯)载人航天器的发展史实

介绍了苏联（俄罗斯）各种载人航天器的研制、试验和使用情况。     

International cooperation and competition in civilian space activities

This article considers how the USA can best maintain its commercial and governmental competitiveness in space, while facilitating private investment and international marketing, and at the same time keeping up significant cooperation with other nations. The current state of US civilian space activities in each of these areas is summarized, and several alternative solutions are presented. The article concludes that strengthening US competition with other space-capable nations, and improving US ability to cooperate effectively, will require careful coordination of the activities of federal agencies with each other and with the private sector.     

Arms control and disarmament in space: the rough road to Vienna 1984: Part I

This article examines the international legal and diplomatic questions relating to arms control and disarmament, focusing on space-based activities. These relate importantly to the development of anti-satellite satellites (ASATs) and ballistic missile defence systems (BMDs). Part I of the article examines the goal of ‘peaceful uses’ of outer space as elaborated in national policies and in international fora, the debate that has has taken place at the international level over the meaning and definition of peaceful purposes, legal manoeuvres, particularly in the UN, and US responses, and recent Soviet initiatives relating to space militarization. Part II will appear in the next issue, and will consider the US Presidential-Congressional dialogue on these questions and recent Presidential initiatives.     

推进剂稳态燃速最优化辨识

考虑侵蚀燃烧对推进剂稳态燃速的影响,将推进剂稳态燃速模型参数辨识问题转化为非线性规划问题求解。采用Powell方法和并行遗传算法组成的混合优化方法,提高了非线性规划问题求解的效率和质量,得到了推进剂稳态燃速模型参数的全局最优辨识值。通过对设计空间的可视化进行优化收敛过程的参数分析,近似得到侵蚀燃烧模型参数的不确定性区间。     

行星际空间环境对探测器可靠性影响分析

空间环境是影响航天器可靠性的重要因素。与地球轨道航天器相比,行星际探测任务可能会遭受更加恶劣的空间环境,例如极端温度环境,辐射环境,腐蚀性大气环境、宇宙尘等,再加上行星际任务寿命长,采用先进的器件和材料,空间环境对行星际探测器的可靠性构成严重的威胁,直接关系到探测目标能否实现。因此考虑空间环境对行星际探测器的影响,开展相关的预先研究无论是对于制定行星际空间探测计划,还是搭载仪器的设计都具有非常重要的意义。文章分析了极端温度、辐射环境和行星表面综合环境对探测器的影响,并对开展相关研究提出了建议。     

GPS接收机中码相位测量精化方法的研究

精确的码相位测量是保证GPS接收机得到精确伪距值进而进行精确定位的一个重要前提。在已有码相位测量精化方法的基础之上提出了两种新的码相位测量精化的方法,讲述了两种方法的原理与具体实现方法,并利用蒙特卡洛方法进行了仿真实验,得到了码相位结果均值、码相位结果均值方差等一系列实验结果,对几种方法的精化效果从精确性、稳定性和跟踪性能等几个方面进行了比较分析,得出了相应的结论。与三角匹配法和二次曲线插值精化法相比,二阶最小二乘拟合精化法和广义延拓逼近精化法有明显优势;广义延拓逼近精化法的精化精度最高、跟踪精度最高,而二阶最小二乘拟合精化法的稳定性最好。     

随机二相码调相PD引信的距离旁瓣抑制

随机二相码调相ＰＤ（脉冲多普勒）引信，是一种较为新颖的噪声调制引信体制。因距离旁瓣的存在会使该体制引信产生概率性的距离模糊，首先分析了其独特的距离旁瓣特性，然后分析了相关器组法进行距离旁瓣抑制的机理和性能，并提出了以限制码的最大游程加惯性积累电路来抑制的方法。分析表明，两者都能对距离旁瓣进行有效的抑制，而后者更适合于引信电路的特点。