欧洲空间操作中心的精密轨道确定

目前,欧洲空间操作中心正在进行着一项需4年时间的开发计划,以支持未来的需要高精度轨道确定的ESA近地飞行任务。该工作是围绕着欧洲空间操作中心已开发的供轨道确定和误差分析用的一个软件系统进行的,该软件含有适合于各种轨道摄动和测量类型的先进模型。除了卫星轨道参数外,它还能对地球物理参数和测地参数进行估计和误差分析。     

广角目视模拟技术的新评价

前言1970年召开了两次飞行模拟技术会议(AIAA 于三月在佛里罗达州卡纳维拉尔角召开,RAES 于十月在英国伦敦召开),但对广角目视模拟技术没有作出客观的评价。在1967年第二届海军训练装置中心和工业会议、1968年3月于洛杉矶召开的 AIAA 会议上,威廉、埃贝林提供了对窄视场目视系统的简要评述。     

Pre-adaptation to shiftwork in space

Astronauts are often required to work in shift schedules. To test pre-mission adaptation strategies and effects on the circadian system, a study was performed using microgravity simulation by head-down bedrest. Eight male subjects were studied over 4 control days, and 7 days each for pre-mission adaptation, bedrest, and readjustment. The circadian system was assessed by monitoring ECG and temperature, and by collecting urine for determination of hormones and electrolytes. Rhythms did not achieve complete adjustment within the adaptation period when the sleep-wake cycle was shortened by 1 h/day, but resynchronization continued during bedrest. After the bedrest period when the time shift was reversed by a 7-h delay within 2 days, resynchronization was achieved satisfactorily only within 7 days. From the results it is concluded that a sleep-wake cycle advance as used in this study is insufficient to keep the circadian system in pace. Under operational conditions the circadian system of astronauts may become longer and more destabilized than under controlled laboratory conditions.     

下一代数字式GPS接收机

讨论由 collins 公司制造的下一代(NGR)数字化 GPS 接收机的结构和技术特点。该计划的目的是开发一种具有较高抗干扰能力的高级 GPS 接收机单片设备(chipset)。计划始于1985年,为不载人和载人飞行器提供小型化接收机技术。目前用于战术导弹的两通道接收机的研制工作已全面开展,用来替换标准高动态接收机 RCVR-3A 型的五通道接收机正在测试和评估中。NGR 设计是从国防高级研究计划机构(DARPA)开发手提式 GPS 接收机使用的数字信号处理体系结构入手的,改进后可提高抗干扰和信号捕获性能。使用可生产、合格及便宜的硅单片微波集成电路(MMIC)和半商品化的数字技术开发 GPS 核心单片设备。另外,所采用的系统设计方法允许重复使用成熟的和确认过的 GPS 软件。     

用于SAR、GMTI和海上监视的X波段宽带试验机载雷达

加拿大渥太华的防务研究和发展部门已完成了一种新型多模X波段宽带试验机载雷达（XWEAR）第一阶段的研制工作，这是对合成孔径雷达（SAR）成像、逆合成孔径雷达（ISAR）、地面动目标显示（GMTI）雷达和海上监视雷达的支持研究，特别集中在对小型目标的探测和远距离的面上目标监视。特别关注的领域有：静止和运动目标的SAR成像技术、海上和陆地动目标的时间一频率分析、用于GMTI的空时自适应处理、对海面电磁后向散射特性的研究、自动目标识别和特征提取的特征产生、以及宽带系统对付电子干扰的抗干扰性分析。第一阶段是以SAR和海上监视模式的飞行试验结束的。第二阶段将进行大范围监视GMTI（WASGMTI）和综合SAR-GMTI模式的飞行试验。简述了试验雷达并介绍了它的数据采集能力。区别特征包括X波段的运行、SAR和海上监视的单通道运行以及WAS-GMTI和综合SAR-GMTI的双通道运行。该新型雷达将现有的数字扫描转换器的用途扩大为控制器，已有的商用元件有：发射机、A／D转换器和计算机电路板。定时电路、波形产生器、单通道和双通道的接收机可以按用户需要定制。     

白沙导弹靶场的相差跟踪测量系统

这种相差测量系统(PDM)是一种射频干涉仪目标跟踪系统,它利用目标所辐射的遥测功率谱进行跟踪。为了增强靶场测量系统现有位置测量的能力,白沙导弹靶场正在自行研制一种PDM系统,作为高机动电子测角系统。该系统由二个远距离数据获取站(RDAS)和一个余弦数据变换设备(CCF)组成。每一个远距离数据获取站由二个正交基线配置的天线阵组成。对远距离数据获取站的硬设备利用了高速射频时分转换开关,以减少远站产生方向余弦所需的硬设备量。方向余弦变换设备收集每个远距离数据获取站的二个方向余弦,然后把方向余弦转换成位置数据,接着传输到靶场控制中心。本文将给出该系统的基本原理,叙述所提出的天线射频切换技术,以及两天线对组成的基线的计算机仿真分析。     

军用靶场在航天运输系统任务中的实际应用

军用靶场历来服务于武器和武器系统性能的鉴定以及改进其设计。可那些已经卷入飞行和大气层外活动的靶场也已经具备了保障正在进行的航天和导弹计划的实际能力。本文阐述了军用靶场保障航天运输系统的能力和一些具体的保障工作。主要着重于C波段雷达跟踪和数据流程,而不是较为熟悉的靶场保障问题。     

减少数字遥测数据中噪声的数值滤波技术

本文介绍了几种事后数值滤波技术。在数字遥测数据用于自动化计算机数据分析以前,利用这些技术减少或/和消除数字遥测数据中的噪声。这种遥测数据噪声来源于遥测载波信号过小或完全丢失,引起接收的脉码调制(PCM)数据出错。剔除错误的采样数据是事后分析中一项特别重要的工作,因为被污染数据可能给自动化计算机事后数据分析过程造成错误或偏差。当这些错误在最终换算后的数据中常接近测量值的上限或下限(数据跳点),很容易从采样数据中滤除。数据噪声偶尔表现为比较小的、不明显的波动,则分析员只有从图形(而不是数表)才能看出有噪声。因此,这类噪声更难于数字滤波。通常,采用手工噪声剔除或平滑,其结果变化较大。其主要缺点是:对现今的高采样率数字系统,采样数据量很大,因而耗时过大。另外,任何一种手工滤波总是对操作员依赖性很大。对错误采样数据的检测和识别显然是数据滤波中最困难的一步。我们已研究出几种识别方法,并在消除和平滑技术以前先加以详细介绍。研究了这些方法的技术局限性,对此也作了介绍。最后,对每种方法用图形绘出滤波处理前后的几组数据例子。     

OPTICAL TELEPHONE CORD PASSING THROUGH LONG PIPE WITH SPIRAL FLOW

A new effective technique, useful in telecommunications industry for passing an optical telephone cord attached to a connector through pipeline,has been developed using the spiral flow. Using this technique, the cord could be passed through a straight pipeline 150 meters long and a roll of vinyl tube 50 meters long. However, under the same condition, the cord could not pass through when using the turbulent flow. To obtain a high speed stable spiral flow, a nozzle with an annular slit connected to a conical cylinder was used. A pressurized fluid with no tangential flow was supplied through this slit and the fluid, passing through the conical cylinder, was deformed into spiral flow with the steeper axial velocity distribution compared to that of turbulence pipe flow due to Coanda effect and instability. As a result, the cord was attracted to the axis area of the pipe, which effectively increased the ability for the work of cord passing. This high ability for cord passing is attributed mainly to the reduct     

STRATOSPHERIC LIGHTER-THAN-AIR POWERED PLATFORM

A feasibility study has been carried out on a high altitude (20km) superpressurcd PLTA(powered lighter-than-air) platform, which has a long service life and larger payload than that of a large artificial satellite. This PLTA platform has an electric propulsion system to cope with wind flow for position keeping and its thruster is driven by solar power acquired through solar cells. Solar energy is to be stored for night use in regenerative fuel cells. The study is focused on energy balance and hull structure analysis of the platform. This platform is particularly capable of conducting high resolution remote sensing and telecommunications relay. This platform can replace a number of ground-based telecommunications relay facilities and can guarantee reasonable radio frequency intensity enough to secure good telecommunications quality. The altitude where the platform resides is the least windy area in the lower stratosphere at a height from which one can have a direct line of sight on the ground within a 1,