风神卫星

正耗资5.5亿美元、历时16年打造、世界上第一颗全面监测全球风况的气象卫星——风神(Aeolus),于北京时间8月23日发射成功,主要用来监测、绘制全球风速风向等风况。风神卫星质量为1260kg,携带一部大型望远镜、一部超灵敏接收器和一款昵称"阿拉丁"(ALADIN)的多普勒测风激光雷达。风神手提"阿拉丁神灯",一天24小时全年无休监视地球风,利用1.5m口径的激光雷达系统,发射紫外线波段激光脉冲,收集散射到大气层(20～30km以下)光粒子,测量光波多普勒效应,由此确定风速、风向、风力等。风神卫星运行在320km     

加拿大雷达星-2的分辨率将达3米

在雷达星-1投入运行3年后,加拿大计划研制下一颗雷达成像卫星—雷达星-2,预计2001年底发射。主承包商为MDA公司。雷达星-2由轨道科学公司的平台和Spar宇航公司的合成孔径雷成构成,天线尺寸15m×1.5m。卫星重2.5 t,平均功率1 kW,峰值功率3 kW(只可持续18 min)。雷达采用电子扫描,工作频率5.3 GHz,按几种方式,分辨率可达3 m～100 m,成像面积为25 km~2～500 km~2,视场10～60°,扫描场1600 km。由于装有640片收/发     

路径积分差分吸收激光雷达反演模型设计与测试

激光雷达作为主动探测手段,能够较好地弥补被动卫星(如OCO-2/3、GOSAT-1/2和Tan Sat等)的不足,实现高精度、全天候和全天时的观测。中国在2022年4月16日成功发射世界首颗基于主动理论探测二氧化碳柱浓度(XCO2)的激光雷达卫星。本文基于前期在秦皇岛的缩比飞行试验数据,围绕优化积分权重函数和优化差分吸收光学厚度两大核心要素,提出了基于光谱能量模型的算法框架。该框架旨在提高基于主动理论的星载激光雷达探测XCO2反演的精度。评估获得光谱能量模型在海上、陆地上的测距精度分别为0.74和6.20 m。论文的工作在10 s滑动平均值下,海洋、城市和山区的平均XCO2值分别为411.07、425.71、417.87 ppm,标准差分别为1.93、0.85、0.96 ppm。综上所述,光谱能量模型对我国发展基于差分吸收激光雷达的二氧化碳浓度算法具有重要的参考意义。     

飞行试验遥测地面站(FTTGS)方案和 QUAD 7系统(上)

飞行试验遥测地面站(FTTGS)由 SNEC 遥测接收子系统;QUAD7实时数据采集/处理子系统和 VAX4300主计算机子系统三大部分组成。遥测接收子系统包括 S 波段自动跟踪天线2通道接收机全向天线,校准天线等众多部件,跟踪速≥30°/s。瞄准精度≤0.1°,工作风速达100km/h;VAX4300计算机系统提供了8VUPS的 CPU 性能。最大主存容量为224MB,最大海量存贮器容量为28GB,I/O 吞吐量高达11.2MB/S;QUAD 7子系统是一个先进的,高性能的数据采集/处理系统,能采集、处理、分配 PCM、PCM-1553、MIL-STD-1553,并行数字,数字离散量和模似量等各类数据,能模拟和监视数据流,能提高可编程的处理,快速建库、编辑动态数据库。文中对各子系统的结构、工作方式、技术规范和有关问题作了介绍,附结构图2幅。列出了有关数据。     

一种大型相控阵雷达外场高精度相位校正方法

针对大型相控阵雷达外场相位校正受风影响无法保证校正精度的难题,本文提出了一种外场高精度相位分级校正方法。采用激光标定法测量标校源风载条件下的晃动曲线和最大晃动速度,根据雷达工作频段及校正精度要求,计算出标校源最大晃动速度条件下的最小保精度校正时间,以最小保精度校正时间作为分级子阵规模划分的依据,通过多级校正完成全阵外场校正。仿真测试结果表明:在5级风载条件下,X波段相位校正精度均方根小于5.8°,最大栅瓣电平降低了9 dB,达到模拟移相器可以实现的精度要求。     

基于航迹关联的抗角闪烁跟踪算法研究

角闪烁背景下，高分辨雷达在近距离跟踪阶段存在不能精确跟踪的问题。针对此问题，分析了基于距离高分辨的单脉冲测角方法，并在此基础上，结合距离向强散射点的幅度特征，提出了一种基于航迹关联的抗角闪烁跟踪算法。算法首先对和通道、方位差通道、俯仰差通道的回波信号分别进行脉压和相参积累；然后在和通道的高分辨一维距离向上实现目标强散射点的检测，依据幅度进行排序并输出各点的距离信息和角度信息；最后利用联合集成概率数据互联算法作为目标跟踪滤波算法进行跟踪。本文通过对ku波段实测数据中入射余角为60°~69°的近距离跟踪部分进行分析，将所提算法与卡尔曼滤波跟踪算法进行了对比，仿真结果表明，本文算法使多目标跟踪的精度得到了提高，具有更好的角闪烁抑制性能。     

回收过程中高空风场的特点及描述

风场对航天器的发射、飞行及落点的影响不可忽略。文章针对回收过程的中高空风场主要因素的基本概念及特点进行了简单综述 ,并阐述了如何用综合风剖面法对回收过程中高空风场进行描述 ,同时给出了中国北方某地区风的测量数据的一些主要统计特性     

风场对舱-伞系统着陆姿态影响的仿真研究

风场对舱-伞系统的落点及姿态稳定性存在不可忽略的影响。文章对某型号飞船在几种不同风场条件下的回收过程进行了仿真研究,着重分析了风对返回舱各项参数的影响,所得结论对回收系统设计具有重要的参考价值。     

翼型伞气动特性风洞试验研究

文章介绍了在8m×6m低速风洞中对某冲压式翼型伞进行的试验研究。文中给出了有关的技术方法,并对典型的试验结果进行了讨论。这一国内首创的风洞试验技术,可为翼型伞设计提供利用其他试验手段难以得到的翼伞操稳特性气动参数。     

风切变与运载火箭设计

本文介绍包括风切变在内的高空风场的统计分析方法以及它在运载火箭设计中的应用。其中综合矢量风剖面是运载火箭设计通用的规范性方法。风场的应用涉及运载火箭姿态控制系统设计、制导精度分析和载荷分析计算等多方面的工作。这里简述其应用要点。     

大型火箭风载试验

全面叙述大型火箭风载试验的各种问题，指出在风载设计中增强火箭原型结构的靶场风载试验和高空风载试验的重要性。     

Algebra and statistics of the solar wind

Statistical studies of properties of the solar wind and interplanetary magnetic field, based on an extended database for the period 1963–2007 including four solar cycles, show that the Gaussian approximation well suites for some parameters as the probability distribution of their numerical values, while for others the lognormal law is preferred. This paper gives an interpretation of these results as associated with predominance of linear or nonlinear processes in composition and interaction of various disturbances and irregularities propagating and originating in the interior of the Sun and its atmosphere, including the solar corona and the solar wind running away from it. Summation of independent random components of disturbances leads, according to the central limit theorem of the probability theory, to the normal (Gaussian) distributions of quantities proper, while their multiplication leads to the normal distributions of logarithms. Thus, one can discuss the algebra of events and associate observed statistical distinctions with one or another process of formation of irregularities in the solar wind. Among them there are impossible events (having null probability) and reliable events (occurring with 100% probability). For better understanding of the relationship between algebra and statistics of events in the solar wind further investigations are necessary.     

翼伞归航准则及测风原理探讨

翼伞作为一种新型气动力减速器日渐受到空间回收技术重视。文中给出了具有非比例自动归航控制的翼伞系统的归航准则(考虑到风的影响)以及利用GPS测量数据计算风场的公式。     

Optimal nodal flyby with near-Earth asteroids using electric sail

The aim of this paper is to quantify the performance of an Electric Solar Wind Sail for accomplishing flyby missions toward one of the two orbital nodes of a near-Earth asteroid. Assuming a simplified, two-dimensional mission scenario, a preliminary mission analysis has been conducted involving the whole known population of those asteroids at the beginning of the 2013 year. The analysis of each mission scenario has been performed within an optimal framework, by calculating the minimum-time trajectory required to reach each orbital node of the target asteroid. A considerable amount of simulation data have been collected, using the spacecraft characteristic acceleration as a parameter to quantify the Electric Solar Wind Sail propulsive performance. The minimum time trajectory exhibits a different structure, which may or may not include a solar wind assist maneuver, depending both on the Sun-node distance and the value of the spacecraft characteristic acceleration. Simulations show that over 60% of near-Earth asteroids can be reached with a total mission time less than 100 days, whereas the entire population can be reached in less than 10 months with a spacecraft characteristic acceleration of 1 mm/s².     

Evolution of salt finger convection with steady wind shear

In oceanographics situations where salt fingers may be an important mechanism for the transport of heat and salt in the vertical direction, velocity shears may also be present. Salt finger convection is analogous to Bénard convection in that the kinetic energy of the motions is obtained from the potential energy stored in the unstable distribution of a stratifying component. On the basis of the thermal analogy it is of interest to discover whether salt fingers are converted into two-dimensional sheets by wind shear, and how the vertical fluxes of heat and salt are changed by wind shear. Salt finger convection under the effect of steady wind shear is theoretically examined in this paper. The evolution of instability developing in the presence of a vertical density gradient disturbance and the horizontal Couette flow is considered near the onset of salt fingers under a moderate rate of shear. We use velocity as the basic variable and solve the pressure Poisson equation in terms of the associated Green function. Growth competition between the longitudinal rolls (LR) and the transverse rolls (TR), whose axes are, respectively, in the direction parallel to and perpendicular to the Couette flow, is investigated by the weakly nonlinear analysis of coupled-mode equations. The results show that the TR mode is stable under a small wind shear and the LR mode is stable for a higher wind shear.