无动量干扰的高效率数控扫描系统

无动量干扰的高效率数控扫描系统是环境和灾害监测与预报小卫星红外相机的重要组成部分。文章介绍了这种扫描系统的硬件设计和软件设计。     

首颗自主地月转移微卫星“龙江二号”

本文对世界首颗独立完成地月转移、近月制动、环月飞行的微卫星“龙江二号”进行了介绍。首先阐述了龙江二号的任务目标和总体方案；然后重点分析了轨道设计与控制、复杂电磁干扰的标定与抑制、宽视场三维基线干涉测量等关键技术难点；接着回顾了任务的实施过程；最后详细介绍了低频射电探测仪、沙特光学相机和VHF/UHF通信模块与学生微型CMOS相机等有效载荷，并展示了上述载荷获取的初步成果。     

A residual based adaptive unscented Kalman filter for fault recovery in attitude determination system of microsatellites

This paper presents an adaptive unscented Kalman filter (AUKF) to recover the satellite attitude in a fault detection and diagnosis (FDD) subsystem of microsatellites. The FDD subsystem includes a filter and an estimator with residual generators, hypothesis tests for fault detections and a reference logic table for fault isolations and fault recovery. The recovery process is based on the monitoring of mean and variance values of each attitude sensor behaviors from residual vectors. In the case of normal work, the residual vectors should be in the form of Gaussian white noise with zero mean and fixed variance. When the hypothesis tests for the residual vectors detect something unusual by comparing the mean and variance values with dynamic thresholds, the AUKF with real-time updated measurement noise covariance matrix will be used to recover the sensor faults. The scheme developed in this paper resolves the problem of the heavy and complex calculations during residual generations and therefore the delay in the isolation process is reduced. The numerical simulations for TSUBAME, a demonstration microsatellite of Tokyo Institute of Technology, are conducted and analyzed to demonstrate the working of the AUKF and FDD subsystem.     

失效航天器姿态接管的SDRE微分博弈控制

针对燃料耗尽的失效航天器姿态接管控制问题，提出多颗微卫星协同实现姿态稳定的状态相关黎卡提方程(SDRE)微分博弈控制方法。首先，将姿态接管问题转化为多颗微卫星的微分博弈问题，基于组合航天器的姿态模型和微卫星的性能指标函数建立多颗微卫星的非线性微分博弈模型，微卫星通过独立优化各自的性能指标函数得到控制策略。其次，引入状态相关系数矩阵，将非线性博弈转化为状态相关线性二次型博弈，采用SDRE方法更方便地逼近微卫星的博弈均衡策略。最终通过李雅普诺夫迭代法求解耦合状态相关黎卡提方程组得到微卫星的状态反馈控制器，实现微卫星的自主决策。数值仿真验证了多颗微卫星采用微分博弈控制方法实现姿态接管的有效性和容错性。     

电磁超材料在超宽带雷达隐身微小卫星设计中的应用

针对微小卫星在雷达频段面临的宽带隐身问题,提出利用电磁超材料实现卫星隐身的设计方案,该方案包括两种不同类型的电磁超材料雷达吸波体。其中多层结构超宽带吸波体利用高阻表面设计耦合型吸波结构,适用于微小卫星星体及太阳能电池阵背光面,工作频带覆盖S、C、X、Ku频段;透光型混合结构宽带吸波体利用高透光的氧化铟锡设计吸波结构,适用于卫星电池阵受光面,隐身频带覆盖X、Ku频段。样件及整星的仿真和实验结果表明,电磁超材料构建的雷达吸波体可以实现超宽频带电磁波的有效吸收。将该材料应用于微小卫星的设计中,可以达到卫星整星RCS缩减的目的。该材料不论是机械强度、密度、透光性,还是抗原子氧剥蚀能力都具备潜在的工程应用价值。     

基于重力梯度杆和磁铁的小卫星三轴姿态控制

运用卫星低轨道两个主要环境力矩（重力梯度矩和地磁力矩）对圆轨道卫星三轴姿态进行被动控制。利用重力梯度矩实现卫星对地指向：卫星上的永久磁铁获取所需的地磁力矩,稳定偏航姿态。给出卫星的姿态分析,并给出仿真结果。从分析和仿真结果可以看出,此卫星具有结构简单、时刻对地定向、低轨道倾角时卫星姿态稳定精度较高的优点。     

基于视线测量的卫星编队机动控制方法

采用视线测量的方法,建立一种编队卫星队形保持与机动的协同控制策略。编队中每一个卫星跟踪自己轨道前方邻近卫星,产生一个视线测量矢量,编队的第一个卫星根据高级控制层指令追踪期望轨道,产生链式编队,将编队卫星之间的视线距离作为反馈控制量来实现队形控制。通过推导J2相对摄动力的表达式,控制模型考虑了模型不确定性和摄动影响,采用滑模控制器,实现了基于视线测量的编队卫星链式跟踪协同控制。仿真算例结果表明,该方法在实现编队卫星队形保持与整体机动控制上具有可行性。     

IONOSAT – Ionospheric satellite cluster

The IONOSAT project (from IONOspheric SATellites) is proposed by National Space Agency of Ukraine for First European Space Program as a part of Space Weather (SW) Program. As it is commonly accepted, Space Weather means the changes of the conditions on the Sun, in solar wind, magnetosphere and ionosphere which may affect the operation and reliability of on-board and ground technological systems and threaten human health. In this chain ionosphere is specific and integral part of SW formation. Moreover, namely in the ionosphere main part of the energy absorption of Sun-activated sporadic corpuscular and radiation fluxes takes places. The excitation of ionosphere by falling fluxes produces its “luminescence” in wide frequency band – from ULF waves till ultraviolet – and by this ionosphere works as an efficient “screen” or SW indicator.A goal of the proposed project is long-term spatial–temporal monitoring of main field and plasma parameters of ionosphere with aim to further develop fundamental conceptions of solar-terrestrial connections physics, nowcasting and forecast of SW, and diagnostics of natural and technogenic hazards with the help of scientific payload installed on-board a cluster of 3 low-Earth orbit (LEO) microsatellites (tentative launch date – 2012 year).The state of the project proposal and realization plans are discussed.     

SMESE: A SMall Explorer for Solar Eruptions

The SMall Explorer for Solar Eruptions (SMESE) mission is a microsatellite proposed by France and China. The payload of SMESE consists of three packages: LYOT (a Lyman imager and a Lyman coronagraph), DESIR (an Infra-Red Telescope working at 35–80 and 100–250 μm), and HEBS (a High-Energy Burst Spectrometer working in X- and γ-rays).

The status of research on flares and coronal mass ejections is briefly reviewed in the context of on-going missions such as SOHO, TRACE and RHESSI. The scientific objectives and the profile of the mission are described. With a launch around 2012–2013, SMESE will provide a unique tool for detecting and understanding eruptions (flares and coronal mass ejections) close to the maximum phase of activity.     

微小卫星多约束姿态机动规划方法

针对微小卫星姿态控制中存在的多重指向约束和角速率约束问题，提出一种基于对数型势函数的多约束姿态机动规划方法。首先针对微小卫星携带的光学传感器需躲避强光天体而天线需指向地面保证对地通信这一约束特性，采用对数型势函数方法保证约束姿态指向满足任务要求;其次，针对姿态角速率限制的问题，引入障碍Lyapunov函数确保姿态角速率始终处于约束范围内。与在线优化方法相比，该方法具有计算量小的显著优势，非常适合星上处理能力有限的微小卫星。此外，考虑外界干扰力矩的影响，引入自适应干扰估计律，增强了控制系统的鲁棒性。最后，通过数学仿真对本文方法进行了校验，仿真结果表明，该方法能够快速实现卫星姿态机动到期望指向，与此同时，在整个姿态机动过程中，均满足多重指向约束和姿态角速率约束 要求 。