椭圆轨道非线性相对运动模型的周期解与应用

在长期的航天器编队飞行中传统的基于线性相对运动模型设计编队保持轨道的方法会引起较多的燃料消耗.首先采用摄动法解析地求得了考虑二阶非线性项时椭圆轨道相对运动模型的周期性条件和周期解;然后以此周期解为参考轨道设计了基于Lyapunov稳定的PD保持控制律.仿真结果表明:基于椭圆轨道非线性相对运动模型的周期解较基于椭圆轨道线性相对运动模型的周期解,精度明显提高;以前者为参考轨道的保持控制与以后者为参考轨道的保持控制相比,燃耗明显降低.     

深空探测中多普勒的建模与应用

针对深空探测中的多普勒观测资料的单程和三程模式,分别给出了瞬时和积分的观测模型,双程多普勒观测模型是三程模式的一个特殊情况.通过比较瞬时和积分多普勒的差异,推断在积分周期取得足够小时,瞬时观测模型与积分模型是一致的.利用2009年8月份对火星探测器MEX的三程多普勒测轨资料的处理,检验了三程多普勒资料观测模型的正确性,利用约一个圈次8小时三程多普勒数据进行轨道计算,定轨结果与欧空局重建轨道位置差约几百米.     

周向总压畸变条件下多级轴流压气机失速首发级预测分析

基于多级轴流压气机的逐级特性,发展了1种预测周向总压畸变条件下多级轴流压气机失速首发级的方法。该方法结合平行压气机模型和级叠加计算方法,以进气畸变条件下多级轴流压气机某级的有效相对气流角达到稳定状态时该级的最大相对气流角为条件,进行多级轴流压气机失速首发级的预测分析。通过对J85—13发动机8级轴流压气机总压畸变试验数据进行模拟计算,预测出该轴流压气机畸变条件下的失速首发级。     

Feasibility of performing space surveillance tasks with a proposed space-based optical architecture

Under ESA contract an industrial consortium including Aboa Space Research Oy (ASRO), the Astronomical Institute of the University of Bern (AIUB), and the Dutch National Aerospace Laboratory (NLR), proposed the observation concept, developed a suitable sensor architecture, and assessed the performance of a space-based optical (SBO) telescope in 2005. The goal of the SBO study was to analyse how the existing knowledge gap in the space debris population in the millimetre and centimetre regime may be closed by means of a passive optical instrument. The SBO instrument was requested to provide statistical information on the space debris population in terms of number of objects and size distribution. The SBO instrument was considered to be a cost-efficient with 20 cm aperture and 6° field-of-view and having flexible integration requirements. It should be possible to integrate the SBO instrument easily as a secondary payload on satellites launched into low-Earth orbits (LEO), or into geostationary orbit (GEO). Thus the selected mission concept only allowed for fix-mounted telescopes, and the pointing direction could be requested freely. Since 2007 ESA focuses space surveillance and tracking activities in the Space Situational Awareness (SSA) preparatory program. Ground-based radars and optical telescopes are studied for the build-up and maintenance of a catalogue of objects. In this paper we analyse how the proposed SBO architecture could contribute to the space surveillance tasks survey and tracking. We assume that the SBO instrumentation is placed into a circular sun-synchronous orbit at 800 km altitude. We discuss the observation conditions of objects at higher altitude, and select an orbit close to the terminator plane. A pointing of the sensor orthogonal to the orbital plane with optimal elevation slightly in positive direction (0° and +5°) is found optimal for accessing the entire GEO regime within one day, implying a very good coverage of controlled objects in GEO, too. Simulations using ESA’s Program for Radar and Optical Observation Forecasting (PROOF) in the version 2005 and a GEO reference population extracted from DISCOS revealed that the proposed pointing scenario provides low phase angles together with low angular velocities of the objects crossing the field-of-view. Radiometric simulations show that the optimal exposure time is 1–2 s, and that spherical objects in GEO with a diameter of below 1 m can be detected. The GEO population can be covered under proper illumination nearly completely, but seasonal drops of the coverage are possible. Subsequent observations of objects are on average at least every 1.5 days, not exceeding 3 days at maximum. A single observation arc spans 3° to 5° on average. Using a simulation environment that connects PROOF to AIUB’s program system CelMech we verify the consistency of the initial orbit determination for five selected test objects on subsequent days as a function of realistic astrometric noise levels. The initial orbit determination is possible. We define requirements for a correlator process essential for catalogue build-up and maintenance. Each single observation should provide an astrometric accuracy of at least 1”–1.5” so that the initially determined orbits are consistent within a few hundred kilometres for the semi-major axis, 0.01 for the eccentricity, and 0.1° for the inclination.     

CubeSail: A low cost CubeSat based solar sail demonstration mission

CubeSail is a nano-solar sail mission based on the 3U CubeSat standard, which is currently being designed and built at the Surrey Space Centre, University of Surrey. CubeSail will have a total mass of around 3 kg and will deploy a 5 × 5 m sail in low Earth orbit. The primary aim of the mission is to demonstrate the concept of solar sailing and end-of-life de-orbiting using the sail membrane as a drag-sail. The spacecraft will have a compact 3-axis stabilised attitude control system, which uses three magnetic torquers aligned with the spacecraft principle axis as well as a novel two-dimensional translation stage separating the spacecraft bus from the sail. CubeSail’s deployment mechanism consists of four novel booms and four-quadrant sail membranes. The proposed booms are made from tape-spring blades and will deploy the sail membrane from a 2U CubeSat standard structure. This paper presents a systems level overview of the CubeSat mission, focusing on the mission orbit and de-orbiting, in addition to the deployment, attitude control and the satellite bus.     

一种提高卫星相对轨道运动全物理仿真逼真度的新方法

现有的卫星控制系统全物理仿真很少对卫星绕地球的轨道运动进行模拟,即使在卫星间相对轨道运动的全物理仿真中也没有考虑地心引力差和惯性力项的存在,因此其逼真度受到了影响.提出一种在共面圆轨道近距离卫星相对运动全物理仿真中引入地心引力差和惯性力项的方法,提高了物理仿真实验的逼真度.     

空间非合作目标的相对导航粒子滤波算法

针对激光交会雷达作为在空间交会对接过程中的相对导航敏感器,研究了未来特殊背景下,非合作目标航天器对雷达信号发射干扰的情况下的相对导航滤波算法.针对高维模型计算量大的特点对传统粒子滤波算法进行了改进,并与扩展卡尔曼滤波器进行了仿真比较,仿真结果表明改进后的粒子滤波器的滤波效果远远优于扩展卡尔曼滤波器,且计算量优于传统粒子滤波.     

基于逐步回归的模型误差估计及在天基测控系统中的应用研究

以双星定位系统的天基测控技术为应用背景,提出了一种能够自适应估计模 型误差的轨道确定方法。详细推导了观测模型中的系统误差形态,建立了能表征实际特征的 部分线性轨道改进模型,并利用二阶段法和核函数估计法对混合误差进行补偿,在此基础上 对补偿模型进行逐步回归分析,从中提取动力学模型误差,从而抑制了动力学模型误差的影 响,提高了轨道改进的精度。在本文的仿真环境下,部分线性轨道改进法能够有效抑制混合 误差对定轨精度的影响,提高天基测控的轨道确定精度。     

马克思相对剩余价值理论的当代启示

马克思的相对剩余价值生产理论,揭示了资本主义生产方式的特殊运动规律,为我们提供了一把认识当代资本主义生产发展和技术进步的钥匙。其所阐明的许多具有普遍性的商品经济基本原理,如关于协作和分工在生产中的作用,以及机器与自动化体系在生产中的应用等论述,对我国发展社会主义市场经济无疑具有重要的指导意义。     

姿态四元数相关问题

介绍了四元数计算中的相关问题,包括四元数与方向余弦阵之间的转换、四元数运动方程、求解四元数运动方程时积分步长的选取和高动态应用中非互易误差的补偿,此外还介绍了对偶四元数的发展。