天基激光移除空间碎片仿真平台研究与开发

为了从空间碎片和天基移除系统两方面分析激光驱动碎片变轨过程,优化移除任务规划和策略,基于真实的可观测空间碎片数据,设计并开发了一套天基激光移除空间碎片三维数值仿真平台。首先从总体设计出发,对三维数值仿真平台的需求分析、总体框架、模块功能进行了明确的描述。其次通过对激光驱动空间碎片变轨过程数学模型的分析,确定了各模块的具体实现方法。最后采用C++/Qt开发了三维数值仿真平台,通过仿真验证了设计平台的有效性。该仿真平台可用于不同天基平台和目标碎片的任务规划、碎片分布热点区域和航天器防护区域的方案设计及空间环境治理体系的优化设计。     

规避时段选择与机动变轨研究

按照空间碎片减缓指南的要求, 当两个空间物体发生碰撞前需要进行规避操作. 本文对规避中涉及到的速度增量与轨道变化的关系进行了分析, 探讨了一些具体的机动变轨方法, 同时还就测站的观测时段问题作了研究, 为碎片预警和航天器的规避提供了有力的支持.      

空间碎片天基监测图像仿真研究

空间碎片天基光学监测可以有效弥补地基监测的时空覆盖缺陷.目前天基观测数据不足甚至没有数据,这给监测系统研制、数据处理算法研究及软件系统研发和验证造成了一定困难.因此,研发能够为相关研究提供空间监测图像的空间碎片天基监测图像仿真软件系统具有重要意义.本文根据天基监测图像的特点,研究基本算法,设计仿真流程,给出仿真图像并对结果进行分析.为得到符合实际观测场景的高精度仿真图像,软件系统采用瞬时惯性坐标系;基于Tycho2星表提出了采用基于索引文件的快速星表查询方法来生成背景星图;利用两行根数（Two-Line Element,TLE）数据集仿真空间碎片观测值;并对结果图像中目标的运行轨迹进行分析,得出天基监测空间目标的成像特性.仿真结果表明,该仿真系统能够针对不同观测条件和观测平台,在兼顾精度与时效性的情况下,获得较为真实的空间碎片天基光学系列观测图像.      

流星参数的数值分析和流星高度分布模型

流星余迹能够被后向散射雷达观测到, 利用观测结果, 可以分析和研究流星的空间分布和时间变化规律. 同时, 利用流星空间分布还可以进行空间碎片的研究. 基于标准理论, 对影响雷达回波功率的主要因素, 例如如双极扩散、余迹的初始半径、流星的有限速度, 以及雷达的脉冲重复频率在不同频率和速度下进行了数值分析和计算, 得到的流星衰减时间及双极扩散系数的观测结果与理论结果一致. 通过对昆明流星雷 达观测到的571632个流星进行统计分析, 得到了流星高度分布统计模型, 并利用该模型的分析结果与不同月份流星的观测数据进行对比, 结果比较一致.      

超高速撞击航天器二次碎片云能量特性分析

为了评估空间碎片超高速撞击航天器的碎片云破坏能力,挖掘超高速撞击数值模 拟结果数据的应用价值,基于9.53 mm铝球以6.64 km/s速度对2.2 mm铝靶撞 击的Ls-Dyna/SPH(Smoothed Particle Hydrodynamic)数值模拟研究结果,对靶后碎片云的 粒子动能进行求和统计,建立了碎片云比动能概念和函数形式;碎片云比动能综合考虑了靶 后所有碎片云粒子的动能,反映了一定距离处垂直于撞击方向平面上单位面积上的碎片云粒 子所蕴含的撞击能量;应用碎片云比动能概念,揭示出随着演化距离的增加,碎片云能量的 衰减规律;通过不同速度条件下的SPH计算,得到了碎片云的比动能函数的曲线形式随撞击 速度的变化规律;最后对采用2种材料模型进行数值模拟所对应的结果误差进行碎片云比动 能函数的曲线比较,反映出数值模拟中不同材料模型引起的差异.      

空间系绳碎片碰撞生存能力研究

空间系绳结构和几何尺寸对其在复杂空间环境中抵抗碎片碰撞的能力有显著影响.本文根据系绳-碎片碰撞模型和泊松分布,计算了双股系绳和带状系绳被碎片割断的概率,分析了太空碎片对系绳生存能力可能造成的影响.双股系绳是由两条平行系绳每隔一段距离打结连接构成,带状系绳可视为一种横截面为矩形的特殊单股系绳.首先对单股系绳被碎片割断的概率进行建模,然后构建双股系绳和带状系绳生存能力函数,最后根据空间碎片环境模型,对比分析具有不同结构、不同尺寸的系绳的生存能力.仿真结果表明,相较于单股系绳,双股系绳和带状系绳的生存能力有明显提高.      

基于相控阵雷达波束篱笆的空间碎片数量与分布估计方法

随着载人航天与空间站等航天活动的增多,不能有效防护、也无法定期跟踪和编目的小尺寸(尤其是1～10 cm)碎片的危害越来越受到关注,这些碎片信息的获取依赖于统计采样技术.针对简化的相控阵雷达波束篱笆空间碎片探测模式,提出了一种采用统计技术估计空间碎片总数量以及高度和倾角分布的方法.将碎片穿越波束篱笆的过程用Poisson分布来建模,根据观测时段内穿越波束篱笆目标的平均到达率及测量的轨道高度和倾角数据来估计给定轨道高度范围或倾角范围内碎片的数量,进而得到碎片的总数量以及碎片数量随轨道高度或倾角的分布.在获取雷达散射截面信息时,该方法还可用于估计碎片数量随尺寸的分布.通过仿真实验验证了该方法的有效性.      

基于卫星编队的空间碎片视觉高精度导航方法

视觉方法被广泛应用于空间碎片这类和卫星之间没有任何通信的非合作目标导航。针对观测过程中视觉传感器的像差偏差引起位置不确定的问题,提出了利用卫星编队的立体视觉导航方法。首先,利用卫星编队构造了长基线的视觉传感器,通过Fisher矩阵对系统的可观测性进行了分析,验证了系统是可观的;其次,对视觉传感器进行了误差分析,通过安排最优视差角,使多颗卫星的观测信息融合达到最优;最后,应用卫星编队的视觉导航方法对空间碎片进行了导航仿真验证。结果表明,基于卫星编队的视觉导航方法可以显著减小观测误差,精度能达到01m量级,而且编队构形简单,易于工程实现。     

雷达波束驻留模式下空间碎片数量的置信区间估计

碎片数量估计是空间碎片环境统计特征描述的重要内容之一,对于空间碎片环境模型验证、航天器碰撞风险分析以及碎片数量增长趋势预测有重要意义.针对波束指向正东、正南任意仰角的雷达波束驻留(Beam-park)模式(天顶指向是波束指向仰角为90°时的特例),给出了一种估计碎片数量置信区间的方法.对于给定轨道高度范围内一个具有穿越雷达波束可能性(即雷达散射截面足够大,且轨道倾角相对测站纬度足够大)的碎片,将其是否真正穿越波束这一随机事件用(0-1)分布来建模,根据所采集的轨道高度和倾角数据,计算出该轨道高度范围内碎片穿越波束的平均概率,进而采用中心极限定理来估计碎片数量的置信区间.仿真结果表明了方法的有效性.      

卫星发射对空间碎片环境影响分析

未来航天发射情况直接影响空间碎片环境，必须对其进行合理规划，以维护外空长期可持续发展.利用中国自主建立的空间碎片长期演化模型（SOLEM），结合蒙特卡洛方法，量化分析了空间物体发射数量、发射质量、发射面积等因子对未来空间碎片环境的影响，进一步研究了大型星座造成的未来空间物体碰撞次数和碎片数量的增加.仿真结果可为合理规划未来的航天发射规模提供理论依据.      

Performance estimation for GEO space surveillance

For space surveillance Europe is currently strongly depending on external sources. Although some European radar and optical facilities for space object tracking exist, there is no operational European space surveillance system. An ESA-funded feasibility study for a future independent European space surveillance capability was performed recently. Some of the main conclusions are presented here. We discuss the surveillance of the geostationary ring (GEO) by evaluating existing and newly designed optical ground-based sensors in terms of their performance. The main performance-related issues – the coverage of the GEO ring and the minimum detectable objects size – are discussed. In order to perform detailed simulations, an observation strategy was defined and algorithms for the correlation of objects with a catalogue and for the maintenance of that catalogue were developed. We used the ESA PROOF software to estimate the sensor performance and AIUB tools to simulate the catalogue correlation. The performance was validated using data from campaigns performed with the ESA Space Debris Telescope at Tenerife, Spain.     

Properties of the high area-to-mass ratio space debris population at high altitudes

In the framework of its space debris research activities ESA established an optical survey program to study the space debris environment at high altitudes, in particular in the geostationary ring and in the geostationary transfer orbit region. The Astronomical Institute of the University of Bern (AIUB) performs these surveys on behalf of ESA using ESA’s 1-m telescope in Tenerife. Regular observations were started in 1999 and are continued during about 120–140 nights per year. Results from these surveys revealed a substantial amount of space debris at high altitudes in the size range from 0.1 to 1 m. Several space debris populations with different dynamical properties were identified in the geostationary ring. During the searches for debris in the geostationary transfer orbit region a new population of objects in unexpected orbits, where no potential progenitors exist, was found. The orbital periods of these objects are clustered around one revolution per day; the eccentricities, however, are scattered between 0 and 0.6. By following-up some of these objects using the ESA telescope and AIUB’s 1-m telescope in Zimmerwald, Switzerland, it was possible to study the properties of this new population. One spectacular finding from monitoring the orbits over time spans of days to months is the fact that these objects must have extreme area-to-mass ratios, which are by several orders of magnitudes higher than for ‘normal-type’ debris. This in turn supports the hypothesis that the new population actually is debris generated in or near the geostationary ring and which is in orbits with periodically varying eccentricity and inclination due to perturbations by solar radiation pressure. In order to further study the nature of these debris, multi-color and temporal photometry (light curves) were acquired with the Zimmerwald telescope. The light curves show strong variations over short time intervals, including signals typical for specular reflections. Some objects exhibit distinct periodic variations with periods ranging from 10 to several 100 s. All this is indicative for objects with complicated shapes and some highly reflective surfaces.     

A robotic telescope network for space debris identification and tracking

The two TAROT (Télescopes à Action Rapide pour les Objets Transitoires; Rapid Action Telescopes for Transient Objects) installations are fully robotic optical observatories with optimized observation scheduling, data processing and archiving. Zadko is a 1 m telescope in Western Australia. The fully robotisation of the Zadko telescope has just been completed; it is now included in the TAROT network. In this paper we provide an overview of this international network of robotic optical telescopes. We discuss the advantages of using the network to participate in a satellite and space debris tracking program. This network will access almost all geostationary belt objects, and provide the first real-time satellite positioning capability. The inclusion of the 1 m Zadko telescope into the network significantly extends the efficiency and sensitivity of the existing two telescope configuration.     

SPACE DEBRIS RESEARCH IN CHINA(2000-2002)

Space debris is is referred to as the human made pollution in the space environment.Ever since the first launch of man made satellite in 1957, millions of kilograms of objects have been sent into the space. Large space objects that are traceable and cataloged by ground base telescope and radar reach around 9 000, becoming grave threat to the social development of human beings as well as astronautics.     

Stacked recurrent neural network based high precision pointing coupled control of the spacecraft and telescopes

In some space missions especially in the field of space gravitational wave detection, the telescope needs to point to a certain target through attitude movement and pointing control. In several mainstream gravitational wave detection missions, the detector usually consists of a cluster of three identical satellites, flying in a quasi-equilateral triangular formation with a big edge length, so every satellite needs two telescopes to point each other and constitute three giant Michelson-Type interferometers. Therefore, a satellite platform system with two telescopes is researched in this paper. This research helps to characterize the attitude motion of a telescope for space astronomical observation or space gravitational wave detection, provides new method on the telescope’s high-precision pointing control. For this purpose, we derive a satellite-telescope coupling attitude model, design the sliding mode controller for satellite and the stacked recurrent neural network adaptive controller for telescope. In the stacked recurrent neural network adaptive controller design, a sliding mode control technology is adopted. In addition, we propose a combinatorial optimization method for network weights in the stacked recurrent neural network training process, that is, the output layer is corrected by the adaptive law, and the correction of other layers adopt the error backpropagation method. Finally, a numerical simulation method verifies the effectiveness of the controller design.     

用于空间站的四重冗余对接控制系统设计

针对空间站所处太空环境的特殊性、对接机构对空间站正常运行的重要性,以及对航天器可靠性要求日益增加的问题,提出在对接控制系统中增加可靠性设计,实现整个机构的高质量、平稳运转。在完成正常控制功能的基础上,在系统中采用了四重冗余的工作机制,包括主备机双热备份、自动/手动控制模式切换、自动控制关闭指令双线发送和工作模式的三取二判断,对四重冗余设计的具体判断流程进行了详细的解释。对控制系统软件进行仿真验证,结果表明：本方法设计的对接控制系统具有高可靠性和故障容错能力。     

The bistatic radar capabilities of the Medicina radiotelescopes in space debris detection and tracking

An accurate measurement of the position and trajectory of the space debris fragments is of primary importance for the characterization of the orbital debris environment. The Medicina Radioastronomical Station is a radio observation facility that is here proposed as receiving part of a ground-based space surveillance system for detecting and tracking space debris at different orbital regions (from Low Earth Orbits up to Geostationary Earth Orbits). The proposed system consists of two bistatic radars formed by the existing Medicina receiving antennas coupled with appropriate transmitters. This paper focuses on the current features and future technical development of the receiving part of the observational setup. Outlines of possible transmitting systems will also be given together with the evaluation of the observation strategies achievable with the proposed facilities.