气动辅助异面变轨在多碎片清除中的应用分析

碎片清除飞行器异面变轨需要消耗大量燃料.从气动辅助异面变轨优化设计及被清除碎片轨道高度差值、倾角差值等参数对变轨性能的影响出发,比较分析了优化气动辅助异面变轨与双脉冲霍曼轨道转移的燃料节约量,研究了不同轨道高度差对于实施气动辅助变轨燃料节约量的影响.当地球静止轨道（GEO）与低地轨道（LEO）间气动辅助变轨优化速度增量约为1.55km·s-1、质量面积比172kg·m-2、比冲310s、轨道倾角变化16°时,燃料节约率约为45%.对比研究了不同轨道高度差LEO轨道间实施气动辅助变轨的燃料节约情况.结果表明:随着轨道高度的增加,气动辅助优化效率逐渐降低;在相同高度轨道间实施异面变轨,随着轨道倾角的增加,气动辅助变轨燃料节约率先增大后减小,倾角改变量约为20°时,燃料节约率最大;当轨道倾角为5°时,采用气动辅助变轨和双脉冲变轨的燃料消耗量相同.      

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.      

天基激光清除空间碎片方案设想

随着空间碎片数量的不断增长,对人类航天事业的发展构成巨大威胁,清除空间碎片已经迫在眉睫。使用激光清除太空垃圾是一种低成本、高效、安全的清除技术。本文介绍了空间碎片的现状和现有清除方法,针对地基清除空间碎片技术存在的局限性,提出了一种天基激光清除空间碎片方案设想。     

航天器双主动交会策略研究

从理论上分析了共面近地圆轨道上的航天器的远程双主动交会的问题.根据轨道动力学基本原理,导出各种情况下特征速度的解析解,为航天器变轨时的燃料消耗分析提供了依据.进一步探讨了航天器轨道转移过程中的时间策略,以保证在不同轨道上运行的航天器在同一时刻、同一空间位置交会.上述理论分析的仿真计算结果表明,双主动交会总特征速度和过程耗时都低于主被动交会情形,单星的燃料消耗大大降低,对大范围快速变轨,优势更加明显.     

针对空间碎片捕获的绕飞轨道设计

地球轨道上日益增长的碎片云已引起各个航天国家的担忧,地球轨道上可编目的空间物体数量30多年内增长了2倍多,若不实施主动清除,碎片的数量将在未来200年内快速增长,给空间系统的安全带来极大的威胁。自然椭圆绕飞轨道可在目标附近长时间绕飞,可保证碎片捕获系统具有长时间的观测、捕获时间。文章提出通过设计绕飞轨道来实现捕获碎片的方案,介绍并分别推导了基于C-W方程和轨道根数两种方式绕飞轨道设计的方法。针对假想的捕获目标,基于轨道根数方法设计了5种脉冲变轨的轨道方案,并进行了相应的轨道算例仿真。仿真结果表明:该方案可适用于任意的初始相位差,具备一定的工程实现意义。     

对一种利用人造粉尘清除空间碎片新方法的理论分析

近地轨道的空间碎片污染日益严重,目前碎片数量已达到历史最高值并可能引发一系列连锁反应.进行主动碎片清除十分必要.利用粉尘主动清除近地轨道空间碎片是一种主动碎片清除的新方法.本文基于此方法的基本原理进行分析研究,建立了单颗碎片与人造粉尘作用的基本假设和机理模型,并对其作用进行定量计算分析;结合碎片的空间密度分布,对该方法的作用效果进行了定量估算,得出一些基本分析结论,有助于对新方法的客观认识.      

航天器轨道交会迭代制导算法

针对航天器轨道交会的脉冲推力模型与实际发动机连续推力模型不相符的问题,研究一种脉冲变轨策略的工程实现方法,使脉冲变轨策略可应用于工程实际.基于Lambert飞行时间定理和遗传算法,研究航天器最优脉冲变轨策略.根据脉冲变轨优化的结果,采用迭代制导算法研究脉冲变轨工程化问题.仿真结果验证了迭代制导算法在航天器轨道交会中的有效性.     

解体速度增量计算方法研究

解体速度增量是解体事件强度的重要指征, 它决定了解体产生碎片的轨道分布. 通过分析解体速度增量可以推断解体强度, 确定解体形式. 解体速度增量有两种计算方法, 即轨道位置演化法和轨道面相交法. 轨道位置演化法是根据解体前后轨道速度的变化直接得到解体速度增量; 而轨道面相交法是利用母体以及解体碎片的球面三角几何关系, 根据解体碎片的倾角和升交点赤经变化, 以及母体轨道的倾角和近地点辐角, 计算解体时刻母体轨道的真近点角, 从而得到解体的时间和速度增量. 相比来说, 轨道位置演化法适用于数据精度高, 解体高度高情况下的解体事件分析, 而轨道面相交法适用于解体高度低, 碎片数据公布时间较为滞后的解体事件分析. 根据解体速度增量的计算方法及其原理, 对两种方法的适用性进行了比较和讨论, 并选取已经发生的三次解体事件, 利用美国公布的TLE数据, 针对具体情况选择计算方法, 给出了三次解体事件发生的时间和解体碎片在空间三个方向上的速度增量.      

Spot 1 end of life disposition manoeuvres

The Earth observation satellites of the SPOT family are on a Sun-synchronous orbit at 822 km altitude. The on-orbit lifetime of objects at this altitude is about two centuries, which represents an important risk to the other satellites.The space debris issue has caused the main Agencies to adopt mitigation guidelines with the objective to reduce the population of objects orbiting the Earth. In 1999, CNES published its own standard presenting the management, design and operation rules. This document is fully compliant with the Inter Agency Space Debris Coordination Committee (IADC) mitigation guidelines approved in 2002 by 11 Space Agencies and submitted to United Nations – Committee on Peaceful Uses of Outer Space in February 2003.The space debris mitigation requirements expressed in the CNES standard and in the IADC mitigation guidelines limit the orbital lifetime in LEO to less than 25 years. Although not applicable to Spot 1, launched earlier in 1986, this rule was voluntarily applied and the decision to deorbit Spot 1 was taken.The corresponding operations, performed in November 2003, were complex due to a large number of constraints such as the unusual flight domain, the on-board sensors, the short ground station visibilities or the uncertainties in the estimation of the remaining fuel in the tanks. In the preliminary phase, the orbit was lowered 15 km below the operational orbit to avoid any collision risk with the other Spot satellites. Then, in a second phase, a series of eight apogee boosts lowered progressively the perigee altitude to 619 km. Finally, a large last manoeuvre was performed to empty the tanks and to reduce the perigee altitude the maximum amount. A succession of four ground stations visibilities allowed a real time monitoring of this manoeuvre. In particular the effect of gas bubbles in the propulsion system was observed through telemetry confirming the fuel depletion. The batteries were then disconnected and the telemetry emitter was switched off. According to the obtained perigee altitude, the on-orbit lifetime of Spot 1 should be about 18 years, which meets the space debris mitigation requirements.     

Accurate orbit predictions for debris orbit manoeuvre using ground-based lasers

Orbit manoeuvre of low Earth orbiting (LEO) debris using ground-based lasers has been proposed as a cost-effective means to avoid debris collisions. This requires the orbit of the debris object to be determined and predicted accurately so that the laser beam can be locked on the debris without the loss of valuable laser operation time. This paper presents the method and results of a short-term accurate LEO (<900 km in altitude) debris orbit prediction study using sparse laser ranging data collected by the EOS Space Debris Tracking System (SDTS). A main development is the estimation of the ballistic coefficients of the LEO objects from their archived long-term two line elements (TLE). When an object is laser tracked for two passes over about 24 h, orbit prediction (OP) accuracy of 10–20 arc seconds for the next 24–48 h can be achieved – the accuracy required for laser debris manoeuvre. The improvements in debris OP accuracy are significant in other applications such as debris conjunction analyses and the realisation of daytime debris laser tracking.     

Orbital debris–debris collision avoidance

We focus on preventing collisions between debris and debris, for which there is no current, effective mitigation strategy. We investigate the feasibility of using a medium-powered (5 kW) ground-based laser combined with a ground-based telescope to prevent collisions between debris objects in low-Earth orbit (LEO). The scheme utilizes photon pressure alone as a means to perturb the orbit of a debris object. Applied over multiple engagements, this alters the debris orbit sufficiently to reduce the risk of an upcoming conjunction. We employ standard assumptions for atmospheric conditions and the resulting beam propagation. Using case studies designed to represent the properties (e.g. area and mass) of the current debris population, we show that one could significantly reduce the risk of nearly half of all catastrophic collisions involving debris using only one such laser/telescope facility. We speculate on whether this could mitigate the debris fragmentation rate such that it falls below the natural debris re-entry rate due to atmospheric drag, and thus whether continuous long-term operation could entirely mitigate the Kessler syndrome in LEO, without need for relatively expensive active debris removal.     

关于HEO空间飞行体的轨道寿命问题

低轨地球卫星的轨道寿命主要取决于大气的耗散作用,其轨道在不断变小(即高度降低)变圆的状态下进入地球稠密大气层中陨落.但HEO(Highly Eccentric Orbit)类型的空间飞行体的运行轨道是一个近地点高度很低,远地点高度却很高的大偏心率椭圆轨道,其轨道寿命主要由第三体(日、月)引力摄动所决定,而且还与其轨道的初始状态有密切关系,特别是慢变量Ω(轨道升交点经度)和ω(轨道近地点幅角),决定了偏心率e的长周期变化状态,从而制约了HEO类型空间飞行体的轨道寿命.本文将根据地球卫星轨道变化规律进行理论分析,阐明这一力学机制,并给出相应的数值验证.      

Space debris mitigation strategies and practices in geosynchronous transfer orbits

Missions to geosynchronous orbits remain one of the most important elements of space launch traffic, accounting for 40% of all missions to Earth orbit and beyond during the four-year period 2000–2003. The vast majority of these missions leave one or more objects in geosynchronous transfer orbits (GTOs), contributing on a short-term or long-term basis to the space debris population. National and international space debris mitigation guidelines seek to curtail the accumulation of debris in orbits which penetrate the regions of low Earth orbit and of geosynchronous orbit. The orbital lifetime of objects in GTO can be greatly influenced by the initial values of perigee, inclination, and right ascension of the orbital plane, leading to orbital lifetimes of from less than one month to more than 100 years. An examination of the characteristic GTOs employed by launch vehicles from around the world has been conducted. The consequences of using perigees above 300 km and super-synchronous apogees, typically above 40,000 km, have been identified. In addition, the differences in orbital behavior of launch vehicle stages and mission-related debris in GTOs have been investigated. Greater coordination and cooperation between space launch service providers and spacecraft designers and owners could significantly improve overall compliance with guidelines to mitigate the accumulation of debris in Earth orbit.     

Estimation of ballistic coefficients of low altitude debris objects from historical two line elements

This paper presents a new method for estimating ballistic coefficients (BCs) of low perigee debris objects from their historical two line elements (TLEs). The method uses the drag perturbation equation of the semi-major axis of the orbit. For an object with perigee altitude below 700 km, the variation in the mean semi-major axis derived from the TLE is mainly caused by the atmospheric drag effect, and therefore is used as the source in the estimation of the ballistic coefficient. The method is tested using the GRACE satellites, and a number of debris objects with external ballistic coefficient values, and agreements of about 10% are achieved.     

多碎片移除过程中的路径优化

采用蚁群优化算法对多碎片移除过程中的路径优化问题进行研究，然后采用改进的最速下降法对移除每块碎片的时间进行合理优化，进一步降低总的速度增量需求.对比轨道高度、轨道倾角或者升交点赤经的顺序后发现，采用蚁群算法优化之后的顺序移除碎片可以大大节省轨道转移所需要的速度增量.选取中国空间活动产生的三组碎片进行优化计算，结果显示在相同的任务时间内，优化后的顺序可能不同于轨道高度、倾角和赤经的顺序，并且优化顺序可以节省更多的速度增量.另外，任务时间也会对碎片的最佳移除顺序产生影响.      

月球探测器转移轨道的特性分析

主要分析了月球探测器由近地点出发，在假定末端条件不变的情况下，其转移轨道的特性参数对初始条件和变轨所需的速度脉冲等的影响；考虑的特性参数的变化包括转移轨道倾角的变化，近地点高度的变化和转移时间的不同．