Technical and legal issues surrounding space debris—India''s position in the UN

This article briefly presents the historical background, as seen by ISRO and India, to the growing problem of space debris. It describes the technical aspects of ISRO's activities in the field of space debris, and the grey areas in technical understanding, which may impede legal discussions. Analysis of the cost and technical aspects of reorbiting satellites from geostationary Earth orbit (GEO) is detailed, since this is an important area for India and other developing countries. The article also briefly describes ISRO's views of the applicability and relevance of the existing space treaties to a possible future legal regime for space debris. Debates are currently taking place in the UN and other multilateral fora on the subject of space debris and the situation is dynamic. The main aim of this article is to inform readers of ISRO's and India's position in the UN on the subject of space debris, in terms of its technical, political and legal aspects. Certain issues of importance from the legal point of view, though not of immediate urgency, are also discussed.     

天基雷达观测空间碎片的研究现状及关键技术分析

文章针对空间碎片观测中尚未得到确切观测数据的危险碎片的观测需求,综合分析了国内外的研究水平和现状,对天基雷达观测的需求和关键技术开展研究,提出了天基空间碎片观测有三个关键技术需要解决,即如何确定雷达工作体制和平台轨道以提高观测效率,如何有效探测尺度只有几个毫米-几个厘米的细小目标,如何对观测到的空间碎片进行分类和精确定轨。     

Passive optical detection of submillimeter and millimeter size space debris in low Earth orbit

Understanding of the space debris environment and accuracy of its observation-validated models are essential for optimal design and safe operation of satellite systems. Existing ground-based optical telescopes and radars are not capable of observing debris smaller than several millimeters in size. A new experimental and instrumental approach – the space-based Local Orbital Debris Environment (LODE) detector – aims at in situ measuring of debris with sizes from 0.2–10 mm near the satellite orbit. The LODE concept relies on a passive optical photon-counting time-tagging imaging system detecting solar photons (in the visible spectral range) reflected by debris crossing the sensor field of view. In contrast, prior feasibility studies of space-based optical sensors considered frame detectors in the focal plane. The article describes the new experimental concept, discusses top-level system parameters and design tradeoffs, outlines an approach to identifying and extracting rare debris detection events from the background, and presents an example of performance characteristics of a LODE sensor with a 6-cm diameter aperture. The article concludes with a discussion of possible sensor applications on satellites.     

The ESA and US reports on space debris : Platform for future policy initiatives

This article examines the development of policy on space debris in the European Space Agency and the USA, comments on its regulatory effectiveness, and proposes further recommendations for consideration when developing future space debris policy. The author argues that the international community must work towards a policy which incorporates an environmental perspective, and discusses the principles which should inform such a perspective.     

Biobjective planning of an active debris removal mission

The growth of the orbital debris population has been a concern to the international space community for several years. Recent studies have shown that the debris environment in Low Earth Orbit (LEO, defined as the region up to 2000 km altitude) has reached a point where the debris population will continue to increase even if all future launches are suspended. As the orbits of these objects often overlap the trajectories of satellites, debris create a potential collision risk. However, several studies show that about 5 objects per year should be removed in order to keep the future LEO environment stable. In this article, we propose a biobjective time dependent traveling salesman problem (BiTDTSP) model for the problem of optimally removing debris and use a branch and bound approach to deal with it.     

Density and mass distributions of orbital debris

Area-to-mass ratios for orbital debris tracked by the U.S. Space Command were calculated from observed changes in apogee and perigee altitude due to atmospheric drag. The area-to-masses observed for the orbital debris were similar to those found for debris from laboratory breakups, and suggest that much of the debris is composed of crumpled thin plates or of insulation material with low effective density. Areas for the debris objects were derived from radar cross-section data. Object masses were calculated from the ratio of the RCS-derived area to the area-to-mass ratio. Analysis of the distributions of fragment masses from the breakups suggests that in many cases, only a portion of the initial object breaks up into small fragments.     

激光驱动微小碎片技术可行性研究试验

文章介绍了激光驱动微小碎片技术的可行性研究试验.试验中,对4种粘膜方法进行了比较,在真空中测出了铝飞片的速度,并进行了两种防护材料的损伤评估.试验结果说明:在地面建立一套完整激光驱动微小碎片模拟装置不但必要,并且是可行的.     

Modeling of Ejecta Produced upon Hypervelocity Impacts

Each time a debris particle or a meteoroid strikes a satellite in orbit, a great amount of secondary particles is ejected in the neighborhood of the impact site. This phenomenon is important in particular for brittle materials, such as those used for solar arrays or thermal control paint. The secondary particles that do not impact other parts of the spacecraft are added to the primary debris population and hence increase the small debris particle flux. We describe an ejecta production model that gives the size and the velocity distribution of ejected particles as a function of primary impact parameters. The model has been used to explain the discrepancy between measurements and modeling of impact crater distribution on the solar arrays of the EuReCa spacecraft.     

Estimation of debris dispersion due to a space vehicle breakup during reentry

This paper studies the problem of the estimation of the extent of the airspace containing falling debris due to a space vehicle breakup. A precise propagation of debris to the ground is not practical for many reasons. There is insufficient knowledge of the initial state vector, ambient wind conditions, and the key parameters including the ballistic coefficients. In addition, propagation of all debris pieces to the ground would require extensive computer time. In this paper, a covariance propagation method is introduced for the estimation of debris dispersion due to a space vehicle breakup. The falling debris is simulated, and the data are analyzed to derive the probability of debris evolution in different altitude layers over time. The concept of positional probability ellipsoids is employed for the visualization of the results. Through a case study, it is shown that while the results of the covariance propagation method are in close agreement with those of the Monte Carlo method, the covariance propagation method is much more computationally efficient than the Monte Carlo method.     

超高速聚能碎片成型的影响因素分析

为了研究超高速聚能驱动装置结构参数对超高速碎片成型的影响,以装置截断体以及药型罩的6个主要尺寸为优化对象,以成型超高速碎片的质量与速度为指标,应用正交设计法设计仿真方案。运用非线性显式动力学软件AUTODYN-2D对超高速碎片的形成进行数值仿真,并对仿真结果进行参数分析。结果表明:对碎片成型速度影响较大的依次为药型罩锥角、截断体小孔厚度、药型罩厚度;对碎片质量影响较大的依次为药型罩锥角、药型罩厚度、截断体小孔厚度。最终根据最优化设计方案得到了速度为11.2 km/s、质量为1.452 g的超高速碎片。     

用于连接与分离的非火工装置

文章主要介绍了几类航天上可用于连接与分离的非火工装置,如基于形状记忆合金(SMA)的连接释放装置,石蜡驱动器,低熔点材料释放装置。非火工装置具有冲击力小、无污染以及可重复使用等优点,非火工装置的这些优点正好是火工装置的不足之处,所以在不能使用火工装置的条件下可以考虑使用非火工装置。文章对接分离装置有一定的参考价值。     

基于不同模型的固体火箭发动机喷射物熔渣特性分析

固体火箭发动机喷射物中的熔渣是航天器防护和空间碎片风险评估关注的对象之一。文章首先介绍国外熔渣建模试验数据及理论模型,主要有NASA熔渣模型、MASTER2005熔渣子模型（以下简称MASTER模型）和麻省理工大学林肯实验室的MIT/LL熔渣模型;再利用NASA和MASTER模型分析熔渣尺寸-数量和质量特性。MASTER模型给出的熔渣数量和质量均低于NASA模型;且MASTER模型认为约91.8%的熔渣尺寸处于25～200 mm区间;尺寸大于250 mm的熔渣质量占熔渣总质量的88%,但其数量只占熔渣总数量的6.3%。以上研究结果为进一步分析熔渣对空间碎片环境的影响奠定了基础,对我国自主开展熔渣模型研究也有一定的参考价值。     

Study on the eddy current damping of the spin dynamics of space debris from the Ariane launcher upper stages

This paper addresses the topic of damping of the spin dynamics of a spatial debris orbiting around the Earth. Such debris, which can consist of parts of heavy launchers such as the Ariane rocket under consideration in this article, are impacted by torques generated by eddy currents as their conducting non-ferromagnetic body orbits through the Earth magnetosphere. Several previous works have focused on describing this induction phenomenon and have proposed analysis of empirical observations of this particular and important effect which has attracted much attention since the number of spatial debris has emerged as a problem for the future of space programs, especially in low orbits. In this paper, we present a relatively comprehensive modeling of the induction phenomenon, by means of Maxwell's equations inside the conducting and non-ferromagnetic body. Through the generalized Ohm's law, we show how one can obtain a partial differential equation with Neumann's boundary conditions problem that, once solved, e.g. through a finite elements method, yields the values of induced currents and braking torques. The case of a depleted upper stage of a heavy launcher, having a cylindrical shape and thin walls is particularly studied. We show a methodology to estimate the decay-rate of the spinning velocity, which is proven to satisfy a first-order asymptotically stable linear dynamics. Special cases consisting of typical orbit of space debris are treated.     

空间碎片撞击在轨感知技术研究综述

随着航天发射活动的日益频繁,空间碎片环境随之恶化。为了应对空间碎片的撞击威胁,人们提出了用空间碎片撞击在轨感知系统实时监测航天器在轨遭受空间碎片撞击的情况。文章在对国内外相关研究机构研究成果的调研基础上,介绍了国内外在空间碎片撞击在轨感知技术领域的研究现状,对各国基于超高速撞击声发射技术的空间碎片撞击在轨感知技术的发展状况进行了全面评述,重点介绍了国内的研究进展。最后基于国内航天事业需要,探讨了未来发展方向。     

空间碎片数据形式及轨道演化算法

根据建立空间碎片工程模型的需要,定义了一种描述单个空间碎片运行位置及其物理特性的数据形式。基于空间碎片运动规律给出了一种用于计算单个空间碎片运行时＂平均位置＂的演化算法。计算的演化结果与STK软件计算的标称轨道比较表明：该演化算法正确。     

空间模拟碎片释放装置技术方案

为配合空间碎片主动清除技术的演示验证试验,提出了一种空间模拟碎片释放装置的技术方案:由模拟碎片及分离解锁装置组成。模拟碎片不具备任何合作特征,最初通过压紧杆与分离解锁装置相连,释放时由火工切割器切断压紧杆,模拟碎片在压缩弹簧的驱动下与分离解锁装置分离。最后,通过静载、模态、运动特性分析及分离解锁试验验证了该释放装置设计的正确性。     

激光驱动典型几何形状碎片运动建模研究

在以往的激光烧蚀驱动移除空间碎片研究中,均假设激光光束覆盖整个所关注的空间碎片。文章提出了焦斑式激光辐照下球体、圆柱体和立方体碎片反喷冲量和运动姿态的计算模型,研究了激光辐照在3种形状碎片不同位置处所产生的反喷冲量和姿态变化规律。结果表明:碎片运动规律与碎片几何形状和激光作用位置有关,当反喷冲量过质心时,碎片获得平动冲量;不过质心时,则会改变碎片的角速度或姿态。研究结果可为激光移除空间碎片研究提供理论参考。     

基于稀疏信号表示的空间碎片成像

地基雷达一直是空间碎片监测的有力工具,研究如何利用它们对尺寸小于距离分辨率的目标进行成像具有重要意义。基于空间碎片通常会围绕它的主轴进行简单的自旋转运动这一事实,通过对目标回波模型的分析,本文提出了一种基于稀疏信号表示的空间碎片成像方法。该方法将成像问题转化为稀疏信号分解问题,首先以各个散射点的散射特性作为元素构建字典,然后通过采用现有的方法对单个距离单元横向回波数据的稀疏信号表示进行求解,最后对求解的结果重新排列以得到目标的二维高分辨图像。仿真实验结果表明了本方法的正确性。     

Will space run out of space? The orbital debris problem and its mitigation

An appraisal of current and future risks from space debris is presented with the aid of calculations carried out by the MASTER model. The efficacy of various technical options -- such as fuel venting, de-orbiting and use of a graveyard orbit -- for counteracting the problem is discussed. The article then focuses on governmental and international cooperative measures and looks at the recent work done by subcommittees of the UN COPUOS.     

The origins of the “Long-term Sustainability of Outer Space Activities” initiative at UN COPUOS

The success of space-based systems worldwide, providing services to society and satisfying defence and security needs, has led to a situation where outer space is increasingly crowded. In addition, the rapid proliferation of space debris threatens the safe utilization of outer space on the most commonly used orbits. Beyond the mitigation of the orbital debris threat, additional measures will be needed to ensure the safety and security of activities in outer space for the long-term. This article describes the initiative to introduce a new agenda item in the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS), first presented to COPUOS delegations in 2007, which led to a formal decision in 2009. This in turn led to the establishment of a dedicated Working Group of the Scientific and Technical Sub-Committee in 2010, with a work plan leading to a report and associated recommendations in 2014. Some references are made to other initiatives affecting space security, such as the Russia–China draft treaty (PPWT) tabled at the Conference on Disarmament and the EU-proposed Code of Conduct.