Active Removal and Situational Awareness of Space Debris in Low Earth Orbits

过去60年来，人类在空间活动产生的碎片积聚已成为一个关键问题，特别是在非常商业化的低地球轨道(LEO)。人们普遍认为，如果人类要继续可持续地利用近地空间，就必须解决这一问题。这一认识推动了对如何遏制空间碎片增长和补救空间环境的密集研究。我建议提高现有解决方案的技术准备水平，增进我们的理解，并开发新的方法来解决这一多方面问题中的关键问题。这项提案的第一个重点是主动清除碎片。目前已就每年清除五至十个大型碎片物体的必要性达成广泛共识；然而，对于部署这项任务的最佳技术还没有达成一致意见。在我先前关于使用系留网捕获大型空间碎片的研究的基础上，我将通过制定和评价收网方法以确保遏制碎片、调查捕获后系统稳定的战略以及通过实验演示用于收集碎片的系留网概念，进一步推进系留网解决办法。对于飞行任务的下一阶段，即产生的系绳追逐者-碎片系统的脱离轨道，我建议研究系绳辅助概念-通过系绳摆动和旋转-将碎片刹车进入向地球大气层下降的轨道。我的第二个研究重点属于对碎片环境的空间态势感知。在这一广阔领域内，我将致力于提高我们对大型空间碎片运动的理解和预测能力，重点是它们的自转运动。这项研究将回答基本的问题：碎片在未来的某个时候会在哪里，它将如何旋转？由于碎片不受控制地翻滚，它们的姿态对轨道上经历的摄动力和扭矩具有时变影响，如空气动力阻力和太阳辐射压力。这些反过来又直接影响碎片的轨道和位置。我们将努力扩大我们对当前扰动效应模型中的不确定性如何影响传播中的不确定性的理解，并制定随机模型来量化这些影响。我们将探索利用观测数据，结合我们的预测模型，制定参数、摄动和碎片姿态运动的估计算法。加拿大是一个太空国家：它发射卫星，加拿大人依赖我们的太空资产在他们的一生中可靠地发挥作用。鉴于空间碎片对功能资产构成的威胁，至关重要的是，我们必须拥有参与未来碎片清除任务的专门知识，以及预测碎片对空间环境影响的知识和工具。

The build-up of debris from human activities in space over the past 60 years has become a critical issue, particularly in the very commercial low Earth orbits (LEO). It is widely accepted that this situation must be addressed if humans are to continue sustainable exploitation of near Earth space. This acknowledgement has spurred intense research on ways to curtail space debris growth, and remediate the space environment. I propose to increase technology readiness levels of existing solutions, to advance our understanding and to develop novel methodologies to address key issues in this multifaceted problem. The first focus of this proposal is on active debris removal. There is now broad consensus on the need to remove five to ten large debris objects per year; yet, there is no agreement on the best technology to deploy for such a mission. Building on my prior research on the use of tethered nets for capture of large space debris, I will further advance the tethered-net solution through the development and evaluation of net closing methods to ensure debris containment; by investigating strategies for system stabilization after capture; and through experimental demonstration of the tethered-net concept for debris capture. For the subsequent phase of the mission, the de-orbiting of the resulting tethered chaser-debris system, I propose to investigate tether-assisted concepts---through tether swinging and spinning---for braking the debris into a descent towards the Earth's atmosphere. My second research focus falls under the umbrella of space situational awareness of the debris environment. Within this broad domain, I will work on improving our understanding and advancing prediction capabilities for the motion of large space debris, with emphasis on their rotational motion. This research will answer the basic questions: where will the debris be at some time in the future and how will it be spinning? Because the debris are tumbling uncontrollably, their attitude has a time-varying effect on the perturbation forces and torques experienced in orbit, such as, the aerodynamic drag and solar radiation pressure. These in turn directly influence the orbit and location of debris. We will work to expand our understanding of how uncertainties in our current models of perturbation effects affect the uncertainties in the propagation and formulate stochastic models to quantify these effects. We will explore the use of observational data, jointly with our predictive models, to formulate estimation algorithms for parameters, perturbations and the attitude motion of the debris. Canada is a space faring nation: it launches satellites and Canadian people depend on our space assets to function reliably over their life-time. Given the threats presented by space debris to functional assets, it is critical that we have expertise to participate in future debris removal missions, as well as, the knowledge and tools to predict the impact of debris on the space environment.