Active Debris Removal Research Articles

Space environment management: Framing the objective and setting priorities for controlling orbital debris risk

Interest in orbital debris risk has been on the rise in recent years, as small satellites are launched in accelerating numbers, proposals for large low-Earth orbit (LEO) constellations mature, and the orbital debris population continues to grow. Environmental models are being exercised to predict collisional risk, private equity is now supporting the development of commercial Space Situational Awareness (SSA) and Active Debris Removal (ADR) services, and debris mitigation best practices and licensing guidelines are being updated by industry groups and national administrations. These are all positive responses to an increasingly challenging space operational environment, but as is often the case, we tend to rush to solutions before adequately defining the problem we are trying to solve. The authors propose Space Safety as a simple objective statement for an industry operating in a debris-laden space environment and establish the lethal nontrackable (LNT) debris population as the primary risk to assured operations in space. The authors then make the case that SAA and Space Traffic Management (STM) alone are insufficient responses to collision risk and propose Space Environment Management (SEM), consisting of both debris mitigation and debris remediation, as a critical component of a comprehensive framework the space community can use to assess the efficacy of its efforts and to prioritize the appropriation of its resources. The paper concludes with recommendations for setting priorities and directing the community's efforts and resources.

Potential Export Control Challenges and Constraints for Emerging Space Debris Detection and Removal Technologies: The Case of On-Orbit Collision

The sustainability of Outer Space in a context of increased human activity in low Earth orbit (“LEO”) has been much debated lately. The discussion focuses on how space debris appears, how they can be limited and, possibly, removed. Commercial proposals for Active Debris Removal (ADR) and providing life-extension services to satellites are slowly emerging as precursory technological tools. Those technologies will involve so-called on-orbit servicing activities (“OOS”), i.e., activities performed on a spacecraft, while it is in or near its operational orbit and will require that one spacecraft approach, rendezvous, and interact with the asset/the debris to be removed; they raise a host of legal, regulatory, and policy challenges that need to be discussed as those projects progressively mature. Those cutting-edge technologies have potent capabilities and a potential for military and missile technology applications. As a result, they will likely be controlled by export control regulations (possibly by US export control regulation) and might fall under the stringent ITAR requirements. OOS inevitably involves the coupling of two different actors, the servicing spacecraft performing the services, and the asset to service. From an export control perspective, depending on the circumstances of each mission, in particular on the nationality of the servicing spacecraft and the one of the debris, the exchange of information between them might qualify as an export of technical data and would need to be licensed and authorized accordingly. In addition, because of the coupling of those two actors, the OOS model presents an inherent complexity: it creates a greater risk of technical failures, in particular of on-orbit collisions. As a consequence, it can induce more opportunities to exchange technical data in a context of urgency that prompts omissions and ultimately, more opportunities for violating export controls. This would apply even if technical data are exchanged for insurance or investigation purposes. Thus, any situation of on-orbit failure in the context of an OOS presents a risk of inadvertent export control. In the past, inadequately managed launch-failure investigations of satellites launched on non-US launchers caused major export control violations and were to have a profound impact on the US export control system. After observing how technological measures can mitigate risks of export control violations, this paper will propose a normative suggestion to mitigate potential ITAR violations and to avoid inadvertent export control situations in case of on-orbit failures in the context of OOS.

An Improved Deep Keypoint Detection Network for Space Targets Pose Estimation

The on-board pose estimation of uncooperative target is an essential ability for close-proximity formation flying missions, on-orbit servicing, active debris removal and space exploration. However, the main issues of this research are: first, traditional pose determination algorithms result in a semantic gap and poor generalization abilities. Second, specific pose information cannot be accurately known in a complicated space target imaging environment. Deep learning methods can effectively solve these problems; thus, we propose a pose estimation algorithm that is based on deep learning. We use keypoints detection method to estimate the pose of space targets. For complicated space target imaging environment, we combined the high-resolution network with dilated convolution and online hard keypoint mining strategy. The improved network pays more attention to the obscured keypoints, has a larger receptive field, and improves the detection accuracy. Extensive experiments have been conducted and the results demonstrate that the proposed algorithms can effectively reduce the error rate of pose estimation and, compared with the related pose estimation methods, our proposed model has a higher detection accuracy and a lower pose determination error rate in the speed dataset.

Laboratory Study of the Active Debris Removal Algorithms on Air-Bearing Test Bed

Space debris removal is one of the most important problems in space exploration. This work is devoted to the development and testing of control algorithms for microsatellites mockups on an aerodynamic table. The mock-ups are equipped with thruster’s simulators to control the motion of the center of mass and angular motion on the plane of the table. The aim of the work is to construct a control algorithm using virtual potential functions and apply it to the problems of rendezvous and docking. Simultaneously with these tasks, the problem of avoiding a collision with an object in the event of a dangerous approach not from the docking side is solved. Also the algorithm for autonomous debris observation of the 3U CubeSat is proposed. The results of the control algorithm tests are presented in the paper.

Development of Wire Actuation 2 Stage Extension Mechanism Considering to Use for Spacecraft

Extension mechanism is attracting attention to use for capturing mechanism of the active debris removal spacecraft. Authors developed the debris capturing end effector consist of multiple wire action 2 stage extension mechanism. This mechanism is selected because of its high extension ratio, fast extending speed, high stiffness and retry capability using single motor. This end effector and mechanism's experimental results showed that it satisfies the requirements. However, this mechanism is not yet evaluated to use in space environment. In this study, wire actuation 2 stage extension mecha- nism's movement is discussed, and equation of motion is proposed to discuss which data to be acquired to evaluate the mechanism to use in space. The device to obtain the data is introduced, and experimental results shows that the introduced device can well acquire the data. Experiment inside the vacuum chamber is also conducted, and the results showed that this mechanism can be used in space environment.

Survey on research and development of on-orbit active debris removal methods

Space debris is growing dramatically with the rapid pace of human exploration of space, which seriously threatens the safety of artificial spacecraft in orbit. Therefore, the active debris removal (ADR) is important. This review aims to review the ADR methods and to advance related research in the future. The current research and development status are clearly demonstrated by mapping knowledge domain and charts. In this paper, the latest research results are classified and summarized in detail from two aspects of space debris capture and removal. The scheme comparison and evaluation of all ADR methods are performed, and the applicable scopes of various methods are summarized. Each ADR method is scored using a cobweb evaluation model based on six indicators. Future development of ADR is discussed to promote further research interest.

Analysis of Envisat’s rotation state using epoch method

Envisat has been identified as a candidate target for active debris removal. The research on its rotation state is of great significance. The specular glint times in optical observation data can be used in fitting the rotation state of Envisat by the epoch method. Using well-observed variations in synodic frequencies, and minimizing the goodness-of-fit indicator by a grid-search, complete spin state solutions can be derived. By this method, Envisat’s spin axis longitude α and latitude δ in the orbital coordinate system can be calculated. The latitude δ oscillates widely with time between -55° and -85° with a mean value of δmean=-67.08°. Its distribution has peaks in two areas around -60° and -80°, which is similar to the results through laser ranging measurements from a single pass. In addition, the precession fit of the spin axis longitude α shows that the spin axis may not precess regularly around the negative normal of the orbital plane. Besides, Envisat’s sidereal period from 2013 to 2015 increases exponentially with the expression: Psid(sec)=121.1·exp(4.462×10-4·t), where t is measured in days from the beginning of 2013, RMS of the fit residuals = 1.8586 s.

The development of commercially viable ADR services: Introduction of a small-satellite grappling interface

OneWeb has begun the deployment of its global internet system – one that will bridge the digital divide and bring internet connectivity to underserved communities throughout the world. The backbone of its network is a constellation of nearly 600 low Earth orbit (LEO) satellites that service user terminals designed for a variety of communication use cases.From its inception, OneWeb has committed itself to the highest standards of responsible design and operational practices and believes that all stakeholders need to take responsibility for the long-term sustainability of space. To assure safe space operations in the presence of collisional hazards, we need to adopt a more comprehensive approach to Space Environment Management (SEM). In addition to improving Space Situational Awareness (SSA), collision avoidance capabilities, and debris mitigation standards, it is critical that the global space community also develop real possibilities for environmental remediation.There are still some technical challenges to solve before Active Debris Removal (ADR) services become a reality, but the more formidable challenge in developing a commercially viable ADR services industry is likely to be cost. It remains to be seen whether mission architectures and business models can be crafted to support price points that are attractive to commercial operators, or whether ADR is destined to be a service only governments can afford.As part of its commitment to space sustainability and environmental stewardship, OneWeb is including a grappling fixture on every one of its satellites to facilitate capture in the event that retrieval should become necessary. In addition, OneWeb has worked with Altius Space Machines over the last three years to develop an advanced grappling fixture that accommodates a number of grappling techniques. Furthermore, over the last three years, OneWeb has worked with Altius Space Machines on advanced grappling techniques in the hopes of standardizing a versatile capture interface for on-orbit servicing, thereby lowering the projected cost of ADR and other services for everyone.The result is Altius’ DogTag™ universal grappling fixture, a low-cost, light-weight, universal interface for small satellites. The primary capture mechanism is magnetic, but it is also designed to support mechanical, adhesive, and penetrating capture techniques as well. Altius was recently awarded a contract for almost 600 fixtures by OneWeb Satellites and will begin delivery of flight hardware in December 2019.

A novel concept of cost-effective active debris removal spacecraft system

Post Mission Disposal (PMD) alone is an insufficient solution to stabilize the orbital debris environment, but combining Active Debris Removal (ADR) with PMD and other means of debris mitigation is considered a promising remediation method. The cost reduction of ADR is essential to make it a sustainable business. The major cost driver of ADR is the ADR spacecraft and its launcher, both of which are largely influenced by the spacecraft size. A trade-off study of the ADR spacecraft system has been conducted to minimize its size, resulting in the novel concept of a cost-effective ADR spacecraft system. The authors introduce the combination of electric propulsion (EP) and air drag utilization for the debris deorbit phase so as to lower the EP requirement, thereby leading to cost reduction of the ADR spacecraft. The minimum delta-V reentry method is also considered to reduce the propellant mass for final reentry. EP performance (e.g. thrust, specific impulse, mass) is modeled as a function of power consumption, and optimum EP performance has been explored to minimize overall mass of the ADR spacecraft, including its electrical power subsystem with this EP model. Given the minimum thrust limit to satisfy the mission duration requirement, a higher thrust-to-power ratio is preferable for debris removal electric propulsion. This paper discusses the optimal EP performance requirements in detail, and the results show that a roughly 500-kg ADR satellite using a 600-W-class Hall thruster can remove about three tons of a rocket body debris from an 800-km circular orbit within 600 days.

Validating the Deployment of a Novel Tether Design for Orbital Debris Removal

With the global push to commercialize space, humans are launching objects into orbit faster than natural effects are removing them. Orbital debris is especially dangerous because it is capable of exponential growth due to cascading collisions between orbiting objects. To ensure the long-term accessibility to space, high-risk objects must be actively removed to limit growth of the orbital debris population. One method of active debris removal is with a tethered net to capture and tow an object out of orbit. This work presents the validation of a proposed novel tether configurations deployment dynamics. Tether elements are simulated using two numerical models: a lumped mass node system connected by massless spring–damper elements, and an absolute nodal coordinate formulation model. Their accuracy to predict the deployment motion of a tether is experimentally determined, and a complete capture scenario using the novel tether design is presented for the first time.

Impact on collision probability by post mission disposal and active debris removal

The collision probabilities of debris objects with and without Post Mission Disposal (PMD) and Active Debris Removal (ADR) are evaluated and discussed. A debris evolutionary model named NEODEEM was jointly developed by Kyushu University and JAXA for use in predicting future debris populations and calculating collision probabilities. The collision probability in each altitude bin is initially compared with and without PMD or ADR. Then a case involving a large satellite constellation is also discussed. The effective number of debris objects at each altitude for the PMD success rates of the large constellation and the collision probability at each altitude are calculated. The collision probability per unit time will increase when a small satellite utilizes a drag augmentation sail or a tether as a PMD device, but the dwell time will be greatly reduced. A collision with a sail or tether will be non-catastrophic collision. Therefore, the use of such devices will reduce the cumulative collision probability and expected number of debris fragments.

Space robot motion planning in the presence of nonconserved linear and angular momenta

On-orbit servicing, active debris removal or assembling large structures on orbit are only some of the tasks that could be accomplished by space robots. In all these cases, a contact between a space robot and the satellite being serviced, deorbited, or assembled will occur. This contact results in a contact force exerted on the space robot, and therefore momenta of the space robot system are no longer conserved. Most of the papers that are concerned with motion planning problems of a space robot manipulator either consider that no external forces or moments are acting on the space robot system or use additional controllers when the space robot is subjected to external forces and moments. Such a controller minimizes end-effector position and orientation errors caused by the changes in system momenta due to external forces and moments acting on this system. The novelty of this work is that it proposes a new method for planning the motion of dual-arm space robot manipulators when linear and angular momenta of the space robot system are not conserved due to external forces and moments acting on the space robot base or/and manipulators’ end-effectors. In the proposed method the changes in system momenta are considered, but no additional controllers are needed. In this paper, we derive the motion planning equations for dual-arm space robot manipulators, where external forces and moments are acting on both satellite and manipulator end-effectors. The proposed method has been verified by numerical simulations, and the results are presented and discussed.

Reduce, Reuse and Recycle: An Environmental Law Approach to Long-term Sustainability of Outer Space

The article conceptualizes the existing international environmental law principles to better understand their applicability to outer space. The article proposes utilizing existing international environmental legal principles to implement the idea of waste hierarchy concept of ‘Reduce, Reuse and Recycle’ to address issues concerning long-term sustainability of outer space. The primary focus is on issues pertaining to transfer of ownership, on-obit servicing, and active debris removal and how they can be used to achieve the sustainable development goals of outer space through the waste hierarchy concept. The article ultimately suggests that existing international environmental law and space law together can ensure an efficient framework to help cope with issues threatening the sustainable use of outer space. The article works towards understanding the importance of bridging the gaps in the existing international space law regime with respect to long-term sustainability of outer space. Space Sustainability, Environmental Law, Transfer of Ownership, On-Orbit Servicing, Active Debris Removal

Inspection of the cis-lunar station using multi-purpose autonomous Cubesats

The close observation of orbiting objects with Cubesats can efficiently support a wide range of applications, such as the inspection of defunct satellites for preparing active debris removal missions, or the inspection of operative spacecraft (International Space Station, telecom satellites) for maintenance purposes. Future applications can involve inspection of deep space objects, for example the cis-lunar human-tended station, that will constitute the Gateway for future exploration missions. From the ISS mission, it has been understood that an inhabited outpost in space needs heavy maintenance for keeping it in operations with the required capabilities and safety level over a long-duration mission. Inspection from outside the station is required for investigation on detected anomalies or for preventing failures, for structural measurements, and in general for monitoring the station configuration. Small space (semi)autonomous drones, such as CubeSats, can be deployed from transportation vehicles or from the station, and used in several phases of the mission, flying in the vicinity of the space habitat. The study presented in this paper investigates the feasibility of operating multi-purpose small inspectors in proximity of the future Lunar Orbiting Platform. The study focuses on the inspection/surveillance mission, for which a concept of operations and architecture have been developed and analysed. In particular, the possibility to have 3D vision and multispectral payloads has been investigated, to enhance inspection capabilities with respect to current state-of-the-art technology.

Orbital-use fees could more than quadruple the value of the space industry

The space industry's rapid recent growth represents the latest tragedy of the commons. Satellites launched into orbit contribute to-and risk damage from-a growing buildup of space debris and other satellites. Collision risk from this orbital congestion is costly to satellite operators. Technological and managerial solutions-such as active debris removal or end-of-life satellite deorbit guidelines-are currently being explored by regulatory authorities. However, none of these approaches address the underlying incentive problem: satellite operators do not account for costs they impose on each other via collision risk. Here, we show that an internationally harmonized orbital-use fee can correct these incentives and substantially increase the value of the space industry. We construct and analyze a coupled physical-economic model of commercial launches and debris accumulation in low-Earth orbit. Similar to carbon taxes, our model projects an optimal fee that rises at a rate of 14% per year, equal to roughly $235,000 per satellite-year in 2040. The long-run value of the satellite industry would more than quadruple by 2040-increasing from around $600 billion under business as usual to around $3 trillion. In contrast, we project that purely technological solutions are unlikely to fully address the problem of orbital congestion. Indeed, we find debris removal sometimes worsens economic damages from congestion by increasing launch incentives. In other sectors, addressing the tragedy of the commons has often been a game of catch-up with substantial social costs. The infant space industry can avert these costs before they escalate.

Tethered towing of defunct satellites with solar panels

Space debris is becoming an increasingly serious threat to human space activities. Active debris removal by connecting a space tug to debris by means of tethers is one of the promising techniques to constrain the debris population. Connection between the tether and the debris is preferred to be realized by tether net, since the tether net have multiple attachment points on the debris, which can damp debris' rotations passively. However, the computation of contact dynamics is very complicated and time-consuming for tether net, especially when the debris is a defunct satellite with solar panels. In this study, a tethered towing system which incorporates the flexibility of solar panels and, in the meantime, has multiple fixed attachment points is proposed. Equations of motion are obtained via Kane's method, and dynamical behaviors are discussed. Numerical results verify the validity of the proposed system, and find that the flexibility of the solar panels improves the passive rotation damping ability of the towing system.

Optimal contact control for space debris detumbling and nutation damping

Space debris detumbling technology can be an effective supplement to the direct capture capability of space robot for simplifying and completing the active debris removal mission. This paper focuses on the optimal contact control for space debris rotation eliminating and nutation damping. Firstly, the space debris attitude motion is analyzed. The space debris detumbling strategy is presented with a designed spring contactor as the detumbling tool. Then, the contact detumbling dynamic models are established, including the spacecraft dynamic models, the contact detection method and the contact force model. Furthermore, an optimal contact control method is developed in order to reduce the three-axis angular velocities of space debris and suppress the nutation at the same time. The stability of the control method is proved by using the Lyapunov argument and the condition for nutation convergence is analyzed. Finally, numerical simulations are carried out to verify the optimal contact control method proposed in this paper. The results illustrate that the control method is effective for space debris detumbling and has certain robustness to the measurement and identification errors.

Introducing the law games: Predicting legal liability and fault in satellite operations

Over recent times there has been a rise in the number of objects placed into Earth orbit. With various countries licensing a number of large constellations, the orbital population is set to increase dramatically. A significant number of technical advances have facilitated this and, in the UK and elsewhere, this has been matched by the updating of legislation and an increased policy focus on the need for increased space surveillance and tracking. The rise of large constellations coupled with an increasing number of experimental techniques such as active debris removal or on-orbit servicing procedures means that establishing fault will be crucial if litigation is to be successful. In doing this, any legal proceedings will look at both norms of behaviour, deviation from which will point towards fault and the types and standard of evidence that will be required.This paper will outline these problems in detail. It will be proposed that what is required to map out the contours of liability are both codification of the norms for satellite operations and clarity on protocols for evidence gathering in cases where fault may be contested in orbital operations. This discussion will identify that a way in which this could be achieved is by the use of “space law games”. These are simulations, similar to military war games, in which fictional scenarios could highlight some of the key legal issues that might need to be dealt with. The paper will outline some of the ways in which the law games might work and pose questions as to what data and other considerations will be needed to make such simulations meaningful.

Space debris ontology for ADR capture methods selection

Studies have concluded that active debris removal (ADR) of the existing in-orbit mass is necessary. However, the quest for an optimal solution does not have a unique answer and the available data often lacks coherence. To improve this situation, modern knowledge representation techniques, that have been shaping the World Wide Web, medicine and pharmacy, should be employed. Prior efforts in the domain of space debris have only focused onto the space situational awareness, neglecting ADR. To bridge this gap we present a domain-ontology of intact derelict objects, i. e. payloads and rocket bodies, for ADR capture methods selection. The ontology is defined on a minimal set of physical, dynamical and statistical parameters of a target object. The practicality and validity of the ontology are demonstrated by applying it onto a database of 30 representative objects, built by combining structured and unstructured data from publicly available sources. The analysis of results proves the ontology capable of inferring the most suited ADR capture methods for considered objects. Furthermore, it confirms its ability to handle the input data from different sources transparently, minimizing user input. The developed ontology provides an initial step towards a more comprehensive knowledge representation framework meant to improve data management and knowledge discovery in the domain of space debris. Furthermore, it provides a tool that should make the initial planning of future ADR missions simpler yet more systematic.

Analytical Framework for Precise Relative Motion in Low Earth Orbits

This work presents a practical and efficient analytical framework for the precise modeling of the relative motion in low Earth orbits. Developed to support the design and verification of relative guidance navigation and control algorithms devoted to spacecraft rendezvous for active debris removal applications, only the orbital perturbation due to nonspherically symmetric mass distribution is considered. The relative motion is modeled in mean relative orbital elements, revisiting the available formulations to include the first-order expansion of the effects due to any even zonal harmonics and the second-order expansion of the unperturbed and terms. Mean/osculating orbital element conversions are obtained by merging a second-order Hamiltonian approach applied to the problem with the Kaula linear perturbation method for the remaining terms of the geopotential. The paper describes the main building blocks of the framework as well as their interfaces because the key aspect to achieve precision is to set up a fully consistent environment. The results show the achievable accuracy under realistic operational conditions for possible guidance and navigation applications.