Design and Operational Elements of the Robotic Subsystem for the e.deorbit Debris Removal Mission

This paper presents a robotic capture concept that was developed as part of the e.deorbit study by ESA. The defective and tumbling satellite ENVISAT was chosen as a potential target to be captured, stabilized, and subsequently de-orbited in a controlled manner. A robotic capture concept was developed that is based on a chaser satellite equipped with a seven degrees-of-freedom dexterous robotic manipulator, holding a dedicated linear two-bracket gripper. The satellite is also equipped with a clamping mechanism for achieving a stiff fixation with the grasped target, following their combined satellite-stack de-tumbling and prior to the execution of the de-orbit maneuver. Driving elements of the robotic design, operations and control are described and analyzed. These include pre and post-capture operations, the task-specific kinematics of the manipulator, the intrinsic mechanical arm flexibility and its effect on the arm's positioning accuracy, visual tracking, as well as the interaction between the manipulator controller and that of the chaser satellite. The kinematics analysis yielded robust reachability of the grasp point. The effects of intrinsic arm flexibility turned out to be noticeable but also effectively scalable through robot joint speed adaption throughout the maneuvers. During most of the critical robot arm operations, the internal robot joint torques are shown to be within the design limits. These limits are only reached for a limiting scenario of tumbling motion of ENVISAT, consisting of an initial pure spin of 5 deg/s about its unstable intermediate axis of inertia. The computer vision performance was found to be satisfactory with respect to positioning accuracy requirements. Further developments are necessary and are being pursued to meet the stringent mission-related robustness requirements. Overall, the analyses conducted in this study showed that the capture and de-orbiting of ENVISAT using the proposed robotic concept is feasible with respect to relevant mission requirements and for most of the operational scenarios considered. Future work aims at developing a combined chaser-robot system controller. This will include a visual servo to minimize the positioning errors during the contact phases of the mission (grasping and clamping). Further validation of the visual tracking in orbital lighting conditions will be pursued

Space Debris as an international safety issue. Case studies in active removing techniques.

Η παρούσα διπλωματική εργασία πραγματοποιήθηκε υπό την αιγίδα του Τμήματος Πληροφορικής & Τηλεπικοινωνιών του Εθνικού και Καποδιστριακού Πανεπιστημίου Αθηνών για το Μεταπτυχιακό Πρόγραμμα Σπουδών «Διαστημικές Τεχνολογίες, Εφαρμογές και Υπηρεσίες». Στόχος της διατριβής ήταν να αναδείξει τη σημασία της έγκαιρης ανάληψης δράσης σε διεθνές επίπεδο, ώστε το ζήτημα των διαστημικών υπολειμμάτων να μην γίνει μείζονα απειλή κατά των επιχειρησιακών διαστημικών συστημάτων και των ανθρώπων που βρίσκονται σε τροχιά γύρω από τη γη. Παρόλο που το θέμα των διαστημικών υπολειμμάτων έχει απασχολήσει τον επιστημονικό, τεχνολογικό και πολιτικό κόσμο σχεδόν από την απαρχή της διαστημικής εποχής, δεν έχει ακόμα βρεθεί ουσιαστική λύση ούτε σε επιστημονικό, ούτε σε τεχνολογικό, ούτε σε πολιτικό επίπεδο. Στα παρακάτω κεφάλαια γίνεται μια ανάλυση του προβλήματος των διαστημικών υπολειμμάτων και αναφέρονται τα τεχνολογικά, νομικά και οικονομικά εμπόδια που παρουσιάζονται σε μια προσπάθεια απομάκρυνσης διαστημικών υπολειμμάτων. Στη συνέχεια αναπτύσσεται η έννοια της ασφάλειας στο διάστημα και πώς αυτή επηρεάζεται από την ύπαρξη διαστημικών υπολειμμάτων. Ταυτόχρονα γίνεται μια ανάλυση του ρίσκου που διέπει τις διαστημικές αποστολές, τόσο σε επίπεδο συστημάτων, όσο και σε επίπεδο ανθρώπινης ζωής σε συνάρτηση με την αύξηση των διαστημικών υπολειμμάτων. Από την ανάλυση αυτή δεικνύεται ότι η αύξηση των διαστημικών υπολειμμάτων λόγω περισσότερων διαστημικών αποστολών, καθώς και το ξεκίνημα της εποχής του διαστημικού τουρισμού, θα αποτελέσει έναν ισχυρό παράγοντα κινδύνου εάν δεν παρθούν άμεσα μέτρα. Στη συνέχεια παρουσιάζονται, σε τεχνικό επίπεδο, οι δυνατότητες εντοπισμού και παρατήρησης των διαστημικών υπολειμμάτων, καθώς και οι προοπτικές αυτών των συστημάτων. Επιπλέον, γίνεται αναφορά στο ποιες θα είναι οι μελλοντικές απαιτήσεις εντοπισμού και παρατήρησης των διαστημικών υπολειμμάτων ώστε να είναι αποτελεσματικές οι αποστολές απομάκρυνσης διαστημικών υπολειμμάτων. Συνεχίζοντας, παρουσιάζονται οι κύριες τεχνικές ενεργητικής απομάκρυνσης διαστημικών υπολειμμάτων, όπως αυτές μελετώνται και κατασκευάζονται από διαστημικούς οργανισμούς και διαστημικές εταιρείες. Τέλος, διενεργείται μια συγκριτική μελέτη των τεχνικών απομάκρυνσης διαστημικών υπολειμμάτων μέσω βαθμολόγησης τεσσάρων κύριων κριτηρίων και παρουσιάζεται ως αποτέλεσμα μια υπόθεση βέλτιστης τεχνολογίας απομάκρυνσης διαστημικών υπολειμμάτων. Από τη ανάλυση της Διπλωματικής Εργασίας γίνεται αντιληπτή η σημαντικότητα του να ληφθούν άμεσα αποφάσεις και να γίνουν οι κατάλληλες ενέργειες, ώστε τα διαστημικά υπολείμματα να μην αποτελέσουν κύριο παράγοντα κινδύνου για την ανθρωπότητα όπως τη γνωρίζουμε σήμερα.This thesis was conducted under the umbrella of the Department of Informatics & Telecommunication of the National and Kapodistrian University of Athens for the Postgraduate Program “Space Technologies, Applications and Services”. The aim of the thesis was to highlight the significance of taking timely action in an international level, for the space debris issue not to become a major threat against the operational space systems and the humans orbiting earth. Although the issue of space debris has occupied the scientific, technological and political world almost since the beginning of the space era, no substantial solution has yet been found either at a scientific, technological or political level. The following chapters provide an analysis of the space debris problem and present the technological, legal, and financial barriers to an effort to remove space debris. Then, the concept of security in space and the way it is affected by the existence of space debris is developed. At the same time, an analysis of the risk that governs space missions, both at the level of operation of space systems and at the level of human life in relation to the increase in space debris, is conducted. This analysis shows that the increase in space debris due to more space missions, as well as the onset of the era of space tourism, will be a strong risk factor if immediate measures are not taken. Then, at a technical level, the possibilities of locating and tracking space debris are presented, as well as the prospects of these technical systems. In addition, the future requirements for space debris detection and tracking, for space debris removal missions to be effective, are presented. Additionally, the main active space debris removal techniques studied and developed by space agencies and space companies are presented. Finally, a comparative study of space debris removal techniques is conducted by scoring four main criteria and a hypothesis of an optimal space debris removal technology is presented as a result. The analysis of the thesis shows the importance of making immediate decisions and taking the appropriate actions so that space debris does not constitute a major risk factor for humanity as we know it today

Robotics and AI-Enabled On-Orbit Operations With Future Generation of Small Satellites

The low-cost and short-lead time of small satellites has led to their use in science-based missions, earth observation, and interplanetary missions. Today, they are also key instruments in orchestrating technological demonstrations for On-Orbit Operations (O 3 ) such as inspection and spacecraft servicing with planned roles in active debris removal and on-orbit assembly. This paper provides an overview of the robotics and autonomous systems (RASs) technologies that enable robotic O 3 on smallsat platforms. Major RAS topics such as sensing & perception, guidance, navigation & control (GN&C) microgravity mobility and mobile manipulation, and autonomy are discussed from the perspective of relevant past and planned missions

Analysis and modeling of satellite flexible bodies in Simscape Multibody

Questa Tesi Magistrale fornisce un’analisi per trovare un metodo numericamente efficiente per modellare i corpi flessibili di un satellite. L’analisi numerica è condotta su MATLAB - Simulink confrontando due rappresentazioni matematiche dei corpi flessibili: il metodo a “parametri forfettari” e il metodo della “trave flessibile”, utilizzati per modellare un pannello solare e un braccio robotico a 3 GdL. Questo studio ha lo scopo di contribuire ad un progetto condotto presso l’Università di Padova in collaborazione con l’Agenzia Spaziale Europea (ESA): esso si concentra sullo sviluppo di tecnologie di Guidance Navigation Control (GNC) per missioni di In-Orbit Servicing (IOS) e Active Debris Removal (ADR), condotte da un veicolo spaziale, dotato di un braccio robotico in grado di afferrare detriti spaziali e agganciare altri satelliti; in particolare, l’attività di ricerca oggetto del contratto è un simulatore della dinamica di scenari per Close Proximity Operations (CPOs), denominato Functional Engineering Simulator (FES). Il pannello solare e il braccio robotico, montati sul satellite, devono essere studiati perché le loro deformazioni possono occasionalmente diventare abbastanza severe da influenzare sia le proprie prestazioni che quelle degli altri sistemi. Se ciò dovesse accadere, le vibrazioni verrebbero notevolmente amplificate, accelerando il tasso di usura meccanica, aumentando il consumo di energia e interferendo con i compiti che necessitano un’alta precisione. Gli obiettivi di questa tesi Magistrale sono: (1) creare un Simulatore adatto per studiare la risposta dinamica del pannello solare soggetto a perturbazioni esterne e gli effetti degli elementi flessibili del braccio robotico durante il suo movimento, (2) confrontare i due metodi dei corpi flessibili in termini di accuratezza dei risultati e tempi di simulazione, (3) trovare il modello matematico che possa rappresentare adeguatamente la teoria dei corpi flessibili, in modo da poter essere utilizzato per modellare un vero simulatore. Il pannello solare è stato modellato secondo due diversi scenari, i quali rappresentano due esempi di architetture di missioni spaziali che prevederanno operazioni con bracci robotici nel prossimo futuro. Il suo comportamento è stato studiato analizzando la risposta degli impulsi causati dalle perturbazioni esterne che agiscono sulla superficie del pannello solare. Invece, il braccio robotico è stato modellato per seguire un percorso rettilineo da un punto iniziale a un punto finale e il comportamento dei suoi elementi flessibili è stato studiato ad ogni istante del suo movimento. Per modellare un elemento del veicolo spaziale, il metodo della trave flessibile utilizza un blocco già esistente di Simscape Multibody. Per questo motivo, esso è stato considerato come metodo di riferimento per verificare l’affidabilità di quello a parametri forfettari, per il quale i risultati hanno dimostrato essere uno metodo valido per descrivere il comportamento dei corpi flessibili di un veicolo spaziale, soprattutto grazie ai suoi rapidi tempi di simulazione, i quali lo rendono adatto per modellare in un vero simulatore.This Master Thesis provides an analysis to find a numerically efficient method to model a satellite flexible bodies in the MATLAB - Simulink environment. The numerical analysis is conducted by comparing two mathematical representations of flexible bodies: the Lumped-parameter method and the Flexible-beam method, which are implemented by the Simulation Tool to model and simulate the dynamics of a solar panel and a 3-DOF robotic arm. This study is on purpose to contribute to a project conducted at the University of Padua in collaboration with the European Space Agency (ESA): it focuses on the development of the Guidance Navigation Control technologies (GNC) suitable to be applied to both In-Orbit Servicing (IOS) and Active Debris Removal (ADR) missions conducted by a chaser spacecraft equipped with a robotic arm that can grab space debris and lock onto other satellites; in particular, the research activity under contract is a simulator of the dynamics of Close Proximity Operations (CPOs) scenarios, called Functional Engineering Simulator (FES). The solar panel and robotic arm mounted on the spacecraft behave as flexible bodies and need to be studied because their deformations may occasionally become severe enough to affect the performance of their respective systems. If these effects occur, vibrations are significantly amplified, accelerating the rate of mechanical wear, increasing power consumption, and interfering with high-precision tasks. The goals of this Master Thesis are: (1) to create a reliable simulation tool to study the dynamic response of the solar panel subject to external perturbations and the effects of the flexible elements of the robotic arm during its motion, (2) to compare the two flexible body methods in terms of accuracy of results and execution time, (3) to find the mathematical model that can adequately represent the flexible body theory so that it can be used to model a real-time simulator. The solar panel is modeled according to two different scenarios, which represent two examples of space mission architectures requiring robotic operations in the near future. Its behavior is studied by analyzing the response to impulses caused by external perturbations acting on the solar panel surface. On the other hand, the robotic arm is modeled to follow a rectilinear path from a starting point to an end point and the behavior of its flexible elements is studied at each time-step of this motion. The flexible-beam method consists of using an existing Simscape Multibody block to model the spacecraft element. Hence, it has been considered as a benchmark in order to verify the reliability of the lumped-parameter method, for which the results demonstrated that it is a valid tool for describing the behavior of flexible bodies of a spacecraft, mainly due to its fast execution times, which make it suitable for modeling in a real-time simulator

ET-Class, an Energy Transfer-based Classification of Space Debris Removal Methods and Missions

Space debris is positioned as a fatal problem for current and future space missions. Many e ective space debris removal methods have been proposed in the past decade, and several techniques have been either tested on the ground or in parabolic ight experiments. Nevertheless, no uncooperative debris has been removed from any orbit until this moment. Therefore, to expand this research eld and progress the development of space debris removal technologies, this paper reviews and compares the existing technologies with past, present, and future methods and missions. Moreover, since one of the critical problems when designing space debris removal solutions is how to transfer the energy between the chaser/de-orbiting kit and target during the rst interaction, this paper proposes a novel classi cation approach, named ET-Class (Energy Transfer Class). This classi cation approach provides an energy-based perspective to the space debris phenomenon by classifying how existing methods dissipate or store energy during rst contact

Robotic Manipulation and Capture in Space: A Survey

Space exploration and exploitation depend on the development of on-orbit robotic capabilities for tasks such as servicing of satellites, removing of orbital debris, or construction and maintenance of orbital assets. Manipulation and capture of objects on-orbit are key enablers for these capabilities. This survey addresses fundamental aspects of manipulation and capture, such as the dynamics of space manipulator systems (SMS), i.e., satellites equipped with manipulators, the contact dynamics between manipulator grippers/payloads and targets, and the methods for identifying properties of SMSs and their targets. Also, it presents recent work of sensing pose and system states, of motion planning for capturing a target, and of feedback control methods for SMS during motion or interaction tasks. Finally, the paper reviews major ground testing testbeds for capture operations, and several notable missions and technologies developed for capture of targets on-orbit

Coulomb drag propulsion experiments of ESTCube-2 and FORESAIL-1

This paper presents two technology experiments – the plasma brake for deorbiting and the electric solar wind sail for interplanetary propulsion – on board the ESTCube-2 and FORESAIL-1 satellites. Since both technologies employ the Coulomb interaction between a charged tether and a plasma flow, they are commonly referred to as Coulomb drag propulsion. The plasma brake operates in the ionosphere, where a negatively charged tether deorbits a satellite. The electric sail operates in the solar wind, where a positively charged tether propels a spacecraft, while an electron emitter removes trapped electrons. Both satellites will be launched in low Earth orbit carrying nearly identical Coulomb drag propulsion experiments, with the main difference being that ESTCube-2 has an electron emitter and it can operate in the positive mode. While solar-wind sailing is not possible in low Earth orbit, ESTCube-2 will space-qualify the components necessary for future electric sail experiments in its authentic environment. The plasma brake can be used on a range of satellite mass classes and orbits. On nanosatellites, the plasma brake is an enabler of deorbiting – a 300-m-long tether fits within half a cubesat unit, and, when charged with -1 kV, can deorbit a 4.5-kg satellite from between a 700- and 500-km altitude in approximately 9–13 months. This paper provides the design and detailed analysis of low-Earth-orbit experiments, as well as the overall mission design of ESTCube-2 and FORESAIL-1.Peer reviewe