CERES :: Browsing by Author "Felicetti, Leonard"

Browsing by Author "Felicetti, Leonard"

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Open Access
Atmospheric effects on testing and calibrating star tracking algorithms
(IEEE, 2023-07-27) Jannin, Louis; Felicetti, Leonard
Star trackers are usually considered to be the most accurate sensors, able to achieve a sub-arcminute precision. Star tracker algorithms are often tested and validated with simulated space views. Testing the algorithms with real space images is expensive as it requires implementing them on existing in-space star trackers, or launching new satellites. This study shows that those algorithms are usually performing poorly with groundbased sky pictures and that some adaptations are necessary to take into account the atmospheric effects. In order to tackle this issue, this study will start by implementing and testing two published Lost-In-Space algorithms with a simulated sensor to compare their performance against various noise sources. After comparing the space-based generated views with groundbased images, an adaptation for the aforementioned algorithms is proposed. In order to counter the effect of atmospheric extinction, the number of stars visible in the image is increased by modifying the field-of-view of the camera, the exposure time and estimating the experimental inter-star angular distance error. The idea is to match the star density used in the state-of-the-art algorithms in the experimental pictures. The modified algorithms are tested with the experimental images, and the adaptation process is validated with a good success rate.
Open Access
An automatic process for sample return missions based on dynamic programming optimization
(AIAA, 2021-12-29) Bellome, Andrea; Sanchez, Joan-Pau; Rico Álvarez, Jose Ignacio; Afsa, Hadrien; Kemble, Stephen; Felicetti, Leonard
This work describes a methodology to design sample return missions and rendezvous trajectories options towards cometary objects. These are visited through a succession of fly-bys with Solar System planets, on an overall Multiple Gravity Assist (MGA) transfer. The method is based upon dynamic programming in conjunction to a specific MGA trajectory optimization model to investigate sample return mission scenarios. The model implemented is based on evaluation of grids of transfers between successive planets. The grid is obtained with Lambert arc transfer for a range of departure dates at one planet and range of time of flight to the next planet. For each successive planet in the sequence, discontinuities between incoming and outgoing Lambert arcs arise, which are in part compensated by the fly-by of the planet and, if required, an additional Δv maneuver is added on the given leg of a planet-to-planet transfer. The solutions identified are validated by re-optimizing the complete MGA trajectories as sequences of swing-bys, Deep Space Maneuvers and Lambert arcs transfers. A procedure for discontinuities removal using position constraints is also presented. Mission scenarios towards Saturn are used to validate the accuracy of proposed methods. Trajectory design for novel sample return options and rendezvous are explored for objects among Jupiter Family Comets (JFCs), as well as for never explored targets and orbital regions, as highly inclined Centaurs objects.
Open Access
Autonomous optical navigation for small spacecraft in cislunar space
(International Astronautical Federation (IAF), 2022-09-22) Wu, Christian Xianyang; Machuca, Pablo; Felicetti, Leonard; Sanchez, Joan-Pau
The Earth-Moon system is expected to be increasingly populated especially due to large space missions like the Lunar Gateway. Communication constellations and small spacecraft are also expected to be deployed in the coming years. However, small spacecraft missions are heavily challenged by limited access and high costs of communicating with ground antennas, and constraints on on-board components. Hence, small spacecraft could greatly benefit from the development of autonomous optical navigation, allowing for higher levels of independence, flexibility, and lower operation costs in a complex environment like cislunar space. The scope of this study is to assess the optical navigation (OPNAV) accuracies achievable through horizon-based position estimation algorithms applied to synthetic images of the Moon. The simulation framework is implemented in Python+Vapory+OpenCV, and it simulates the image acquisition process at different solar phase angles and distances (including camera performance), and the processing of images (involving limb-fitting, centroiding and relative position estimation). A conventional ellipse fitting (EF) technique and the recently proposed Christian-Robinson (CR) approach are compared. Lastly, a Monte Carlo analysis allows to assess the effects of different sources of errors and uncertainties and to gain a better understanding of the navigation accuracies that may be obtained in future cislunar scenarios of interest. Preliminary results show that the CR algorithm consistently provides better performance than the EF technique, both in accuracy and computational time. The resulting errors in range estimation depend on distance, with values of approximately 22 km at a distance of 20, 000 km and up to 422 km at a distance of 150, 000 km. In terms of cross-axis distance estimation, the errors present values around 3.55 km (36 arcsec) at 20, 000 km, and 11.85 km (16 arcsec) at 150, 000 km. Furthermore, simulation outcomes show near normally distributed OPNAV performance with standard deviations around 0.68 km and 0.73 arcsec. A power law function is also provided to approximate the trend of OPNAV accuracies as a function of the distance relative to the observed body, is found based on the outcome of this study. Colour maps illustrating OPNAV accuracies as a function of observation geometry provide a comprehensive picture of the expected performance of OPNAV depending on distance and orientation relative to the observed object.
Open Access
Calibration and testing strategies to correct atmospheric effects on star tracking algorithms
(Elsevier, 2024-01-31) Jannin, Louis; Felicetti, Leonard
Star trackers are usually considered to be the most accurate sensors, able to achieve a sub-arcminute precision. Star tracker algorithms are often tested and validated with simulated space views. Testing the algorithms with real space images is expensive as it requires implementing them on existing in-space star trackers, or to launch new satellites. This study shows that those algorithms are usually performing poorly with ground-based sky pictures and that some adaptations are necessary to take into account the atmospheric effects. The adaptation of star tracking algorithms to ground pictures could ease the prototyping phase for new star trackers, or for ground-based and air-borne star trackers, without the need to buy specific testing simulators. In order to tackle this issue, this study will start by implementing and testing two published Lost-In-Space algorithms with a simulated sensor to compare their performance against various noise sources. After comparing the space-based generated views with ground-based images, an adaptation for the aforementioned algorithms is proposed. In order to counter the effect of atmospheric extinction, the number of stars visible in the image is increased by modifying the field-of-view of the camera, the exposure time and estimating the experimental inter-star angular distance error. The idea is to match the star density used in the state-of-the-art algorithms in the experimental pictures. The modified algorithms are tested with the experimental images, and the adaptation process is validated with a good success rate.
Open Access
Collision analysis for multiple satellites released from a common dispenser
(ESA Conference Bureau / ATPI Corporate Events, 2023-06-16) D'Anniballe, Antonio; Felicetti, Leonard; Hobbs, Stephen
The number of small spacecraft launched to space has increased dramatically in the past few years, and with the emergence of mega-constellations it is projected to increase even more in the coming decades. Small satellites are usually launched together in rideshare launches and released from a common dispenser when reaching nominal orbit. Due to the lack of available measurement and control capabilities, the release phase is vulnerable to collision risk, as small uncertainties in the initial position can quickly grow causing a high probability of collision. In this paper a framework for analysing the safety of a genric dispenser is proposed and applied to the study of a cylindrical dispenser. Through numerical simulations and linear covariance propagation, the evolution of the spacecraft state is retrieved and used for computing a set of performance metrics, such as the total probability of collision and the number of conjunction events. This method is then applied to a parametric analysis of the dispenser, examining how the performance metrics vary with parameters such as the velocity of release or the time between releases. The results thus obtained will be relevant to the safe design of spacecraft dispensers.
Open Access
Collision-avoiding model predictive rendezvous strategy to tumbling launcher stages
(AIAA, 2023-06-07) Ramírez, Jesús; Felicetti, Leonard; Varagnolo, Damiano
This paper considers the situation where a small satellite shall autonomously rendezvous with a tumbling object in a circular low Earth orbit (LEO) and derives a path-based model predictive controller that uses the docking point state and position of the chaser to guide it to a safe docking autonomously. The strategy embeds collision avoidance elements and reduces the computational effort for calculating the pulses to be provided by the thrusters through opportune algebraic manipulations, a Runge–Kutta 4 propagation method using linearized state transition matrices, and implicit embedding of dynamically equivalent thrust models, leading to constant state propagation matrices. Furthermore, the inputs design optimization problem and the embedded collision avoidance scheme are modeled and explicitly crafted as convex problems, contributing positively to low computational requirements. The docking and collision avoidance capabilities of the proposed scheme are extensively tested in an environment that accounts for all the perturbations relevant to LEO frameworks, for realistic thrust schemes, and for uncertainties in the measurement. Numerical results assess which tumbling objects can be docked or not by means of the proposed schemes as a function of the tumbling rates versus the thrust capabilities and hardware uncertainty of the docker.
Open Access
A computationally efficient model predictive control scheme for space debris rendezvous
(Elsevier, 2019-11-25) Larsén, Alexander Korsfeldt; Chen, Yutao; Bruschetta, Mattia; Carli, Ruggero; Cenedese, Angelo; Varagnolo, Damiano; Felicetti, Leonard
We propose a non-linear model predictive scheme for planning fuel efficient maneuvers of small spacecrafts that shall rendezvous space debris. The paper addresses the specific issues of potential limited on-board computational capabilities and low-thrust actuators in the chasing spacecraft, and solves them by using a novel MatLab-based toolbox for real-time non-linear model predictive control (MPC) called MATMPC. This tool computes the MPC rendezvous maneuvering solution in a numerically efficient way, and this allows to greatly extend the prediction horizon length. This implies that the overall MPC scheme can compute solutions that account for the long time-scales that usually characterize the low-thrust rendezvous maneuvers. The so-developed controller is then tested in a realistic scenario that includes all the near- Earth environmental disturbances. We thus show, through numerical simulations, that this MPC method can successfully be used to perform a fuel-efficient rendezvous maneuver with an uncontrolled object, plus evaluate performance indexes such as mission duration, fuel consumption, and robustness against sensor and process noises.
Open Access
Conceptual design study based on defined parameters for next-generation Martian rotorcrafts
(IEEE, 2024-05-13) Youhanna, Vishal; Felicetti, Leonard; Ignatyev, Dmitry
The remarkable achievement of NASA’s Ingenuity Helicopter has opened exciting possibilities for the future exploration of Mars, suggesting that aerobots will play a crucial role alongside rovers and landers. However, Ingenuity’s capabilities are limited by its small and relatively basic design. This limitation is primarily evident in its restricted long-range endurance and limited capacity for scientific payloads. To address these shortcomings and advance the field of Martian drone technology, this paper introduces a practical approach to optimising the Martian rotorcraft concepts within the set parameters. The primary objective of these concepts is to enhance performance, endurance, and payload capacity to meet more demanding requirements for future Martian aerobot missions. The paper addresses an essential phase in the design process—an initial sizing of rotary electric vertical takeoff and landing (eVTOL) configurations. This phase is informed by a comprehensive parametric analysis, which considers various factors affecting the performance of drones during hover (stationary flight), vertical climb (ascending flight), and forward flight. The analysis is based on the principles of simplified rotorcraft momentum theory, a foundational concept in rotorcraft engineering. These Martian drone concepts are tailored to address the more challenging mission requirements that future Martian exploration missions are likely to demand. These requirements may include extended flight durations, increased payload capacity to accommodate scientific instruments, and the ability to cover larger areas on the Martian surface. Importantly, the designs are constrained by the maximum size of the spacecraft aeroshell, ensuring that they can be safely transported to Mars within the confines of the protective aeroshell. Among the various configurations considered in this study, a tandem rotorcraft configuration emerged as the most efficient option. This configuration is expected to attain a balance between performance, endurance, and payload capacity, making it a promising choice for future Martian aerobot missions. In contrast, the analysis revealed that a conventional single main rotor configuration within the defined parameters performed poorly in meeting the requirements of the mission.
Embargo
Convex–concave optimization for a launch vehicle ascent trajectory with chance constraints
(Elsevier, 2024-04-18) Sun, Xin; Chai, Senchun; Chai, Runqi; Zhang, Baihai; Felicetti, Leonard; Tsourdos, Antonios
The objective of this paper is to present a convex–concave optimization approach for solving the problem of a multistage launch vehicle ascent trajectory. The proposed method combines convex–concave decomposition and successive linearization techniques to generate a new sequence of convex subproblems to replace the original non-convex problem. Bernstein approximation is used to transform the chance constraints into convex ones. A hp-adaptive pseudospectral scheme is employed to discretize the optimal control problem into a nonlinear programming problem with less computation cost. The performance of the proposed strategy is compared against other typical techniques in a selection of test case scenarios. Numerical results demonstrate the viability of the method and show pros and cons of the proposed technique.
Open Access
Design of a debris removal & on-orbit maintenance mission for mega-constellations
(IEEE, 2023-05-15) Felicetti, Leonard; Basuiau, Mathieu; Belshi, Esli; Diener, Nell; Kutyla, Oskar; Laing, Callum; Noyon, Luka; Owen, Rhodri; Patayane, Shubham; Penney, Joshua; Rapicault, Aurélien; Rowling, Samuel; Shaikh, Shifa; Sherry, Florence; Weber, Alice
This paper shows the results of the design of a mission providing a service of maintenance and removal of mega-constellations. The innovative concept inspiring the design of DeBROOM 2 , Debris Removal and On-Orbit Maintenance Mission, is that a combination of different services can be performed in a modular and standardized way by a single unit servicing satellites in each orbital plane of the constellation. This is achieved through a servicer, which carries both the equipment to refuel target satellites and active-debris removal and propulsive kits, dedicated to the extension of the mission lifetime of cooperative OneWeb satellites, via the takeover of the attitude and orbital control system, as well as to de-orbit uncooperative faulty OneWeb satellites from LEO. The design covers all the areas of system level design, including the definition of system and mission requirements, concept of operations, and mission concept design, along with the design of the servicer and propulsive kits. The paper highlights and identifies the key challenges, the main drivers, and the major traded-off options during the mission concept design. Particular focus is given to the mission analysis aspects, with a computation of the delta-V that characterizes the key maneuvers necessary to serve one or a selection of orbital planes constituting the mega-constellation. The feasibility of the mission is demonstrated by the relevant budgets, along with the utilization of high TRL and COTS components in almost all the key elements of the mission.
Open Access
Design of a pipeline for satellite-aided capture at the giant planets of the solar system
(IEEE, 2024-05-13) Garny, Hugo; Bellome, Andrea; Felicetti, Leonard
For orbiters aiming at the outer planets of our solar system, most of the ∆V cost is associated with the final insertion at the targeted planet. An efficient way of reducing this cost is using flybys of the moons of the planet to reduce the energy of the orbit at arrival, called satellite-aided capture. Designing a full transfer from the Earth to an outer planet, including multiple gravity assists and satellite-aided capture raises important issues that must be addressed. One of them is the multiple control parameters that are required to compute such a trajectory. These parameters must be varied over a large array of values to guarantee that all possibilities are covered with enough precision, ensuring that the final trajectory is the best possible. Current approaches on satellite-aided capture mainly focus on designing trajectories inside the sphere of influence of the targeted planet, with no or minimal focus on linking it to the interplanetary trajectory. However, it remains to create a full pipeline to compute a transfer trajectory from the Earth to an outer planet of the solar system using multiple gravity assists and satellite-aided capture. This paper will focus on creating such a pipeline for orbiters targeting Jupiter, Saturn, Uranus, and Neptune. First, different multiple gravity assists sequences are computed, allowing to make a choice based on transfer time and ∆V cost. This is obtained with a multi-objective dynamic programming exploration, allowing to capture optimal Pareto fronts of ∆V and time of flight in limited computational effort. This transfer sets initial conditions of the satellite-aided capture. Multiple capture sequences are computed around these initial conditions allowing to choose the one minimizing the insertion ∆V . Finally, the last branch of the interplanetary transfer is modified to meet the updated initial conditions of the interplanetary transfer. To compute the satellite-aided capture, the branches between the moons of the sequences are simulated using Lambert arcs. The flybys are approximated as discrete events and are computed to meet the conditions set by the previous and following branches. This pipeline is capable of reproducing scenarios of previous missions to Jupiter and Saturn, ensuring proper functioning of the code. It can also be used to design new trajectories for orbiter at Uranus and Neptune, which have only been visited by Voyager 2 during flybys.
Open Access
Design of an optical system for a Multi-CubeSats debris surveillance mission
(Elsevier, 2023-06-13) Pineau, Dan; Felicetti, Leonard
The detection and observation of space debris in Low Earth Orbit is generally carried out through the use of ground based radars and telescopes. These instruments allow for a precise reconstruction of the space debris trajectories, and therefore represent a key asset for planning avoidance maneuvers when threats of collisions are predicted. The recent deployment of mega-constellations, with the consequent increase of the number of satellites, imposes new challenges in terms of simultaneous tracking capability and readiness of the current space situational awareness systems. This adds to the current need to track small and dull objects to further mitigate the probability of triggering cascade collisions. However, ground based observations are limited due to their intrinsic sensibility to atmospheric refraction, their diurnal inoperability and their dependence on meteorological hazards. This paper proposes to study the feasibility and the benefits of a potential deployment of a constellation of CubeSats in Low Earth Orbit, to acquire optical observations of space debris with enhanced accuracy, as part of the ORCA mission: Orbit Refinement for Collision Avoidance. Here, the focus is on the optical design of the payload instrument to be integrated onboard of the orbiting platforms. The study trades-off the current state-of-art of optical detection technologies, by assessing their performance against a set of specific requirements: (a) the minimization of the uncertainty associated to the image resolution; (b) a field of view that maximizes the extent of the monitored area; (c) an optimal exposure time to avoid under or overexposure of the image; (d) minimization of the effects of light diffraction and above all, (e) the maximization of the signal to noise ratio to detect the smallest and dullest objects possible. Several configurations of optical systems are then chosen as suitable for the ORCA constellation, also considering the system design implications of its integration into a CubeSat, such as size requirements. Commercial Off-The-Shelf hardware are explored and performances of the optical system are evaluated through numerical simulations in order to estimate the detectable sizes of space debris while taking into account their potential distances from the sensor. This paper concludes with estimates of the impact of the ORCA mission on space situational awareness for decades to come.
Open Access
Direct visual servoing and interaction control for a two-arms on-orbit servicing spacecraft
(Elsevier, 2021-12-29) Ramón, José Luis; Pomares, Jorge; Felicetti, Leonard
A direct visual-servoing algorithm for control of a space-based two-arm manipulator is proposed in this paper. The algorithm can be utilized in a two-arm manipulators configuration, where one of the arms performs the manipulation and the second arm is dedicated to the observation of the target zone of manipulation. The algorithm utilizes both visual features extracted from onboard cameras and force and torque measured at the manipulator's end-effector to control the movements of the manipulator during on-orbit servicing operations. The algorithm takes into account the relative dynamics of the bodies involved, it relies on images taken independently from de-localized cameras, e.g. at the end-effector of a second manipulator, and it integrates an impedance control for the compensation of eventual contact reactions when the end effector touches and operates the target body. The analytical derivations demonstrate the stability of the algorithm and incorporate an impedance compliance strategy into an optimal framework formulation. Simulations results in two different scenarios have been presented to show the adequate behavior of the presented approach in on-orbit-servicing operations.
Open Access
Diversity-based heuristic search for multiple-asteroid tours
(IEEE, 2024-05-13) Grabowski, Jan; Bellome, Andrea; Felicetti, Leonard
An asteroid tour is a sequence of asteroid flybys performed by a spacecraft in a single mission. Visiting different types of asteroids would be of a great scientific return, but planning such type of mission is highly complex. This is because the combinatorial problem of selecting sequences of asteroids is coupled with optimal control problem of finding viable trajectories in terms of transfer times and manoeuvre locations. The combinatorial problem can be tackled with heuristic algorithms that explore the search space to find optimized flyby sequences of asteroids. This paper proposes a search strategy to increase the diversity of the set of flyby sequences found from the resolution of the optimization problem. The goal is to find a tree exploration method that will improve the quality of the solutions by increasing the number of targets encountered and eliminating duplicated sequences while preserving the average ∆v cost. A diversity measure for a set of solutions is defined based on the ∆v cost of the transfer and the nature of the asteroids in the sequences. A variant of the Beam Search (BS) algorithm, referred to as Diversity Search (DS), is tested. Unlike BS, the DS algorithm eliminates duplicated sequences from the final set of solutions. New asteroid tours are found, allowing to reach targets with a higher inclination or eccentricity, but the average ∆v of a flyby sequence is higher than solutions found with BS. A hybrid search strategy using BS and DS is explored. The goal is to reduce the search space with respect to two criteria: ∆v and diversity score. By pruning the search space according to ∆v first, the hybrid search algorithm is able to generate a diverse set of asteroid tours while preserving the total ∆v of the solutions. Compared to DS, less new asteroids are encountered in the solutions but the average ∆v remains similar to results obtained with BS.
Open Access
Dust impact and attitude analysis for JAXA’s probe on the Comet Interceptor mission
(Elsevier, 2022-07-20) Machuca, P.; Ozaki, N.; Sa´nchez, J. P.; Felicetti, Leonard
Comet Interceptor (Comet-I), to be launched in 2029 as a piggyback to ESA’s ARIEL mission, is aimed to perform the first fly-by of a pristine long-period comet. The mission will be composed of a main spacecraft, SC A (ESA), and two small probes to be released prior to the fly-by, SC B1 (JAXA) and SC B2 (ESA). This work analyzes the attitude performance of JAXA’s 24U-sized spacecraft through the dust environment of a yet-to-be-discovered target comet. Main challenges to the mission are associated to the high levels of uncertainty and extremity of fly-by conditions: highly-active dust environment, uncertain fly-by altitude (750 ± 250 km (1σ), as of 2021), and large and unknown relative fly-by speeds (15–70 km/s). A Monte Carlo analysis is performed to characterize the effect of dust particle impacts on the attitude of SC B1, and to evaluate the likelihood of satisfying pointing and angular velocity requirements of the science camera. Analysis initially shows that particles of mass 10−8–10−5 kg represent the most relevant source of perturbation due to their transferred angular momentum and likelihood of being encountered, and saturation of reaction wheels is shown unlikely given the large fly-by speeds and short fly-by durations (20 min–2 h). More detailed analysis ultimately suggests a probability larger than 90% of satisfying science camera requirements despite the extreme, uncertain fly-by conditions, dust environment, and component inaccuracies (star tracker, gyroscopes, and reaction wheels). Results also show that upgrading the reaction wheel that is implemented along the camera line-of-sight can improve, but only marginally, attitude performance, and proper alignment of solar arrays parallel to the incoming flow of particles is shown essential to maximize probability of success.
Open Access
Efficiency of tree-search like heuristics to solve complex mixed-integer programming problems applied to the design of optimal space trajectories
(IAF, 2021-10-25) Bellome, Andrea; Carrillo, Maria; Sanchez Cuartielles, Joan Pau; Del Ser, J.; Kemble, Stephen; Felicetti, Leonard
In the past, space trajectory optimization was limited to optimal design of transfers to single destinations, where optimality refers to minimum propellant consumption or transfer time. New technologies, and a more daring approach to space, are today making the space community consider missions that target multiple destinations. In the present paper, we focus on missions that aim to visit multiple asteroids within a single launch. The trajectory design of these missions is complicated by the fact that the asteroid sequences are not known a priori but are the objective of the optimization itself. Usually, these problems are formulated as global optimization (GO) problems, under the formulation of mixed-integer non-linear programming (MINLP), on which the decision variables assume both continuous and discrete values. However, beyond the aim of finding the global optimum, mission designers are usually interested in providing a wide range of mission design options reflecting the multi-modality of the problems at hand. In this sense, a Constraint Satisfaction Problem (CSP) formulation is also relevant. In this manuscript, we focus on these two needs (i.e. tackling both the GO and the CSP) for the asteroid tour problem. First, a tree-search algorithm based upon the Bellman’s principle of optimality is described using dynamic programming approach to address the feasibility of solving the GO problem. This results in an efficient and scalable procedure to obtain global optimum solutions within large datasets of asteroids. Secondly, tree-search strategies like Beam Search and Ant Colony Optimization with back-tracking are tested over the CSP formulations. Results reveal that BS handles better the multi-modality of the search space when compared to ACO, as this latter solver has a bias towards elite solutions, which eventually hinders the diversity needed to efficiently cope with CSP over graphs.
Open Access
Futuristic Martian aerobot design
(2022-08-26) Youhanna, Vishal; Ignatyev, Dmitry; Felicetti, Leonard
NASA’s Ingenuity Helicopter has proved that flight is possible on Mars with its ingenious yet elementary design, but it lacks long-range endurance and the capacity to carry any dedicated scientific instruments. In this paper, we propose a preliminary study for an innovative development in the series of Martian drones. The Futuristic Mars Aerobot Design (FuMAD) proposes a foldable winged drone based on Ingenuity’s rotors design for enhancing long-range endurance and payload capacity.
Open Access
Image-based visual servoing control for spacecraft formation flying
(IEEE, 2020-08-21) Felicetti, Leonard; Pomares, Jorge
This paper proposes an image-based visual-servoing algorithm that allows for optimal formation control. The proposed distributed controller utilizes visual features of other team members, retrieved from images captured by onboard cameras, to autonomously plan and perform formation acquisition, keeping or reconfiguration maneuvers. The problems of minimization of the control effort is analyzed and the paper proposes an optimal framework for developing controllers that address the issue. The viability of such a technique is explored through numerical simulations.
Open Access
In-orbit assembly: a baseline for large space structures through standardised tiles and interfaceable elements
(International Astronautical Federation (IAF), 2023-07-04) Ji Zhang, Yi Qiang; Wright, Rachel; Alão, Sara; Arora, Triyan Pal; Fernandes, James Nathan; Haskett, Roman; Idiondo, Xabier; Kreutz, Adrien; Rodriguez Gomez, Pablo Javier; Martinez Galisteo, Maria; Santín, Óscar; Soltani, Yacine; Felicetti, Leonard; Upadhyayn, Saurabh
Novel mission concepts of large space infrastructures such as Space-Based Solar power, Large Scale Communications, ultra-wide telescopes, are not possible without in-situ assembly, due to modern launch vehicle constraints. Some of the key challenges of in-orbit assembly of large structures are standardized components, efficient and simple robotic assembly and structural integrity in the build. This paper will detail an in-depth technology demonstration mission description of an in-orbit assembly mission utilizing robotic assemblers. To do so, we propose utilizing a standardized and modular tile, or building block, that can embed diverse types of payloads, provide locomotion, and acts as a structural element by creating a more robust and sounder base frame. This multipurpose tile reduces production costs. Two launches will be considered: a Hub station with the necessary mission subsystems; and a Supply Vehicle with cargo storage capability for the tile components. The aim is to highlight and test the aforementioned novel technologies to be used in space assembly. The mass and cost budgets will highlight the relationship between in-orbit mass injected and necessary cost, and any other requirements necessary for scalability.  For the demonstration building of the desired structure the Hub and Supply vehicle will rendezvous and dock in a Sun Synchronous Earth orbit. A 6 degree of freedom robotic arm will navigate with the aid of a path planning algorithm through an electrically powered rail system embedded on the backside of the tile structure, performing the assembly process. The locomotion will be aided by tracks and ball joint interfaces for the rail. The tiles would be picked by the arm and transported from the cargo vehicle to its destination, interlocked with other tiles through an interface, building up the size of the structure and the reach of the assembler. The payload interface on the frontside of tile is designed to accept various kinds than can be replaceable. The Hub will provide AOCS, power, and communications to the structure during assembly.  The information presented in this paper is intended to be used as a starting point and reference source for sustainable future developments regarding in-orbit assembly of large space infrastructures. Our design is developed as a baseline, we have considered studies and have demonstrated the scalability capabilities of the proposed approach using standardized tiles. The scalability model created by this concept enables through a streamlined and efficient manner projects for years to come.
Open Access
A mission architecture and systems level design of navigation, robotics and grappling hardware for an on-orbit servicing spacecraft
(UKSEDS, 2020-10-10) Easdown, William; Felicetti, Leonard
On-orbit servicing (OOS) includes a range of servicing types that increase the lifetime of a satellite and its performance, as well as ensuring that it does not contribute to the growing issue of space debris. The avoidance of satellites becoming derelict is particularly important given the rise of ‘mega-constellations’. With the first cases of it in the 1970s, OOS has been achieved many times using crewed missions and robots controlled from the ground or by astronauts, for example during repairs and upgrades to the Hubble Space Telescope (HST) and on the International Space Station (ISS). This has allowed various space agencies and other organisations to mature processes and tools for several OOS mission types. The Northrop Grumman Mission Extension Vehicle-1’s (MEV-1) success servicing Intelsat 901 in early 2020 demonstrated that OOS is now viable from a commercial as well as technical standpoint. However, due to low technology maturity, autonomous rendezvous and proximity operations (RPO) and servicing remain challenging, despite autonomous rendezvous and docking with space stations having been demonstrated many times. This report will investigate the current state of the art in OOS and which technologies require further development to enable widespread adoption of OOS. A mission architecture to support OOS of satellites in the highest populated orbits will be described. Using this architecture, the report will focus on the selection of hardware required for guidance, navigation and control (GNC), for relative navigation towards and docking with the target satellite and of robotics to service the target. The report will use the design of the OneWeb satellites as a baseline for the target spacecraft but will also show how the servicing spacecraft’s services could be applied to a range of orbits and target spacecraft