CubeSats have become versatile platforms for various space missions(e.g.,on-orbit servicing and debris removal)owing to their low cost and flexibility.Many space tasks involve proximity operations that require precise...CubeSats have become versatile platforms for various space missions(e.g.,on-orbit servicing and debris removal)owing to their low cost and flexibility.Many space tasks involve proximity operations that require precise guidance,navigation,and control(GNC)algorithms.Vision-based navigation is attracting interest for such operations.However,extreme lighting conditions in space challenge optical techniques.The on-ground validation of such navigation systems for orbital GNC becomes crucial to ensure their reliability during space operations.These systems undergo rigorous testing within their anticipated operational parameters,including the exploration of potential edge cases.The ability of GNC algorithms to function effectively under extreme space conditions that exceed anticipated scenarios is crucial,particularly in space missions where the scope of errors is negligible.This paper presents the ground validation of a GNC algorithm designed for autonomous satellite rendezvous by leveraging hardware-in-the-loop experiments.This study focuses on two key areas.First,the rationale underlying the augmentation of the robot workspace(six-degree-of-freedom UR10e robot+linear rail)is investigated to emulate relatively longer trajectories with complete position and orientation states.Second,the control algorithm is assessed in response to uncertain pose observations from a vision-based navigation system.The results indicate increased control costs with uncertain navigation and exemplify the importance of on-ground testing for system validation before launch,particularly in extreme cases that are typically difficult to assess using software-based testing.展开更多
Establishing a sustainable mining expedition for the asteroids of the main belt over the 2035–2050 horizon is the visionary problem of the 12th Global Trajectory Optimisation Competition. A fleet of mining ships must...Establishing a sustainable mining expedition for the asteroids of the main belt over the 2035–2050 horizon is the visionary problem of the 12th Global Trajectory Optimisation Competition. A fleet of mining ships must rendezvous twice with asteroids to deploy miners and collect minerals. In this paper, we describe the approach of the CS Group team, OptimiCS, to solve this challenging problem. We present the symmetrical construction of upstream and downstream semi-sequences of asteroids, maximizing the mining time expectancy via a beam search with tabu iterations, and the composition of these semi-sequences into complete fleet routes, maximizing the total collected mass via simulated annealing. While representative Earth–asteroid legs are precomputed, the delta-V costs of the asteroid-to-asteroid hops composing the sequences are initially approximated during exploration via a method that refines the accuracy of the maximum initial mass. The resulting high-fidelity trajectories are adjusted and optimized via a direct method and nonlinear programming.展开更多
Fuel-optimal orbit-attitude motion planning for spacecraft close-range rendezvous and synchronization requires solving a two-point boundary value problem with continuous input actuation.This paper presents a geometric...Fuel-optimal orbit-attitude motion planning for spacecraft close-range rendezvous and synchronization requires solving a two-point boundary value problem with continuous input actuation.This paper presents a geometric approach to the problem,which not only encompasses both translational and rotational dynamics,but also incorporates a novel adaptive multiplier method to enforce actuation constraints during the optimization process.Further,in the case of underactuation,such as small single-thruster spacecraft,the paper proposes a guided technique for the geometric approach to direct the attitude using the optimal translational trajectory.The geometric approach is verified through several case studies,where it is compared against a direct method optimization and a concurrent controller,to demonstrate the computational efficiency as well as resulting optimal trajectories of the approach.展开更多
The accuracy of angles-only initial orbit determination(IOD)is significantly compromised when only a short-arc orbit is observed.The ill-conditioned problem in matrices due to weak geometric constraints caused by shor...The accuracy of angles-only initial orbit determination(IOD)is significantly compromised when only a short-arc orbit is observed.The ill-conditioned problem in matrices due to weak geometric constraints caused by short arcs and observation errors typically causes significant errors in the estimated ranges and thus unsatisfactory IOD.This paper presents a critical analysis of the ill-conditioned problem using the Gooding algorithm and proposes several techniques to improve it.On the basis of multiple observations,a least-squares method is proposed to solve the ranges at the first and last epochs.For the short-arc case,the ridge estimation technique is applied to mitigate the ill-conditioned problem.To determine whether an orbit is eccentric,a procedure to assess orbit eccentricity is developed via the range-search method,which aims to provide reasonably accurate initial ranges to the Gooding algorithm.Finally,an eccentricity-constraint technique for the Gooding algorithm is proposed for cases where the orbit is determined to be nearly circular.The performances of these techniques on space-based simulation data are assessed,and an improved Gooding algorithm(I-Gooding)suitable for various observation conditions is proposed.The I-Gooding algorithm is subsequently applied to process actual ground-based observations.The results show that its accuracy in estimating the semimajor axis is 47%higher than that afforded by the standard Gooding algorithm.展开更多
The performance of space antennas is significantly affected by thermal deformation owing to the harsh thermal environment in space.This results in potential degradation in pointing accuracy and overall functionality.T...The performance of space antennas is significantly affected by thermal deformation owing to the harsh thermal environment in space.This results in potential degradation in pointing accuracy and overall functionality.This study focused on the analysis and control of thermal deformation in large-scale two-dimensional planar phased array antennas.Employing the finite element method,we developed a comprehensive thermal and structural model of the antenna.This enabled us to simulate the steady-state temperature field and the associated thermal deformation at various orbital positions.To address this deformation issue,we propose an innovative shape-control approach that utilizes distributed cable actuators.The shape control challenge was reformulated into a layered optimization problem concerning actuator placement and force application.In the outer optimization layer,a discrete particle swarm optimization algorithm was used to determine the optimal locations for the actuators.In the inner optimization layer,quadratic programming was subsequently applied to calculate the optimal control forces for each actuator.We validated the proposed method by numerically simulating a novel large-scale two-dimensional planar phased array antenna.The results demonstrated the effectiveness of our method in mitigating thermal deformation and maintaining the structural integrity and shape accuracy of the antennas.展开更多
The influence of a disturbing gravity field on the impact points of long-range vehicles(LRVs)has become increasingly prominent,which is an important factor affecting the accuracy of impact point prediction(IPP).To ach...The influence of a disturbing gravity field on the impact points of long-range vehicles(LRVs)has become increasingly prominent,which is an important factor affecting the accuracy of impact point prediction(IPP).To achieve high-accuracy and fast IPP for LRVs under the influence of a disturbing gravity field,a data-driven multi-level IPP method is proposed to balance the prediction accuracy and real-time performance.At the first level,the impact point of the current flight state is predicted based on elliptical trajectory theory,and the impact deviation of the elliptical trajectory(ID-ET)is calculated.At the second and third levels,a neural network(NN)model is established to learn the ID-ET caused by the J2 term and re-entry aerodynamic drag as well as that caused by the disturbing gravity field.To improve the NN prediction performance,an auxiliary circle is applied to decouple the ID-ET.To reduce the difficulty of NN learning,a training strategy is designed based on the idea of curriculum learning,which improves training accuracy.At the same time,a hybrid sample generation strategy is proposed to improve the NN generalization ability.A detailed simulation experiment is designed to analyze the advantages and computational complexity of the proposed method.The simulation results showed that the proposed model has a high prediction accuracy,strong generalization ability,and good real-time performance under the influence of the disturbing gravity field and re-entry aerodynamic drag.Among the 317,360 samples contained in the training and test sets,the 3σ prediction error was 6.21 m.On an STM32F407 single-chip microcomputer,the IPP required 3.415 ms.The proposed method can provide support for the design of guidance algorithms and is applicable to engineering practice.展开更多
Escalating concerns about climate change and the limitations of alternative energy sources have renewed interest in space-based solar power.Among numerous concepts proposed for space-based solar power,the modular flat...Escalating concerns about climate change and the limitations of alternative energy sources have renewed interest in space-based solar power.Among numerous concepts proposed for space-based solar power,the modular flat-plane sandwich configuration has emerged as a promising candidate,owing to its structural simplicity that lends itself well to recent advancements in wireless power transmission and on-orbit robotic assembly.As a consequence of its simple structure,there are also new challenges with respect to attitude design due to the coupling of sunlight collection and power beaming on opposing sides of the flat plane.This paper develops a versatile attitude trajectory optimization approach that maximizes power-beaming efficiency for modular space-based solar power configurations in Molniya orbits while minimizing the attitude control effort.The developed optimization approach employs a genetic algorithm to study two attitude design strategies.The first attitude design strategy investigates initially spinning configurations about the ecliptic normal and compares the power-beaming efficiency against solutions using near-optimal attitude and spin axis parameters for a one-year period determined through optimization.The second attitude design strategy employs multiple runs of a genetic algorithm discretized at different time of the year,each determining an inertially fixed attitude optimized for a one-month period.These attitudes are then used to design attitude maneuvers,each with an axis and rate of actuation designed analytically.The outcomes of this study determined several viable attitude trajectory optimization and design strategies for multiple space-based solar power system configurations,which generate attitude trajectories that maximize power beaming in Molniya orbits while minimizing attitude control effort.展开更多
We present the solution approach developed by the team“TheAntipodes”during the 12th edition of the Global Trajectory Optimization Competition(GTOC12).An overview of the approach is as follows:(1)generate asteroid su...We present the solution approach developed by the team“TheAntipodes”during the 12th edition of the Global Trajectory Optimization Competition(GTOC12).An overview of the approach is as follows:(1)generate asteroid subsets,(2)chain building with beam search,(3)convex low-thrust trajectory optimization,(4)manual refinement of rendezvous times,and(5)optimal solution set selection.The generation of asteroid subsets involves a heuristic process tofind sets of asteroids that are likely to permit high-scoring asteroid chains.Asteroid sequences“chains”are built within each subset through a beam search based on Lambert transfers.Low-thrust trajectory optimization involves the use of sequential convex programming(SCP),where a specialized formulationfinds the mass-optimal control for each ship’s trajectory within seconds.Once a feasible trajectory has been found,the rendezvous times are manually refined with the aid of the control profile from the optimal solution.Each ship’s individual solution is then placed into a pool where the feasible set that maximizes thefinal score is extracted using a genetic algorithm.Ourfinal submitted solution placedfifth with a score of 15,489.展开更多
The Hayabusa2 extended mission,named Hayabusa2#(SHARP:Small Hazardous Asteroid Reconnaissance Probe),is planned to rendezvous with the fast-rotating asteroid 1998 KY26 in 2031.Hayabusa2#will be the first ever mission ...The Hayabusa2 extended mission,named Hayabusa2#(SHARP:Small Hazardous Asteroid Reconnaissance Probe),is planned to rendezvous with the fast-rotating asteroid 1998 KY26 in 2031.Hayabusa2#will be the first ever mission to rendezvous with such a rapidly rotating small asteroid,posing significant challenges because of its distinctive dynamical environment.In this paper,we investigate potential target marker(TM)deployment strategies,for both landing and orbiting scenarios,to maximize science acquisition.In particular,we model the surface and orbital environments to identify feasible target market operations and present landing site selection strategies and candidate insertion orbits considering realistic deployment errors.The TM is one of the only two remaining deployable payloads,and therefore,can play a critical role during the extended mission phase.Our results show that surface operations can be extremely challenging whereas orbit operations could help us gain valuable information on the asteroid's gravity field.Overall,this research contributes to the exploration and characterization of extremely small bodies specifically through the use of artificial objects,in this case the target marker.展开更多
In 2023, the 12th edition of Global Trajectory Competition was organized around the problem referred to as “Sustainable Asteroid Mining”. This paper reports the developments that led to the solution proposed by ESA...In 2023, the 12th edition of Global Trajectory Competition was organized around the problem referred to as “Sustainable Asteroid Mining”. This paper reports the developments that led to the solution proposed by ESA’s Advanced Concepts Team. Beyond the fact that the proposed approach failed to rank higher than fourth in the final competition leader-board, several innovative fundamental methodologies were developed which have a broader application. In particular, new methods based on machine learning as well as on manipulating the fundamental laws of astrodynamics were developed and able to fill with remarkable accuracy the gap between full low-thrust trajectories and their representation as impulsive Lambert transfers. A novel technique was devised to formulate the challenge of optimal subset selection from a repository of pre-existing optimal mining trajectories as an integer linear programming problem. Finally, the fundamental problem of searching for single optimal mining trajectories (mining and collecting all resources), albeit ignoring the possibility of having intra-ship collaboration and thus sub-optimal in the case of the GTOC12 problem, was efficiently solved by means of a novel search based on a look-ahead score and thus making sure to select asteroids that had chances to be re-visited later on.展开更多
The removal of large space debris from a geostationary orbit to a disposal orbit via an ion beam shepherd spacecraft was considered in this study,with attention given to the electrostatic effect.The generation of an i...The removal of large space debris from a geostationary orbit to a disposal orbit via an ion beam shepherd spacecraft was considered in this study,with attention given to the electrostatic effect.The generation of an ion force,which provides contactless thrust,occurs because of the transfer of momentum from the ions of the engine plume of the spacecraft to the space debris.This process is accompanied by the transfer of a positive charge to the space debris.As a result,electrostatic interactions occur between the spacecraft and space debris.The goals of this study were to assess the influence of this effect on the dynamics of space debris during contactless ion beam-assisted removal and to develop hybrid contactless transportation schemes based on the use of an ion beam and electrostatic interactions.A mathematical model describing the motion of space debris and spacecraft under the influence of ionic and electrostatic forces and torques was developed.The concepts of electrostatic ion beam shepherd,electrostatic tractor with ion beam,and charged ion beam shepherd were proposed and compared.The results of numerical simulations revealed that the electrostatic ion beam shepherd scheme is preferable from the perspective of minimizing fuel costs when solving the problem of removing space debris from a geostationary orbit.A control law for the spacecraft charge needed for space-debris detumbling during ion-beam transportation is proposed.A numerical simulation of space debris removal was performed via a hybrid scheme.展开更多
Nowadays,the use of Machine Learning(ML)onboard Earth Observation(EO)satellites has been investigated for a plethora of applications relying on multispectral and hyperspectral imaging.Traditionally,these studies have ...Nowadays,the use of Machine Learning(ML)onboard Earth Observation(EO)satellites has been investigated for a plethora of applications relying on multispectral and hyperspectral imaging.Traditionally,these studies have heavily relied on high-end data products,subjected to extensive pre-processing chains natively designed to be executed on the ground.However,replicating such algorithms onboard EO satellites poses significant challenges due to their computational intensity and need for additional metadata,which are typically unavailable on board.Because of that,current missions exploring onboard ML models implement simplified but still complex processing chains that imitate their on-ground counterparts.Despite these advancements,the potential of ML models to process raw satellite data directly remains largely unexplored.To fill this gap,this paper investigates the feasibility of applying ML models directly to Sentinel-2 raw data to perform thermal hotspot classification.This approach significantly limits the processing steps to simple and lightweight algorithms to achieve real-time processing of data with low power consumption.To this aim,we present an end-to-end(E2E)pipeline to create a binary classification map of Sentinel-2 raw granules,where each point suggests the absence/presence of a thermal anomaly in a square area of 2.5 km.To this aim,lightweight coarse spatial registration is applied to register three different bands,and an EfficientNetlite0 model is used to perform the classification of the various bands.The trained models achieve an average Matthew’s correlation coefficient(MCC)score of 0.854(on 5 seeds)and a maximum MCC of 0.90 on a geographically tripartite dataset of cropped images from the THRawS dataset.The proposed E2E pipeline is capable of processing a Sentinel-2 granule in 1.8 s and within 6.4 W peak power on a combination of Raspberry PI 4 and CogniSat-XE2 board,demonstrating real-time performance.展开更多
A lunar global positioning-navigation-timing (PNT) and communication system can greatly support the exploration and exploitation of the Moon. In this study, the application of the stable orbits of the L1 and L2 halo f...A lunar global positioning-navigation-timing (PNT) and communication system can greatly support the exploration and exploitation of the Moon. In this study, the application of the stable orbits of the L1 and L2 halo families and the unstable orbits of L3 in the Earth-Moon system is analyzed, and a design is proposed. L3 halo orbits are considered for a continuous line-of-sight satellite infrastructure for the Earth-Moon communication, thereby providing an opportunity for ground stations on the Earth to participate in lunar missions even if they do not directly see the Moon. In this study, a constellation of 26 satellites distributed over a lunar segment, made of four halo orbits of L1 and L2, and a terrestrial segment, made of two halo orbits of L3, is designed;this constellation facilitates global and continuative Earth-Moon communication and provides accurate and continuous lunar PNT service. According to a station-keeping analysis in the framework of the elliptical restricted three-body problem, the maintenance cost for approximately 60 d was 0.76 m/s for the lunar segment and 0.02 m/s for the terrestrial segment.展开更多
This paper presents the solutions and results of the 12th edition of the Global Trajectory Optimization Competition (GTOC12) of the National University of Defense and Technology. To address the complex interstellar mi...This paper presents the solutions and results of the 12th edition of the Global Trajectory Optimization Competition (GTOC12) of the National University of Defense and Technology. To address the complex interstellar mining problem proposed by GTOC12, our solution is divided into two stages. The first stage focuses on preliminary work, including the target selection, the establishment of departure and return databases, and the development of methods to estimate transfer costs, with the aim of enhancing planning efficiency during the global planning phase. The second stage involves trajectory optimization for multiple mining ships, including single-mining-ship trajectory optimization and a multiship iterative process. For single-mining-ship trajectory optimization, the method involves three steps: first, employ a heuristic method for planning the first rendezvous sequences;second, utilize an ant colony optimization (ACO) algorithm for planning the second rendezvous sequences;and third, apply a differential evolution (DE) algorithm alongside an indirect method to refine rendezvous times and low-thrust trajectories. Through the implementation of a multiship iterative strategy, the team accomplished trajectory optimization for multiple mining ships that met the constraints. The final score submitted by the team was 15,160.946, which achieved the sixth place in the competition.展开更多
Comet exploration missions represented by the Comet Interceptor mission have attracted our attention to unravel the origin of our solar system.However,it is difficult to know the details of orbital data about long per...Comet exploration missions represented by the Comet Interceptor mission have attracted our attention to unravel the origin of our solar system.However,it is difficult to know the details of orbital data about long period comets(LPCs)until their approach.Additionally,the amount of fuel consumption by the current intercept approach depends on the intersection points of cometary orbits with the ecliptic plane.To address these challenges,designing low-energy transfer trajectories suitable for the observation of LPCs is necessary.This paper introduces a novel approach bv utilizing invariant manifold structures in the Sun-Earth circular restricted three-body problem for comet missions with multiple probes.As candidates for departure orbits,periodic orbits and quasi-periodic orbits are considered.Based on the optimal control theory,low-thrust trajectories to improve mission efficiency for enlarging the reachable domain of multiple probes are designed by leveraging invariant manifolds.The trajectories guided by invariant manifolds and optimal control theory facilitate formation flying,multi-point observations,and explorations of unknown comets by multiple probes.展开更多
This paper presents new methods for spacecraft relative pose estimation using the Unscented Kalman Filter(UKF),taking into account non-additive process and measurement noises.A twistor model is employed to represent t...This paper presents new methods for spacecraft relative pose estimation using the Unscented Kalman Filter(UKF),taking into account non-additive process and measurement noises.A twistor model is employed to represent the spacecraft's relative 6-DOF motion of the chaser with respect to the target,expressed in the chaser body frame.The twistor model utilizes Modified Rodrigues Parameters(MRPs)to represent attitude with a minimal number of parameters,eliminating the need for the normalization constraint that exists in the quaternion-based model.Additionally,it incorporates both relative position and attitude in a single model,addressing kinematic coupling of states and simplifying the estimator design.Despite numerous existing pose estimation algorithms,many rely on the simplification of additive noise assumptions.This work enhances the robustness and improves the convergence of non-additive noise algorithms by deriving two methods to accurately approximate process and measurement noise covariance matrices for systems with non-additive noises.The first method utilizes the Stirling Interpolation Formula(SIF)to obtain equivalent process and measurement noise covariance matrices.The second method employs State Noise Compensation(SNC)to derive the equivalent process noise covariance matrix and uses SIF to compute the equivalent measurement noise covariance matrix.These methods are integrated into the UKF framework for estimating the relative pose of spacecraft in proximity operations,demonstrated through two scenarios:one with a cooperative target using Position Sensing Diodes(PSDs)and another with an uncooperative target using LiDAR for 3-D imaging.The effectiveness of these methods is validated against others in the literature through Monte Carlo simulations,showcasing their faster convergence and robust performance.展开更多
The increasing population of resident space objects is currently fostering many space surveillance initiatives.In this framework,on-ground multireceiver radars allow to reconstruct the target angular track,but the arr...The increasing population of resident space objects is currently fostering many space surveillance initiatives.In this framework,on-ground multireceiver radars allow to reconstruct the target angular track,but the array configuration may cause the presence of multiple solutions and,if no pass prediction is available,the ambiguity cannot be solved a-priori.This work proposes an evolution of the Music Approach for Track Estimate and Refinement(MATER)algorithm.Given two different signals reflected by the same target,at each observation epoch their Direction Of Arrival(DOA)is estimated from the signal Covariance Matrix(CM)through the MUltiple SIgnal Classification(MUSIC)algorithm.Then,the possible ambiguous estimations are solved through the delta-k technique:the correct DOA is considered as the one featuring the smallest angular deviation comparing the two CM results.This process is repeated for all the epochs,and the DOAs are clustered according to the RANdom SAmple Consensus(RANSAC)algorithm.Finally,the most populated cluster is considered as the correct one,and the angular track is computed through a time regression of the two angular coordinates.The evolution of MATER algorithm is tested through numerical simulations.The algorithm converges to the correct solution in 100%of the cases,with an angular accuracy in the order of 1-10 mdeg.展开更多
Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies.A multi-node lander with flexible connections can improve the st...Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies.A multi-node lander with flexible connections can improve the stability of a small celestial body landing.However,this also poses new challenges,particularly for landing guidance in hazardous terrain.To address this problem,an equivalent simplified dynamic model of a multi-node flexible lander is first constructed,and its flat output is determined.Subsequently,a trajectoryplanning method combining the flow and vector fields is designed to avoid collision,and the parameters of the vector field are optimized online according to the dynamic and obstacle constraints during the descent process to obtain a more suitable trajectory.Finally,the effectiveness of the proposed trajectory-planning method is verified through comparative simulations of landing and obstacle avoidance from the hover point to the landing area.This study offers new prospects for upcoming small celestial body landing missions in complex terrains.展开更多
Asteroid mining is a potentially lucrative method for extracting resources from space. Water resources found on asteroids can serve as fuel supplies for spacecrafts in deep space, and some asteroids are rich in precio...Asteroid mining is a potentially lucrative method for extracting resources from space. Water resources found on asteroids can serve as fuel supplies for spacecrafts in deep space, and some asteroids are rich in precious metals, offering immense potential economic value. The 12th Global Trajectory Optimization Competition, held in 2023, introduced a challenge to trajectory design for sustainable asteroid mining. Participating teams were tasked with maximizing the mining quantity over a 15-yr period by utilizing as many mining ships as possible to depart from the Earth, deploy miners on multiple asteroids, recover minerals, and return to the Earth. Σ team devised a strategy in which one ship completes one sequence, enabling the collection of minerals from 203 asteroids using 26 mining ships. This paper outlines the design methodology and outcomes of this approach, encompassing a preliminary analysis of the problem, optimization for the Earth departure and return, flight sequence search, and low-thrust conversion and optimization. Through methods such as asteroid selection and clustering, database building for Earth–asteroid transfers, global search with an impulsive model, local optimization with a low-thrust model, and conversion of remaining fuel into mining time, the computational efficiency was significantly enhanced, fuel consumption per unit mineral collection was reduced, and mining quantity was improved. Finally, the design outcomes of this approach are presented. The proposed trajectory design method enables the completion of multiple asteroid rendezvouses in a short time, providing valuable insights for future missions involving a single spacecraft conducting multiple rendezvouses with multiple asteroids.展开更多
基金supported by the Luxembourg National Research Fund:INTER20/EUROSTARS/15254521/VBN/Olivares Mendez.The project,E115088-VBN,has received funding from the Eurostars-2 Joint Programme with cofunding from the European Union’s Horizon 2020 Research and Innovation Programme.
文摘CubeSats have become versatile platforms for various space missions(e.g.,on-orbit servicing and debris removal)owing to their low cost and flexibility.Many space tasks involve proximity operations that require precise guidance,navigation,and control(GNC)algorithms.Vision-based navigation is attracting interest for such operations.However,extreme lighting conditions in space challenge optical techniques.The on-ground validation of such navigation systems for orbital GNC becomes crucial to ensure their reliability during space operations.These systems undergo rigorous testing within their anticipated operational parameters,including the exploration of potential edge cases.The ability of GNC algorithms to function effectively under extreme space conditions that exceed anticipated scenarios is crucial,particularly in space missions where the scope of errors is negligible.This paper presents the ground validation of a GNC algorithm designed for autonomous satellite rendezvous by leveraging hardware-in-the-loop experiments.This study focuses on two key areas.First,the rationale underlying the augmentation of the robot workspace(six-degree-of-freedom UR10e robot+linear rail)is investigated to emulate relatively longer trajectories with complete position and orientation states.Second,the control algorithm is assessed in response to uncertain pose observations from a vision-based navigation system.The results indicate increased control costs with uncertain navigation and exemplify the importance of on-ground testing for system validation before launch,particularly in extreme cases that are typically difficult to assess using software-based testing.
文摘Establishing a sustainable mining expedition for the asteroids of the main belt over the 2035–2050 horizon is the visionary problem of the 12th Global Trajectory Optimisation Competition. A fleet of mining ships must rendezvous twice with asteroids to deploy miners and collect minerals. In this paper, we describe the approach of the CS Group team, OptimiCS, to solve this challenging problem. We present the symmetrical construction of upstream and downstream semi-sequences of asteroids, maximizing the mining time expectancy via a beam search with tabu iterations, and the composition of these semi-sequences into complete fleet routes, maximizing the total collected mass via simulated annealing. While representative Earth–asteroid legs are precomputed, the delta-V costs of the asteroid-to-asteroid hops composing the sequences are initially approximated during exploration via a method that refines the accuracy of the maximum initial mass. The resulting high-fidelity trajectories are adjusted and optimized via a direct method and nonlinear programming.
文摘Fuel-optimal orbit-attitude motion planning for spacecraft close-range rendezvous and synchronization requires solving a two-point boundary value problem with continuous input actuation.This paper presents a geometric approach to the problem,which not only encompasses both translational and rotational dynamics,but also incorporates a novel adaptive multiplier method to enforce actuation constraints during the optimization process.Further,in the case of underactuation,such as small single-thruster spacecraft,the paper proposes a guided technique for the geometric approach to direct the attitude using the optimal translational trajectory.The geometric approach is verified through several case studies,where it is compared against a direct method optimization and a concurrent controller,to demonstrate the computational efficiency as well as resulting optimal trajectories of the approach.
基金supported by the Special Fund of the Hubei Luojia Laboratory(Grant No.230100003)the Chongqing Municipal Natural Science Foundation of the General Program(Grant No.CSTB2022NSCQ-MSX1093)the Science and Technology Research Program of the Chongqing Municipal Education Commission(Grant No.KJQN202200701)。
文摘The accuracy of angles-only initial orbit determination(IOD)is significantly compromised when only a short-arc orbit is observed.The ill-conditioned problem in matrices due to weak geometric constraints caused by short arcs and observation errors typically causes significant errors in the estimated ranges and thus unsatisfactory IOD.This paper presents a critical analysis of the ill-conditioned problem using the Gooding algorithm and proposes several techniques to improve it.On the basis of multiple observations,a least-squares method is proposed to solve the ranges at the first and last epochs.For the short-arc case,the ridge estimation technique is applied to mitigate the ill-conditioned problem.To determine whether an orbit is eccentric,a procedure to assess orbit eccentricity is developed via the range-search method,which aims to provide reasonably accurate initial ranges to the Gooding algorithm.Finally,an eccentricity-constraint technique for the Gooding algorithm is proposed for cases where the orbit is determined to be nearly circular.The performances of these techniques on space-based simulation data are assessed,and an improved Gooding algorithm(I-Gooding)suitable for various observation conditions is proposed.The I-Gooding algorithm is subsequently applied to process actual ground-based observations.The results show that its accuracy in estimating the semimajor axis is 47%higher than that afforded by the standard Gooding algorithm.
基金the National Natural Science Foundation of China(grant numbers 12172214 and 12102252)Fundamental Research Funds for the Central Universities(grant number USCAST2023-25).
文摘The performance of space antennas is significantly affected by thermal deformation owing to the harsh thermal environment in space.This results in potential degradation in pointing accuracy and overall functionality.This study focused on the analysis and control of thermal deformation in large-scale two-dimensional planar phased array antennas.Employing the finite element method,we developed a comprehensive thermal and structural model of the antenna.This enabled us to simulate the steady-state temperature field and the associated thermal deformation at various orbital positions.To address this deformation issue,we propose an innovative shape-control approach that utilizes distributed cable actuators.The shape control challenge was reformulated into a layered optimization problem concerning actuator placement and force application.In the outer optimization layer,a discrete particle swarm optimization algorithm was used to determine the optimal locations for the actuators.In the inner optimization layer,quadratic programming was subsequently applied to calculate the optimal control forces for each actuator.We validated the proposed method by numerically simulating a novel large-scale two-dimensional planar phased array antenna.The results demonstrated the effectiveness of our method in mitigating thermal deformation and maintaining the structural integrity and shape accuracy of the antennas.
基金co-supported by the National Natural Science Foundation of China(Grant No.62103432)the China Postdoctoral Science Foundation(Grant No.284881)the Young Talent fund of the University Association for Science and Technology in Shaanxi,China(Grant No.20210108).
文摘The influence of a disturbing gravity field on the impact points of long-range vehicles(LRVs)has become increasingly prominent,which is an important factor affecting the accuracy of impact point prediction(IPP).To achieve high-accuracy and fast IPP for LRVs under the influence of a disturbing gravity field,a data-driven multi-level IPP method is proposed to balance the prediction accuracy and real-time performance.At the first level,the impact point of the current flight state is predicted based on elliptical trajectory theory,and the impact deviation of the elliptical trajectory(ID-ET)is calculated.At the second and third levels,a neural network(NN)model is established to learn the ID-ET caused by the J2 term and re-entry aerodynamic drag as well as that caused by the disturbing gravity field.To improve the NN prediction performance,an auxiliary circle is applied to decouple the ID-ET.To reduce the difficulty of NN learning,a training strategy is designed based on the idea of curriculum learning,which improves training accuracy.At the same time,a hybrid sample generation strategy is proposed to improve the NN generalization ability.A detailed simulation experiment is designed to analyze the advantages and computational complexity of the proposed method.The simulation results showed that the proposed model has a high prediction accuracy,strong generalization ability,and good real-time performance under the influence of the disturbing gravity field and re-entry aerodynamic drag.Among the 317,360 samples contained in the training and test sets,the 3σ prediction error was 6.21 m.On an STM32F407 single-chip microcomputer,the IPP required 3.415 ms.The proposed method can provide support for the design of guidance algorithms and is applicable to engineering practice.
基金supported by Virtus Solis Technologies,Inc.,under the Clarkson University Master Collaboration Agreement No.21-09,Project No.22-04.
文摘Escalating concerns about climate change and the limitations of alternative energy sources have renewed interest in space-based solar power.Among numerous concepts proposed for space-based solar power,the modular flat-plane sandwich configuration has emerged as a promising candidate,owing to its structural simplicity that lends itself well to recent advancements in wireless power transmission and on-orbit robotic assembly.As a consequence of its simple structure,there are also new challenges with respect to attitude design due to the coupling of sunlight collection and power beaming on opposing sides of the flat plane.This paper develops a versatile attitude trajectory optimization approach that maximizes power-beaming efficiency for modular space-based solar power configurations in Molniya orbits while minimizing the attitude control effort.The developed optimization approach employs a genetic algorithm to study two attitude design strategies.The first attitude design strategy investigates initially spinning configurations about the ecliptic normal and compares the power-beaming efficiency against solutions using near-optimal attitude and spin axis parameters for a one-year period determined through optimization.The second attitude design strategy employs multiple runs of a genetic algorithm discretized at different time of the year,each determining an inertially fixed attitude optimized for a one-month period.These attitudes are then used to design attitude maneuvers,each with an axis and rate of actuation designed analytically.The outcomes of this study determined several viable attitude trajectory optimization and design strategies for multiple space-based solar power system configurations,which generate attitude trajectories that maximize power beaming in Molniya orbits while minimizing attitude control effort.
文摘We present the solution approach developed by the team“TheAntipodes”during the 12th edition of the Global Trajectory Optimization Competition(GTOC12).An overview of the approach is as follows:(1)generate asteroid subsets,(2)chain building with beam search,(3)convex low-thrust trajectory optimization,(4)manual refinement of rendezvous times,and(5)optimal solution set selection.The generation of asteroid subsets involves a heuristic process tofind sets of asteroids that are likely to permit high-scoring asteroid chains.Asteroid sequences“chains”are built within each subset through a beam search based on Lambert transfers.Low-thrust trajectory optimization involves the use of sequential convex programming(SCP),where a specialized formulationfinds the mass-optimal control for each ship’s trajectory within seconds.Once a feasible trajectory has been found,the rendezvous times are manually refined with the aid of the control profile from the optimal solution.Each ship’s individual solution is then placed into a pool where the feasible set that maximizes thefinal score is extracted using a genetic algorithm.Ourfinal submitted solution placedfifth with a score of 15,489.
基金the financial support offered by the la Caixa Foundation(ID 100010434)under agreement LCF/BQ/AA20/11820034 to support the Ph.D.studies of A.P.F.This project has received funding from the European Union's Horizon 2020 research+1 种基金innovation programme under the Marie Sklodowska-Curie grant agreement No.896404-CRADLEThis work was supported by JSPS KAKENHI Grant Number JP22H01687.
文摘The Hayabusa2 extended mission,named Hayabusa2#(SHARP:Small Hazardous Asteroid Reconnaissance Probe),is planned to rendezvous with the fast-rotating asteroid 1998 KY26 in 2031.Hayabusa2#will be the first ever mission to rendezvous with such a rapidly rotating small asteroid,posing significant challenges because of its distinctive dynamical environment.In this paper,we investigate potential target marker(TM)deployment strategies,for both landing and orbiting scenarios,to maximize science acquisition.In particular,we model the surface and orbital environments to identify feasible target market operations and present landing site selection strategies and candidate insertion orbits considering realistic deployment errors.The TM is one of the only two remaining deployable payloads,and therefore,can play a critical role during the extended mission phase.Our results show that surface operations can be extremely challenging whereas orbit operations could help us gain valuable information on the asteroid's gravity field.Overall,this research contributes to the exploration and characterization of extremely small bodies specifically through the use of artificial objects,in this case the target marker.
文摘In 2023, the 12th edition of Global Trajectory Competition was organized around the problem referred to as “Sustainable Asteroid Mining”. This paper reports the developments that led to the solution proposed by ESA’s Advanced Concepts Team. Beyond the fact that the proposed approach failed to rank higher than fourth in the final competition leader-board, several innovative fundamental methodologies were developed which have a broader application. In particular, new methods based on machine learning as well as on manipulating the fundamental laws of astrodynamics were developed and able to fill with remarkable accuracy the gap between full low-thrust trajectories and their representation as impulsive Lambert transfers. A novel technique was devised to formulate the challenge of optimal subset selection from a repository of pre-existing optimal mining trajectories as an integer linear programming problem. Finally, the fundamental problem of searching for single optimal mining trajectories (mining and collecting all resources), albeit ignoring the possibility of having intra-ship collaboration and thus sub-optimal in the case of the GTOC12 problem, was efficiently solved by means of a novel search based on a look-ahead score and thus making sure to select asteroids that had chances to be re-visited later on.
基金supported by the Russian Science Foundation(Project No.22-19-00160,https://rscf.ru/en/project/22-19-00160/).
文摘The removal of large space debris from a geostationary orbit to a disposal orbit via an ion beam shepherd spacecraft was considered in this study,with attention given to the electrostatic effect.The generation of an ion force,which provides contactless thrust,occurs because of the transfer of momentum from the ions of the engine plume of the spacecraft to the space debris.This process is accompanied by the transfer of a positive charge to the space debris.As a result,electrostatic interactions occur between the spacecraft and space debris.The goals of this study were to assess the influence of this effect on the dynamics of space debris during contactless ion beam-assisted removal and to develop hybrid contactless transportation schemes based on the use of an ion beam and electrostatic interactions.A mathematical model describing the motion of space debris and spacecraft under the influence of ionic and electrostatic forces and torques was developed.The concepts of electrostatic ion beam shepherd,electrostatic tractor with ion beam,and charged ion beam shepherd were proposed and compared.The results of numerical simulations revealed that the electrostatic ion beam shepherd scheme is preferable from the perspective of minimizing fuel costs when solving the problem of removing space debris from a geostationary orbit.A control law for the spacecraft charge needed for space-debris detumbling during ion-beam transportation is proposed.A numerical simulation of space debris removal was performed via a hybrid scheme.
文摘Nowadays,the use of Machine Learning(ML)onboard Earth Observation(EO)satellites has been investigated for a plethora of applications relying on multispectral and hyperspectral imaging.Traditionally,these studies have heavily relied on high-end data products,subjected to extensive pre-processing chains natively designed to be executed on the ground.However,replicating such algorithms onboard EO satellites poses significant challenges due to their computational intensity and need for additional metadata,which are typically unavailable on board.Because of that,current missions exploring onboard ML models implement simplified but still complex processing chains that imitate their on-ground counterparts.Despite these advancements,the potential of ML models to process raw satellite data directly remains largely unexplored.To fill this gap,this paper investigates the feasibility of applying ML models directly to Sentinel-2 raw data to perform thermal hotspot classification.This approach significantly limits the processing steps to simple and lightweight algorithms to achieve real-time processing of data with low power consumption.To this aim,we present an end-to-end(E2E)pipeline to create a binary classification map of Sentinel-2 raw granules,where each point suggests the absence/presence of a thermal anomaly in a square area of 2.5 km.To this aim,lightweight coarse spatial registration is applied to register three different bands,and an EfficientNetlite0 model is used to perform the classification of the various bands.The trained models achieve an average Matthew’s correlation coefficient(MCC)score of 0.854(on 5 seeds)and a maximum MCC of 0.90 on a geographically tripartite dataset of cropped images from the THRawS dataset.The proposed E2E pipeline is capable of processing a Sentinel-2 granule in 1.8 s and within 6.4 W peak power on a combination of Raspberry PI 4 and CogniSat-XE2 board,demonstrating real-time performance.
基金provided by Universitàdegli Studi di Roma La Sapienza within the CRUI-CARE Agreement.
文摘A lunar global positioning-navigation-timing (PNT) and communication system can greatly support the exploration and exploitation of the Moon. In this study, the application of the stable orbits of the L1 and L2 halo families and the unstable orbits of L3 in the Earth-Moon system is analyzed, and a design is proposed. L3 halo orbits are considered for a continuous line-of-sight satellite infrastructure for the Earth-Moon communication, thereby providing an opportunity for ground stations on the Earth to participate in lunar missions even if they do not directly see the Moon. In this study, a constellation of 26 satellites distributed over a lunar segment, made of four halo orbits of L1 and L2, and a terrestrial segment, made of two halo orbits of L3, is designed;this constellation facilitates global and continuative Earth-Moon communication and provides accurate and continuous lunar PNT service. According to a station-keeping analysis in the framework of the elliptical restricted three-body problem, the maintenance cost for approximately 60 d was 0.76 m/s for the lunar segment and 0.02 m/s for the terrestrial segment.
文摘This paper presents the solutions and results of the 12th edition of the Global Trajectory Optimization Competition (GTOC12) of the National University of Defense and Technology. To address the complex interstellar mining problem proposed by GTOC12, our solution is divided into two stages. The first stage focuses on preliminary work, including the target selection, the establishment of departure and return databases, and the development of methods to estimate transfer costs, with the aim of enhancing planning efficiency during the global planning phase. The second stage involves trajectory optimization for multiple mining ships, including single-mining-ship trajectory optimization and a multiship iterative process. For single-mining-ship trajectory optimization, the method involves three steps: first, employ a heuristic method for planning the first rendezvous sequences;second, utilize an ant colony optimization (ACO) algorithm for planning the second rendezvous sequences;and third, apply a differential evolution (DE) algorithm alongside an indirect method to refine rendezvous times and low-thrust trajectories. Through the implementation of a multiship iterative strategy, the team accomplished trajectory optimization for multiple mining ships that met the constraints. The final score submitted by the team was 15,160.946, which achieved the sixth place in the competition.
基金The work of the second author was supported by JSPS KAKENHI(Grant Number JP 23KJ1692)The work of the third author was partially supported by Japan Science and Technology Agency,Fusion Oriented Research for Disruptive Science and Technology(JST FOREST Program)(Grant Number JPMJFR206M)Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science(Grant Number 22H03663).
文摘Comet exploration missions represented by the Comet Interceptor mission have attracted our attention to unravel the origin of our solar system.However,it is difficult to know the details of orbital data about long period comets(LPCs)until their approach.Additionally,the amount of fuel consumption by the current intercept approach depends on the intersection points of cometary orbits with the ecliptic plane.To address these challenges,designing low-energy transfer trajectories suitable for the observation of LPCs is necessary.This paper introduces a novel approach bv utilizing invariant manifold structures in the Sun-Earth circular restricted three-body problem for comet missions with multiple probes.As candidates for departure orbits,periodic orbits and quasi-periodic orbits are considered.Based on the optimal control theory,low-thrust trajectories to improve mission efficiency for enlarging the reachable domain of multiple probes are designed by leveraging invariant manifolds.The trajectories guided by invariant manifolds and optimal control theory facilitate formation flying,multi-point observations,and explorations of unknown comets by multiple probes.
基金the startup and UPAR grants funded by College of Engineering at United Arab Emirates University(UAEU).The grant codes are G00003527 and G00004562.
文摘This paper presents new methods for spacecraft relative pose estimation using the Unscented Kalman Filter(UKF),taking into account non-additive process and measurement noises.A twistor model is employed to represent the spacecraft's relative 6-DOF motion of the chaser with respect to the target,expressed in the chaser body frame.The twistor model utilizes Modified Rodrigues Parameters(MRPs)to represent attitude with a minimal number of parameters,eliminating the need for the normalization constraint that exists in the quaternion-based model.Additionally,it incorporates both relative position and attitude in a single model,addressing kinematic coupling of states and simplifying the estimator design.Despite numerous existing pose estimation algorithms,many rely on the simplification of additive noise assumptions.This work enhances the robustness and improves the convergence of non-additive noise algorithms by deriving two methods to accurately approximate process and measurement noise covariance matrices for systems with non-additive noises.The first method utilizes the Stirling Interpolation Formula(SIF)to obtain equivalent process and measurement noise covariance matrices.The second method employs State Noise Compensation(SNC)to derive the equivalent process noise covariance matrix and uses SIF to compute the equivalent measurement noise covariance matrix.These methods are integrated into the UKF framework for estimating the relative pose of spacecraft in proximity operations,demonstrated through two scenarios:one with a cooperative target using Position Sensing Diodes(PSDs)and another with an uncooperative target using LiDAR for 3-D imaging.The effectiveness of these methods is validated against others in the literature through Monte Carlo simulations,showcasing their faster convergence and robust performance.
基金support from the Italian Space Agency through the grant agreement no.2023-50-HH.0(Detriti spaziali e sostenibilitàdelle attivitàspaziali a lungo-termine).
文摘The increasing population of resident space objects is currently fostering many space surveillance initiatives.In this framework,on-ground multireceiver radars allow to reconstruct the target angular track,but the array configuration may cause the presence of multiple solutions and,if no pass prediction is available,the ambiguity cannot be solved a-priori.This work proposes an evolution of the Music Approach for Track Estimate and Refinement(MATER)algorithm.Given two different signals reflected by the same target,at each observation epoch their Direction Of Arrival(DOA)is estimated from the signal Covariance Matrix(CM)through the MUltiple SIgnal Classification(MUSIC)algorithm.Then,the possible ambiguous estimations are solved through the delta-k technique:the correct DOA is considered as the one featuring the smallest angular deviation comparing the two CM results.This process is repeated for all the epochs,and the DOAs are clustered according to the RANdom SAmple Consensus(RANSAC)algorithm.Finally,the most populated cluster is considered as the correct one,and the angular track is computed through a time regression of the two angular coordinates.The evolution of MATER algorithm is tested through numerical simulations.The algorithm converges to the correct solution in 100%of the cases,with an angular accuracy in the order of 1-10 mdeg.
基金the National Key R&D Program(grant number 2019YFA0706500)the National Defense Basic Research Projects(grant number JCKY2021603B030).
文摘Traditional landers typically encounter difficulties achieving stable landings because of the weak gravity and complex terrain of small celestial bodies.A multi-node lander with flexible connections can improve the stability of a small celestial body landing.However,this also poses new challenges,particularly for landing guidance in hazardous terrain.To address this problem,an equivalent simplified dynamic model of a multi-node flexible lander is first constructed,and its flat output is determined.Subsequently,a trajectoryplanning method combining the flow and vector fields is designed to avoid collision,and the parameters of the vector field are optimized online according to the dynamic and obstacle constraints during the descent process to obtain a more suitable trajectory.Finally,the effectiveness of the proposed trajectory-planning method is verified through comparative simulations of landing and obstacle avoidance from the hover point to the landing area.This study offers new prospects for upcoming small celestial body landing missions in complex terrains.
基金supported by the Space Debris and Near-Earth Asteroid Defense Research Project(KJSP2023020303)Youliang Wang is grateful to the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2022146).
文摘Asteroid mining is a potentially lucrative method for extracting resources from space. Water resources found on asteroids can serve as fuel supplies for spacecrafts in deep space, and some asteroids are rich in precious metals, offering immense potential economic value. The 12th Global Trajectory Optimization Competition, held in 2023, introduced a challenge to trajectory design for sustainable asteroid mining. Participating teams were tasked with maximizing the mining quantity over a 15-yr period by utilizing as many mining ships as possible to depart from the Earth, deploy miners on multiple asteroids, recover minerals, and return to the Earth. Σ team devised a strategy in which one ship completes one sequence, enabling the collection of minerals from 203 asteroids using 26 mining ships. This paper outlines the design methodology and outcomes of this approach, encompassing a preliminary analysis of the problem, optimization for the Earth departure and return, flight sequence search, and low-thrust conversion and optimization. Through methods such as asteroid selection and clustering, database building for Earth–asteroid transfers, global search with an impulsive model, local optimization with a low-thrust model, and conversion of remaining fuel into mining time, the computational efficiency was significantly enhanced, fuel consumption per unit mineral collection was reduced, and mining quantity was improved. Finally, the design outcomes of this approach are presented. The proposed trajectory design method enables the completion of multiple asteroid rendezvouses in a short time, providing valuable insights for future missions involving a single spacecraft conducting multiple rendezvouses with multiple asteroids.
