Target Satellite Research Articles

Исследование проектно-конструкторского облика декартовой двигательной установки автономного стыковочного модуля для захвата мишени

The concept of building an orbital complex for operational interception of a target is proposed, including in its composition the method of ballistic construction of operational interception, recommendations to the design appearance of the Cartesian propulsion system of the autonomous docking module, functioning at the stage of close-in guidance during tether delivery from the upper stage to the target, at the stage of capture and transfer of the target to the disposal orbit as part of the rotating tether space system. As a criterion for selecting the Cartesian propulsion system design (fuel reserves, thrust of each chamber and their number, minimum change in the coordinates of the autonomous docking module center of mass over the entire interval of Cartesian propulsion system operation), the minimum mass of the autonomous docking module is taken. For comparison, two methods of constructing the ballistic scheme of target intercept are considered: the classical method, with the orbital complex entering the target orbit with zero relative velocities, and the method based on the use of rotating tether space system, with the orbital complex entering the target intercept orbit with velocities at the rendezvous point of up to 200 m/s.

Aerocapture Optimization Method with Lift–Drag Joint Modulation Suitable for Variable Structure Spacecraft

Aerocapture, the action of delivering a vehicle from a hyperbolic orbit to a planetary orbit by using the aerodynamic force, could potentially lower fuel consumption. By controlling the direction and size of the aerodynamic force, the vehicle can accurately enter the target orbit. This paper focuses on a preliminary study of the optimal trajectory for aerocapture on the basis of a novel flight control option, which considers lift and drag joint modulation so as to suit variable structure spacecraft. In the preliminary evaluation of such a flight control option, the aerocapture corridors under lift modulation and drag modulation and the influence of the ballistic coefficient on aerocapture were analyzed, demonstrating that joint modulation can achieve complementary advantages compared with pure lift modulation and drag modulation. Based on this flight control option, optimal aerocapture trajectories with different path constraints, target orbital constraints and control variable constraints were found. It bears noting that both the bank angle and the reference area were taken as control variables for lift modulation and drag modulation, respectively, during the atmospheric flight in the process of designing the optimal trajectories. The optimal results indicate that the flight control option with lift and drag joint modulation can greatly broaden the necessary conditions for aerocapture and extend the target orbital range.

Nonlinear Model Predictive Control of J2-perturbed impulsive transfer trajectories in long-range rendezvous missions

This paper develops a Nonlinear Model Predictive Control (NMPC) strategy for robust tracking of multi-impulse smooth transfer trajectories in J2-perturbed orbital environments. The reference trajectories are designed for long-range rendezvous of servicing satellites with orbiting targets. In the proposed NMPC, the control signals are velocity increments at the impulse times, and the prediction horizon is variable due to the impulsive nature of the reference trajectories. The reference control input and the impulse times are pre-specified by the reference trajectory. Then, the NMPC calculates the optimal correction control vector to track the trajectory with minimum deviation and control effort, during the time between two consecutive impulses. To arrive near the target at the end of the transfer, the optimization in the last horizon is modified to be free-final-time, with an added soft constraint to minimize the final distance between the servicer and the target satellite. To avoid singularities in the mean dynamics of the J2-perturbed servicer, the equinoctial orbital elements are used in the process model. We also include the first-order long-periodic effects in this model. We investigate the robustness of the proposed NMPC in a simulation environment that additionally models: (i) the first-order short-periodic effects, (ii) a bounded uncertain acceleration to capture unmodelled dynamics, and (iii) burning time for satellite thrusters. Finally, an evolutionary optimization algorithm is implemented and embedded in the controller to decrease the computational complexity and to handle impulsive control inputs. Simulation results are provided to illustrate the tracking effectiveness of the developed controller.

Deep-Learning-Based Satellite Relative Pose Estimation Using Monocular Optical Images and 3D Structural Information

Relative pose estimation of a satellite is an essential task for aerospace missions, such as on-orbit servicing and close proximity formation flying. However, the changeable situation makes precise relative pose estimation difficult. This paper introduces a deep-learning-based satellite relative pose estimation method for monocular optical images. The method is geared towards uncooperative target satellites with known 3D models. This paper proposes a novel convolutional neural network combined with 3D prior knowledge expressed by the 3D model in the form of the point cloud. The method utilizes point cloud convolution to extract features from the point cloud. To make the result more precise, a loss function that is more suitable for satellite pose estimation tasks is designed. For training and testing the proposed method, large amounts of data are required. This paper constructs a satellite pose estimation dataset BUAA-SID-POSE 1.0 by simulation. The proposed method is applied to the dataset and shows desirable performance on the pose estimation task. The proposed technique can be used to accomplish monocular vision-based relative pose estimation tasks in space-borne applications.

Self-Organizing Control of Mega Constellations for Continuous Earth Observation

This work presents a novel self-organizing control method for mega constellations to meet the continuous Earth observation requirements. In order to decrease the TT&C pressure caused by numerous satellites, constellation satellites are not controlled according to the designed configurations but are controlled with respect to intersatellite constraints. By analyzing the street-of-coverage (SOC) of coplanar constellation satellites, the continuous coverage constraint of the mega constellation is transformed into constraints of the right ascension of ascending node (RAAN) and relative motion bound between every two adjacent coplanar satellites. The proposed continuous coverage constraint can be satisfied by most ongoing or planned mega constellations. Artificial potential functions (APFs) are used to realize self-organizing control. The scale-independent relative orbital elements (SIROEs) are innovatively presented as the self-organizing control variables. Using the Gaussian equations and Lyapunov’s theory, the stability of the APF control in quadratic form is proven, from which it can be concluded that the APF control variables of the controlled satellite should have the same time derivative as the target satellite states under two-body Keplerian motion condition, and SIROEs are ideal choices. The proposed controllers and self-organizing rules are verified in the sub-constellation of the GW-2 mega constellation by simulation. The results demonstrate the goodness in control effect and ground coverage performance.

Robust Near-Optimal Aerocapture Guidance Method Based on Saturation Function

Aerocapture maneuvers refer to a single atmospheric crossing to deplete orbital energy and establish a closed orbit. During the atmospheric flight, adjusting the spacecraft’s vertical lift component in an optimal manner, bang-bang bank control, will minimize the propulsion fuel consumption required to establish the target orbit. However, such methods have been suffering from the performance’s oversensitivity to the control’s instantaneous switching time and poor robustness. To address these problems, we propose a new numerical predictor-corrector guidance algorithm based on the saturation function profile in this paper. The saturation function is used to basically simulate the bang-bang control structure, which enhances the algorithm’s robustness by reducing its dependence on the relevant parameters without losing too much optimality. Monte Carlo simulations in both Earth and Mars scenarios demonstrate the robustness, accuracy, and near-optimal performance of the proposed guidance method.

J2 섭동을 고려한 랑데부 및 도킹 시뮬레이션

In this paper, simulation analysis for close operation during rendezvous/docking considering perturbation was described. The technology to control satellites based on their relative motion is expected to be a very important core technology. Rendezvous/docking is a technology underlying on-orbit servicing technology and is an essential process for approaching a target satellite. Therefore, in this paper, we introduce a feedback control system for rendezvous/docking verification considering gravity perturbation and analyze the rendezvous/docking situation through the proper gain value.

Phasing with near rectilinear Halo orbits: Design and comparison

In the next future, space agencies are planning to return to the Moon. The objective is to assemble an orbiting space station, called Gateway, on a Near Rectilinear Halo Orbit around the Moon as a base for future Moon and deep space missions. Within this framework, multiple side missions will be planned to sustain the Gateway (Artemis mission). The proposed work is thought in framework of the preliminary design of future cargo missions, in particular on the design of an efficient phasing trajectory, under the Circular Restricted Three body problem hypotheses, to bring a cargo vehicle from the end of the Earth-Moon transfer to the beginning of the proximity operations such as rendezvous and docking with the space station. The work aims covering the lack of literature in phasing trajectories with the NRHO by proposing three different strategies to connect the Earth-Moon transfer trajectory with the proximity operations. The three strategies are classified based on the choice of the parking orbits or the choice of the manifolds. Two strategies use butterfly and Halo orbits to park the vehicle before transferring to the target orbit. The third strategy, instead, uses manifolds to allow a direct phasing. In the paper, the three innovative strategies are designed and compare in a specific scenario.

Analysis on navigation accuracy of high orbit spacecraft based on BDS GEO and IGSO satellites

To make up for the insufficiency of earth-based TT&C systems, the use of GNSS technology for high-orbit spacecraft navigation and orbit determination has become a new technology. It is of great value to applying Geosynchronous Earth Orbit (GEO) and Inclined GeoStationary Orbit (IGSO) navigation satellites for supporting the navigation of high-orbit spacecraft since there are three different types of navigation satellites in BeiDou Navigation Satellite System (BDS): Medium Earth Orbit (MEO), GEO and IGSO. This paper conducts simulation experiments based on Two-Line Orbital Element (TLE) data to analyze and demonstrate the role of these satellites in the navigation of high-orbit spacecraft. Firstly, the spacecraft in GEO was used as the target satellite to conduct navigation experiments. Experiments show that for the spacecraft on the GEO orbit, after adding GEO and IGSO respectively on the basis of receiving MEO navigation satellite signals, the accuracies were improved by 7.22 % and 6.06 % respectively. When adding both GEO and IGSO navigation satellites at the same time, the accuracy can reach 16 m. In the second place, navigation and positioning experiments were carried out on three high elliptical orbit (HEO) satellites with different semimajor axis (32037.2 km, 42385.9 km, 67509.6 km). The experiments show that the number of visible satellites has been improved significantly after adding GEO and IGSO navigation satellites at the same time. The visible satellites in these three orbits were improved by 32.84 %, 41.12 % and 37.68 %, respectively compared with only observing MEO satellites.The RMS values of the navigation positioning errors of these three orbits are 25.59 m, 87.58 m and 712.48 m, respectively.

Coordinated hierarchical control of space robotic safe manipulation with load sharing

This research explores an integrated control technique for a dual-armed space robot that has captured a tumbling satellite. The compliant behavior for safe manipulation in-orbit is achieved using the external impedance at the target level. First, considering the control moment constraints imposed on the target body, a fast detumbling strategy is proposed using dynamic movement primitives method with normalized time. Following the capturing of a non-cooperative target, a coordinated hierarchical control scheme is developed with multi-arm space robotic dynamics modeling to direct the space robot in carrying out the pre-planned detumbling strategy. The proposed control scheme incorporates external impedance, internal force control and load sharing. Finally, numerical simulation with a sample case of two collaborative seven-degree-of-freedom space robotic arms capturing a tumbling target satellite verifies the viability and efficacy of the presented control strategy.

Cislunar Periodic Orbits for Earth–Moon and Lagrange Point Surveillance

International attention is being increasingly placed on the cislunar region of space, which offers to serve as the new high ground for land- and space-based operations. With an anticipated surge in cislunar traffic, it is paramount to be able to detect and track all objects in cislunar space to optimize mission readiness and prevent catastrophic collisions. Cislunar periodic orbits provide an elegant means to fill the observational capability gaps that are present in ground-based and/or near-Earth space-based sensors. In this research, cislunar periodic orbits are identified that provide frequent-to-consistent coverage of the and regions. Specifically, select orbits are analyzed, both individually and within a multiorbit sensor architecture, for their effectiveness (in terms of percent of visibility time) at monitoring target satellites in Lyapunov and halo orbits about the Earth–moon and Lagrange points. The results of this research show cislunar periodic orbits to be highly effective in monitoring Lyapunov and halo orbits about the Earth–moon and Lagrange points. Particular figures and the overall methodology are derived from a paper presented at the 2021 ASCEND Conference (Wilmer, A. P., Bettinger, R. A., and Little, B. D., “Cislunar Periodic Orbit Constellation Assessment for Space Domain Awareness of L1 and L2 Halo Orbits,” 2021 ASCEND Conference, 2021.).

Mixed-integer GA optimization for the tracking control of a formation of small satellites equipped with multi-constrained electric thrusters

A formation mission scenario is considered, consisting of small satellites (Chasers) that must keep a reference trajectory with respect to a larger and non-cooperating Target satellite. The Chaser must perform its formation guidance and control tasks within the framework of its thruster constraints: the case of a low thrust electrical engine is here considered. The constraints of such a thruster are relevant to number and orientation of thrusters, the admissible thrust levels and minimum and maximum ON time. The control algorithm developed to satisfy all these constraints is a model predictive control based on a mixed-integer genetic algorithm optimization, which provides a fast estimate of the necessary scheduled actions. The algorithm takes J2 and drag perturbations into account; at the scope a differential orbital parameters linear relative dynamics model has been used, while the real-world dynamics is represented by a high precision orbital propagator. The developed orbital controller is particularly effective when trajectory keeping is required; different relative configurations, like Helix or Train formations, are taken as benchmark trajectories. The results show promising and robust performance in counteracting differential perturbations, even in the case in which the Target satellite performs scheduled orbital maneuvers which are not timely communicated to the Chaser satellite.

Fault-tolerant state estimation methods of cluster satellites

This study is devoted Global Navigation Satellite System (GNSS) based fault-tolerant state estimation technique within formation satellite flight which used the pseudo-ranging distance model. Fault-tolerant Kalman filters obtain the relative satellite state estimations via measurement of the actual distance between 4 Global Positioning Systems (GPS) satellites and target/tracker satellites. The Keplerian equations and orbit elements are used for detecting target and tracker satellites’ dynamic models. J2 orbit perturbation is considered within the relative state estimation stage via covariance matrices of target and tracker satellites’ positioning stages. The novel approach is fault-tolerant relative satellite state estimations are proposed via two different techniques. One of them is reconfiguration fault-tolerant cluster satellite localization, and the other is adaptively faulting-tolerant cluster satellite localization. The Extended Kalman Filter (EKF) is used for target and tracker satellite orbital state estimations and measurement errors. The Reconfigurable and the adaptive algorithms detected and corrected the GPS measurement errors during relative satellite motion.

Статистическое уточнение импульса последействия маршевого двигателя разгонного блока «Фрегат» для повышения точности выведения космических аппаратов

As it is known from practice, the most important influence on the accuracy of the payload launching into the target orbit is exerted by measurement errors of the command instrumentation system sensors, as well as by the sustainer afteraction pulse spread. A method is considered to increase accuracy of launching into a given orbit using the Fregat upper stage by refining the sustainer afteraction pulse. According to the results of launches, actual errors in the realized orbit linear parameters were recalculated in the afteraction pulse deviations. Then, the afteraction pulse average value was refined by statistical analysis in several iterations, which made it possible to significantly reduce the launching errors and confirm correctness of the developed technique.

Оцінка можливості застосування автофажних двигунів в системах відводу космічних об’єктів

This article is devoted ascent depreciation in an earth orbit of space crafts for different functions that allow to solve many problems connected with space activity, in particular, maintenance of wider use of space resources and more effective clearing of a near space from space debris. The last is particularly true for bulky space objects of a technogenic origin which can be deorbit from earth orbits by using the special means for deorbiting injection into the target orbit by launch vehicles. As the ascent of such means for deorbiting by orbital launch vehicle demands significant financial expenses, for their decreased application of easy autophagy launch vehicles with burned fuel tanks is offered. The basic making unit of such launch vehicles is an autophagy engine. The design of autophage engine design and the principle of its operation of the version with compulsory fuel supply to the combustion chamber are presented and the expediency of use of such an engine for small spaceships in case of the impossibility of application of rather heavy usual systems of storage and fuel supply is shown. However, now the weight of the accepted systems of compulsory fuel supply autophagy engines for spaceships remains significant for launch vehicles. As one of the alternative ways of a feed the engine of autophagy launch vehicle, the capability of submission by using the inertia of the most fuel charge is considered. The unit of the autophagy engine contains an evaporator and works in a pulse mode, supplying fuel supply between momentums at the moment of low pressure in the engine. The effect of retardation (easings), representing pressure decrease and engine thrusts in flight time is established. This effect is called by the forces of inertia acting on the sliding engine, and has экспоненциальную an easing picture. Considering the effect of retardation, a system of the equations for calculating kinematic and design data of the launch vehicle with the autophagy engine is offered. The received results of the research have scientific and practical value and can find wide applications in the design of schemes and deorbiting means.

Predictive motion control for autonomous capture of a tumbling target with a space manipulator

In this study, an autonomous capture framework was proposed for a tumbling target satellite with a space manipulator. First, the motion model of a tumbling target was constructed and the motion properties were analyzed. Subsequently, a predictive motion control method was introduced to compensate for the time delay owing to image processing and to predict the tumbling motion of the target. Stability analysis was conducted using a Lyapunov function. To address the problem of large position and attitude deviations of the tumbling target, different autonomous capture strategies, that is, non-fixed-point position-based capture and area-based capture, were proposed to capture different parts of the target, such as the docking ring and side surfaces, which are important for practical applications. The capture conditions were created and compared, where the non-fixed-point position capture strategy and area-based capture strategy had a larger pose tolerance than the traditional fixed-point position methods. Finally, the framework was tested using Adams/Simulink co-simulations. The results validated the autonomous capture process and proposed alternatives for practical applications.

Formation Flight for Close Satellites With GPS-Based State Estimation Method

This article focuses on the specification of satellite relative state estimations with an Extended Kalman filter (EKF) using the target and tracker satellite positioning derived from the Newton Raphson Method (NRM). Although not true in real applications, it is assumed that the system dynamic model and measurements are correct in state estimations with EKF approximation. In this study, target and tracker satellite initial condition values have been taken from simulation data. Orbital states are Keplerian orbital parameters, and Global Positioning System (GPS) receiver values are the Earth-Centered Inertial (ECI) reference frame. The Pseudo-ranging approach has been used to find the positions of the target and tracker satellites. The random errors have also been considered for the actual distance between the target and tracker satellites. In this study, satellite relative state vectors have been estimated with an analyzed scenario which the target and tracker satellites localization have been estimated individually.

Instance Segmentation for Feature Recognition on Noncooperative Resident Space Objects

Active debris removal and unmanned on-orbit servicing missions have gained interest in the last few years, along with the possibility to perform them through the use of an autonomous chasing spacecraft. In this work, new resources are proposed to aid the implementation of guidance, navigation, and control algorithms for satellites devoted to the inspection of noncooperative targets before any proximity operation is initiated. In particular, the use of convolutional neural networks (CNN) performing object detection and instance segmentation is proposed, and its effectiveness in recognizing the components and parts of the target satellite is evaluated. Yet, no reliable training images dataset of this kind exists to date. A tailored and publicly available software has been developed to overcome this limitation by generating synthetic images. Computer-aided design models of existing satellites are loaded on a three-dimensional animation software and used to programmatically render images of the objects from different points of view and in different lighting conditions, together with the necessary ground truth labels and masks for each image. The results show how a relatively low number of iterations is sufficient for a CNN trained on such datasets to reach a mean average precision value in line with state-of-the-art performances achieved by CNN in common datasets. An assessment of the performance of the neural network when trained on different conditions is provided. To conclude, the method is tested on real images from the Mission Extension Vehicle-1 on-orbit servicing mission, showing that using only artificially generated images to train the model does not compromise the learning process.

Impact of Mega Constellations on Geospace Safety

The extent of the impact of mega constellations on the low-orbiting geospace environment, which has not yet been assessed in more concrete quantitative terms, is an extremely important issue to consider as mega constellations are built. Satellite safety and lifetime can clearly represent the situation of space targets, and thus can reflect the impact of mega constellations on geospace security. Three target satellites with different characteristics were selected and the Accepted Collision Probability Level (ACPL) was calculated to obtain the impact of Starlink on satellite mission lifetime. Upon considering Starlink without early avoidance control, the lifetimes of the three target satellites were shortened by 56.21%, 99.09%, and 99.82%, respectively. After 10 revolutions of early avoidance control, two were shortened to 92.166% and 91.99%, while the lifetime of JILIN-01 was extended by 155.44%. After joining Starlink, the total risk became larger; even if the target satellite avoided control far more frequently than before joining Starlink, it will face a worse geospace environment. Adopting the most aggressive orbit avoidance control cannot avoid the deterioration of the geospace environment from the perspective of satellite lifetime, which is an irreversible and deteriorating process.

Random access optimization for initial access and seamless handover for 5G-satellite network

Satellite communication is becoming an indispensable component of the 5G global networks. Considering the unique characteristics of the satellite communications such as long round trip delay, large cell radius and high satellite speed, initial access and handover are necessary to be improved to guarantee the stable communication for 5G-satellite network, which usually use the random access procedure in traditional terrestrial communication and is not suitable for satellite scenario. Therefore, a 2-step random access for 5G-satellite network (TRAS) and a seamless MC-controlled handover for 5G-satellite network (SMHOS) are proposed in this paper. In particular, the access delay can be reduced and the success rate of access can be improved since the access procedure is simplified and the contention occurs only when the UEs select the same Physical Random Access Channel (PRACH) occasion and Physical Uplink Shared Channel (PUSCH) occasion in TRAS. Moreover, in SMHOS, the management center (MC) can predict the handover of the UE and inform the next satellite to send a broadcast message with embedded information about the reserved PUSCH time–frequency resource. The UE can access to the target satellite immediately when the handover occurs, therefore, seamless handover is realized. Simulation results demonstrate the effectiveness of our TRAS and SMHOS.