Search Results (255)

To meet the in-orbit performance verification requirements of a drag-free control system for gravitational wave detection satellites, this study develops a ground simulation platform using the H-infinity ($H_{\infty }$) control method in Simulink. The FPGA implementation accelerates the core algorithm of drag-free control. A frequency-domain linear robust control design is employed, with a frequency pre-warped bilinear transformation method used to discretize the multi-degree-of-freedom controller. The established control system model includes 18 degrees of freedom, with 12 from the dual test masses (TM) and 6 from the satellite body. The two test masses are spatially arranged in a symmetric configuration, and their control structure also exhibits symmetry. A rapid reconfigurable hardware architecture is utilized, and the Vitis Model Composer tool is employed to efficiently translate the Simulink algorithm model into hardware description language, reducing the processing delay of the core control algorithm to the nanosecond level. Through a 15-channel gradient test comparison, the FPGA platform maintains numerical equivalence with the Simulink platform (maximum error of ${10}^{-13}$). Experimental results show that the hardware acceleration improves dynamic response speed by an order of magnitude, achieving position control accuracy of ±5 μm and attitude accuracy of ±10 μrad, with overall processing latency at the microsecond level. This method provides a reliable engineering validation approach for ultra-precision control systems in gravitational wave detection. Full article

The issue of in-orbit optimal safe surrounding control for service satellite (SSat) formation against a huge unknown target satellite (TSat) with specific structures is solved by using relative measurements only, and an optimal cooperative safe surrounding (OCSS) hybrid controller achieving both target tracking (TT) and configuration tracking (CT) is proposed corresponding to the two equal sub-objectives. Facing the challenges caused by incomplete information of the TSat, by using relative measurements only, the initial-condition-free boundaries are constructed by an arctan-based state transformation to directly constrain the target tracking error to perform prescribed transient and steady-state behaviors. Based on the shared TT control law, optimal collision-free CT controllers for all SSats are further solved via a nonzero-sum differential game, where the collision threat from all SSats and target structures are modeled by a novel circumscribed-sphere model. Finally, the effectiveness and advantages of the proposed OCSS control technique is verified by simulation results. Full article

In the last decades, small satellites such as CubeSats and PocketQubes have become popular platforms for scientific and applied missions in low Earth orbit (LEO). However, prolonged exposure to atomic oxygen, ultraviolet radiation, and thermal cycling in LEO leads to gradual degradation of onboard solar panels, reducing mission lifetime and performance. This study addresses the need to quantify and compare the degradation behavior of different solar cell technologies and protective coatings used in nanosatellites and pico-satellites. The aim is to evaluate the in-orbit performance of monocrystalline silicon (Si), gallium arsenide (GaAs), triple-junction (TJ) structures, and copper indium gallium selenide (CIGS) cells under varying orbital and satellite parameters. Telemetry data from recent small satellite missions launched after 2020, combined with numerical modeling in GNU Octave, were used to assess degradation trends. The models were validated using empirical mission data, and statistical goodness-of-fit metrics (RMSE, R²) were applied to evaluate linear and exponential degradation patterns. Results show that TJ cells exhibit the highest resistance to LEO-induced degradation, while Si-based panels experience more pronounced power loss, especially in orbits below 500 km. Furthermore, smaller satellites (<10 kg) display higher degradation rates due to lower thermal inertia and limited shielding. These findings provide practical guidance for the selection of solar cell technologies, anti-degradation coatings, and protective strategies for long-duration CubeSat missions in diverse LEO environments. Full article

Since 2019, Starlink satellites, with their innovative flat-panel design and unprecedented number in orbit, have transformed the traditional satellite industry. Due to their mass production characteristics, flat-panel satellites face a pressing need for satellite layout optimization design (SLOD), particularly for feasible optimization results applicable in engineering. Existing layout optimization algorithms often focus on theoretical optima, computational efficiency, and multi-objective capabilities. Most algorithms are validated exclusively through numerical or CAD-based simulations, leaving their engineering applicability under-reported. This paper establishes a simplified mathematical model of SLOD with consideration for the key features of flat-panel satellites. Furthermore, we propose a differential evolution algorithm that leverages local optima for the layout optimization design of flat-panel satellites. By making targeted and limited improvements to initial human-designed layouts, the algorithm generates practical engineering solutions that significantly enhance the stacking efficiency, mass properties, and thermal distribution of flat-panel satellites. Finally, the effectiveness and engineering feasibility of the algorithm were verified through the design of Longjiang-3, China’s first flat-panel satellite, and the results were also validated in orbit. Compared with the baseline configuration, the optimized layout reduces the principal moment of inertia by 6.6% and the satellite module height by 3.5%. It also achieves a significant improvement in thermal power uniformity across the structure. Overall, the key layout metrics are enhanced by 26%. The present research results provide a theoretical basis and engineering solutions for the SLOD of flat-panel satellites. Full article

In order to provide a theoretical basis for the thermal analysis and management of spacecraft/payload interstellar pointing attitudes, which are used for inter-satellite communication, this paper develops an analytical method for solar heat flux under pointing attitudes. The key to solving solar heat flux is calculating the angle between the sun vector and the normal vector of the object surface. Therefore, a method for calculating the included angle is proposed. Firstly, a coordinate system was constructed based on the pointing attitude. Secondly, the angle between the coordinate axis vector and solar vector variation with a true anomaly was calculated. Finally, the reaching direct solar heat flux was obtained using an analytical method or commercial software. Based on the proposed method, the direct solar heat flux of relay satellites in commonly used lunar orbits, including Halo orbits and highly elliptic orbits, was calculated. Thermal analysis on the payload of interstellar laser communication was also conducted in this paper. The calculated temperatures of each mirror ranged from 16.6 °C to 21.2 °C. The highest temperature of the sensor was 20.9 °C, with a 2.3 °C difference from the in-orbit data. The results indicate that the external heat flux analysis method proposed in this article is realistic and reasonable. Full article

The New Space movement led to an exponential increase in the number of the smallest satellites in orbit in the last two decades. The number of required communication channels increased with that as well and revealed the limitations of classical radio frequency channels. Free-space optical communication overcomes these challenges and has been successfully demonstrated, with operational systems in orbit on large and small satellites. The next step is to miniaturize the technology of laser communication to make it usable on CubeSats. Thus, the German Aerospace Center (DLR) developed, together with Tesat-Spacecom GmbH & Co. KG in Backnang, Germany, a highly miniaturized and power-efficient laser terminal, which is based on a potential customer’s use case. OSIRIS4CubeSat uses a new patented design that combines electronics and optomechanics into a single system architecture to achieve a high compactness following the CubeSat standard. Interfaces and software protocols that follow established standards allowed for an easy transition to the industry for a commercial mass market. The successful demonstration of OSIRIS4CubeSat during the PIXL-1 mission proved its capabilities and the advantages of free-space optical communication in the final environment. This paper gives an overview of the system architecture and the development of the single subsystems. The system’s capabilities are verified by the already published in-orbit demonstration results. Full article

This study focuses on the problem of identifying and extracting the magnetopause boundary of the Earth’s magnetosphere using the Soft X-ray Imager (SXI) onboard the Solar Wind Magnetosphere Ionosphere Link Explorer (SMILE) mission. The SXI employs lobster-eye optics to perform panoramic imaging of the magnetosphere based on the Solar Wind Charge Exchange (SWCX) mechanism. However, several factors are expected to hinder future in-orbit observations, including the intrinsically low signal-to-noise ratio (SNR) of soft-X-ray emission, pronounced vignetting, and the non-uniform effective-area distribution of lobster-eye optics. These limitations could severely constrain the accurate interpretation of magnetospheric structures—especially the magnetopause boundary. To address these challenges, a boundary detection approach is developed that combines image calibration with denoising based on deep image prior (DIP). The method begins with calibration procedures to correct for vignetting and effective area variations in the SXI images, thereby restoring the accurate brightness distribution and improving spatial uniformity. Subsequently, a DIP-based denoising technique is introduced, which leverages the structural prior inherent in convolutional neural networks to suppress high-frequency noise without pretraining. This enhances the continuity and recognizability of boundary structures within the image. Experiments use ideal magnetospheric images generated from magnetohydrodynamic (MHD) simulations as reference data. The results demonstrate that the proposed method significantly improves the accuracy of magnetopause boundary identification under medium and high solar wind number density conditions (N = 10–20 cm⁻³). The extracted boundary curves consistently achieve a normalized mean squared error (NMSE) below 0.05 compared to the reference models. Additionally, the DIP-processed images show notable improvements in peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM), indicating enhanced image quality and structural fidelity. This method provides adequate technical support for the precise extraction of magnetopause boundary structures in soft X-ray observations and holds substantial scientific and practical value. Full article

Magnetic levitation enables the confinement and melting of conductive metals using alternating magnetic fields, eliminating the need for a crucible or other contact supports. This makes the technology particularly suitable for applications where container use is impractical, such as preventing contamination between the melt and the crucible, handling high-purity materials, or facilitating in-orbit operations. For a given coil design and load, selecting the appropriate feeding parameters, such as the current and frequency, is crucial to ensure the correct operation of the device. This study investigates the optimal current and frequency values required to levitate an aluminum billet using a proposed longitudinal electromagnetic levitator, which represents an initial prototype of a more complex system for automated material manipulation. The analysis was conducted through 2D and 3D finite element method (FEM) simulations, assessing the equilibrium position and stability with respect to translations and rotations under various operating conditions. The study identifies an operating configuration that ensures vertical stability while minimizing excessive heating, in order to obtain a sufficiently long confinement time before the melting point is reached. A fully coupled 2D thermal simulation was then performed to assess the billet’s heating rate under the selected operating conditions. Finally, an experiment was conducted on a prototype to confirm billet levitation. Full article

The sensitivity analysis of line-of-sight estimation to measurement errors in the L-shaped antenna array contributes to the deeper understanding of how the measurement errors affect a 3D localization system aimed to be used in the next generation of inter-satellite links. First, the proposed 3D localization model in the Cartesian coordinate system is given, where, for simplicity, the origin of the coordinate system is the origin of the L-shaped antenna array. The proposed localization method relies on three measurements: range measurement and line-of sight angles with the x- and y-axis, respectively. The sensitivity analysis revealed that the variation in the L-shaped antenna array geometry (variation of the antennas placements) has an impact on the 3D positioning precision: a misplaced antenna—placed closer than intended—will have a larger line-of-sight error for small distances/ranges in the presence of range measurement errors. Notably, a misplaced antenna will result in a larger line-of-sight error for large distances/ranges in the presence of phase measurement errors. Full article

In order to solve the problems of low tracking accuracy of in-orbit satellites by ground stations and slow processing speed of satellite target tracking images, this paper proposes an orbital satellite regional tracking and prediction model based on graph convolutional networks (GCNs). By performing superpixel segmentation on the satellite tracking image information, we constructed an intra-frame superpixel seed graph node network, enabling the conversion of spatial optical image information into artificial-intelligence-based graph feature data. On this basis, we propose and build an in-orbit satellite region of interest prediction model, which effectively enhances the perception of in-orbit satellite feature information and can be used for in-orbit target prediction. This model, for the first time, combines intra-frame and inter-frame graph structures to improve the sensitivity of GCNs to the spatial feature information of in-orbit satellites. Finally, the model is trained and validated using real satellite target tracking image datasets, demonstrating the effectiveness of the proposed model. Full article

A novel interactive maintenance method for space station in-orbit devices using scene semantic segmentation technology is proposed. First, a wearable and handheld system is designed to capture images from the astronaut in the space station’s front view scene and play these images on a handheld terminal in real-time. Second, the proposed system quantitatively evaluates the environmental lighting condition in the scene by calculating image quality evaluation parameters. If the lighting condition is not proper, a prompt message will be given to the astronaut to remind him or her to adjust the environment illumination. Third, our system adopts an improved DeepLabV3+ network for semantic segmentation of these astronauts’ forward view scene images. Regarding the improved network, the original backbone network is replaced with a lightweight convolutional neural network, i.e., the MobileNetV2, with a smaller model scale and computational complexity. The convolutional block attention module (CBAM) is introduced to improve the network’s feature perception ability. The atrous spatial pyramid pooling (ASPP) module is also considered to enable an accurate calculation of encoding multi-scale information. Extensive simulation experiment results indicate that the accuracy, precision, and average intersection over the union of the proposed algorithm can be better than 95.0%, 96.0%, and 89.0%, respectively. And the ground application experiments have also shown that our proposed technique can effectively shorten the working time of the system user. Full article

In this paper, a novel optimization framework based on 3D Gaussian splatting (3DGS) for high-fidelity 3D reconstruction of space targets under exposure bracketing conditions is studied. In the considered scenario, multi-view optical imagery captures space targets under complex and dynamic illumination, where severe inter-frame brightness variations degrade reconstruction quality by introducing photometric inconsistencies and blurring fine geometric details. Unlike existing methods, we explicitly address these challenges by integrating exposure-aware adaptive refinement and edge-preserving regularization into the 3DGS pipeline. Specifically, we propose an exposure bracketing-oriented bounding box (OBB) regional densification strategy to dynamically identify and refine under-reconstructed regions. In addition, we introduce a Sobel edge regularization mechanism to guide the learning of sharp geometric features and improve texture fidelity. To validate the framework, experiments are conducted on both a custom OBR-ST dataset and the public SHIRT dataset, demonstrating that our method significantly outperforms state-of-the-art techniques in geometric accuracy and visual quality under exposure-bracketing scenarios. The results highlight the effectiveness of our approach in enabling robust in-orbit perception for space applications. Full article

All-solid-state lithium-ion batteries (ASSBs) have a wide operating temperature range (−40 °C to +120 °C) and are expected to be applied to lunar exploration, which has become increasingly active in recent years. Since a ground development test confirmed that ASSBs are tolerant of the space environment, in this study, a space demonstration test is conducted on the International Space Station (ISS). The battery was exposed in the ISS Exposed Section for 434 days. A total of 562 charge–discharge cycle tests were conducted, in addition to basic charge–discharge characterization, with no significant degradation observed in the charge–discharge characteristics or battery appearance. These results confirm that the battery operates reliably even in a complex space environment. This test confirmed that the lifetime characteristics of ASSBs can be estimated via ground-based charge–discharge characteristics, encouraging their potential application in space exploration. Full article

The extensive application of CubeSats in fields such as communication, remote sensing, and scientific exploration highlights their significant engineering value. With the growth of CubeSat dimensions towards 12U and beyond, their potential for engineering applications has further expanded. However, strict size constraints significantly limit the layout design space, causing difficulties in satellite system design through multiple iterations. To address these practical issues, this paper proposes an engineering-oriented layout optimization and trade-off design approach tailored specifically for 12U CubeSats, employing a hybrid optimization framework combining GRASP and NSGA-III algorithms. The proposed methodology facilitates initial feasibility analysis, informed trade-off decisions during iterative design, and detailed optimization in later stages, thereby improving design efficiency and practicality. The proposed optimization systematically explores design compromises considering conflicting objectives such as mass properties, thermal management, and spacing constraints. The ASRTU Friendship MicroSat, a 12U CubeSat, serves as a case study, with in-orbit performance validating the proposed approach. Results demonstrate that the optimized layouts effectively address complex engineering constraints, enabling satellite design teams to successfully achieve optimized layout solutions in practical engineering applications. Full article

This paper explores the usage of LEO-PNT (Positioning, Navigation, and Timing) for providing navigation integrity to GNSS (Global Navigation Satellite System) constellations. LEO mega-constellations, which are positioned between GNSSs and users, offer closer-to-the user geometry, improving performance, reducing the time to alarm (TTA) and enabling integrity monitoring without complex ground segments of any sort. The aim is to use future LEO mega-constellations as integrity monitors for a forthcoming European Global Navigation Satellite System (EGNSS) specifically focused on automotive users, which has minimal onboard satellite capabilities and no ground involvement. This plan builds on earlier studies, anticipating the performance of the upcoming LEO-PNT In-Orbit Demonstration. Full article