Search Results (320)

Spaceflight associated neuro-ocular syndrome (SANS) is a significant ophthalmic complication observed in astronauts during and after long-duration missions, characterized by optic disc edema, globe flattening, choroidal folds, and hyperopic shifts. Unlike papilledema in terrestrial idiopathic intracranial hypertension, optic disc edema in SANS is often asymmetric. The mechanisms underlying this asymmetry remain poorly understood. In this narrative review, we synthesize and critically interpret existing clinical observations, anatomical studies, neuroimaging findings, and experimental evidence, and propose that uneven ocular venous congestion, arising from microgravity-induced cephalad fluid shifts, pre-existing transverse sinus asymmetry, and orbital venous overload, leads to asymmetric optic disc edema by differentially disrupting anterograde ocular glymphatic transport between the eyes. This mechanistic framework highlights the interplay between venous hemodynamics and ocular glymphatic flow as a key factor in SANS pathophysiology. Targeted in-flight monitoring and ground-based analog studies will be essential to rigorously test this hypothesis. To this end, we outline a feasible experimental approach that prospectively integrates preflight cerebral magnetic resonance venography, providing data on transverse sinus dominance, with serial in-flight ophthalmic imaging on the International Space Station. This combined strategy could directly determine whether dural venous sinus anatomy predisposes to uneven ocular venous congestion and asymmetric optic disc edema in microgravity. Insights gained from this work may guide the development of effective countermeasures against SANS and broaden our understanding of ocular fluid dynamics under conditions of altered venous physiology on Earth. Full article

Recent space missions demand higher pointing accuracy, smoother attitude transitions and lower energy consumption than those typically achievable with conventional control approaches. This motivates the exploration of intelligent and nonlinear control methods. The FuzzyBuzz experiment investigates the application of fuzzy logic for spacecraft attitude control using NASA’s Astrobee robotic system aboard the International Space Station. Unlike traditional control methods, fuzzy logic introduces a rule-based approach capable of handling uncertainties and nonlinearities inherent in space environments, making it particularly suited for autonomous operations in microgravity. The objective of FuzzyBuzz is to evaluate the effectiveness of fuzzy controllers compared to traditional linear ones, such as Proportional–Integral–Derivative (PID) and $H_{\infty }$ controllers. In addition, a comparison with a nonlinear controller based on a Model Predictive Control (MPC) strategy is considered. The controllers will be tested through predefined attitude maneuvers, evaluating precision, energy efficiency, and real-time adaptability. This work presents the design of the FuzzyBuzz experiment, including the software architecture, simulation environment, experiment protocol, and the development of a fuzzy logic-based attitude control system for Astrobee robots. The proposed fuzzy controller and a PID controller are optimized using a Multi-Objective Particle Swarm Optimization (MOPSO) method, providing a range of operational points with different trade-offs between two metrics, related to convergence time and energy consumption. Results show that the PID controller is better suited for scenarios demanding low convergence times, whereas the fuzzy controller provides smoother responses, reduced steady-state error, and maintains convergence under significant parametric uncertainties. Results from $H_{\infty }$ and MPC controllers will be reported once the in-orbit experiment is performed. Full article

In this paper, the effects of gravity-gradient potential on a spacecraft of arbitrary shape are outlined. The potential expressing the planet’s gravity-gradient torque on a triaxial spacecraft is formed. The planet’s shape is considered oblate spheroidal, and the dimensions of the spacecraft are assumed small compared to its distance from the center of the planet. The radial, transverse and normal components of the Lorentz force, in terms of orbital elements, are constructed. The variations in the orbital elements due to both gravity-gradient potential and Lorentz force are derived. The charges per unit mass needed to balance such perturbation are obtained. The symmetrical results in mathematical equations are obvious. The International Space Station (ISS) is used as an example to test our model. A three-dimensional diagram was plotted to illustrate the charge per unit mass with the shape and size of the orbits. Full article

Archaeological sites characterized by the coexistence of extensive above-ground terrain and hypogeum structures present major challenges for accurate and comprehensive geospatial documentation. Conventional survey approaches—such as static terrestrial laser scanning (TLS), total-station measurements, and aerial photogrammetry—often suffer from operational constraints, particularly in the presence of narrow underground spaces, low or absent illumination, harsh environmental conditions, and restrictions on UAV deployment. Additional complexity arises when both surface and subterranean elements must be consistently georeferenced to a common global reference system, especially where establishing a traditional topographic–geodetic control network is impractical. Within the framework of the EIMAWA Egyptian–Italian Mission conducted by the University of Milano since 2018, the Geomatics group of the University of Bologna designed and implemented a multi-scale multi-technique 3D documentation workflow, with a prominent role assumed by Simultaneous Localization and Mapping (SLAM) mobile laser scanning. The approach was supported by GNSS measurements providing centimetric accuracy. SLAM was employed to document both the surface necropolis and multiple hypogeal tombs, enabling rapid acquisition of dense three-dimensional data in environments where traditional techniques are limited. All datasets were integrated within a unified reference system, resulting in a coherent, multi-layered spatial dataset representing both landscape and underground spaces. The results demonstrate that SLAM can produce dense point clouds that document at few-centimetric level accuracy and continuously both above- and below-ground contexts. Quantitative analyses of the co-registration and mutual alignment of multiple SLAM datasets confirm a high degree of internal consistency, further enhanced through post-processing refinement. Overall, the experience indicates that this solution represents a practical and reliable technique for complex archaeological surveying. Full article

Atmospheric refraction often influences the localization accuracy of ground-based radar for detecting space targets. Traditional methods generally utilize the measured troposphere and ionosphere data from the local station for atmospheric refraction correction and thus neglect the influence of atmospheric horizontal inhomogeneity. However, in practice, a horizontally inhomogeneous ionosphere often causes considerable residual errors in the measured range and elevation angle after refraction correction, especially for targets with low elevation angles. The ionospheric electron density profile along the wave propagation path is significantly different from that in the vertical direction of the local station, which further brings about challenges in the modeling and correction of atmospheric refraction errors. To address the above challenge, the effect of a horizontally inhomogeneous ionosphere on the range and elevation angle measured by ground-based radar is analyzed, and a geographic division modeling strategy for the ionospheric electron density along the propagation path for atmospheric refraction correction is proposed in this paper. The simulation results show that the oblique electron density distribution obtained from the proposed model agrees well with the results calculated by the International Reference Ionosphere (IRI) model, and the proposed methodology effectively suppresses residual errors in radar atmospheric refraction correction in the low-elevation detection case. Full article

The Atomic Clock Ensemble in Space (ACES) mission, currently operating aboard the International Space Station (ISS), is designed to provide high-precision time and frequency measurements and to test fundamental aspects of relativistic physics. Gravitational redshift (GRS), a fundamental prediction of General Relativity (GR), implies that clocks positioned at different gravitational potentials experience relative time dilation. Previous GRS experiments have focused primarily on microwave technologies, with negligible experimental coverage in the optical domain, particularly for ground-to-space links. Motivated by the European Laser Timing (ELT) experiment and the high-precision laser-cooled cesium clock aboard ACES, we introduce and evaluate an optical time-transfer method designed to achieve high-accuracy measurements of GRS. In the absence of actual ELT/ACES optical data, a high-fidelity numerical simulation framework was developed to assess the performance of this method. The framework incorporates representative ELT/ACES mission parameters, including the space-based cesium clock and the H-MASER clock located at the reference ground station, both providing frequency stability at the level of ${10}^{-15}$ for 1000 s averaging time. Applying a $\pm 1\sigma$ filtering criterion, we obtain a simulated dataset comprising 33 ELT/ACES passes, representing a total observation time of 4.38 h over a single week. Analysis of this high-fidelity dataset reveals a GRS deviation from GR of $(-7.19\pm 0.63)\times {10}^{-5}$, achieving a 3.4 orders of magnitude improvement over the best previous laser-ranging experiment conducted at the University of Maryland (UMD), USA, 51 years ago. These simulation results demonstrate that the optical time-transfer link constitutes a powerful tool for testing fundamental physics and, when combined with next-generation optical atomic clocks, enables unprecedented capabilities in space-based timekeeping and geoscience applications. Full article

As a typical example of a high-density city, Macau’s medical resource allocation system, a key component of the city’s complex socio-technical system, suffers from significant spatial imbalances, which restricts the overall effectiveness of the medical service system. Based on the perspective of systems science theory, regards the allocation of medical resources as a dynamic system with multiple coupled factors. It comprehensively utilizes systems research methods such as POI data mining and space syntax analysis and employs techniques such as kernel density analysis and spatial structure coupling models to systematically evaluate the spatial structure, resource accessibility, and service balance of Macau’s medical service system. It found that (1) the Macau Peninsula has concentrated core medical resources, such as the Conde de São Januário Hospital (CHCSJ) and Kiang Wu Hospital, which form a core subsystem with high service saturation. Excessive concentration of resources has led to high concentration of a certain type of facility. (2) Taipa Island and the Cotai Reclamation Area have created an extended subsystem of medical resources along with urban development. However, the northern area does not have enough facilities, and its internal structure is not balanced. (3) Coloane Island has only basic health stations remaining, forming a marginal subsystem with scarce medical resources, which has a significant hierarchical gap with the core and extended subsystems. This spatial pattern of “saturated Macau peninsula, expanded Taipa Island, and sparse Coloane Island” is essentially a concrete manifestation of the imbalance between the medical resource allocation system and the urban spatial development system. Therefore, based on system optimization theory, it proposes constructing a multi-level, networked spatial system for medical facilities to promote the coordinated operation of various regional medical subsystems and achieve overall functional optimization and a balanced layout for Macau’s medical service system. This research analyzes the imbalance mechanism of high-density urban public service systems using systems science methods, providing not only a scientific basis for the precise optimization of Macau’s medical resource allocation system but also a practical reference for the planning and governance of similar high-density urban public service systems under a systems thinking framework. Full article

Climate change has intensified the need for adaptation in urban environments, yet its integration into historic urban squares, where recreational activities were heavily concentrated, has remained underexplored. In this context, the study examined the square located between Hagia Sophia and the Blue Mosque, which is also defined as an urban recreation area and a focal point of culture-based tourism, during periods of extreme weather conditions and high flows of both local (n = 152), and international tourists (n = 236), evaluating it through different spatial activity typologies. A total of 388 participants were surveyed at 25 survey points within the square, while meteorological parameters were obtained from meteorological stations. The findings showed that the lowest level of heat stress across all typologies corresponded to “slight heat stress,” while user responses varied according to spatial characteristics. In movement spaces, the absence of shading elements increased both heat stress and shade demand, whereas in stationary spaces, the presence of trees reduced heat stress but preferences for lower air humidity persisted even under shaded conditions. Sky openness was not identified as a direct determinant of thermal sensation, with meteorological and perceptual factors proving more influential. PET explained approximately 65% of the variation in MTSV among tourists, compared to 55% among local residents. Across typologies, only increases in air temperature negatively affected thermal satisfaction. Moreover, tourists perceived the square more holistically and reported higher satisfaction compared to locals, whose environmental demands were distinct. These results highlighted the importance of spatial activity typologies in shaping thermal experience and underlined the necessity of design strategies that extended beyond heat-mitigation measures. Holistic and flexible approaches that accounted for user profiles, activity types, and intensity of use were found to be essential for improving thermal comfort in historic urban squares with diverse spatial configurations. Full article

Additive manufacturing (AM) is increasingly recognized as a critical enabler for sustainable space exploration, offering on-demand fabrication, reduced reliance on Earth-based resupply, and enhanced mission autonomy. Over the past decade, in-space AM has progressed from early polymer extrusion experiments aboard the International Space Station (ISS) to the demonstration of multi-material capabilities involving polymers, metals, ceramics, recycling systems, and in situ resource utilization (ISRU) concepts. This review provides a comprehensive synthesis of AM technologies developed for space applications, with emphasis on demonstrated flight heritage, process behavior under microgravity and vacuum conditions, and materials validated in orbit. The paper surveys major AM process families relevant to space, including fused filament fabrication, directed energy deposition, ceramic stereolithography, bioprinting, and closed-loop recycling systems. Key ISS-based platforms—such as the Additive Manufacturing Facility, Ceramic Manufacturing Module, and Refabricator—are reviewed to assess technological maturity and system-level integration. Materials performance across polymers, metals, ceramics, and regolith-based feedstocks is discussed, highlighting the influence of microgravity, thermal transport, and environmental exposure. By comparing in-space results with terrestrial and reduced-gravity studies, this review identifies consistent trends, critical limitations, and remaining knowledge gaps, providing a structured perspective on the readiness of in-space additive manufacturing for future orbital and deep-space missions. Full article

Electrochemical energy storage is pivotal in constructing new-type power systems. However, the large-scale deployment of energy storage stations poses severe safety challenges, particularly the risk of deflagration. The coupling of combustible accumulation within battery systems and the confined structure of storage units can trigger cascading thermal runaway and deflagration accidents. Existing research still falls short in systematically analyzing the deflagration risks and process evolution mechanisms in energy storage stations. To address this gap, this study develops a probabilistic risk assessment model that enables analysis of risk propagation through the integration of fault tree analysis (FTA) with a static fuzzy Bayesian network (BN). The proposed approach delineates the complete risk evolution pathway from battery thermal runaway to deflagration in a confined space. Diagnostic reasoning identifies a dominant risk escalation path initiated by internal short circuits, leading to thermal runaway, flammable gas release, and pressure accumulation due to inadequate pressure relief. Sensitivity analysis highlights gases ejected during thermal runaway (C22) and lack of pressure relief devices or insufficient venting area (C31) as the most influential risk drivers. This study thus offers a practical, model-based framework for enhancing targeted risk prevention and safety resilience in electrochemical energy storage station infrastructure. Full article

Focusing on the construction of a 58-m-diameter double-layer steel space frame dome at the Han Culture Museum Assembly Hall, this study addresses scheme selection and safety control challenges in staggered jacking of large-span spatial structures. A three-dimensional finite element model in MIDAS Gen simulated the three-stage jacking process to compare three temporary support layouts. Numerical evaluation metrics included maximum vertical displacements, peak internal forces, the proportion of members undergoing stress state transitions, and spatio-temporal evolution of stress concentrations. Scheme B demonstrated superior performance, reducing peak vertical displacement by 44% under critical conditions, lowering peak stresses, and enabling more uniform internal force redistribution—effectively mitigating tension–compression cycling and buckling risks. Crucially, only nodal displacements and support elevations were monitored in situ using a 3D system based on magnetic prisms and total stations; no strain or force measurements were conducted due to practical constraints during construction. Monitoring data show good agreement with simulated displacements and support elevations under Scheme B, validating the model’s deformation response. However, localized deviations—including a 29 mm deflection discrepancy and elevation errors up to 28 mm—reveal the influence of uneven boundary conditions, with potential implications for long-term structural behavior. The findings confirm that numerical predictions of deformation are reliable, while internal forces remain unvalidated by field data. The integrated approach of “scheme comparison–construction simulation–full-process displacement monitoring” proves effective for safety control and decision-making in complex jacking operations, offering a transferable framework for similar large-span double-layer space frame projects. Full article

Thermal runaway events in energy storage power stations exhibit distinct acoustic characteristic signals. Three-dimensional localization of the sound source is of significant importance for achieving precise firefighting interventions. This study proposes an internal fault localization method for power stations based on the acoustic signals from pressure relief valves of energy storage battery packs. By deploying four microphones to capture the acoustic signals from the battery pack pressure relief valves, the spatial location of the faulty pack can be calculated using a three-dimensional localization model trained on a Back Propagation (BP) neural network. The localization accuracy of this model is better than 0.5 m, with the majority of measurement points achieving an accuracy of less than 0.3 m, meeting the requirements for battery pack-level localization. A key advantage of this method is its low sensitivity to time delay measurement errors caused by reverberation and reflections in enclosed spaces. Reliable and stable localization of pressure relief sound sources can be achieved through multiple training sessions within the battery cabin, which facilitates practical deployment. Full article

The Galileo Search and Rescue (SAR) service is the contribution from the European constellation to the international Cospas–Sarsat system. This system uses a variety of space and ground infrastructure to detect and localize distress signals from beacons on the 406 MHz frequency. Satellites in different orbits detect the signals coming from the Earth and transmit them back to Earth stations that route them to the appropriate government authorities. On top of the standard detection and relay service, the Galileo constellation is the first to offer a Return Link Service (RLS) that acknowledges the processing of the distress signal with a Return Link Message (RLM) back to the originating beacon. This RLM is transmitted in the SAR field of the E1 signal I/NAV message, which allocates 20 bits every 2 s page. Therefore, transmitting a short RLM (80 bits) takes four consecutive pages or eight seconds. Moreover, each RLM is transmitted in parallel from two Galileo satellites. The RLS has been active since 2020, avoiding the spotlight of the GNSS community. This paper presents an analysis of the SAR Return Link Messages extracted from more than 3 months of signal-in-space data to investigate the current bandwidth use, monitor the type of SAR usage, and detect anomalies in the service. To extract and parse the Return Link Messages, we have developed and published an open-source Python library called GalileoSARlib on GitHub, which is also detailed in the paper. Full article

The Survey Camera (SC) is the key instrument of the China Space Station Telescope (CSST), with its imaging performance significantly constrained by microvibrations from internal sources such as the shutter and cryocoolers. This paper proposes a systematic microvibration suppression scheme integrating disturbance source control, payload isolation, and transfer path optimization to meet the stringent requirements. The Cryocooler Assembly (CCA) compressor adopts a symmetric piston layout and a real-time vibration cancellation algorithm to reduce the vibration. Coupled with a vibration isolator designed by combining hydraulic damping and a flexible structure, it achieves a vibration isolation efficiency of 95%. The shutter adopts dual-blade symmetric design with sinusoidal angular acceleration control, ensuring its vibrations fall within the compensable range of the Fast Steering Mirror (FSM). And the finite element optimization method is used to optimize the dynamic characteristics of the Support Structure (SST) made of M55J carbon fiber composite material, to avoid resonance in the critical frequency bands. System-level tests on the integrated SC show that the RMS values of vibration force and torque within 8–300 Hz are 0.25 N and 0.08 N·m, respectively, meeting design specifications. This scheme validates effective microvibration control, guaranteeing the SC’s high-resolution imaging capability for the CSST mission. Full article

With the advancement of China’s space sector, the China Space Station has transitioned from the research and construction phase to the application and development phase. This evolution signifies that payload missions in orbit are now being comprehensively executed. As a result, the management and control of payload operations face numerous challenges, including substantial workloads, extended timelines, complex operational requirements, multifaceted collaborations, and dynamic conditions. To ensure the safe and efficient implementation of extensive space science missions under the China Manned Space Program, as well as to optimize the utilization of space resources and enhance application outcomes, it is imperative to systematically assess and synthesize the requirements for in-orbit management of space applications. Employing a task-oriented framework, this study compares the organizational structures of both domestic and international space stations, providing a comprehensive overview of the operational management model for space application systems. It delineates strategies for in-orbit operation management encompassing task planning, operational supervision, anomaly detection, data analysis, and personnel coordination. Furthermore, the article evaluates the current status of in-orbit operation management and highlights significant scientific achievements. Finally, it addresses the challenges and future prospects, with particular emphasis on digitization, intelligent systems, and space–ground collaborative mechanism. Full article