空间科学学报

Downward Continuation Method Using Equivalent Source Technique with Full-Parameter Joint Estimation

, Available online , doi: 10.11728/cjss2026-0025

Abstract(9) PDF 7636KB(1)

Abstract:
To address accuracy limitations in equivalent source-based downward continuation arising from fixed equivalent source positioning, a novel magnetic field continuation technique dynamically optimizing equivalent source parameters is proposed. Traditional approaches utilizing predefined subsurface equivalent source configurations exhibit inherent deviations from geological realities, resulting in substantial errors during deep magnetic field characterization. In contrast, simultaneous three-dimensional dynamic optimization of both equivalent source positions and magnetic moments yields enhanced structural congruence with geological formations. Simulation results demonstrate that the proposed method improves the continuation accuracy by more than one order of magnitude compared to the single-layer and multi-layer fixed-source methods. This advancement provides enhanced precision for critical applications including deep-sea mineral exploration, crustal fault identification, and geomagnetic navigation systems.

A Fast Atmospheric Correction Model for L-band Spaceborne Microwave Radiometer Based on Neural Network

, Available online , doi: 10.11728/cjss2026-0030

Abstract(8) PDF 3587KB(1)

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Atmospheric correction is critical for the application of spaceborne microwave radiometers. After the successful launch of China's HY-4 satellite, the sea surface salinity detection accuracy is expected to be further improved, which puts higher demands on the accuracy of atmospheric correction. In this context, the neural network is used for the atmospheric correction of L-band spaceborne microwave radiometers for the first time. Firstly, the traditional top-of-atmosphere brightness temperature model was reformulated, yielding a novel linear atmospheric correction equation with respect to the Earth's surface brightness temperature. The slope and intercept of this equation can serve directly as the atmospheric correction coefficients for modeling purposes, thus improving efficiency and accuracy. Secondly, based on the MPM93 atmospheric radiative transfer model and ERA5 hourly reanalysis data, the sensitivity of surface water vapor density and total column water vapor was analyzed for the purpose of optimizing the model input parameter. Thirdly, the A-B coefficients atmospheric correction model was developed using the neural network method, which can greatly simplify the atmospheric correction process. Finally, comprehensive comparative tests were performed using the Peng model and SMAP L1B data. The results demonstrate that the A-B model has good consistency with the Peng model, and has an average error of about 0.03K compared to the SMAP L1B data. This proves the accuracy and reliability of the A-B model, and provide a reliable basis for its future atmospheric correction applications in China's ocean salinity satellite mission.

In-orbit Validation of SEM-II onboard FengYun-3E（For "Commemorating the 90th Anniversary of Professor Xiao Zuo's Birth."）

, Available online , doi: 10.11728/cjss2025-0226

Abstract(96) PDF 2319KB(9)

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The new generation of space environment monitor (SEM), SEM-II, onboard the Chinese meteorological satellite, FengYun-3E, has the abilities to measure the charged particles ﬂux with the particle energy from 30 eV to 300 MeV in multi-directions, the satellite surface potential, the radiation dose in sensors, and the geomagnetic field variations. The space environment detections derived from SEM-II can be utilized for satellite security designs, scientiﬁc studies, development of radiation belt models, and space weather event monitoring or disaster warning. In this paper, we introduce the SEM-II’s instrument characteristics, interpret the in-orbit calibration algorithm, perform the quantitative test to check the particle and the magnetic field detections’ accuracies by the cross-calibration methods, and do the qualitative test to check if the radiation dose and the surface potential detections follow the nature law of space environment by comparing with the historical records. The instruments’ responses to the space weather events are also presented.

A Study of the Occultation and Extinction of the Celestial X-ray Source Scorpius X-1 by Jupiter's Atmosphere

, Available online , doi: 10.11728/cjss2025-0185

Abstract(85) PDF 2068KB(10)

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Jupiter, as a typical gas giant in the solar system, harbors atmospheric composition that carries crucial information about the early evolution of the solar system. Based on the principle of X-ray occultation, this study investigates the extinction process of X-rays in Jupiter's atmosphere using Scorpius X-1 as a background source. By establishing a 1-D forward radiation transfer model, incorporating atmospheric density profiles generated by Photochem and absorption cross-sections from the XCOM database, we calculated atmospheric transmittance. The radiation spectrum of Scorpius X-1 was simulated using XSPEC, enabling systematic analysis of the attenuation characteristics of transmission spectra, light curves, and energy spectra. The results indicate that as the photon energy increases from 0.1 keV to 500 keV, the penetration depth of X-rays gradually increases, with photons reaching a minimum altitude of 139 km. Analysis of light curves shows that both the initiation and completion altitudes of high-energy photon extinction are lower than those of low-energy photons. Energy spectra analysis reveals that low-energy photons experience more significant attenuation, and the degree of attenuation intensifies with decreasing altitude. Simulations based on the NICER detector response matrix demonstrate that increasing the number of detection modules can enhance the photon count; using four NICER-like detection modules reduces the minimum detectable altitude for photons to 183.5 km. This research provides a theoretical foundation for the payload design of China's "Tianwen-4" Jupiter system exploration mission, scheduled for launch around 2030, and opens up new technical avenues for probing Jupiter's upper atmosphere.

PRELIMINARY RESULTS AND ANALYSIS OF AERIAL FLIGHT TEST OF TYPICAL GLACIERS ON THE QINGHAI TIBET PLATEAU USING DUAL FREQUENCY ULTRA WIDEBAND ACTIVE AND PASSIVE GLACIER DETECTOR

, Available online , doi: 10.11728/cjss2025-0100

Abstract(103) PDF 1748KB(10)

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The cryosphere plays an important role in the climate system and the interaction of multiple spheres. The key elements of the cryosphere, such as ice sheet, sea ice, snow cover, and frozen soil, are the recorders and main driving factors of global climate change. The change of glacier reserves in the Asian water tower area, with Qinghai Tibet Tianshan Altai Mountains as the core, has a significant impact on the runoff recharge function of major rivers in the lower reaches of China. Microwave detection has the advantages of strong penetration, sensitivity to the distribution and changes of water, and not limited by light. It can penetrate the sub surface layer several meters to several kilometers below the surface of the ice cover. By detecting the radiation and scattering characteristics of the material under the ice, the layered structure, temperature profile, density, and dielectric constant of the sub surface layer of the ice cover can be inverted. This project has developed a P/L dual frequency ultra wideband active and passive glacier radar. P-band microwaves can penetrate ice sheets several meters to several kilometers below the surface, while L-band microwaves are suitable for detecting snow information on ice sheet surfaces. Combined with the high resolution and strong detectability provided by the ultra wideband linear frequency modulation pulse compression system, it can achieve precise detection of glacier radiation and scattering characteristics. Through airborne flight tests conducted on the Guliya Glaciers and Laohugou No.12 Glacier in 2024, it was proven that P-band signals have glacier depth detection capabilities, with a penetration distance of over 370 meters . L-band signals provide richer information on the ice surface and shallow ice, with a detection depth of over 100 meters. In terms of ice depth calculation, a simulation model was established based on actual measurement data, and the ice depth at the ice core position was calculated to be about 309.81 meters, which is 0.08 meters different from the ice core length of 309.73 meters.. Radiant brightness temperature also shows a correlation with altitude and glacier volume. These pieces of information provide data basis and model foundation for future polar glacier detection and spaceborne cryosphere detection in the future.

, Available online , doi: 10.11728/cjss2025-0106

Abstract(64) PDF 2635KB(12)

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Simulation Research on Magnetic Core Material Characteristics of Fluxgate Sensors

, Available online , doi: 10.11728/cjss2026-0012

Abstract(120) PDF 1693KB(15)

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The hysteresis characteristics of the magnetic core fundamentally dictate the performance limits of fluxgate sensors. To address the lack of standardized comparative data and the scarcity of Jiles-Atherton (J-A) model parameters required for high-fidelity simulations, this study establishes an integrated evaluation framework linking hysteresis parameter identification to sensor performance simulation. First, Sobol global sensitivity analysis is employed to quantify the governing mechanisms of microscopic parameters on macroscopic magnetic properties. Second, a physics-constrained hybrid optimization algorithm is proposed for J-A parameter identification, achieving a computational efficiency improvement of approximately 16 times compared to traditional differential evolution methods. Subsequently, a finite element simulation platform for fluxgate sensors is developed. A simulation parameter library covering seven mainstream soft magnetic materials is constructed, with its predictive capability validated against experimental data from the literature. Leveraging this library, the sensitivity characteristics of different materials are quantitatively compared under unified excitation conditions. Furthermore, the study reveals a convergence trend in size-dependent attenuation rates for materials with varying permeabilities during core miniaturization. This work provides a quantitative tool for the material selection and structural optimization of fluxgate sensors.

Seasonal Variability of the DE3 Tide at 160 km Altitude Based on GOLD Observations (2019–2023) (Special Issue in Honor of Professor Xiao Zuo’s 90th Birthday)

, Available online , doi: 10.11728/cjss2025-0230

Abstract(77) PDF 1499KB(12)

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This study aims to reveal the seasonal evolution characteristics of atmospheric tides in the middle thermosphere (160 km) and fill the observational gap in the 110–200 km "thermospheric gap" region. Based on the geostationary orbit observation data from NASA's GOLD mission during 2019–2023, the spatio-temporal sequences of amplitude and phase of the non-migrating diurnal tide (DE3) are extracted from the temperature field using the wavenumber spectrum analysis method and weighted least squares fitting, combined with Empirical Orthogonal Function (EOF) decomposition to analyze its dominant modes. The results show that the DE3 tide at 160 km exhibits distinct seasonal characteristics compared with those in the mesosphere and lower thermosphere (MLT), with its amplitude peak stably locked after the autumnal equinox (September–November). The explosive enhancement and phase mutation occurring in the autumn of 2021 reveal the nonlinearity and complexity of tidal dynamic processes at this altitude. EOF analysis further confirms that the DE3 signal is not dominated by a single mode but is jointly constructed by the equatorial symmetric mode and the hemispheric asymmetric regulatory mode. This study verifies that the autumn peak structure is an inherent climatological attribute of the tide at this altitude, providing key observational evidence for understanding the synergistic modulation of lower atmospheric forcing and thermospheric in-situ processes.

Detection of Weak Lensed Gravitational Waves in the Millihertz Band Using Extended LSTM Network

, Available online , doi: 10.11728/cjss2026-0040

Abstract(157) PDF 978KB(25)

Abstract:
Space-based gravitational wave missions are expected to detect a statistically significant population of gravitational wave lensing events, offering new opportunities for cosmology and fundamental physics. In the millihertz band, the GW wavelength can be comparable to the Schwarzschild radius of the lens, giving rise to prominent wave-optics effects. To meet the need for rapid identification among large volumes of candidate events in future surveys, conventional matched filtering and Bayesian parameter estimation pipelines are often computationally expensive and thus less suited to fast pre-screening. In this work, we propose an extended long short-term memory (xLSTM)-based lensing feature extraction model. By processing whitened frequency-domain data from the A and E channels of space-borne detectors, the model leverages a matrix-memory structure to effectively capture diffraction-induced amplitude patterns across the millihertz band. Experiments on a mixed lensing dataset show that the proposed method achieves AUC > 0.99 and provides improved detection capability over baseline models in the low false positive rate regime. The performance remains stable under representative lens models, including the point-mass and the singular isothermal sphere lens, demonstrating good cross-model generalization; the method also retains an advantage at low signal-to-noise ratios. Owing to its low inference-time cost, this approach can serve as an efficient pre-screening tool for future searches for lensed GW candidates in space-based observations.

Effects of Thermal Deformation on a Parabolic Cylindrical Reflector Antenna for a Spaceborne One-Dimensional Synthetic Aperture Microwave Radiometer

, Available online , doi: 10.11728/cjss2026-0033

Abstract(200) PDF 1782KB(24)

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The Microwave Imager Combined Active and Passive (MICAP) is a primary payload onboard the HY-4A ocean salinity observation satellite. It integrates L-, C-, and K-band synthetic aperture microwave radiometers with an L-band microwave scatterometer, enabling high-precision measurements of sea surface salinity, sea surface temperature, and sea surface wind fields. The active and passive subsystems share a parabolic cylindrical reflector antenna, whose radiation-pattern geometric accuracy and stability are critical to synthetic aperture radiometer imaging performance. During in-orbit operation, thermally induced structural deformation can cause the in-orbit antenna pattern to deviate from that measured on the ground. These discrepancies propagate through the system response matrix into brightness temperature (BT) retrieval, leading to systematic retrieval errors. Conventional thermo–structural–electromagnetic coupled modeling requires high-fidelity finite-element analysis of the deformed reflector surface followed by electromagnetic simulations, which is computationally expensive and unsuitable for rapid end-to-end performance evaluation. To address this limitation, a rigid-body displacement equivalence algorithm is proposed to model reflector thermal deformation and is applied to the MICAP one-dimensional interferometric radiometer. The method approximates thermal deformation by applying rigid translations and rotations to the nominal reflector surface. The fit is considered acceptable when the root-mean-square (RMS) residual between the equivalent and deformed surfaces is below 0.001 times the operating wavelength. Based on the equivalent reflector model, the antenna radiation pattern is computed and used for forward radiometer simulation and subsequent BT retrieval, enabling rapid end-to-end evaluation from thermal loading to BT retrieval performance. A sensitivity analysis of two critical degrees of freedom is further conducted to quantify their impact on BT retrieval accuracy. Results demonstrate that the proposed method substantially reduces computational cost while maintaining high accuracy, providing an efficient and practical framework for on-orbit performance assessment and error compensation in spaceborne synthetic aperture radiometers.

Recent research progress on the midnight collapse of ionospheric electron density

, Available online , doi: 10.11728/cjss2026-0027

Abstract(182) PDF 1736KB(24)

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The midnight collapse is a typical structural variation in the nighttime evolution of ionospheric electron density, reflecting vertical ion transport and its dynamical modulation in the nighttime ionosphere. Since the phenomenon was first observed, extensive studies have been conducted by the international scientific community to investigate its morphological characteristics and underlying physical mechanisms, using a variety of approaches including ground-based radar observations, satellite measurements, and numerical model simulations. This paper systematically reviews several decades of research progress on the midnight collapse, with particular emphasis on its principal morphological features under different seasonal conditions and levels of geomagnetic activity. Focusing on the physical mechanisms, we highlight the dominant role of vertical ion drift in the formation and evolution of the midnight collapse and further analyze the key factors controlling variations in vertical ion drift. On this basis, future research directions for the midnight collapse and related nighttime ionospheric dynamical processes are discussed in light of recent observational and theoretical advances. This paper is dedicated to commemorating the 90th anniversary of the birth of Professor Xiao Zuo, an outstanding scientist in the field of ionospheric physics and space science in China, and aims to honor his pioneering contributions to the advancement of ionospheric and space science research through a comprehensive synthesis of this representative ionospheric phenomenon.

Brief Analysis of Development Status and Key Technologies of Space Metal Additive Manufacturing

, Available online , doi: 10.11728/cjss2025-0245

Abstract(148) PDF 2685KB(23)

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Space manufacturing technology has important application value in the field of deep space exploration, and it is an advanced technology developed by various aerospace powers. At present, the space manufacturing of non-metallic materials has been realized. However, there are still many problems in the space manufacturing of metal materials, such as the complex control of material forming process and the limitation of load energy consumption. How to choose the optimal technical route, process parameters, and how to design microgravity experiments have become the key challenges to solve the space manufacturing of metal materials. This paper introduces the current metal additive manufacturing experiments and research carried out in the microgravity environment, and analyzes the difficulties and difficulties faced by metal material microgravity additive manufacturing. This paper focuses on the advanced manufacturing technology which is feasible and promising for space application, and discusses the future development direction from three aspects : metal material system research, key technology breakthrough and engineering application prospect, in order to provide reference for the development of metal material space manufacturing technology.

Simulation of the Wide Field soft gamma-ray Polarimeter in Wide Band X-Ray Polarization and Imaging Telescope

, Available online , doi: 10.11728/cjss2025-0193

Abstract(162) PDF 1417KB(20)

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Polarization measurements of X-rays and soft gamma rays can reveal the geometry of the emission region, magnetic field structures, radiation mechanisms, and the environment along the propagation path, serving as a probe for astrophysical research. The Wide Band X-ray Polarization and imaging Telescope (WXPT) can perform polarization measurements over 3~500 keV, filling the gap in hard X-ray and soft gamma-ray polarimetry. The wide-field soft gamma-ray polarimeter is an important payload on this telescope, covering 50~500 keV, and is composed of a plastic scintillator and CsI. Using Geant4, we carried out physics simulations of the wide-field soft gamma-ray polarimeter. The results show a detection efficiency greater than 15% and a minimum detectable polarization (MDP) of 8%.

Introduction to the Langfang L&S-band Precision Solar Radio Flux Telescope and Its Observation Results

, Available online , doi: 10.11728/cjss2025-0248

Abstract(286) PDF 2474KB(35)

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Intense solar radio burst events in the L-band are one of the potential factors affecting the stability of navigation and communication. To address this, Yunnan Observatories, Chinese Academy of Sciences, and National Space Science Center, Chinese Academy of Sciences, have specifically developed the Langfang L&S-band Precision Solar Radio Flux Telescope, which conducts real-time monitoring of 8 frequency points in the L-band and 2840 MHz (i.e., the F10.7 index) in the S-band. The system adopts real-time calibration technology, which switches the antenna and matched load to access the receiver in real time, and uses the noise power difference between the antenna input signal and the 50Ω matched load as observation data. This reduces the receiver gain variation caused by temperature and other factors, and improves the stability of observation data. Currently, the telescope is in good operating condition. Through 1333 days of continuous observation, the correlation coefficient between its key space weather indicator data (F10.7 index) and international data reaches 0.95. During this period, multiple events of solar radio bursts affecting navigation signals have been captured. This verifies the effectiveness of the radio telescope in monitoring key space weather indices and provides technical support for long-term services to space weather users in the future.

Automatic Calibration of an All-Sky Camera Based on Constellation Recognition

, Available online , doi: 10.11728/cjss2025-0234

Abstract(203) PDF 1994KB(30)

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The intrinsic distortion of the fisheye lens in an all-sky camera can significantly alter the mapping between pixel coordinates and the true azimuth and zenith angles, making high-quality training star points essential for geometric correction prior to physical analysis. Because lens calibration models are sensitive to their initial parameters, traditional calibration methods based on manual annotation or rule-based matching often struggle to achieve both high efficiency and high accuracy. In this study, we propose an automated calibration method for all-sky cameras based on constellation recognition. The method first uses deep learning to automatically construct high-quality training star points to initialize the lens calibration model, and then iteratively improves the calibration accuracy by progressively expanding the training set. Experiments on observational data from an all-sky airglow imager at the Xinglong station of the Meridian Project show that the constellation recognition model achieves an mAP_50-95 of 0.985, and the resulting geometric calibration yields azimuth and zenith-angle correction errors within 2' , significantly outperforming a conventional distance-matching approach (within 45' ). This study provides an efficient and high-precision solution for automated calibration of all-sky cameras.

Influence of Background Heavy Ions on Fast Magnetosonic Waves Excited by Proton Shell Velocity Distributions

, Available online , doi: 10.11728/cjss2025-0228

Abstract(162) PDF 939KB(26)

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Fast magnetosonic waves observed in the Earth’s inner magnetosphere are considered to be excited through the proton Bernstein instability driven by proton velocity distributions with a positive slope along the perpendicular velocity. The present study employs linear kinetic plasma theory to investigate how the concentrations of cool background helium and oxygen ions affect the growth rate of the proton Bernstein instability driven by proton shell velocity distributions. The results demonstrate that increasing the concentrations of these heavy ions makes the unstable waves move to larger wave numbers (smaller wavelengths). At the same time, their overall growth rate increases and their harmonic numbers shift toward lower frequencies. In addition, these changes of the proton Bernstein instability are more pronounced when the concentration of background oxygen ions increases, compared with that of helium ions. Finally, the reasons for these changes are explained and discussed.

A Retrieval Method for Sea Surface Rainfall under Tropical Cyclones Based on Airborne Microwave Radiometer Data

, Available online , doi: 10.11728/cjss2025-0173

Abstract(215) PDF 3276KB(29)

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Severe convective weather systems such as tropical cyclones are often accompanied by intense precipitation. Accurate retrieval of sea surface rainfall rate at high temporal and spatial resolutions is crucial for disaster prevention and mitigation, numerical weather prediction, and the investigation of the fine-scale structure of typhoons. In this study, a coupled cloud–rain atmospheric radiative transfer model combined with a nonlinear least-squares inversion technique is developed to retrieve sea surface rainfall rate under tropical cyclone conditions. To address the overestimation of surface emissivity by the FASTEM-5 model at moderate-to-high wind speeds (25 ~ 45 m·s^-1), a wind-speed-dependent emissivity correction term is introduced.The corrected emissivity model exhibits improved consistency with that derived from SFMR (Stepped-Frequency Microwave Radiometer) observations, with a mean absolute error less than 0.02. Furthermore, the absorption effects of oxygen, water vapor, and cloud liquid water are incorporated into the radiative transfer calculations, and the corrected emissivity model is used to simulate brightness temperatures. The results show that the simulated brightness temperatures exhibit mean biases ranging from −1.56 K to −2.14 K and standard deviations between 1.64 K and 1.87 K relative to observations. Based on SFMR flight data collected from multiple tropical cyclones during 2014 ~ 2023, the retrieved rainfall rates exhibit a root-mean-square error (RMSE) of 2.54 mm·h^-1 and a correlation coefficient of 0.915, demonstrating the robustness and accuracy of the proposed rainfall retrieval algorithm in typhoon environments.

Comparative Study of VLF Cutoff Frequency Extraction Methods for the Earth–Ionosphere Waveguide

, Available online , doi: 10.11728/cjss2025-0241

Abstract(276) PDF 1388KB(31)

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The first cutoff frequency of the Earth–ionosphere waveguide is a key parameter for characterizing the effective reflection height of the lower ionospheric D region, and its retrieval is highly sensitive to methodological choices. Using nighttime VLF electric field power spectra measured by the DEMETER satellite during 2006–2009, this study systematically compares critical procedures involved in cutoff frequency extraction, including two identification methods (the Toledo local minimum method and the V-shaped criterion), two statistical sequences (detect-then-average versus average-then-detect), and a continuous-point merging strategy. Seven representative latitude grids spanning 55°N to 55°S over the central Pacific Ocean are selected to evaluate detection performance and its impact on reflection height estimation. The results show that the Toledo method achieves higher detection coverage but with a relatively low accuracy (26.4%), whereas the V-shaped criterion yields fewer detections but a significantly higher accuracy (66.8%). The average-then-detect strategy fails completely at high latitudes and leads to a systematic underestimation of the cutoff frequency by approximately 15–40 Hz. The continuous-point merging strategy has a relatively minor influence, with differences of about 12 Hz. The global distribution of VLF reflection heights derived using the V-shaped criterion combined with the detect-then-average and merging strategy indicates that reflection heights over oceans are generally lower than those over land, persistent low-reflection-height bands exist over the equatorial Atlantic and Indian Oceans, and pronounced seasonal variations with amplitudes of 10–15 km occur at middle and high latitudes. Overall, the results suggest that the V-shaped criterion combined with the detect-then-average strategy is more suitable for climatological studies of cutoff frequency and lower ionospheric D-region reflection height.

, Available online , doi: 10.11728/cjss2026-0042

Abstract(248) PDF 1528KB(42)

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High-Spatial-Resolution Signal Processing for the Airborne Rotating-Antenna Microwave Scatterometers

, Available online , doi: 10.11728/cjss2026-0039

Abstract(220) PDF 1684KB(35)

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The rotating-antenna microwave scatterometer is characterized by its wide observation swath, simple system architecture, and cost-effectiveness, thus being widely applied in the remote sensing of sea surface winds. However, conventional microwave scatterometers are generally real-aperture radars, which makes it challenging to obtain high-spatial-resolution measurements of surface backscattering coefficients. To address this limitation, this paper takes an airborne platform as an example, and proposes a high-spatial-resolution signal processing scheme for the rotating-antenna microwave scatterometers, with the aim of achieving both high spatial resolution and wide observation swath based on the Doppler Beam Sharpening (DBS) technique. The variation of spatial resolution with scanning azimuth angle is firstly investigated following a signal-level simulation workflow, which includes signal transmission and reception, pulse compression, Doppler sharpening, etc. The results demonstrate that DBS generally results in a much finer spatial resolution (within 75% of the observation swath) than that of conventional scatterometers. Furthermore, numerical simulations are used to quantify the impact of signal-to-noise ratio (SNR) on the quality of DBS “images”, providing theoretical and technical supports for the quantitative applications of scatterometers. Although this study is based on an airborne platform, it provides crucial algorithmic support and validation for the spaceborne rotating scatterometers to break through mesoscale limitations and move towards sub-mesoscale remote sensing applications.

Position Correction Method for Solar Radio Images under Ionospheric Influence

, Available online , doi: 10.11728/cjss2026-0032

Abstract(193) PDF 1331KB(32)

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The ionospheric influence is one of the major challenges in low-frequency radio astronomy data processing. Effects such as absorption, scattering, and Faraday rotation caused by the ionosphere can lead to positional shifts of target sources in images obtained by ground-based telescopes, with the impact being particularly significant at low frequencies. This paper first designs a fully connected network based on an Autoencoder (AE) model to classify telescope observation images into "good" and "bad" categories. Subsequently, an unsupervised learning-based algorithm for solar position identification, tracking, and correction is developed. Through a target tracking and correction network combined with an iterative validation model, this algorithm performs position correction on video images where the target source position is shifted due to ionospheric effects. Experiments conducted on LOFAR solar image sequences (105 videos, 23,292 images; frequency range 19.9–78.5 MHz) demonstrate that the proposed algorithm effectively corrects ionospheric positional deviations. It converges within an average of 7.17 iterations at a processing speed of 6.18 frames per second (fps).

Analysis of Seasonal Glint Phenomenon of Two GEO Satellites

, Available online , doi: 10.11728/cjss2026-0015

Abstract(256) PDF 3254KB(36)

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Seasonal glint, a unique phenomenon of GEO satellites, is caused by the special solar illumination condition and the motion characteristics of solar panels. The characteristics of glint is summarized based on the glints of two GEO satellites after the autumnal equinox. And the reason of glint is analyzed and the glint condition is displayed. Moreover, the solar panel offset of the two satellites is estimated from the peak feature of light curves. The light curve during glints is compared with that of before glints, and concludes the law of glints. Finally, glint intensity of different satellites is compared and quantified. The results can provide guidance for observation planning and reference for object characterization.

A Prediction Method for M(3000)F2 in Mid-latitude Region Based on Statistical Machine Learning

, Available online , doi: 10.11728/cjss2026-0011

Abstract(312) PDF 2322KB(34)

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The ionospheric F2 layer 3000 km propagation factor M(3000)F2 is a key parameter supporting frequency selection and system performance evaluation in High Frequency (HF) communication. Accurate M(3000)F2 prediction is critical for reliable communication but remains challenging. The uneven spatial distribution of ionospheric observation instruments and strong temporal variability of the ionosphere limit the performance of conventional prediction methods. To address this issue, a statistical machine learning (SML) model is developed to predict M(3000)F2. Harmonic decomposition is introduced to describe nonlinear and periodic variations of M(3000)F2 at different temporal scales. A stratified validation strategy is also employed to improve model robustness, ensuring that validation samples cover different solar activity levels. The paper analyzes data from nine mid-latitude ionospheric stations, spanning 1996 to 2024. Five solar activity indices are considered, including F10.7, sunspot number, Lyman-α, MgII, and extreme ultraviolet. Their predictive performance is examined both individually and in combination. The results indicate that the optimal model configuration uses Lyman-α, month, and universal time as input variables. Compared with the International Reference Ionosphere (IRI) model, the SML model achieves smaller prediction errors. The mean absolute error and root mean square error are reduced by 0.05 and 0.08, while the coefficient of determination increases by 0.39. These improvements correspond to 38.46%, 42.11%, and 48.15%, respectively. The proposed model maintains stable predictive performance under different solar activity phases, geographical locations, and seasonal conditions, suggesting its applicability to HF communication frequency management and space weather applications.

Comparative Study of Super Substorms During Geomagnetic Storm Time and Non-storm Time

, Available online , doi: 10.11728/cjss2026-0009

Abstract(221) PDF 2790KB(31)

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As a fundamental coupling mode between the solar wind, magnetosphere, and ionosphere, substorms have profound impacts on the near-Earth space environment. Super substorms refer to those during which the maximum value of AE or SME index exceeds 2000 nT, featuring stronger energy injection processes and different response modes compared with normal substorms. In this study, based on an existing substorm list, we selected two cases of super substorms with similar solar wind conditions—one occurring during a geomagnetic storm and the other during a non-storm period. Using in-situ observation data from geosynchronous orbit satellites LNAL and GOES, auroral electrojet and ring current parameters from OMNI and SuperMAG, as well as numerical simulation results from the CIMI model, we conduct comparative analysis of these two cases from the perspectives of particle injection, energy input, and ring current dynamics. The results show that: (1) During geomagnetic storms, the propagation distance of super substorm signals may be shorter than that during non-storm periods, primarily due to differences in the background plasma environment; (2) During non-storm periods, the SME index of super substorms exhibits a distinct bimodal structure as a function of local time; (3) The occurrence of geomagnetic storms leads to enhanced oxygen ion flux, thereby intensifying the ring current during super substorms. By studying the similarities and differences between super substorms during and outside of geomagnetic storms, this research can better serve future studies on the physical processes and impact mechanisms of super substorms, as well as the relationship between super substorms and geomagnetic storms, further promoting the understanding of space weather and the Earth-space environment.

, Available online , doi: 10.11728/cjss2026-0003

Abstract(242) PDF 2031KB(31)

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Effects of Different Exercises during 90-Day Head-Down Tilt Bed Rest on Post-Bed Rest Walking Gait

, Available online , doi: 10.11728/cjss2026-0001

Abstract(231) PDF 1366KB(31)

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Background: Head-down bed rest (HDBR) is a common method for simulating microgravity. Prolonged HDBR leads to adaptive changes in gait cycle, joint angle, and muscle activation. These changes may affect the efficiency and stability of daily activities and task execution. Therefore, it is necessary to optimize current exercise training protocols to maintain astronauts' ability to perform critical tasks and extend mission duration.
Objective: To investigate the effects of HDBR and different exercise training on walking gait biomechanics and lower limb muscle activation.
Methods: Thirty-six participants underwent a 90-day HDBR and were randomly divided into five groups: Group A (control group, 8 participants, no exercise training), Group B (7 participants, HDBR + aerobic training), Group C (7 participants, HDBR + high-load resistance training), Group D (7 participants, HDBR + aerobic training + low-load resistance training), and Group E (7 participants, HDBR + aerobic training + high-load resistance training). Gait and surface electromyography analysis were conducted 1 day before bed rest, 3 day after getting up, and 24 day after getting up.
Results: 1) Test time significantly affected single support phase, double support phase, swing phase, step rate, min and max hip angles, min and max knee angles, knee range of motion (ROM), min and max ankle angles, and activation of major lower limb muscles (P < 0.05). 2) Group significantly influenced stance phase, step rate, step length, walking speed, min ankle angle, ankle ROM, lateral gastrocnemius activation, and soleus activation (P < 0.05).
Conclusion: 1) Adaptive changes in walking gait were characterized by increased support phase, decreased swing phase, and reduced step rate, reflecting changes in motor control strategies. 2) Exercise training interventions primarily improved ankle motion and enhanced activation of calf muscles, but had limited effects on hip and knee motion as well as thigh muscle activation. Among all training protocols, high-load resistance training was crucial for maintaining and recovering lower limb walking gait, especially when combined with aerobic training. 3) Recovery effects indicated that lower limb motor control had not recovered to previous level in 24 day after getting up, but ankle recovered faster than hip and knee.

Ionospheric Signatures of the 2025 Mw 7.7 Myanmar Earthquake Revealed by GNSS Observations

, Available online , doi: 10.11728/cjss2025-0247

Abstract(303) PDF 1269KB(35)

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This study investigates co-seismic ionospheric disturbances (CSIDs) triggered by the Mw 7.7 strike-slip earthquake in Myanmar on 28 March 2025, with a focus on how complex source rupture processes influence the earthquake–atmosphere–ionosphere coupling. High spatiotemporal resolution total electron content (TEC) data from the ground-based GNSS networks IONISE and IGS are employed. CSID signals are effectively extracted through sliding-window detrending and a fourth-order Butterworth band-pass filter with a period band of 2–6 minutes. Results show that during 06:36–06:39 UTC, a clear “N”-shaped disturbance with a dominant period of approximately 5 minutes and a peak amplitude of 0.97 TECU emerged in the near-field region (<1000 km from the epicenter). The disturbance exhibits pronounced east-west azimuthal asymmetry, with significantly larger amplitudes in the eastern sector (azimuth 30°–225°) compared to the west. This asymmetry is consistently observed across multiple satellites with diverse viewing geometries—including near-zenith and geostationary satellites—ruling out line-of-sight geometric effects or geomagnetic modulation as primary causes. The horizontal propagation velocity of the CSID ranges from 1.6 to 3.4 km/s, showing clear azimuthal dependence and aligning closely with surface Rayleigh wave speeds, indicating that the disturbance is predominantly excited by the Rayleigh wave mode. This azimuthal asymmetry is reasonably explained by the earthquake’s rupture dynamics—initial bilateral propagation followed by a unidirectional southward supershear rupture—which enhances Rayleigh wave radiation in specific directions via Mach wave effects. This study demonstrates that GNSS-derived TEC observations can effectively capture the directionality and dynamic details of coseismic rupture, providing critical observational constraints for characterizing Rayleigh wave radiation patterns and advancing our understanding of cross-layer coupling processes.

Statistical Study of Plasmaspheric Plumes based on THEMIS observations

, Available online , doi: 10.11728/cjss2025-0240

Abstract(230) PDF 1435KB(33)

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We present a statistical survey of 488 detached plasmaspheric plume crossings identified by THEMIS from 2011 to 2022, characterizing their spatial distribution, densities and morphological properties. Plumes occur primarily at L = 5 – 8.5 and those on the duskside exhibit the highest densities, occurrence rates, and radial widths (∆L) among all MLT sectors. Dayside plumes extend to larger L than those in other MLT sectors, indicating a sunward-wrapping geometry originating from the duskside. The electron densities of plumes typically concentrate in the range of 60 – 90 cm⁻³. Plume densities decrease outward from L = 5 – 6, indicating progressive dilution with radial extension. Both positive gradients (Gpos ) and negative gradients (Gneg ) decrease systematically with L while showing a pronounced dawn–dusk asymmetry, with stronger gradients on the dawnside and weaker gradients on the duskside for L > 6. The radial widths of most plumes are within the range of ∆L = 0.2 – 1.0. Plume electron density increases with ∆L, suggesting that narrower plume is accompanied by a faster reduction in electron density. These results provide a comprehensive statistical framework for understanding plume formation, evolution, and their role in magnetospheric dynamics.

Research on Coupled Ionosphere-Thermosphere Model for Spaceborne Intelligent Platforms

, Available online , doi: 10.11728/cjss2025-0239

Abstract(195) PDF 836KB(35)

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With the development of space systems toward autonomy and intelligence, the traditional “space-sensed, ground-computed” model for space-environment support can no longer meet the needs of real-time response and autonomous decision-making. Aiming at the urgent demand of satellite platforms for real-time space-environment information, this study carries out an onboard-oriented reconstruction of the autonomous global ionosphere–thermosphere coupled model GCITEM-IGGCAS. Focusing on three major challenges encountered during in-orbit operation-system adaptability, computational efficiency, and real-time performance-this work implements several key upgrades, including adaptation and robustness enhancement of the operating environment, optimization of computational efficiency, and the construction of standardized data interfaces. Based on preserving the original physical core, the upgraded model significantly improves operational robustness, computational efficiency, and dynamic responsiveness across diverse onboard platforms. Simulation results demonstrate that the model can stably output key environmental parameters, such as thermospheric neutral density and ionospheric total electron content, whose spatial distributions are physically consistent. This indicates strong potential for providing real-time environmental inputs for tasks such as autonomous orbit management and enhanced communication and navigation. The study offers a feasible pathway for transforming high-end scientific models into intelligent onboard modules, and is of great significance for advancing “space-sensed, space-computed” capabilities.

Analysis of Micrometeoroid Environment Characteristics Using Meteor Radar Data from the Meridian Project

, Available online , doi: 10.11728/cjss2025-0236

Abstract(190) PDF 2677KB(34)

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Micrometeoroids represent a significant factor threatening the safety of China's spacecraft in space. Historically, numerous incidents of spacecraft anomalies due to meteoroid impacts have been reported, therefore, conducting modeling studies on the meteoroid environment is of great significance. This study utilizes observational data from the Mohe Station of China's Meridian Project to inverse the characteristics of micrometeoroids in near-Earth space, analyze the spatiotemporal distribution characteristics of micrometeoroids over China's mid-to-high latitudes (including their number, velocity, altitude, azimuth, zenith angle, and flux), and retrieve their physical properties such as mass. The results indicate that meteoroid activity exhibits distinct seasonal and diurnal variations: activity is higher in summer than in winter and significantly higher at night than during daytime. In addition, the spatial distribution of meteoroids is non-uniform and primarily concentrated in the northwest direction; their velocities predominantly range between 20 and 80 km/s, and altitudes are mainly concentrated between 75 and 125 km. Comparing the inversed flux results with the classical Grün model revealed good consistency between the two sets of results for larger-sized meteoroids' flux. This research can provide technical support for developing China's independent meteoroid environment modeling studies.

Development of Space Particle Radiation Detection and Protection Technology

, Available online , doi: 10.11728/cjss2025-0233

Abstract(217) PDF 1240KB(36)

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As human space activities extend from low Earth orbit to the cislunar region and interplanetary space, space radiation has emerged as a fundamental safety issue constraining mission reliability and the feasibility of long-term human presence beyond Earth. Characterized by multiple sources, high particle energies, and strong temporal variability, the space radiation environment poses persistent and unpredictable risks to spacecraft systems and human health. For deep-space exploration missions beyond geomagnetic shielding, the spatiotemporal behavior and interaction mechanisms of space radiation become increasingly complex, placing higher demands on the effectiveness of radiation protection. In response, a systematic framework integrating environmental characterization, detection technologies, and protective interventions is needed. This paper reviews the characteristics of the space radiation environment, methods for radiation detection, as well as passive, active, and biomedical radiation protection approaches. Research progress of representative space missions is summarized and discussed. These studies provide a theoretical basis for radiation safety management in manned spaceflight and offer important references for the development of protection strategies and engineering paradigms in deep space exploration.

An observational study of low-latitude ionospheric disturbances using the Low lAtitude long Range Ionospheric raDar

, Available online , doi: 10.11728/cjss2025-0207

Abstract(226) PDF 2484KB(34)

Abstract:
In the low-latitude ionosphere, the equatorial plasma bubble (EPB) irregularities and traveling ionospheric disturbances (TID) are two important space weather phenomena. These disturbances can affect radio wave propagation, disrupting satellite communications and navigation positioning systems. Due to the limitations of ground-based detection techniques, substantial observational gaps remain regarding ionospheric TIDs and irregularities over low-latitude oceanic regions. This study introduces an over-the-horizon detection method for low-latitude ionospheric disturbances using the Low-lAtitude long Range Ionospheric raDar (LARID) located in Hainan, China. By resolving the elevation angle of arrival based on the phase difference between the radar's main array and interferometer array, LARID can determine the spatial location of ionospheric disturbances. Leveraging its multi-beam observation capability, we have achieved two-dimensional imaging of TID structures and retrieved their wavelengths and propagation directions. The localization results for EPBs show good agreement with S4 index data from GNSS receivers. Significant differences exist between the observed TIDs and GNSS TEC measurements, which may be partly attributed to the filtering effect of daytime westward wind fields on atmospheric gravity waves. While LARID is currently only capable of observing quasi-east/west propagating TIDs and ionospheric irregularities along the east-west direction, this study finally proposes a method to extend its observational azimuth to full 360° coverage. Ray-tracing experiments demonstrate that this expansion can effectively enhance LARID's detection coverage for background ionospheric disturbances and irregularities.

Anomaly Detection Method for Satellite Telemetry Parameters Based on Adversarial Autoencoders and Spatiotemporal Feature Fusion

, Available online , doi: 10.11728/cjss2025-0219

Abstract(220) PDF 1650KB(32)

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Abstract Satellite telemetry data play a critical role in ground operation and management systems for evaluating the on-orbit performance and health status of spacecraft. Telemetry parameters, generated by sensors and controllers, are inherently multivariate time series characterized by strong correlations, quasi-periodicity, high noise levels, and missing values. Many traditional methods fail to effectively capture temporal dependencies and inter-parameter coupling relationships, making it difficult to identify complex anomalies in multivariate telemetry data and resulting in suboptimal detection performance. To address these limitations, this paper proposes an anomaly detection method based on adversarial autoencoders and spatiotemporal feature fusion. Specifically, multiscale temporal features are first extracted using temporal convolutional networks. Long-term dependency structures among parameters are then constructed by similarity modeling, while short-term interaction structures are built by integrating embedding vectors with sliding-window inputs. A graph neural network is employed to model the inter-parameter relationships. Finally, an improved autoencoder is incorporated into an adversarial training framework to enhance robustness against noise perturbations and missing data. Experimental results on real satellite telemetry data and public datasets demonstrate that the proposed method effectively captures complex spatiotemporal dependencies among telemetry parameters and outperforms existing methods in terms of detection accuracy, significantly improving the accuracy and robustness of multivariate telemetry anomaly detection.

Research Progress on the Effects of Solar Flares on the Thermosphere-Ionosphere-Magnetosphere System

, Available online , doi: 10.11728/cjss2025-0218

Abstract(268) PDF 3142KB(33)

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Solar flares, a major form of solar eruptive activities, release strong electromagnetic radiation that can disrupt the Earth’s Thermosphere-Ionosphere-Magnetosphere (M-I-T) coupling system. In the past decade, significant progress has been made. This review systematically overviews the multi-scale effects of solar flares on the M-I-T system and their coupling mechanisms. For the thermospheric response, we highlight flare-induced heating, changes in neutral composition, and atmospheric dynamical processes; for the ionospheric disturbances, we review the sudden photoionization response, variations in electron density, and the restructuring of electric fields and current systems via electrodynamic processes. Special attention is given to the delayed effects of the flare extreme ultraviolet late phases on the ionosphere. In magnetospheric coupling, we discuss the modulation of field-aligned currents and magnetospheric convection structures through changes in polar conductivity. We also explore the nonlinear coupling characteristics under the combined influence of solar flares and geomagnetic storms. We highlight the significant contribution made by Chinese researchers to the understanding of flare energy transmission and distribution mechanisms within the M-I-T system.

Prediction of Low-Altitude Debris Orbit Decay Based on the Seq2Seq Model

, Available online , doi: 10.11728/cjss2025-0208

Abstract(164) PDF 1617KB(33)

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The number of low Earth orbit (LEO) space debris continues to rise, rendering orbital decay prediction a critical task for space safety and reentry risk assessment. However, Two-Line Elements (TLE) exhibit high noise in the LEO region, coupled with strong nonlinearity in the decay process, which results in considerable errors in the long-term extrapolation of traditional methods. To address this issue, this study constructs an equal-altitude interval time series based on TLE data via height-time scatter fitting and fixed-altitude step inverse sampling. Concurrently, a sequence-to-sequence (Seq2Seq) gated recurrent unit (GRU) multi-step decay time prediction model is employed, leveraging an encoder-decoder structure to extract nonlinear decay patterns and achieve remaining lifetime prediction for different altitude segments. Experiments conducted on debris from the COSMOS 1408 and COSMOS 2251 breakup events demonstrate that the model attains mean absolute errors of 0.088 h, 0.142 h, and 0.587 h at initial altitudes of 250 km, 300 km, and 350 km, respectively. The relative error at 350 km is constrained within the range of 10%–25%, significantly outperforming the SGP4 model. This proposed method provides effective support for orbital congestion assessment and reentry timing analysis.

Satellite Telemetry Parameter Prediction Based on a Linear-Decoder Combination

, Available online , doi: 10.11728/cjss2025-0204

Abstract(199) PDF 837KB(26)

Abstract:
The status monitoring, operational analysis, and anomaly detection of on-orbit satellites are critical to ensuring their safe and reliable operation, and play an important role in improving the efficiency of on-orbit management. Predicting the trend of satellite telemetry time series data is essential for anomaly detection and safe operation. With the increasing complexity of satellite systems and diversification of missions, the scale and dimensionality of telemetry data have rapidly expanded. Traditional prediction and detection methods based on empirical rules or simple statistical models struggle to meet the demands for efficient analysis and rapid response. Specifically, due to the lack of obvious periodic features in telemetry parameters, traditional methods face difficulties in effective modeling, resulting in insufficient prediction accuracy. This paper proposes a prediction model based on a linear-decoder combination. The model decomposes the time series to extract trend and seasonal components separately, and employs multi-granularity embedding strategies within the decoder to effectively capture both local and global temporal features. In the experimental section, the proposed method is applied to real telemetry data from an on-orbit satellite and compared against public time series forecasting datasets, demonstrating its feasibility and effectiveness.

Study on Influencing Factors of Jet Dust Removal for Typical Sharp Lunar Dust under Lunar Environment Conditions

, Available online , doi: 10.11728/cjss2025-0130

Abstract(177) PDF 4196KB(33)

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Dust adhesion and contamination are critical issues in the lunar environment that must be addressed during lunar exploration missions. Jet dust removal is an efficient active cleaning technology. This paper investigates the factors that influence the removal of sharp lunar dust using a jet. First, ground simulation experiments were conducted to explore these factors. The results indicate that increasing the jet nozzle radius, jet angle, nozzle distance from the origin and gas stagnation pressure all significantly improves dust removal efficiency. For instance, raising the jet nozzle radius from 1 mm to 4 mm increased final removal efficiency from 82.09% to 97.83%. Similarly, raising the jet angle from 15° to 90° increased the final removal efficiency from 80.31% to 99.99%. Furthermore, a numerical simulation was conducted using a typical sharp lunar dust contact model and the discrete element method, as well as the rarefied gas dynamics DSMC algorithm. This analysis examined the efficiency of the jet dust removal system and the factors influencing this efficiency, as well as the thermoelectric effects caused by temperature and potential differences in the lunar environment. The results of the numerical simulation show that, as the lunar surface potential increases from 10 V to 25 V, the final removal efficiency improves from 88.92% to 94.1%. Similarly, when the temperature difference increases from 0 K to 300 K, the final removal efficiency improves from 88.92% to 91.6%. Comparing the experimental and simulation results verified the accuracy of the numerical model and identified the factors influencing jet dust removal and the sharp angular characteristics of typical lunar dust. It also revealed the impact of electrodynamic thermal effects on the efficiency of jet dust removal. This study systematically revealed the parameters influencing jet dust removal and the removal efficiency of sharp lunar dust in the lunar environment.

, Available online , doi: 10.11728/cjss2025-0198

Abstract(302) PDF 2240KB(47)

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Design of Low Earth Orbit Satellite Observation System Based on Total Station Architecture

, Available online , doi: 10.11728/cjss2025-0183

Abstract(321) PDF 2000KB(43)

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The small-scale optical observation system offers significant advantages, including compact size, low cost, and high flexibility in deployment, making it a promising direction for the future development of ground-based optical monitoring systems. However, conventional small-scale optical systems suffer from substantial axis misalignment, limited azimuth precision, and low pixel resolution, which collectively degrade the validity and reliability of observational data. To address these limitations in the context of low-orbit satellite observation, targeted enhancements to small-scale optical systems are essential to improve data quality and support more effective monitoring. This paper presents a novel small-scale low-orbit satellite observation system based on a total station architecture, integrating near-infrared imaging and polarization detection techniques. By leveraging the total station’s high measurement accuracy and advanced automation capabilities, the proposed system significantly enhances the capability for optical detection of low-orbit targets. The design demonstrates practical value and provides a reference framework for the development of compact, high-performance low-orbit object observation systems.

An Integrated Direction-Finding Method Based on L1-Norm Correlation Interferometer and MUSIC Algorithm

, Available online , doi: 10.11728/cjss2025-0181

Abstract(336) PDF 771KB(41)

Abstract:
Direction finding of radiation sources is one of the key technologies for space situational awareness. High accuracy and real-time performance of direction-finding systems are of great significance in the rapidly changing electromagnetic battlefield. Traditional correlative interferometer algorithms are simple in implementation but suffer from low elevation resolution and insufficient accuracy, while the MUSIC algorithm achieves high precision at the cost of high computational complexity, resulting in poor real-time performance.To address these issues, this paper proposes and implements an integrated direction-finding method combining an L1-norm-based correlative interferometer and the MUSIC algorithm. First, at the algorithmic level, an improved correlation coefficient based on the L1 norm is introduced to replace the nonlinear similarity computation in the traditional correlative interferometer. This approach maintains sensitivity to elevation angles while simplifying trigonometric operations into hardware-friendly basic arithmetic, thereby reducing the design complexity on FPGA. Second, at the system architecture level, an integrated processing framework of “interferometer coarse estimation – MUSIC fine estimation” is constructed. The coarse estimation results from the interferometer serve as prior information for the MUSIC algorithm, constraining the spectral peak search within a small local neighborhood. Finally, comparative analysis between MATLAB simulations and FPGA computation results demonstrates that the relative errors between the fixed-point FPGA implementation and floating-point MATLAB computation of all core modules remain below the order of 1.0×10⁻⁶. While ensuring accuracy, the proposed method reduces direction-finding time by 98% compared with the full-space search of the pure MUSIC algorithm, thus verifying the effectiveness, real-time capability, and high precision of the proposed approach. This work provides a technical foundation for the development of next-generation high-performance, low-power satellite-borne electronic reconnaissance and situational awareness systems.

Spectral Unmixing of Aluminum-Rich Clay Minerals with Radiative Transfer Models and Its Implications for Martian Remote Sensing

, Available online , doi: 10.11728/cjss2025-0180

Abstract(470) PDF 914KB(102)

Abstract:
The relative abundances of aluminum-rich clay minerals such as kaolinite and montmorillonite in Martian weathering profiles reflect variations in chemical weathering intensity and paleoclimatic conditions. Accurate quantification of these minerals is essential for reconstructing early Martian environments and evaluating their potential habitability. Spectral unmixing provides a powerful means to retrieve mineral abundances, yet its accuracy remains uncertain due to limited laboratory validation, particularly for hydrated mineral mixtures with overlapping absorption features. In this study, two sets of laboratory-prepared mixtures (kaolinite–montmorillonite and kaolinite–opal, comprising 12 spectra) were analyzed using two widely applied radiative transfer models for planetary spectroscopy, the Hapke model and the Shkuratov model. The results show that the Shkuratov model achieved abundance errors below 10% in seven samples and between 10–20% in two samples, while the Hapke model produced only three samples below 10% and seven between 10–20%. Overall, the Shkuratov model demonstrated higher inversion accuracy. This work provides an experimental validation framework for quantitative spectral unmixing of Martian aluminum clays and offers methodological guidance for analyzing more complex hydrated mineral mixtures in future study.

Lunar soil simulant and its application in space civil engineering

, Available online , doi: 10.11728/cjss2025-0178

Abstract(720) PDF 531KB(122)

Abstract:
One of the hot research directions in space civil engineering is the exploration of constructing stations on celestial bodies beyond Earth, a journey that will commence from the Moon. This paper provides a systematic review of the research progress on lunar regolith simulants and their geotechnical engineering applications. It elaborates on the definition, composition, mechanical properties, and density of lunar regolith, highlighting its significant differences from terrestrial soil in terms of composition and particle morphology. Three main development methods for lunar regolith simulants are summarized, and the characteristics of various domestic and international simulants are described categorically, with particular attention paid to the development of new simulants based on the Chang'e-5 lunar samples. Finally, the application of simulants as construction materials for lunar base building is discussed. Concurrently, the paper reviews the standardized testing methods for simulants in geotechnical mechanics experiments and their application in large-scale geotechnical engineering experiments, aiming to establish a standardized evaluation system. This work provides crucial theoretical and technical support for the future development of lunar regolith simulants and the construction of lunar bases.

Responses of Ionospheric TEC to Geomagnetic Storms from 1998 to 2023 in East Asia and North America

, Available online , doi: 10.11728/cjss2025-0169

Abstract(342) PDF 1785KB(42)

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This paper investigates responses of ionospheric TEC in East Asian and North America to geomagnetic storms with 563 events during 1998–2023. Superposed epoch analysis are performed on the TEC data aligned by each storm’s main phase onset (MPO) using superposed epoch analysis (SEA). To resolve local-time controls, storms are binned into 24 groups by the UT hour of MPO, and TEC responses are evaluated by latitude band and season. The results show that when the MPO occurs during local daytime, TEC almost invariably exhibits an immediate positive-phase disturbance; when the MPO occurs at local night, a brief and weak positive phase is typically followed promptly by a transition to a negative phase. In latitude, lower latitudes display stronger and longer-lasting positive disturbances with a later onset of the negative phase, whereas higher latitudes exhibit smaller positive amplitudes with a slightly delayed occurrence, together with an earlier onset and relatively larger magnitude of the negative phase. Seasonally, winter and the equinoxes more readily produce significant and persistent positive TEC peaks during the main phase; by contrast, in summer the main-phase positive is comparatively weak, and the recovery phase more readily begins earlier and remains negative. Our study consolidates the day–night asymmetry, latitudinal and seasonal dependence of storm-time TEC responses.

Ion Cyclotron Instability Driven by Ion Temperature Anisotropy Based on the PIC Method

, Available online , doi: 10.11728/cjss2025-0168

Abstract(278) PDF 2469KB(44)

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Electromagnetic ion cyclotron instability (EMIC) is a significant plasma instability driven by ion temperature anisotropy, widely observed in diverse spatial and experimental plasma environments such as Earth's magnetosphere, planetary magnetospheres, solar wind, and magnetic confinement fusion devices. As a typical anisotropy-driven instability, EMIC exerts a crucial influence on energy transport and particle heating processes in magnetized plasmas. Among these, ion cyclotron resonance heating is recognized as a key mechanism for achieving efficient plasma heating. This study employs a one-dimensional three-component particle-in-cell (PIC) method to numerically investigate the nonlinear evolution of EMIC under periodic boundary conditions. The Boris algorithm advances particle motion, while the fast Fourier transform (FFT) is utilized for diagnosing and analyzing the electromagnetic field spectrum. Numerical results indicate that increased ion temperature anisotropy significantly enhances the instability growth rate while altering the wave spectrum structure and dispersion characteristics. As anisotropy intensifies, ion vertical energy progressively converts to parallel energy, revealing the energy coupling mechanism during wave-particle interactions. This study provides important insights for deepening the understanding of ion heating and acceleration mechanisms in both space and laboratory plasmas.

Correlation Study on Ground-Based Neutron CountsBased on the ForbushDecrease Event of May 10, 2024

, Available online , doi: 10.11728/cjss2025-0163

Abstract(272) PDF 1251KB(39)

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On May 10, 2024, the Earth’s magnetosphere experienced the strongest geomagnetic storm in nearly two decades, accompanied by a significant Forbush decrease (FD) event. In this study, we collected 10-minute interval neutron count variation data from the global ground-based neutron monitor network in May 2024, which had undergone dual corrections for atmospheric pressure and detection efficiency. A rational function model was employed to fit and analyze the data, yielding the temporal structure of the FD event. Furthermore, a correlation analysis was conducted between this temporal structure and the geographical information parameters of the ground-based neutron monitoring stations. The results indicated that the decrease time of the FD event is positively correlated with both the altitude and the geomagnetic cutoff rigidity of the neutron monitor stations. The recovery time shows a positive correlation with altitude, geographic longitude, and the absolute value of geographic latitude. The amplitude of the decrease is strongly positively correlated with the absolute value of geographic latitude, but strongly negatively correlated with geomagnetic cutoff rigidity. The end time of the decrease exhibits a strong positive correlation with both altitude and geomagnetic cutoff rigidity.

A Dataset of F10.7 index of Hebei Langfang station (2022-2024)

, Available online , doi: 10.11728/cjss2025-0132

Abstract(683) PDF 1719KB(102)

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The solar F10.7 index is an important parameter for characterizing the level of solar activity, which has important scientific significance and engineering application value for its real-time accurate monitoring. In order to improve its independent monitoring capabilities, the National Space Science Center of the Chinese Academy of Sciences built a solar radio telescope in Langfang, Hebei Province in 2019, and the telescope officially produced scientific data in January 2022. Based on the monitoring data of the Langfang Solar Radio Telescope, this dataset constructs the autonomous solar radiation index F10.7 from 2022 to 2024, which has high quality reliability, has a high correlation coefficient with the international F10.7 index, and can reflect the level of solar activity, which has important application value.

Research on the Sloshing Suppression Performance of Baffles in Partially Filled Liquid Storage Tanks

, Available online , doi: 10.11728/cjss2025-0125

Abstract(493) PDF 868KB(97)

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As an essential technology for maintaining the stable operation of spacecraft propulsion systems, the management of liquid propellants in storage tanks holds significant practical importance. Therefore, research on fluid management devices—such as slosh baffles—is of great relevance. This study conducts detailed numerical simulations and experimental investigations on the effects of different baffle configurations on liquid sloshing characteristics in partially filled storage tanks under terrestrial gravity. Numerical simulations were performed on the sloshing processes of tanks equipped with various baffle structures. The frequency and damping ratio of the liquid sloshing, extracted from the simulation data, were used to characterize the oscillation response of the liquid to external excitations. The results indicate that, compared with the original configuration (Configuration 1), Configuration 2 (baffles with near-wall blades) reduces the oscillation amplitude of the liquid mass center and increases the damping ratio. Configuration 4 (double-sided perforated baffles) halves the liquid oscillation decay time and significantly enhances the damping ratio. In contrast, Configuration 3 (single-sided perforated baffle) deteriorates the damping performance. Sloshing experiments further verify the reliability of the numerically obtained damping ratios.

Advances in Global Atmospheric Electric Circuit Research and Environmental Interactions

, Available online , doi: 10.11728/cjss2025-0085

Abstract(308) PDF 621KB(41)

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The rapid advancement of Earth and space exploration technologies has significantly enhanced studies of the global atmospheric electric circuit (GEC) through satellite-based lightning observations, ground-based monitoring networks, and optical emission measurements between clouds and the ionosphere. This paper analyzes the interaction mechanisms between electric currents across different atmospheric layers and various generators within the GEC system. We examine the influences of aerosols and cosmic rays on GEC dynamics, explore its coupling with climate change mechanisms, and investigate its interactions within solar-terrestrial relationships. Furthermore, we outline emerging trends in global atmospheric electric field research and environmental applications.The global atmospheric electric field model provides a fundamental theoretical framework for understanding multi-sphere coupling processes on Earth, offering significant scientific value for space weather prediction, meteorological phenomena interpretation, and geological process analysis. An integrated multi-platform observation network - comprising satellites, aerostats, unmanned aerial systems, aerial remote sensing platforms, and ground-based monitoring stations - enables comprehensive three-dimensional dynamic monitoring of global atmospheric electric fields.From a physical mechanism perspective, measurable anomalies in the global atmospheric electric field demonstrate correlations with: (1) solar activity variations, (2) thunderstorm electrification processes, and (3) characteristic negative anomalies preceding seismic events. The atmospheric ionization processes induced by radon gas emissions have been identified as potentially critical indicators for short-term earthquake forecasting. These findings suggest substantial application potential for global atmospheric electric field research in aerospace safety systems, advanced meteorological studies, and solar-terrestrial interaction investigations.

, Available online , doi: 10.11728/cjss2025-0059

Abstract(304) PDF 1537KB(38)

Abstract:

Hybrid Lunar Walking Path Planning Based on Improved Bi-RRT and A*

, Available online , doi: 10.11728/cjss2025-0129

Abstract(314) PDF 1135KB(40)

Abstract:
This paper proposes a hybrid path‑planning algorithm that integrates an improved Bidirectional Rapidly‑exploring Random Tree (Bi‑RRT) with an enhanced A* search to support safe astronaut traversal on the lunar surface under complex constraints. First, an obstacle density adaptive goal-bias Bi-RRT algorithm is used to rapidly explore complex lunar terrain and generate an initial feasible path, effectively managing the computational challenges posed by large-scale search spaces. Then, the search space is constructed by morphological expansion operation on the initial feasible path, which provides effective guidance for fine path optimization. Finally, within this region a multi‑constraint weighted A* algorithm plans the final path, focusing on balancing multiple indicators such as energy consumption, risk, and illumination conditions. Experiments on real lunar terrain data show that the hybrid method achieves a superior balance across path length, success rate, metabolic energy consumption, risk avoidance, and illumination conditions when compared with existing planners. By uniting the fast exploration of Bi-RRT with the precise optimisation of the weighted A*, the algorithm improves both efficiency and quality of path planning in complex lunar environments and provides an efficient, reliable solution for astronaut lunar walking.

Study on the Fusionand Validation of Sea Surface Height Anomaly Field based on the Radar Altimeters Onboard HY-2C/D Satellites

, Available online , doi: 10.11728/cjss2025-0049

Abstract(302) PDF 2920KB(44)

Abstract:
Spaceborne radar altimeters can provide high-precision global sea surface height (SSH) observations regularly. However, the spatial resolution from a single satellite is relatively sparse. To facilitate the study of mesoscale ocean phenomena, multi-satellite data fusion techniques are essential. The HY-2C/D satellites, operating in inclined orbits with configurations similar to the advanced Jason series (e.g., Jason-3), are particularly suitable as data sources for SSH fusion. Although multiple operational fused SSH anomaly fields (e.g., the MIOST product) exist internationally, none currently incorporate China's HY-2C/D data. This study performed cross-calibration for the HY-2C/D radar altimeters against Jason-3 to correct systematic biases and compute sea surface height anomalies (SSHA). Using the Optimal Interpolation (OI) method, we integrated HY-2C/D data into the MIOST background field to generate a fused SSH anomaly field for the South China Sea (10°×10°). In constructing the OI's critical variance-covariance matrix, the diagonal elements were derived from the standard deviations of HY-2C/D post-calibration data, while covariance terms were determined based on the power spectrum characteristics of SSHA. Validation using tide gauge data from the Wanshan Calibration Site (China's operational altimeter calibration field) demonstrated that the fusion of HY-2C and HY-2D data reduced the root-mean-square error (RMSE) of SSHA sequences relative to ground truth. This study confirms the contribution of HY-2C/D data to fused satellite altimetry products.

A method study for comprehensive diagnostics of multivariate telemetry parameters in spacecraft

, Available online , doi: 10.11728/cjss2025-0110

Abstract(448) PDF 1401KB(39)

Abstract:
In order to improve the comprehensive diagnostic efficiency of spacecraft on orbit, a comprehensive diagnostic method is proposed based on mixed weighted and dynamic time warping (DTW) algorithms. Firstly, a mixed weighted method combining normalization and the analytic hierarchy process (AHP) is applied to determine the weighting coefficients of multivariate telemetry parameters for spacecraft. Using these weighting coefficients, comprehensive characteristic parameters representing the operational state of the spacecraft can be obtained, thereby transforming multi-parameter diagnosis into single comprehensive characteristic curve analysis. Secondly, a DTW distance calculation method is introduced, which converts the comprehensive characteristic parameter judgment into a time-series similarity measurement problem. Finally, by comparing the optimal DTW distance of comprehensive characteristic parameters with the measurement threshold, the integrated diagnostic of multiple parameters for spacecraft can be achieved. By applying the method described in this paper, a comprehensive diagnostic of the depressurization process during an astronaut’s extravehicular activity was conducted. The analysis results indicate that the method features high sensitivity, simple computation and easy implementation, providing an effective method for the diagnosis of key events and health management of spacecraft in orbit.

Polar Ionospheric TEC Inversion Based On Spaceborne Fully Polarimetric SAR and Its Response to Aurora

, Available online , doi: 10.11728/cjss2025-0244

Abstract(377) PDF 1412KB(101)

Abstract:
The enhancement of ionospheric total electron content(TEC)caused by auroral activity will have a significant impact on the L-band electromagnetic wave signal emitted by the spaceborne fully polarimetric synthetic aperture radar(SAR)system,resulting in additional phase error and polarization distortion.By solving the Faraday rotation angle(FRA)in the signal,the high-precision and high-resolution ionospheric TEC variation characteristics can be retrieved.In this paper,31 scenes of fully polarimetric SAR image data are used to calculate the polar ionospheric TEC using four typical FRA inversion algorithms,and the results are compared with the local ground-based GNSS-TEC observation results.The influence of auroral activity on SAR signal quality is quantitatively analyzed.The results show that among the four algorithms used,the polar TEC obtained by the B&B algorithm is the most consistent with the observed value.The TEC enhancement caused by the auroral arc will significantly affect the SAR signal,making its FRA significantly increased,while the cross-circular polarization product is reduced,that is,the signal-to-noise ratio is reduced.The research shows that the fully polarimetric SAR based on B&B algorithm can effectively invert the polar TEC,which provides a new technical means for studying the polar ionospheric TEC disturbance and its relationship with auroral activity.

, Available online , doi: 10.11728/cjss2025-0237

Abstract(494) PDF 4911KB(101)

Abstract:

Ground calibration method for water content measurement with lunar soil volatile matter measuring instrument

, Available online , doi: 10.11728/cjss2025-0107

Abstract(515) PDF 1460KB(96)

Abstract:
The detection of water content in the polar regions of the moon is of great significance in scientific research and resource utilization. The Chang 'e-7 mission is scheduled to be launched to the South Pole of the moon in 2026 to explore water ice. The lunar soil volatile matter measuring instrument it carries needs to complete calibration tests before launch. The lunar soil volatile matter measuring instrument consists of four parts including a micro sampling unit. The measurement process includes nine steps such as sampling, transfer, and heating release. There are various errors such as sample weight errors. To ensure measurement accuracy, ground calibration is required: the vacuum specification standard calibrates the pressure output by controlling different temperature points. The calibration of the mass spectrometer is verified for sensitivity by means of the vacuum system and the injection system. The copper hydroxide test can be used to eliminate sampling transfer errors and verify systematic errors. The full-process calibration of water-containing simulated lunar soil simulates the in-orbit environment to verify the full-process error. Through these calibration methods, the randomness and temperature drift of barometric measurement can be constrained, and the residual errors of the system can be corrected, providing methodological support for the inversion of on-orbit data on lunar soil water content.

Chinese Geomagnetic Index Based on Chinese Meridian Project Geomagnetic Data

, Available online , doi: 10.11728/cjss2025-0200

Abstract(509) PDF 2019KB(93)

Abstract:
The great disturbances of the horizontal component of the geomagnetic field in mid-low latitudes caused by the ring current in the Earth's magnetosphere can be characterized by the Disturbance Storm Time (Dst) index and the symmetric H component (SYM-H) index. The Dst index and SYM-H index are important indicators for measuring geomagnetic activity, which can clearly reflect the commencement and intensity of geomagnetic storms. Due to the asymmetry of ring current during geomagnetic storms, there are significant differences in the geomagnetic disturbance intensity in different regions. As global geomagnetic index, Dst index and SYM-H index may not accurately describe the geomagnetic disturbance situation in China. We uses geomagnetic data from four stations in Lhasa, Chengdu, Wuhan, and Hangzhou of the Chinese Meridian Project from 2010 to 2024 to calculate the Chinese geomagnetic index (cDst index, cSYM-H index), and compares and analyzes them with the global geomagnetic index (Dst index, SYM-H index). The results indicate that the two types of Chinese geomagnetic index can more accurately describe the characteristics of geomagnetic disturbances in China, and their differences from the global geomagnetic index show a dawn-dusk dependence: The absolute value of the Chinese geomagnetic index is greater than the global geomagnetic index when China is located on the dusk side, and is less when China is on the dawn side. Correspondingly, the number of Chinese geomagnetic disturbances is more than geomagnetic storms when China is located on the dusk side, and is less when China is on the dawn side. The physical mechanism of these phenomena is closely related to the dawn-dusk asymmetry of the ring current. Meanwhile, based on the Chinese geomagnetic index, the global geomagnetic index can be effectively obtained, and the results are in good agreement. Therefore, when the global geomagnetic index cannot be obtained, high-quality supplementary data can be provided.

Occultation Distribution and Collaborative Observations of Fengyun Meteorological Satellites and Commercial Satellites

, Available online , doi: 10.11728/cjss2025-0213

Abstract(357) PDF 5672KB(94)

Abstract:
GNSS radio occultation (RO) serves as a key technique for constructing a global high-precision atmospheric and ionospheric sounding capabilities. China’s operational Fengyun-3 (FY-3) RO system produces data of exceptional quality, characterized by high accuracy, stability, and standardization, making it the current accuracy benchmark in RO sounding. However, due to its orbital configuration, the FY-3 system alone still exhibits coverage gaps in equatorial and polar regions. In recent years, the rapid development of commercial constellations such as Tianmu and Yunyao has enabled multi-source RO cooperative observations, offering a promising approach to enhance the spatiotemporal density of RO data. Based on RO measurements from the FY-3, Tianmu, and Yunyao constellations, this study systematically evaluates the spatial distribution characteristics and joint observation benefits of the three systems. Results demonstrate that integrating commercial constellations significantly increases the number of global RO events and improves coverage at low and high latitudes. Local time coverage is also enhanced from segmented intervals to nearly continuous throughout the day. Despite the considerable improvement in observational density, data overconcentration in certain mid-latitude areas and small-scale gaps under high-resolution analysis remain, indicating that orbital configurations and constellation coordination require further optimization. This study provides quantitative references for the future collaborative development of China’s FY-3 and commercial RO constellations.

Infrared Dim-Small Target Detection Based on NSCT and Three-layer Window Local Contrast

, Available online , doi: 10.11728/cjss2025-0082

Abstract(340)

Abstract:
When using a sliding window to calculate local contrast, when the sliding window size is larger than the target size in the original image, it will cause a "swelling effect" that causes the target to be missed. In order to solve the above problems, this paper proposes an infrared weak target detection algorithm based on non-subsampled contour wave transform and local contrast of three-layer window. According to the global sparsity of the target on the infrared image, the non-subsampled contour wave transform is introduced to decompose the image into low-frequency and high-frequency sub-graphs, and the differential image of high-frequency and low-frequency subgraphs is constructed. Guided filtering can effectively enhance the signal strength of the target and increase the gray difference between the target area and the background neighborhood, and then calculate the local contrast with the three-layer sliding window for background suppression and target enhancement, and then construct a confidence map. In order to test the effectiveness of the proposed method, six groups of open-source infrared sequence images were selected for comparative experiments, each group of sequences included 30 frames of images, with different backgrounds and large differences, the experimental results showed that the algorithm effectively avoided the problem of target missed detection caused by the "expansion effect", and the ROC curve, PR curve and AUC value were used to evaluate the experimental results, and compared with the existing 8 algorithms, the proposed method in the ROC curve was in sequence 1, sequence 2 and sequence 6. A higher detection rate was always maintained at the same false alarm rate, and the AUC value was the highest of all methods, and the AUC value was also the second best value in the remaining sequences 3, 4, and 5. Similarly, in the PR curve, the proposed method maintains the highest precision under the same recall rate in sequence 2 and sequence 3, with AUC values of 0.9309 and 0.9506, which have good improvements in background suppression, target enhancement and accuracy.

, Available online , doi: 10.11728/cjss2025-0139

Abstract(458) PDF 936KB(116)

Abstract:

Mid-term Forecasting Study of Solar F_10.7Index Using LSTM-NN Hybrid Model

, Available online , doi: 10.11728/cjss2025-0159

Abstract(453) PDF 2942KB(104)

Abstract:
Addressing the critical challenge that existing statistical analysis and machine learning-based time series forecasting methods struggle to simultaneously capture temporal dependencies and nonlinear characteristics in solar F10.7 cm flux time series—particularly the anomalous fluctuations caused by radio burst events during solar maximum years, which lead to significantly higher prediction errors compared to solar minimum years—this paper proposes a mid-term forecasting method for the solar F10.7 index. The method innovatively integrates Long Short-Term Memory (Long Short-Term Memory network) and fully connected Neural Networks (NN), and incorporates influential factors related to the Sunspot Number (SSN), constructing a hybrid prediction model driven by multiple input variables based on LSTM-NN. Using measured F10.7 data from Solar Cycle 24, seven-day-ahead prediction experiments were conducted. The results demonstrate that the model achieves a prediction correlation coefficient of R=0.95 and a Root Mean Square Error (RMSE) of 11.27 sfu, reducing the prediction error by 7.5% compared to single-input-variable models, with particularly significant improvement in prediction accuracy during solar maximum intervals (error reduction of 8.5%). Through systematic analysis and experimental validation, it is proven that this hybrid model can effectively characterize complex solar activity features, fully leverage the informational value embedded in SSN sequences, and significantly enhance the accuracy and reliability of F10.7 index time series forecasting.

, Available online , doi: 10.11728/cjss2025-0199

Abstract(396) PDF 2164KB(99)

Abstract:

An Ionospheric Space Weather Data Assimilation System over China based on Meridian Project GNSS Measurements

, Available online , doi: 10.11728/cjss2025-0182

Abstract(562) PDF 3868KB(114)

Abstract:
The successful deployment and national acceptance of the second phase of the Chinese Meridian Project (CMP), a major national scientific and technological infrastructure, signify a substantial leap forward in China’s space environment monitoring capabilities. In particular, CMP’s ionospheric monitoring network has greatly strengthened both research and operational capabilities in ionospheric space weather. This study presents a new-generation ionospheric space weather data assimilation system for China and adjacent regions, based on GNSS observations from the CMP. Leveraging stable and robust data from 85 GNSS stations from CMP and the International GNSS Service, the system integrates multi-constellation GNSS measurements from GPS, GLONASS, Beidou, and Galileo as input and employs a three-dimensional variational assimilation approach. It generates high-precision and operational ionospheric space weather products, represented by ionospheric TEC, covering China and adjacent regions (15^o-55^oN，70^o-140^oE), which significantly improves the ability to reconstruct and characterize ionospheric disturbances over China. This data assimilation system can provide diverse ionospheric space weather products, including gridded TEC, delta TEC, and the Rate of TEC Change Index (ROTI), with a high spatial-temporal resolution of 1°×1° and 15 minutes. These ionospheric products are routinely updated and publicly available via the website of Space Environment Prediction Center (http://www.sepc.ac.cn/TEC_chn.php) at the National Space Science Center, Chinese Academy of Sciences. Beyond enabling high-fidelity monitoring of the ionospheric space environment over China and adjacent regions, this system also supports in-depth investigation of multi-scale ionospheric variations and irregularity characteristics. In addition, it delivers timely, accurate, and effective ionospheric error correction and space weather information for satellite navigation, radar imaging, shortwave communication, and space weather nowcasting.

Research on Middle and low latitude ionospheric storms

, Available online , doi: 10.11728/cjss2025-0205

Abstract(483) PDF 1278KB(122)

Abstract:
This article reviews the works made by the team of the Institute of Geology and Geophysics, Chinese Academy of Sciences in the field of ionospheric storms in recent years. The following five aspects will be outlined: (1) The large-scale characteristics and longitude dependence of ionospheric geomagnetic storms responses in the middle and low latitudes; (2) The coupling process of the ionosphere-thermosphere system during storms; (3) Electrodynamics and dynamic response processes and mechanisms of the ionosphere at low latitudes during storms; (4) Evolution and mechanism of ionospheric irregularities in the middle and low latitudes during storms; (5) Modeling and prediction of parameters during ionospheric storms. These works, by leveraging global and regional multi-source observations, numerical simulations, statistical analyses, and deep learning, systematically reveal the temporal evolution characteristics and spatial dependence of mid-low latitude ionospheric storms, and also explore their underlying physical mechanisms.

A study on the propagation and evolution of MSTID events in China's low-latitude region during 7–8 December 2019

, Available online , doi: 10.11728/cjss2025-0221

Abstract(391) PDF 2178KB(90)

Abstract:
This study investigates a nighttime medium-scale traveling ionospheric disturbance (MSTID) event observed over the low-latitude Fuke Station (19.5°N, 109.1°E) in China on December 7–8, 2019. The analysis incorporates airglow data from the Chinese Meridian Project, digisonde observations, and simulations from the Thermosphere–Ionosphere Electrodynamics General Circulation Model (TIE-GCM). The results show that the observed structures correspond to typical Northern Hemisphere MSTIDs, with bands aligned in the northwest–southeast direction and propagating southwestward. During propagation, a chasing phenomenon occurred in which the latter dark band caught up and interacted with the earlier one. The TIE-GCM simulations suggest that the chasing process was primarily governed by the combined effect of the gradient in the background zonal wind and the enhanced electron density distribution within the equatorial ionization anomaly region at low latitudes.

Multi-Instrument Observations of the Evolution of STEVE under Weak-disturbed Geomagnetic Conditions

, Available online , doi: 10.11728/cjss2025-0201

Abstract(495) PDF 2190KB(91)

Abstract:
STEVE (Strong Thermal Emission Velocity Enhancement) is a white/mauve optical arc in the subauroral region ionosphere that reflects the coupling among the ionosphere, magnetosphere, and thermosphere. We analyze a STEVE event on 16 April 2021 using multi-instrument observations to investigate its morphological evolution and energy sources under relatively quiet solar wind and weakly disturbed geomagnetic conditions. By integrating optical observations from THEMIS all-sky imagers with ionospheric and magnetospheric measurements from GNSS TEC, the Swarm satellites, AMPERE field-aligned currents, NOAA POSE, and the Arase (ERG) spacecraft, we find that this STEVE event lasted for approximately 1.5 hours and evolved into Picket Fence structures. The STEVE region exhibited typical localized signatures of electron heating, electron density depletion, fast westward ion flow, and downward field-aligned currents. The elevated westward plasma velocity (~4 km/s), together with the unusually high electron temperatures (~8,000 K during STEVE and >20,000 K during the picket fence), suggests that frictional heating associated with subauroral ion drifts (SAIDs) alone cannot account for the observed thermal enhancement. Magnetospheric observations reveal broadband electron energy flux enhancements (dominated by <10 keV electrons), indicating that low-energy electron precipitation likely supplied additional energy to the STEVE region. This study demonstrates that, even during weakly disturbed periods, the combined effects of SAID and low-energy electron precipitation can substantially elevate electron temperatures in the subauroral ionosphere, thereby facilitating the formation of STEVE and picket-fence structures.

Review of the Development of the In-Satellite Particle Detector for the China-Brazil Earth Resources Satellite-1

, Available online , doi: 10.11728/cjss2025-0164

Abstract(357) PDF 929KB(92)

Abstract:

Progress in Research on Mirror and Electromagnetic Cyclotron Instabilities of Multi-component Ions

, Available online , doi: 10.11728/cjss2025-0176

Abstract(519) PDF 1119KB(93)

Abstract:
The mirror instability and electromagnetic ion cyclotron (EMIC) instability, driven by ion perpendicular temperature anisotropy, are ubiquitous in space plasmas and play important roles on the evolution of substorm and storm.This paper outlines the physical mechanisms of these two instabilities based on magnetohydrodynamics (MHD) and kinetic theory, and reviews the fundamental theoretical research results on the two instabilities under the condition of a single ion component (proton). The progress on two types of instability in multi-component ions was further reviewed with a focus on exploring the impact of the heavy ions (He⁺、O⁺) in the Earth's magnetosphere on these two types of instability. The theoretical derivation and numerical simulation related to instability thresholds and growth rates in multi-ion plasmas were summarized, and challenges in current research were dynamically analyzed including but not limited to non-Maxwellian ion distributions and nonlinear evolution of instability. To comprehensively reveal the regulatory effects of multi-ion components on these two types of instability and their significance in global kinetics, future research requires a combination of more systematic theories, advanced numerical simulations, and more satellite observations, which will provide important basis for a deeper understanding of energy transport and wave particle interactions in space plasmas.

One method integrating P.452 with SRTM3 for interference evaluation of Satellite-Ground reverse communication link

, Available online , doi: 10.11728/cjss2025-0074

Abstract(414) PDF 811KB(96)

Abstract:
In intersecting areas of terrestrial radio services and space radio services, there is currently no well-established model for quantifying the interference of Satellite-to-Ground reverse communication link. This study investigates the physical parameters and algorithms of ITU-R P.452 and P.2001 propagation models to develop a methodology integrating with SRTM3 digital elevation model for evaluate the interference in the frequency range of Satellite-to-Ground reverse communication link. Through a comparative evaluation of ITU Study Group 3 measurement data against predicted data from two models across five globally representative regions, this study identifies appropriate radio propagation models in different scenarios. The methodology that P.452 model integrating SRTM3 provides references for investigation of in-orbit interference and frequency compatibility assessment on Satellite-to-Ground reverse communication link.

Performance Analysis of Multi-GNSS Occultation Electron Density Profiles from the Tianmu-1 Constellation

, Available online , doi: 10.11728/cjss2025-0118

Abstract(687) PDF 2046KB(123)

Abstract:
Tianmu-1 is China’s first occultation meteorological constellation capable of on-orbit compatibility among BeiDou, GPS, Galileo and GLONASS. Using the ionospheric electron-density profiles retrieved by Tianmu-1 occultations in March 2025, we analyzed the daily number of occultations and their global distribution. The quality of the peak electron density (NmF2), F2-layer peak height (HmF2) and total electron content (TEC) derived from Tianmu-1 was assessed against F2-layer critical frequency (foF2) and peak height (hmF2) measured by ionosondes, and against the post-processed Global Ionospheric Map (GIM) TEC provided by the International GNSS Service (IGS). The results show that Tianmu-1-derived NmF2 correlates with ionosonde data at 0.93, with zero mean bias, 17.9 % mean relative bias and an RMSE of 0.27 × 10⁶ el cm⁻³. For HmF2, the correlation is 0.75, the mean bias is also zero, the mean relative bias is 6.83 %, and the RMSE is 29.6 km. After mapping Tianmu-1 TEC to the ground-to-GNSS-satellite altitude range with the NeQuick model, the TEC accuracies for GPS, BDS, GLONASS and Galileo are comparable when referenced to IGS GIM TEC, yielding RMSEs of 9.64, 9.52, 9.75 and 9.56 TECu, respectively. Compared with the IRI 2020 model, the NeQuick-normalized results exhibit better agreement with IGS GIM TEC: the mean bias is only −1.87 TECu and the RMSE is reduced to 9.62 TECu, whereas the IRI model produces a mean bias of −5.59 TECu and an RMSE of 10.69 TECu.

Propagation of waves in the middle and upper atmosphere excited by intense events at the earth’s surface and lower atmosphere

, Available online , doi: 10.11728/cjss2025-0154

Abstract(655) PDF 1621KB(107)

Abstract:
Severe events in the Earth's surface and lower atmosphere—such as volcanic eruptions, earthquakes, typhoons, thunderstorms, and anthropogenic explosions—can excite various types of waves. These waves propagate into the middle/upper atmosphere and ionosphere in the form of acoustic and gravity waves, exerting significant impacts on these regions. Such events provide typical case studies for investigating the physical mechanisms of coupling between Earth's various spheres. This paper reviews the observational and research findings of Professor Xiao Zuo's team regarding the effects of severe events like earthquakes and typhoons on the ionosphere. The paper also highlights the establishment of a dual-layer airglow observation network over China and the utilization of this detection system to study the propagation characteristics and effects of gravity waves excited by events such as volcanic eruptions, typhoons, and thunderstorms in the middle/upper atmosphere and ionosphere. The research results reveal that although gravity waves generated by volcanic eruptions cannot propagate directly over long distances in the middle and upper atmosphere, they can achieve extensive and long-range transmission through ocean-atmosphere interactions. The background atmospheric structure plays a crucial role in gravity wave propagation, with atmospheric waveguides enabling anomalous long-distance propagation of gravity waves. Although small- to medium-scale gravity waves have difficulty directly propagating upward to the thermosphere, secondary wave mechanisms can effectively facilitate their propagation from the middle atmosphere to the upper atmosphere. Furthermore, studies on typhoon events provide direct observational evidence of how severe lower atmospheric events influence the upper atmosphere and ionosphere.

Research on Ground Simulation Method of Heat Transfer Characteristics for Space High-Temperature Material Experimental Furnace Based on Data-Driven Approach

, Available online , doi: 10.11728/cjss2023-0023

Abstract(971) PDF 1291KB(142)

Abstract:
The temperature stability during the crystal growth process has a significant impact on the morphology and structure of the crystal. In order to improve the quality of crystals, it is necessary to ensure the stability of temperature throughout the crystal growth process. Currently, in China, PID controllers are used to control the crystal growth temperature in space high-temperature material science experimental furnaces. Due to the limited and scarce opportunities for space experiments, the tuning of control parameters needs to be completed on the ground. However, due to the difference in heat transfer between the ground and space environments, there are differences in the heat transfer characteristics of the furnace, and its transfer functions are also different. If the control parameters tuned on the ground are directly applied to space conditions, it will result in a worse temperature control effect. To address this, this paper proposes a data-driven depressurization method that approximates and simulates the heat transfer characteristics of the furnace under microgravity environments on the ground, and provides the pressure values for ground adaptation conditions. This overcomes the problem of the traditional depressurization method being difficult to determine the pressure value for ground adaptation conditions due to lack of prior knowledge.

Nighttime Exospheric Temperature Maximum During Quiet Time of Solar Minimum Period Based on Swarm Satellites

, Available online , doi: 10.11728/cjss2024-0032

Abstract(879) PDF 2230KB(107)

Abstract:
The nighttime exospheric temperature maximum is an important part of the characteristics of upper atmospheric temperature variations, which contributes to the understanding of atmospheric temperature and the improvement of the neutral atmosphere model. Previously, due to the scarcity of upper thermosphere temperature observations, studies of the nighttime exospheric temperature maximum were mainly based on single-site and joint observation of ground-based FPI stations as well as simulation studies of the phenomena and mechanisms of various neutral atmosphere models and ionospheric models. The work in this paper carries out the statistics of global and seasonal variations of the nighttime exospheric temperature maximum during solar minimum period by deriving the exospheric temperature obtained from the neutral density of the Swarm satellite accelerometer. The results show that the stronger the solar activity is, the higher the probability and intensity of the occurrence of the nighttime exospheric temperature maximum, and the higher the probability of multiple maximum peaks. When F10.7 is between 80 and 100, the temperature enhancement occurs in all four seasons and in different longitude sectors, but with differences in morphology and intensity. For F10.7 less than 80, the temperature enhancement is stronger and longer in spring and fall, and weaker in summer and winter. In addition, the presence or absence of nocturnal enhancement varies from sector to sector.

, Available online , doi: 10.11728/cjss2024-0019

Abstract(1199) PDF 902KB(143)

Abstract:
The new electromagnetic catapult microgravity device employs linear motors to drive the experimental module in vertical motion, simulating a microgravity environment. In comparison to traditional drop tower methods, utilizing a catapult for parabolic motion significantly extends the duration microgravity time. However, the linear motor's drive introduces new challenges in ensuring a high level of microgravity quality. To meet the experimental requirements of microgravity science, this paper conducts a model analysis of the segmented dragging system of the electromagnetic catapult drop tower. It proposes a segmented control scheme and designs a displacement-tracking control algorithm for addressing motor coordination issues affecting microgravity levels and the coordination between inner capsule and outer capsule. This ultimately achieves prevention of disturbance from outer capsule to the inner capsule. The practical system has been constructed and put into operation, employing the motor control method outlined in the paper, enabling microgravity time around 4 seconds. This research provides crucial support for the development of microgravity experimental devices.

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