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Key Performance Test Methods for Digital Subsystem of L-band One-Dimensional Synthetic Aperture Radiometer for Ocean Salinity Satellite
SHI Yuelun, TANG Yueying, HAN Donghao
, Available online  , doi: 10.11728/cjss2026.01.2025-0014
Abstract(270) FullText HTML (34) PDF 3851KB(10)
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The Microwave Imager Combined Active and Passive (MICAP), the first ocean salinity detection satellite in China, realizes the global scale measurement of key geophysical elements such as ocean salinity and soil moisture through multi-factor fusion inversion. The high-sensitivity L-band one-dimensional Synthetic Aperture Radiometer (SAR), serving as the primary detector for MICAP, features a digitally implemented subsystem with a distributed architecture that constitutes the core module of the radiometer's receiving chain. The subsystem’s key performance indicators directly affect the measurement accuracy of both the radiometer and MICAP in detecting ocean salinity, thus the mission imposes stringent performance requirements. This study addresses the high-precision performance testing needs of the distributed digital subsystem, focusing on challenges such as synchronized multi-node data acquisition under a distributed framework and separation of hardware-software coupling performance. The testing method employs multi-device synchronous triggering and the Integrated Logic Analyzer (ILA) tool embedded in the FPGA of front-end data acquisition units to achieve synchronous capture of original AD sampling data from 24 channels across multiple individual units. This solution resolves the absence of original data aggregation points among multiple front-end data acquisition units in the distributed architecture. Furthermore, the study proposes a bidirectional verification framework for both hardware and system-level performance. The hardware performance is tested by analyzing raw acquired data, while the integrated hardware-software performance is evaluated by processing the end-to-end scientific data packets. This methodology achieves decoupled testing of the hardware and software performance of the distributed digital subsystem. The actual test results, including amplitude consistency ≤0.4 dB, phase consistency ≤1º, and correlation bias ≤–38 dB, meet the mission's specified requirements. The research results have been applied to the MICAP engineering development, providing critical technical support for the performance verification and optimization of the distributed digital subsystem of ocean salinity satellite synthetic aperture radiometer.
Video Super-resolution Method for Spacecraft Approaching and Detecting Asteroids
CHEN Yuhan, CHEN Yu, DENG Li, CHEN Shi
, Available online  , doi: 10.11728/cjss2026.01.2025-0002
Abstract(217) FullText HTML (47) PDF 3706KB(10)
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In the imaging process of approach detection, dynamic image sequences often have problems such as image blur and insufficient resolution due to platform movement and jitter. This paper studies the super-resolution of image sequences in the process of approach detection and proposes a video super-resolution method based on Basic VSR++. By introducing spatial and channel attention mechanisms to enhance the model’s ability to extract detail features, combined with shared projection weights, multi-group mechanisms and sampling point modulation, the effect of the alignment module is improved. While improving the network feature extraction capability, it makes up for the shortcomings of regular convolution in long-distance dependency and adaptive spatial aggregation. At the same time, downsampling is combined with a low-pass filter to reduce the high-frequency components of the image, which improves the robustness of the model to slight image jitter. In addition, a new upsampling module is introduced to combine local and global features, generate an adaptive upsampling kernel to expand the receptive field, and better restore the global structure and reconstruct details. The simulation experimental results show that the proposed method improves the Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity (SSIM) indicators by 2.2% and 2.1% respectively compared with the original method, which proves the effectiveness of the method proposed in this paper in improving the quality super-resolution reconstruction of the image sequence in close proximity.
New Method and Accuracy Analysis for Medium and Long-term Orbit Prediction of BDS-3 Satellites
HUANG Jin, CHEN Yanling, LI Liang, ZHOU Shanshi, HUANG Yong, HU Xiaogong
, Available online  , doi: 10.11728/cjss2026.01.2025-0020
Abstract(454) FullText HTML (80) PDF 16524KB(38)
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Long-term orbit prediction serves as an effective method to suppress the overall rotation of the inertial frame in autonomous navigation of satellite navigation systems, and the main factor influencing the accuracy of long-term orbit prediction is the uncertainty associated with the solar radiation pressure perturbation model. This paper proposes a method of modeling and updating the ECOM-5 solar radiation pressure model parameters for long-term orbit prediction, and evaluates its performance by fully utilizing the correlation between the solar radiation pressure coefficient and the solar altitude angle. Taking 24 Medium Earth Orbit (MEO) satellites and 2 Inclined Geosynchronous Orbit (IGSO) satellites of the Beidou-3 Global Navigation Satellite System (BDS-3) as examples, 18 groups of 90-day orbits were predicted from 1 January 2022 to 1 June 2023. Then the precise ephemeris of the Center for Orbit Determination in Europe (CODE) was used as the reference orbit to evaluate the performance of long-term orbit prediction. The experimental results indicate that when adopting the new orbit prediction method proposed in this paper for 90-day orbit prediction of navigation satellites, for MEO satellites, the average Root Mean Square (RMS) of the three-dimensional position error on the 30th, 60th, and 90th day is approximately 180 m, 650 m, and 1.4 km, respectively, and that of the average URE RMS of the orbit is 18.79, 61.43, 124.00 m, respectively; The RMS mean values of the orbital inclination angle error $\Delta i $ are 6.07, 9.76, 12.38 mas, respectively, and those of the right ascension of the ascending node error $\Delta \varOmega $ are 6.47, 11.24, 14.88 mas, respectively; for IGSO satellites, the average RMS of the three-dimensional position error on the 30th, 60th, and 90th day is approximately 300, 1000, 2200 m, respectively, while the prediction errors of i and Ω are comparable to those of MEO satellites. Therefore, it can be concluded that the method in this paper exhibits high accuracy in long-term orbital predicting positions and orbital orientation parameters i and Ω, which is expected to provide essential support for mitigating the overall rotation of autonomous navigation of navigation satellite constellations.
Regional GNSS Elevation Anomaly Fitting Method Based on IHHO-LSSVM
HE Guanghuan, LI Jiang, REN Chao, TANG Shihua, SHEN Yun, LIU Yintao, ZHANG Yan
, Available online  , doi: 10.11728/cjss2026.01.2024-0180
Abstract(314) FullText HTML (45) PDF 4183KB(3)
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In order to effectively address the challenge of obtaining high-precision elevation outliers in complex geographical areas, this paper proposes an innovative elevation anomaly fitting method based on IHHO-LSSVM. The study begins with an improved Harris Hawk Optimization (HHO) algorithm through the implementation of nonlinear convergence factors, optimized jump distances, and adaptive weights. These improvements significantly enhance the algorithm’s ability to escape local optima and improve convergence efficiency, thereby providing a more robust optimization framework for subsequent model parameter tuning. Subsequently, the improved HHO algorithm is employed to determine more accurate regularization parameters and kernel functions for the Least Squares Support Vector Machine (LSSVM) elevation anomaly fitting model. This optimization process ensures that the LSSVM model achieves higher precision and better generalization capabilities in elevation anomaly fitting tasks. To thoroughly validate the adaptability and robustness of the proposed elevation anomaly combination model in complex terrains, extensive experiments were conducted using engineering case data from two distinct geographical regions: a bridge strip area and a karst surface area. The evaluation was based on the Root Mean Square Error (RMSE) of the elevation anomaly values as the primary metric, with additional consideration given to computational efficiency and model stability. The experimental results demonstrate that in both the bridge strip area and karst surface area, the IHHO-LSSVM method outperforms the conventional HHO-LSSVM and standard LSSVM methods in terms of external conformity accuracy, stability, and adaptability. Specifically, the IHHO-LSSVM method achieves remarkable accuracy levels of 0.0101 meters in the bridge strip area and 0.0125 meters in the karst surface area, representing significant improvements over traditional methods. Furthermore, the proposed method exhibits superior stability across different terrain types, with reduced variance in prediction errors. These findings not only highlight the superior performance of the proposed method but also provide valuable insights and a reliable reference for the establishment of GNSS elevation anomaly fitting models in various complex terrains. The study contributes to the field of geodetic surveying by offering a more precise and robust solution for elevation anomaly fitting, particularly in challenging geographical conditions.
Research on the Performance of Beidou-3 Broadcast Ephemeris and Ionospheric Model from 2020 to 2025
HAO Xinyu, HE Qianqian, YAN Bo, LIU Lei
, Available online  , doi: 10.11728/cjss2026.01.2025-0101
Abstract(295) FullText HTML (64) PDF 7159KB(7)
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The BeiDou Navigation Satellite System (BDS-3) officially began providing global services on 31 July 2020. As the core component of satellite navigation systems, the space segment’s service capability determines the overall system performance. This paper first introduces calculation and analysis methods for broadcast orbit errors, broadcast clock errors, Signal-in-space range error and broadcast ionospheric errors. Then, based on the final products of German Geosciences Research Centre (GFZ)and International Global Navigation Satellite System Monitoring and Assessment System (iGMAS), it conducts an evaluation of the changes in broadcast ephemeris accuracy and ionospheric model precision throughout a complete cycle from 2020 to 2025. Research shows that the BDS-3 broadcast orbit error shows a clear dependence on satellite type, with MEO satellites outperforming IGSO satellites. Compared with GFZ products, the 95% RMS of the radial, along-track and cross-track error falls from 0.104, 0.482, 0.589 m respectively in 2020 to 0.080, 0.351, 0.364 m respectively in 2025; and compared with iGMAS products, these data fall from 0.086, 0.386, 0.461 m respectively in 2020 to 0.073 m、0.341 m、0.350 m in 2025. Regarding broadcast clock error, based on GFZ products, the 95% RMS improves from 0.705 m in 2020 to 0.540 m in 2025; and based on iGMAS products, the 95% RMS in 2020 is 0.811 m and 0.640 m in 2025.The SISRE of MEO satellites is generally smaller than that of IGSO satellites, and the statistical accuracies of 95% RMS of SISRE in 2020 based on GFZ and iGMAS products reaches 0.705 m and 0.817 m, and in 2025 reaches 0.549 m and 0.645 m, respectively. In terms of ionospheric model errors, throughout the evaluation period, the Klobuchar model exhibited a relatively broad distribution range of VTEC values. The BDGIM model demonstrated a more concentrated frequency distribution in the low VTEC intervals, while the Klobuchar model showed a relatively dispersed distribution in the high VTEC intervals. Compared with CODE and IGMAS ionospheric products, during the solar minimum period (2020), the BDGIM model achieved average VTEC RMS values of 3.193, 6.240, 1.570 TECU and 3.176, 6.790, 1.480 TECU, respectively, while the Klobuchar model yielded 7.359, 35.440, 4.350 TECU and 7.367, 35.930, 4.140 TECU, respectively. During the solar maximum period (2025), the average VTEC RMS values increased to 11.481 TECU and 10.493 TECU, 22.211 TECU and 21.802 TECU, respectively. Based on CODE products as reference, the maximum and minimum VTEC RMS values for the Klobuchar model and BDGIM model were 34.500, 10.400 TECU and 35.330, 6.640 TECU, respectively. The corresponding data referenced against IGMAS products reached 33.810, 10.000 TECU and 35.950, 5.890 TECU, respectively. And the assessment results can provide support for BDS performance optimization.
Standand Dataset of Solar Lyman-Alpha Flare Events in 2024
LU Lei, FENG Li, LI Hui
, Available online  , doi: 10.11728/cjss2026.01.2025-0079
Abstract(970) FullText HTML (388) PDF 1927KB(4)
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Solar flares are the most intense eruptive phenomena in the solar atmosphere, releasing large amounts of energy and producing electromagnetic radiation across various wavelengths. Research on solar flares is crucial for understanding solar activity, space weather forecasting, and protecting the Earth’s space environment. Based on the full-disk solar images in the Lyman-alpha waveband (121.6±7.5 nm) collected by the Solar Disk Imager (SDI) carried by the China’s ASO-S satellite, this dataset systematically records solar flare events observed in the Lyman-alpha band throughout 2024 using an independently developed automatic solar flare identification and key parameter extraction algorithm. This algorithm effectively avoids interference from cosmic rays and particle storms, identifies flares of different intensity levels, and can separately identify and track multiple flares occurring simultaneously on the solar disk. The dataset includes key parameters such as flare start and end times, duration, location, and significance, and contains data products including flare identification process documentation, flare event lists, quick-view images of flares at peak moments, and movies of flare regions. This dataset provides important scientific data support for solar physics research, space weather forecasting, and related fields.
Observation and Analysis of Plasma Bubbles in Hainan During the Magnetic Storm in March 2015
LIN Yusha, LI Chen, SHI Mengxi, JI Xinlin
, Available online  , doi: 10.11728/cjss2026.01.2025-0004
Abstract(298) FullText HTML (58) PDF 6379KB(13)
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This study utilizes the optical observation data from the 630 nm all-sky airglow imager, the data from the ionospheric digital ionosonde, and the data of the echo intensity of the Very High Frequency (VHF) coherent scatter radar at the Fuke Station in Hainan of the Meridian Project (19.5°N, 109.1°E). In combination with the geomagnetic horizontal component data from the Dalat Geomagnetic Station (11.9°N, 108.5°E; GL:2.5°) and the PHU Thuy Geomagnetic Station (21.0°N, 105.9°E; GL:11.5°), as well as the observations of the interplanetary magnetic field and solar wind speed from the ACE satellite, the study is carried out on the variations of the ionospheric plasma bubbles/irregularity structures over Hainan during the super geomagnetic storm in March 2015. The results show that the appearance of pre-midnight plasma bubbles and the uplift of the virtual height at the bottom of the ionosphere after sunset were observed both before and after the geomagnetic storm. However, the plasma bubbles observed after the end of the geomagnetic storm were of a fossil structure, which may be due to the fact that the ionospheric electric field during the occurrence period of the plasma bubbles on that day showed a westward polarity, which was not conducive to the development of the plasma bubbles. The uplift of the virtual height at the bottom of the ionosphere during the geomagnetic storm was significantly suppressed, and no plasma bubbles were observed at the Fuke station. The analysis of the variations of the interplanetary electric/magnetic field and the geomagnetic horizontal component shows that the Pre-Reversal Enhancement (PRE) electric field before the ionospheric reversal during the geomagnetic storm may have been successively suppressed by the over-shielding penetrating electric field with a westward polarity and the Disturbance Dynamo Electric Field (DDEF), resulting in a decrease in the Rayleigh-Taylor instability, which is not conducive to the development of the plasma bubble/ionospheric irregularity structures.
Standard Dataset of Ionospheric Equatorial Plasma Bubbles over Southern China Based on Airglow Observations
ZHONG Jia, ZOU Ziming, XU Jiyao, WU Kun, SUN Longchang, YUAN Wei, HU Xiaoyan
, Available online  , doi: 10.11728/cjss2026.01.2025-0097
Abstract(537) FullText HTML (154) PDF 7647KB(11)
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Airglow imaging observations, with their high spatiotemporal resolution and large-scale continuous monitoring capability, provide a crucial approach to studying the fine horizontal structures and evolutionary characteristics of ionospheric equatorial plasma bubbles. However, the current lack of high-quality, professionally annotated plasma bubble datasets severely restricts the application of supervised Artificial Intelligence (AI) algorithms in this field. To address this issue, this study constructs the first standardized dataset of ionospheric plasma bubbles based on airglow observations, including plasma bubble event data products and precise contour annotation data products. The dataset is derived from continuous observations over a full solar activity cycle (2012–2022) by a 630 nm band airglow imager at the Qujing Station in Yunnan, China. All raw data underwent standardized preprocessing, including image enhancement, azimuth correction, geometric distortion correction, and geographic coordinate projection. Expert teams then performed plasma bubble event identification and contour annotation. With a high temporal resolution of 3 minutes, the dataset systematically documents plasma bubble events under varying solar activity intensities, covering multiple typical morphologies such as “shaped”I- and “Y-shaped” structures. This dataset provides high-quality benchmark data for developing high-precision supervised AI algorithms, facilitating automated detection and morphological evolution research of ionospheric plasma bubbles based on airglow imaging.
Doppler Spectrum Analysis of Ground Echoes from Spaceborne Doppler Scatterometer
CHEN Shaohan, DONG Xiaolong, ZHU Di, ZHANG Jingyu
, Available online  , doi: 10.11728/cjss2025.06.2024-0182
Abstract(839) FullText HTML (285) PDF 5429KB(10)
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Sea surface current fields are important oceanic and climatic variables. Due to its capability for global coverage and direct observation of sub-mesoscale sea surface current fields, the Doppler scatterometer has become a frontier in ocean remote sensing technology research. The calibration and quantitative measurement of the Doppler scatterometer are the foundations and prerequisites for current field observations, as well as a critical core issue that needs to be addressed. This paper develops a ground-scatter-echo simulation model and uses it to simulate and analyze the Doppler spectra of natural extended targets that could potentially serve for Doppler scatterometer calibration. First, the variation characteristics of the Doppler spectrum were compared with different platform velocities, incidence angles, and azimuth angles. The results indicate that platform motion speed is the primary factor affecting Doppler spectrum characteristics, while variations in incident and azimuth angles also have significant impacts. Then, the Doppler spectral characteristics of ground extended targets were analyzed with different terrain-undulation conditions, namely varying height variation and central height. Simulation results indicate that targets with larger height variation exhibit greater Doppler spectral frequency shifts, whereas changes in central height have little effect on the Doppler spectral characteristics. Therefore, in the selection of calibration targets, relatively flat extended targets should be chosen, while the absolute elevation of the target is not a critical factor. Finally, an analysis of the ground echo Doppler frequency shift was conducted and validated using the DEM model. The findings of this study will provide support for further research on Doppler scatterometer calibration.
Research on the Electromagnetic Locking Device Design for Aerial Towed System Probe Docking
ZHAO Junjie, JIANG Yong, WU Fuzhang
, Available online  , doi: 10.11728/cjss2025.06.2024-0196
Abstract(263) FullText HTML (54) PDF 1018KB(12)
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The aerial towing system consists of a towing aircraft platform, a cable, and a towed body. It can perform tasks such as material transportation and load recovery, significantly expanding the scope of aerial operation space. During the connection process between the towed body and the towing aircraft platform, the towed body faces difficulties in connection due to the interference from the wake flow field of the towing aircraft platform and the influence of airflow on the flexible cable. Therefore, a detailed study on the docking method is required. The research object is the aerial towed system probe docking. An electromagnetic locking device is designed. The electromagnetic locking principle of rapid locking and emergency release is given. By establishing the finite element model considering the docking process, the response data of the electromagnetic docking mechanism is obtained considering the electromagnetic force as a variable. When the capacitor is used for power supply, the maximum electromagnetic force can reach more than 1000 N under the condition of 2 mm×15 mm wire gauge when the capacitor is above 0.5 F. This docking electromagnetic locking device in this paper provides a new idea for the air docking design.
Design of Finite Frequency Domain Disturbance Rejection Controller for the Drag-free Spacecraft in Space-borne Gravitational Wave Detection
XU Qianjiao, CUI Bing, WANG Pengcheng, XIA Yuanqing, ZHANG Yonghe
, Available online  , doi: 10.11728/cjss2024.05.2024-0022
Abstract(916) FullText HTML (294) PDF 5881KB(69)
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In space-borne gravitational wave detection, there are technical challenges in designing the controller for the drag-free spacecraft with dual test masses. These difficulties arise from constraints within the limited measurement frequency domain and the necessity for a high-precision control index. In this paper, a design method of disturbance rejection controller in the finite frequency domain based on the generalized Kalman-Yakubovich-Popov (GKYP) lemma is proposed. Firstly, to address the performance constraints within the designated frequency band of the detection mission, a finite frequency domain control performance index in the form of a frequency response function is constructed. This index is meticulously developed by amalgamating the sensitivity and complementary sensitivity control indexes. Then, a control structure with fixed-order characteristics for output feedback is proposed, and a method for selecting controller parameters based on the GKYP lemma is established. By this, a finite frequency domain disturbance-resistant controller design method is constructed. In contrast to current drag-free controller design methods, the proposed approach significantly diminishes the conservatism in the control index. This realizes the precise design of the controller in the specified frequency band, ultimately resulting in a reduction in the order of the controller. Finally, numerical simulations demonstrate that the proposed method successfully meets the control performance index for each loop of the drag-free system even in the presence of complex disturbances and noises.

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ISSN 2097-7689       CN 11-1783/V

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