空间科学学报

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Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes/issues, but are citable by Digital Object Identifier (DOI).

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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(795) FullText HTML (256) PDF 5429KB(9)

Abstract:
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(226) FullText HTML (44) PDF 1018KB(10)

Abstract:
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(867) FullText HTML (274) PDF 5881KB(67)

Abstract:
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.