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25 June 2022, Volume 42 Issue 3 Previous Issue    Next Issue

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Development status and prospect of satellite-based surveying YANG Yuanxi, WANG Jianrong, LOU Liangsheng, SUN Zhongmiao, XIAO Yun, MIAO Yuzhe 2022, 42 (3):  1-9.  doi: 10.16708/j.cnki.1000-758X.2022.0031 Abstract ( 961 )   PDF (918KB) ( 1004 )   Save Satellite-based surveying is the main platform of global fundamental surveying, including satellite topographic survey, satellite gravimetry, satellite magnetic measuring, satellite altimetry, etc. The developments of satellite-based measuring projects have experienced “return type measuring satellite project”, “transmission type measuring satellite project” and some of “loads integration measuring satellite project”. This paper firstly reviews the development history and current situation of international satellite-based surveying projects, then analyzes the roles of China′s satellite-based surveying projects in various stages, including some existing problems. Finally, the ideas for the future development of satellite-based surveying are put forward. Related Articles | Metrics

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Space robotic manipulation: a multi-task learning perspective LI Linfeng, XIE Yongchun 2022, 42 (3):  10-24.  doi: 10.16708/j.cnki.1000-758X.2022.0032 Abstract ( 880 )   PDF (3443KB) ( 652 )   Save It is a technological development trend in recent years to apply space robot in place of spaceman to perform on-orbit service tasks. Using deep neural network controller, the learning-based space robotic manipulation has shown good potential in adaptability to the unstructured space environments and applicability in fileds such as high earth orbit, extraterrestrial planet exploration, etc. At present, a large number of studies focus on single task robotic manipulation learning problems, for either onground robots or in-space robots. From a new perspective of multi-task learning, a thorough literature review on multi-task robot learning was made, including algorithms and robotic applications therein. To further apply the state-of-the-art multi-task robot learning algorthms, main technical challenges were analyzed and suggestions on key technology development were given. The breakthrough of the above challenges will increase the overall autonomy and robustness level of the space robot system, which is expected to further facilitate the development of China′s on-orbit service towards completely unmanned autonomy. Related Articles | Metrics

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Research of thrust measurement for space electric propulsion ZHANG Lupeng, YANG Xin, CHANG Lei, XU Qian, ZHOU Haishan, LUO Guangnan 2022, 42 (3):  25-38.  doi: 10.16708/j.cnki.1000-758X.2022.0033 Abstract ( 591 )   PDF (8286KB) ( 999 )   Save  Accurate measurement of thrust is very important in the development and planning of space electric propulsion.In recent years,with the increasing of complexity and task difficulty for electric propulsion,higher requirements are put forward for the evaluation techniques and methods of thrust performance.In response to this demand,a review of the thrust measurement for space electric propulsion was presented.Measurement methods and the underlying mechanisms,technical features and applications were covered.The methods of thrust measurement can be divided into direct measurement and indirect measurement.The former mainly includes balance structure,torsional pendulum,suspension and inverted pendulum,while the latter mainly includes target and cantilever beam.The advantages and disadvantages of these measurement methods were summarized and compared,which provided a reference for developers to design the thrust measuring system.The key problems in the five segments including system design,system calibration,system response,system response measurement and calculation of thrust during the process of thrust measurement were described in detail,and the corresponding improvement methods were proposed.To serve as a reference for future thrust measurement research,suggestions were also provided by considering the development trend of electric propulsion and its demand of thrust measurement. Related Articles | Metrics

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Multi-satellite responsive inspection mission planning with multiple constraints PENG Chenyuan, ZHANG Jin, YAN Bing, ZHOU Hongxi, LUO Yazhong 2022, 42 (3):  39-48.  doi: 10.16708/j.cnki.1000-758X.2022.0034 Abstract ( 356 )   PDF (4964KB) ( 393 )   Save Multi-satellite responsive inspection mission refers to the fact that multiple target satellites appear unknown, and the inspection service platform carries out orbit transfer within a short period of time, and carries a number of sub spacecraft to perform overflight inspection on the targets. For mission planning of this kind of problem, the platform phasing strategy based on coplanar maneuver was firstly presented and a screening calculation model of inspection window satisfying the constraints of illumination and maneuvering ability was established. Secondly, a greedy search and multiround planning method was proposed to determine the task assignment scheme and inspection order. Finally, this method’s effectiveness was tested under high precision orbit model and it was compared with hybrid en-coding genetic algorithm. In the example, the optimization effect of this method is slightly better than that of hybrid en-coding genetic algorithm and the efficiency is about 227 times of the latter, which indicates that greedy search algorithm and multiround planning method are more suitable for solving this problem efficiently. Related Articles | Metrics

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Numerical methods for collaborative workspace of multi-space-robot system GONG Kejie, WANG Yong, DUAN Yurui, MEI Yafei, LIAO Ying 2022, 42 (3):  49-57.  doi: 10.16708/j.cnki.1000-758X.2022.0035 Abstract ( 262 )   PDF (4340KB) ( 336 )   Save Aiming at the application scenarios where it may be difficult for a single space robot to perform independently during on-orbit serving process in the future, a multi-space-robot serving system was designed. However, collaborative workspace of multi-space-robot system has rarely been studied. Considering that workspace is very difficult to calculate with analytical method, a numerical calculation method was proposed for ordinary collaborative workspace based on Monte Carlo method. Furthermore, aiming at the particularity of space robot collaboration, the concept of generalized collaborative workspace was proposed, and a numerical solution method was presented. The simulation results show that the attitude constraint of the base causes reduction of collaborative workspace. Moreover, the scope of the generalized collaborative workspace is obviously larger than the general one. The conclusions can provide quantitative basis for space robot task design and planning. Related Articles | Metrics

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Research on composite scanning strategy for high-probability acquisition of deep space cooperative targets HU Hang, LIU Lei, LI Cong, CAO Gui Xing 2022, 42 (3):  58-66.  doi: 10.16708/j.cnki.1000-758X.2022.0036 Abstract ( 288 )   PDF (4030KB) ( 198 )   Save Aiming at the problems of large time delay, significant jitter of optical axis and large uncertain field of target position in long-distance inter-satellite laser communication link building with deep space cooperative target, an anti-jitter and high-probability acquisition composite scanning strategy based on two-stage actuator was proposed. The uncertain field of target position was divided into equalsized square subfields. Raster scanning was adopted in subfields, which was realized by the fast steering mirror. The subfields were covered in raster spiral scanning sequence, the transition between which was realized by the servo turntable. Considering the jitter of optical axis, the size of subfields as well as the overlapped parts of scanning spots was optimized through genetic algorithm. The scanning scheme with optimized parameters was obtained and validated by simulation. The simulation results of 1000 times Monte Carlo shooting show that under the consideration of a 3.6mrad uncertain field with the laser beam divergence of 0.1mrad and the standard deviation of optical axis jitter of 5μrad, the acquisition probability is 99.2%, the scanning time of uncertain field is 41.34s, and the average scanning time of the target is 9.62s,based on the optimized scanning scheme. Related Articles | Metrics

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Satellite integrated navigation method based on starlight angular distance/laser ranging LI Daiwei, DAN Peng, HE Boyong, CHEN Yuchang, ZHANG Yinfa, SHI Feng 2022, 42 (3):  67-73.  doi: 10.16708/j.cnki.1000-758X.2022.0037 Abstract ( 307 )   PDF (3629KB) ( 341 )   Save In order to improve the accuracy of satellite autonomous celestial navigation, an integrated navigation method combining celestial navigation with laser ranging was proposed.Laser ranging can directly obtain the highprecision distance information from satellite to ground reference beacon.The usage of laser ranging auxiliary data in astronomical navigation system with star angular distance as observation measurement can expand the dimension of filter observation and improve the filtering effect.Since the integrated navigation system is a nonlinear system, in order to avoid the second-order truncation error caused by the linearization of Taylor expansion, the UKF filtering method was used for the information fusion of integrated navigation system.Simulation results show that the proposed integrated navigation method can significantly improve the navigation accuracy and filter performance. Related Articles | Metrics

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Booster pose estimation based on 3D point cloud reconstruction XIAO Aiqun, JIANG Hongxiang 2022, 42 (3):  74-81.  doi: 10.16708/j.cnki.1000-758X.2022.0038 Abstract ( 238 )   PDF (4437KB) ( 134 )   Save  Booster separation is one of the important actions in the launching process of the carrier rocket. The commonly used LiDAR pose measurement technology is severely affected by external factors during the separation stage for the booster,so it is difficult to accurately obtain the pose of booster. To improve the anti-interference ability of pose estimation,the vision-based pose measurement technology was utilized for booster. A 3D point cloud reconstruction network whose input was the image and output was corresponding 3D point cloud was built and trained on the imagepoint cloud dataset,which was constructed during the separation of booster. During testing,the pose estimation was completed via principal component analysis on the reconstructed booster point cloud. All the experimental results illustrate that pose changes can be measured precisely by the built network according to the simulation image data during the separation stage for booster. Under the R2score metric,the prediction scores for the three-dimensional coordinates are all above 0.98.For the attitude angle,the average error is about 21°,and the prediction scores are all above 0.80. Related Articles | Metrics

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Deployable paraboloid space antenna with adjustable one-layer cable-net reflector LI Hao, DENG Zehua, LI Qi 2022, 42 (3):  82-92.  doi: 10.16708/j.cnki.1000-758X.2022.0039 Abstract ( 283 )   PDF (14009KB) ( 261 )   Save There remains ongoing demands of high precision deployable antennas with large aperture in many space applications. A novel concept of one-layer cable-net antenna was proposed. The one-layer cable-net antenna is much simpler in topology, and the surface precision of which can be easily adjusted by adjusting the length of its central column. The method for predicting the internal cable forces was presented, and the form-finding method was proposed based on the energy method. Based on the theoretical analysis, the finite element model of a one-layer-cable-net antenna with 50m aperture was established. Through FEA, both the principle of the proposed concept and the feasibility of in-orbit adjustment of the surface precision were approved. Theoretical analysis and FEA both indicate that, with a uniform temperature variation of 100℃,the RMS surface error of a 50m one-layer cable-net antenna can be reduced to 5mm.  Related Articles | Metrics

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Quality validation of HJ-1B satellite land surface temperature products based on DTW ZHANG Qi, LI Dacheng, LI Hua, DUAN Sibo, ZHANG Xiaoyu, HAN Qijin, GAO Haixia 2022, 42 (3):  93-104.  doi: 10.16708/j.cnki.1000-758X.2022.0040 Abstract ( 232 )   PDF (7784KB) ( 85 )   Save The HJ-1B satellite thermal infrared data is widely used,but the quality validation of its surface temperature retrieval products is not yet perfect.In response to this problem,part of multiple underlying surfaces in the Heihe River Basin was taken as the research area,HJ-1B data was used as the research data,and universal single-channel algorithm was used to invert the surface temperature of the different underlying surface research areas.The inversion results were verified using the ground observation site data of the Heihe River Basin and MODIS surface temperature data.Dynamic time warping was introduced to evaluate timing similarity.The results show that the relative deviation between the HJ-1B surface temperature inversion product and the ground observation value for desert and desert sites is within 1K,and the root mean square error(RMSE) is about 0.5K.The deviation for vegetation and crop sites is within 2K,and the RMSE is 1.2K.The evaluation result of the time-series mismatched data using DTW is consistent with the performance of existing indicators.The relative deviations between the HJ-1B surface temperature inversion products and the surface stations are lower than those between the HJ-1B surface temperature inversion products and the MODIS surface temperature inversion products. Related Articles | Metrics

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Improved U-Net network and its application of road extraction in remote sensing image KONG Jiayuan , ZHANG Hesheng 2022, 42 (3):  105-113.  doi: 10.16708/j.cnki.1000-758X.2022.0041 Abstract ( 358 )   PDF (10925KB) ( 334 )   Save High resolution remote sensing image segmentation has a good application prospect in the military and civil fields, but due to the complex background conditions and the obstruction of interferences, the existing algorithms can’t extract road details from remote sensing images. Based on the improved U-Net network model, MDAU-Net (multi dimension attention U-Net) network structure model was proposed. The U-Net network structure was deepened to a seven-layer structure to improve the ability of fine segmentation of roads. A new multidimensional attention module,which was called MD-MECA (multi dimension modified efficient channel attention), was proposed to optimize the feature transfer in the coding part. DropBlock and Batch Normalization were used to resolve the overfitting during network training. The experimental results show that the improved algorithm can effectively improve the road extraction effect, and the accuracy rate on the test set reaches 97.04%. Related Articles | Metrics

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Ionospheric sounding and compensation based on the spaceborne SA WANG Cheng, ZHAO Haisheng, LIU Bo, CHEN Liang, XIAO Peng, LIU Lu, LIU Min, SUI Xianghong, GUO Wulong 2022, 42 (3):  114-123.  doi: 10.16708/j.cnki.1000-758X.2022.0042 Abstract ( 268 )   PDF (5510KB) ( 360 )   Save The spaceborne synthetic aperture radar (SAR) at low frequencies can be affected by the ionosphere, the relevant compensation therefore needs to be considered in low-frequency SAR system design. Aiming at this issue, a model of Legendre orthogonal polynomials to evaluate the ionospheric effects was first proposed in this paper, which was suitable for the SAR systems with low frequency and wide band. This new model can avoid coupling of traditional model. Then, based on the signal echo, the compensation techniques for ionospheric dispersion and Faraday rotation were analyzed, which avoided traditional ionosphere data with low accuracy, different paths and ground receiving stations. Based on the autofocus algorithm, the compensation precision of dispersion can reach 04TECU, which can significantly improve the SAR image quality. Compared with the results of official website, a further 27% reduction of Faraday rotation error is achieved according to the information of scattering matrix. At last, the joint observation with PALSAR and ionosonde was applied. The accuracy of the result was improved by 30% compared with the result based on only the ionosonde. This study can provide technical support for the future system design of spaceborne SAR at low frequencies. Related Articles | Metrics

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A multi-stage filter for autonomous navigation of formation satellites based on inter-satellite measurements ZHOU Bochao, LI Yong 2022, 42 (3):  124-131.  doi: 10.16708/j.cnki.1000-758X.2022.0043 Abstract ( 211 )   PDF (2918KB) ( 150 )   Save  Autonomous orbit determination,whose goal is to determine the position and velocity based solely on the sensors onboard the spacecraft,is a basic requirement of autonomous operation in formation satellite systems.Relative position measurement is a practical method in autonomous navigation systems while achieving relative position between multiple satellites needs a great number of sensors.For the purpose of satellite payload optimization,a switching measurement scheme was proposed to reduce the number of sensors needed.A general method of autonomous navigation using relative position is the extended Kalman filter (EKF) algorithm.In order to reduce the computational cost of orbit estimators,the filter was subdivided into several parallel sub-KFs,so called multi-stage Kalman filter (MSKF).In addition,in the switching sensor scheme,part of the sub-KFs could be simplified into state prediction only so that the computation load could be further reduced.The number of floating point operations,i.e. FLOPS,was calculated to compare the computational load of MSKF with that of general EKF algorithm.Simulation result shows that the decoupled algorithm has an equivalent performance in navigation accuracy with a much less computational complexity. Related Articles | Metrics

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Multi-temporal and multi-channel cloud detection algorithm based on GF-4 data WANG Jihui, LI Feng, LU Ming, MA Jun, GUO Yi 2022, 42 (3):  132-140.  doi: 10.16708/j.cnki.1000-758X.2022.0044 Abstract ( 256 )   PDF (5546KB) ( 223 )   Save Aiming at the problem that the traditional cloud detection algorithm is difficult to distinguish between clouds and ice pixels due to the lack of bands of the Gaofen-4 (GF-4) satellite imagery, a multi-temporal and multi-channel cloud detection algorithm was proposed. The algorithm first carried out the radiation calibration and registration of the GF-4 satellite image, used the spectral difference between the cloud and the typical ground surface to obtain potential cloud pixels, and then used the difference between the sequence GF-4 satellite image to identify cloud pixels. Finally, the mid-infrared band was used to retrieve the brightness temperature of the surface to remove the ice and snow pixels. The algorithm was verified in three research areas of Hainan, Liaoning and Anhui, and the detection results were compared with the detection results of traditional single-phase cloud detection algorithm, SVM cloud detection algorithm, and RTD cloud detection algorithm. The results show that the algorithm is better than the others. The proposed algorithm has an accurate recognition rate of more than 90%, and the false detection rate is less than 5%, which is conducive to further use of GF-4 satellite imagery. Related Articles | Metrics

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Moving vehicle detection of video satellite based on ViBE and object-oriented classification LU Ming, LI Feng, ZHANG Nan, YANG Xue, LU Xiaotian, XIN Lei, LIU Yang 2022, 42 (3):  141-149.  doi: 10.16708/j.cnki.1000-758X.2022.0045 Abstract ( 245 )   PDF (8443KB) ( 71 )   Save To improve the detection quality of moving vehicles from video satellites,study was carried out from two dimensions: increasing the number of correct detection of moving objects and suppressing the number of false detection of moving objects.A new moving vehicle detection method was proposed based on the visual background extractor (ViBE) algorithm and the object-oriented classification technology in remote sensing field.By optimizing the parameters of the ViBE,real moving objects can be obtained as much as possible,but this introduced a lot of false objects to some extent.Therefore,according to the interdependent relationship between moving vehicles and road,objectoriented classification method was adopted to extract road and further filter the false objects produced by ViBE.A total of eight features including the mean value and standard deviation of spectral attribute,average gray value and entropy in the convolution kernel of texture attribute,area,length,tightness and extension of spatial geometric attributes were used.The results show that, compared with the three frames difference method and ViBE detection method,the moving vehicles detection accuracy of the proposed method has been significantly improved.The detection precision P of three frames difference method,ViBE and VOMVD for moving objects are 70.91%,61.49% and 85.71% respectively,the recall R is 84.78%,98.91% and 97.83% respectively,and the F score is 77.23%,75.83% and 91.37% respectively.The effect of the proposed method on moving vehicles detection has been improved effectively. Related Articles | Metrics