To solve the special requirements of the high orbit optical remote sensing satellite for the thermal deformation of the platform the thermal deformation test and measurement scheme of the satellite platform is designe...To solve the special requirements of the high orbit optical remote sensing satellite for the thermal deformation of the platform the thermal deformation test and measurement scheme of the satellite platform is designed. Through the comparative analysis of test results the rationality of the thermal deformation design of the platform structure is verified. The results of thermal deformation measurement show that the maximum deformation of A camera mounting surface is 57.5〃 and the maximum deformation of B camera mounting surface points to 79.3〃 which can be used as the basis for thermal deformation prediction of satellite during the orbit operation.展开更多
The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progres...The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conic-approximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.展开更多
Based on the concept of DIY, this paper demonstrates the essential potential of DIY manufacturing technology in the application of space equipment. According to the future space technology development trends, the futu...Based on the concept of DIY, this paper demonstrates the essential potential of DIY manufacturing technology in the application of space equipment. According to the future space technology development trends, the future spacecraft DIY idea and system standard are proposed. The standardized, modularized and serialized micro/nano-satellite DIY products are introduced. Finally, a commercial remote sensing satellite system based on spacecraft DIY is designed and its application prospect is analyzed.展开更多
Previous studies have shown that there is an obvious coupling relationship between the installation location of the external cathode and the magnetic separatrix in the plume region of a Hall thruster.In this paper,the...Previous studies have shown that there is an obvious coupling relationship between the installation location of the external cathode and the magnetic separatrix in the plume region of a Hall thruster.In this paper,the particle-in-cell simulation method is used to compare the thruster discharge process under the conditions of different position relationships between the cathode and the magnetic separatrix.By comparing the distribution of electron conduction,potential,plasma density and other microscopic parameters,we try to explain the formation mechanism of the discharge difference.The simulation results show that the cathode inside and outside the magnetic separatrix has a significant effect on the distribution of potential and plasma density.When the cathode is located on the outer side of the magnetic separatrix,the potential above the plume region is relatively low,and there is a strong potential gradient above the plume region.This potential gradient is more conducive to the radial diffusion of ions above the plume,which is the main reason for the strong divergence of the plume.The distribution of ion density is also consistent with the distribution of potential.When the cathode is located on the outer side of the magnetic separatrix,the radial diffusion of ions in the plume region is enhanced.Meanwhile,by comparing the results of electron conduction,it is found that the traiectories of electrons emitted from the cathode are significantly different between the inner and outer sides of the magnetic separatrix.This is mainly because the electrons are affected by the magnetic mirror effect of the magnetic tip,which makes it difficult for the electrons to move across the magnetic separatrix.This is the main reason for the difference in potential distribution.In this paper,the simulation results of macroscopic parameters under several conditions are also compared,and they are consistent with the experimental results.The cathode is located on the inner side of the magnetic separatrix,which can effectively reduce the plume divergence angle and improve the thrust.In this paper,the cathode moves from R=50 mm to R=35 mm along the radial direction,the thrust increases by 3.6 mN and the plume divergence angle decreases by 23.77%.Combined with the comparison of the ionization region and the peak ion density,it is found that the main reason for the change in thrust is the change in the radial diffusion of ions in the plume region.展开更多
The energetic particle detector on China's space station can determine the energy, flux, and direction of medium-and highenergy protons, electrons, heavy ions, and neutrons within the path of the station's orb...The energetic particle detector on China's space station can determine the energy, flux, and direction of medium-and highenergy protons, electrons, heavy ions, and neutrons within the path of the station's orbit. It also assesses the linear energy transfer(LET)spectra and radiation dose rates generated by these particles. Neutron detection is a significant component of this work, utilizing a new type of Cs_(2)LiYCl_(6): Ce scintillator material along with plastic scintillators as sensors. In-orbit testing has demonstrated the efficient identification of space neutrons and gamma rays(n/γ). This data plays a crucial role in supporting manned space engineering, scientific research, and other related fields.展开更多
Satellite observation schedule is investigated in this paper.A mission planning algorithm of task clustering is proposed to improve the observation efficiency of agile satellite.The newly developed method can make the...Satellite observation schedule is investigated in this paper.A mission planning algorithm of task clustering is proposed to improve the observation efficiency of agile satellite.The newly developed method can make the satellite observe more targets and therefore save observation resources.First,for the densely distributed target points,a preprocessing scheme based on task clustering is proposed.The target points are clustered according to the distance condition.Second,the local observation path is generated by Tabu algorithm in the inner layer of cluster regions.Third,considering the scatter and cluster sets,the global observation path is obtained by adopting Tabu algorithm in the outer layer.Simulation results show that the algorithm can effectively reduce the task planning time of large-scale point targets while ensuring the optimal solution quality.展开更多
A quasi-three dimensional model is proposed for the vibration analysis of functionally graded(FG)micro-beams with general boundary conditions based on the modified strain gradient theory.To consider the effects of tra...A quasi-three dimensional model is proposed for the vibration analysis of functionally graded(FG)micro-beams with general boundary conditions based on the modified strain gradient theory.To consider the effects of transverse shear and nor-mal deformations,a general displacement field is achieved by relaxing the assumption of the constant transverse displacement through the thickness.The conventional beam theories including the classical beam theory,the first-order beam theory,and the higher-order beam theory are regarded as the special cases of this model.The material proper-ties changing gradually along the thickness direction are calculated by the Mori-Tanaka scheme.The energy-based formulation is derived by a variational method integrated with the penalty function method,where the Chebyshev orthogonal polynomials are used as the basis function of the displacement variables.The formulation is validated by some comparative examples,and then the parametric studies are conducted to investigate the effects of transverse shear and normal deformations on vibration behaviors.展开更多
The Solar Polar ORbit Telescope(SPORT) project for space weather mission has been under intensive scientific and engineering background studies since it was incorporated into the Chinese Space Science Strategic Pionee...The Solar Polar ORbit Telescope(SPORT) project for space weather mission has been under intensive scientific and engineering background studies since it was incorporated into the Chinese Space Science Strategic Pioneer Project in 2011.SPORT is designed to carry a suite of remote-sensing and in-situ instruments to observe Coronal Mass Ejections(CMEs),energetic particles,solar high-latitude magnetism,and the fast solar wind from a polar orbit around the Sun.The first extended view of the polar regions of the Sun and the ecliptic enabled by SPORT will provide a unique opportunity to study CME propagation through the inner heliosphere,and the solar high-latitude magnetism giving rise to eruptions and the fast solar wind.Coordinated observations between SPORT and other spaceborne/ground-based facilities within the International Living With a Star(ILWS) framework can significantly enhance scientific output.SPORT is now competing for official selection and implementation during China's 13 th Five-Year Plan period of 2016-2020.展开更多
A method to tighten the cloud screening thresholds based on local conditions is used to provide more stringent schemes for Orbiting Carbon Observatory-2(OCO-2)cloud screening algorithms.Cloud screening strategies are ...A method to tighten the cloud screening thresholds based on local conditions is used to provide more stringent schemes for Orbiting Carbon Observatory-2(OCO-2)cloud screening algorithms.Cloud screening strategies are essential to remove scenes with significant cloud and/or aerosol contamination from OCO-2 observations,which helps to save on the data processing cost and ensure high quality retrievals of the column-averaged CO2 dry air mole fraction(XCO2).Based on the radiance measurements in the 0.76μm O2A band,1.61μm(weak),and 2.06μm(strong)CO2 bands,the current combination of the A-Band Preprocessor(ABP)algorithm and Iterative Maximum A Posteriori(IMAP)Differential Optical Absorption Spectroscopy(DOAS)Preprocessor(IDP)algorithm passes around 20%-25%of all soundings,which means that some contaminated scenes also pass the screening process.In this work,three independent pairs of threshold parameters used in the ABP and IDP algorithms are sufficiently tuned until the overall pass rate is close to the monthly clear-sky fraction from the MODIS cloud mask.The tightened thresholds are applied to observations over land surfaces in Europe and Japan in 2016.The results show improvement of agreement and positive predictive value compared to the collocated MODIS cloud mask,especially in summer and fall.In addition,analysis indicates that XCO2 retrievals with more stringent thresholds are in closer agreement with measurements from collocated Total Carbon Column Observing Network(TCCON)sites.展开更多
We investigated the sensitivities of atom interferometers in the usual fringe-scanning method （FSM） versus the fringe- locking method （FLM）. The theoretical analysis shows that for typical noises in atom interfero...We investigated the sensitivities of atom interferometers in the usual fringe-scanning method （FSM） versus the fringe- locking method （FLM）. The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.展开更多
The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to ...The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.展开更多
Ground and space-based observations of the geomagnetic field are usually a superposition of different sources from the Earth’s core,lithosphere,ocean,ionosphere,and magnetosphere,and also from field-aligned currents ...Ground and space-based observations of the geomagnetic field are usually a superposition of different sources from the Earth’s core,lithosphere,ocean,ionosphere,and magnetosphere,and also from field-aligned currents coupling the ionosphere and magnetosphere—the meridional currents that connect the two hemispheres and the induced currents due to the variations of fields over time.The fluctuation of magnetic fields generated by these highly dynamic space currents greatly limits the accuracy of the geomagnetic models.In order to better accomplish the scientific objectives of Macao Science Satellite-1(MSS-1),and to improve existing geomagnetic field models,we present here for the first time a self-consistent coupling of solar wind,magnetosphere,and ionosphere,which represents the most developed numerical simulation method for space physics research so far,making it possible to quantify the contribution of different current systems to the total observed magnetic field(B).The results show that numerical simulation can capture main magnetic disturbance characteristics with significant precision.Partial ring current is a major contributor to the latitudinal magnetic perturbation near the equator.Magnetopause and magnetotail currents affect the radial magnetic perturbation around the mid-latitudes.Field-aligned and Pedersen currents produce significant longitudinal and latitudinal magnetic perturbations at high latitudes.展开更多
Rotation modulation technique is generally used to improve the performance of aviation and marine inertial navigation system.Considering of the performance requirements from current aerospace to MEMS micro-nano inerti...Rotation modulation technique is generally used to improve the performance of aviation and marine inertial navigation system.Considering of the performance requirements from current aerospace to MEMS micro-nano inertial device,this paper proposedrotary inertial device modulation technology application methods on the satellite.Firstly,taking the advantage ofultrasonic motor,like high resolution,fast response,electromagnetic compatibility,a lowmagnetic,high-precision and appropriate for use on satellite ultrasonic motor modulation turntable was developed.Then,through theoretical modeling and simulations,the rotation modulation technology was verified to improvethe precise of satellite attitude measurementeffectively,equivalent toimprove the accuracy of MEMS gyro over an order of magnitude.This work helpsachieve the application of rotation modulation technology in aerospace and acceleratethe promotion of the MEMS gyro in satellite attitude measurement.展开更多
Carbon nanotube(CNT)-reinforced composites have ultra-high elastic moduli,low densities,and fibrous structures.This paper presents the multi-scale finite element modeling of CNT-reinforced polymer composites from micr...Carbon nanotube(CNT)-reinforced composites have ultra-high elastic moduli,low densities,and fibrous structures.This paper presents the multi-scale finite element modeling of CNT-reinforced polymer composites from micro-to macro-scales.The nanocomposites were modeled using representative volume elements(RVEs),and finite element code was written to simulate the modeling and loading procedure and obtain equivalent mechanical properties of the RVEs with various volume fractions of CNTs,which can be used directly in the follow-up simulation studies on the macroscopic model of CNT-reinforced nanocomposites.When using the programming to simulate the deformation and fracture process of the CNT-reinforced epoxy composites,the mechanical parameters and stress-strain curves of the composites on themacro-scale were obtained by endowing the elements of the lattice models withRVE parameters.Tensile experiments of the CNT-reinforced composites were also carried out.The validity of the finite element simulation method was verified by comparing the results of the simulations and experiments.Finite element models of functionally graded CNT-reinforced composites(FG-CNTRC)with different distributions were established,and the tensile and three-point-bending conditions for various graded material models were simulated by the methods of lattice model and birth-death element to obtain the tensile and bending parameters.In addition,the influence of the distribution and volume ratio of the CNTs on the performance of the graded composite material structures was also analyzed.展开更多
In cryogenic wind tunnel tests,piezoelectric stacks are adopted to realize the vibration control of the cantilever sting.However,the free stroke and blocking force of the piezoelectric stack would decrease dramaticall...In cryogenic wind tunnel tests,piezoelectric stacks are adopted to realize the vibration control of the cantilever sting.However,the free stroke and blocking force of the piezoelectric stack would decrease dramatically as the temperature decreases.This paper proposes a convenient and effective warming structure for the piezoelectric stack,which could keep it working at operating temperatures when the ambient temperature drops.The piezoelectric stack actuator is wrapped with the heating film,and this resulting assembly is then wrapped with the aerogel material for thermal insulation.Both ends of the piezoelectric stack actuator make direct contact with the payload structure.Both one-dimensional and two-dimensional theoretical analyses of the heating conduction problem of the piezoelectric stack actuator are conducted.These analyses results are compared with those of the finite element simulation analysis.The finite element method results show a good consistency with the two-dimensional theoretical results,and a slight deviation of only 0.91 K is observed,indicating its potential for protecting piezoelectric stacks at low temperatures.展开更多
Geosynchronous orbit is located in the ring current region,where the energetic particle emission environment challenges the ion deflection design limit of the Energetic Neutral Atom(ENA)imager.Therefore,there is no me...Geosynchronous orbit is located in the ring current region,where the energetic particle emission environment challenges the ion deflection design limit of the Energetic Neutral Atom(ENA)imager.Therefore,there is no measurement record of ENA imaging in this area before.On the basis of possessing the patent of high-energy ion deflection technology,ENA imaging under different Kp index in geosynchronous orbit is simulated.The simulation images show the characteristics of low-altitude ENA emission source and the rough sketch of magnetosphere.Due to the north-south conjugation observation of geosynchronous orbit,the simulated ENA images at different positions all have north-south symmetry.Aiming at the unsolved problems,such as the input source of ring current energetic ions during geomagnetic activities and its evolution process,we analyzed the possible results of ENA imaging combined with in-situ particle measurements in the same satellite,as well as the subversion effect of any north-south asymmetry of ENA map on the inversion model.展开更多
In this work,we have carried out a simulation study on the discharge process of Hall thrusters under the conditions of different neutral gas radial supply positions based on the particle-in-cell(PIC)and Monte Carlo co...In this work,we have carried out a simulation study on the discharge process of Hall thrusters under the conditions of different neutral gas radial supply positions based on the particle-in-cell(PIC)and Monte Carlo collision(MCC)methods.This paper compares the two-dimensional(2D)distributions of neutral gas,plasma and wall erosion-related parameters under different neutral gas supply positions.The comparison results show that the change of the neutral gas supply position affects the radial distribution uniformity of the neutral gas and plasma in the channel.From the comparison of the density peaks,it can be found that the neutral gas density and the plasma density peak under the upper gas supply condition are relatively low,and the plasma density peak is 22.49%lower than the density peak under the middle gas supply condition.Meanwhile,as the radial position of the gas supply moves from the lower gas supply to the upper gas supply,the position of the ionization zone also gradually moves toward the anode.The results of erosion-related parameter distribution comparison show that the change of gas supply location has an obvious influence on erosion rate and erosion range.In terms of erosion rate,the wall erosion rate is relatively low under the upper gas supply condition,and the peak erosion rates of the inner and outer walls are 33.3%and 29.9%lower than those under the other two conditions.In terms of erosion range,as the gas supply position moves from the lower gas supply position to the upper gas supply position,the erosion range gradually increases from5 to 7.5 mm.展开更多
A quantum cascade laser（QCL） based system for simultaneous detection of CO and CO_2 is developed.The QCL can scan over two neighboring CO（2055.40 cm^（-1）） and CO_2（2055.16 cm^（-1）） lines with a single curren...A quantum cascade laser（QCL） based system for simultaneous detection of CO and CO_2 is developed.The QCL can scan over two neighboring CO（2055.40 cm^（-1）） and CO_2（2055.16 cm^（-1）） lines with a single current scan.The wavelength modulation spectroscopy（ f = 20 k Hz） is utilized to enhance the signal-to-noise ratio.A white cell with an effective optical path length of 74 m is used.The calibration of the sensor is performed and minimum detection limits of 1.3 ppb（1 × 10^（-9））for CO and 0.44 ppm（1 × 10^（-6）） for CO_2 are achieved.展开更多
According to the oversampling imaging characteristics, an infrared small target detection method based on deep learning is proposed. A 7-layer deep convolutional neural network(CNN) is designed to automatically extrac...According to the oversampling imaging characteristics, an infrared small target detection method based on deep learning is proposed. A 7-layer deep convolutional neural network(CNN) is designed to automatically extract small target features and suppress clutters in an end-to-end manner. The input of CNN is an original oversampling image while the output is a cluttersuppressed feature map. The CNN contains only convolution and non-linear operations, and the resolution of the output feature map is the same as that of the input image. The L1-norm loss function is used, and a mass of training data is generated to train the network effectively. Results show that compared with several baseline methods, the proposed method improves the signal clutter ratio gain and background suppression factor by 3–4 orders of magnitude, and has more powerful target detection performance.展开更多
The Chinese HαSolar Explorer(CHASE)is designed to test a newly developed satellite platform and conduct solar observations.The scientific payload of the satellite is an Hαimaging spectrograph(HIS),which can,for the ...The Chinese HαSolar Explorer(CHASE)is designed to test a newly developed satellite platform and conduct solar observations.The scientific payload of the satellite is an Hαimaging spectrograph(HIS),which can,for the first time,acquire full-disk spectroscopic solar observations in the Hαwaveband.This paper briefly introduces CHASE/HIS including its scientific objectives,technical parameters,scientific application system,etc.The CHASE mission is scheduled to launch in 2021.It will complement the observations by on-orbit solar spacecraft(such as SDO,IRIS,STEREO and PSP),as well as future solar missions of the Solar Orbiter and Advanced Space-based Solar Observatory(ASO-S).展开更多
基金Sponsored by the Military Commission on Science and Technology(Grant No.17-163-18-XJ-001-054-01)
文摘To solve the special requirements of the high orbit optical remote sensing satellite for the thermal deformation of the platform the thermal deformation test and measurement scheme of the satellite platform is designed. Through the comparative analysis of test results the rationality of the thermal deformation design of the platform structure is verified. The results of thermal deformation measurement show that the maximum deformation of A camera mounting surface is 57.5〃 and the maximum deformation of B camera mounting surface points to 79.3〃 which can be used as the basis for thermal deformation prediction of satellite during the orbit operation.
基金supported by National Key R&D Program of China (2022YFF0709101)China National Space Administration (D050104)National Natural Science Foundation of China (62105244 and U2030111)。
文摘The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conic-approximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.
文摘Based on the concept of DIY, this paper demonstrates the essential potential of DIY manufacturing technology in the application of space equipment. According to the future space technology development trends, the future spacecraft DIY idea and system standard are proposed. The standardized, modularized and serialized micro/nano-satellite DIY products are introduced. Finally, a commercial remote sensing satellite system based on spacecraft DIY is designed and its application prospect is analyzed.
基金supported by the Shanghai 2022 Science and Technology Innovation Action Plan(No.22YF1446800)。
文摘Previous studies have shown that there is an obvious coupling relationship between the installation location of the external cathode and the magnetic separatrix in the plume region of a Hall thruster.In this paper,the particle-in-cell simulation method is used to compare the thruster discharge process under the conditions of different position relationships between the cathode and the magnetic separatrix.By comparing the distribution of electron conduction,potential,plasma density and other microscopic parameters,we try to explain the formation mechanism of the discharge difference.The simulation results show that the cathode inside and outside the magnetic separatrix has a significant effect on the distribution of potential and plasma density.When the cathode is located on the outer side of the magnetic separatrix,the potential above the plume region is relatively low,and there is a strong potential gradient above the plume region.This potential gradient is more conducive to the radial diffusion of ions above the plume,which is the main reason for the strong divergence of the plume.The distribution of ion density is also consistent with the distribution of potential.When the cathode is located on the outer side of the magnetic separatrix,the radial diffusion of ions in the plume region is enhanced.Meanwhile,by comparing the results of electron conduction,it is found that the traiectories of electrons emitted from the cathode are significantly different between the inner and outer sides of the magnetic separatrix.This is mainly because the electrons are affected by the magnetic mirror effect of the magnetic tip,which makes it difficult for the electrons to move across the magnetic separatrix.This is the main reason for the difference in potential distribution.In this paper,the simulation results of macroscopic parameters under several conditions are also compared,and they are consistent with the experimental results.The cathode is located on the inner side of the magnetic separatrix,which can effectively reduce the plume divergence angle and improve the thrust.In this paper,the cathode moves from R=50 mm to R=35 mm along the radial direction,the thrust increases by 3.6 mN and the plume divergence angle decreases by 23.77%.Combined with the comparison of the ionization region and the peak ion density,it is found that the main reason for the change in thrust is the change in the radial diffusion of ions in the plume region.
基金This mission was supported by the China Manned Space Office。
文摘The energetic particle detector on China's space station can determine the energy, flux, and direction of medium-and highenergy protons, electrons, heavy ions, and neutrons within the path of the station's orbit. It also assesses the linear energy transfer(LET)spectra and radiation dose rates generated by these particles. Neutron detection is a significant component of this work, utilizing a new type of Cs_(2)LiYCl_(6): Ce scintillator material along with plastic scintillators as sensors. In-orbit testing has demonstrated the efficient identification of space neutrons and gamma rays(n/γ). This data plays a crucial role in supporting manned space engineering, scientific research, and other related fields.
基金the National Key Research and Development Program of China(Grant No.2016YFB0500801)sponsored by Qing Lan Project.
文摘Satellite observation schedule is investigated in this paper.A mission planning algorithm of task clustering is proposed to improve the observation efficiency of agile satellite.The newly developed method can make the satellite observe more targets and therefore save observation resources.First,for the densely distributed target points,a preprocessing scheme based on task clustering is proposed.The target points are clustered according to the distance condition.Second,the local observation path is generated by Tabu algorithm in the inner layer of cluster regions.Third,considering the scatter and cluster sets,the global observation path is obtained by adopting Tabu algorithm in the outer layer.Simulation results show that the algorithm can effectively reduce the task planning time of large-scale point targets while ensuring the optimal solution quality.
基金Project supported by the National Natural Science Foundation of China(Nos.51805250 and 11602145)the Natural Science Foundation of Jiangsu Province of China(No.BK20180429)+1 种基金the China Postdoctoral Science Foundation(No.2019M660114)the Jiangsu Planned Projects for Postdoctoral Research Funds of China(No.2019K054)。
文摘A quasi-three dimensional model is proposed for the vibration analysis of functionally graded(FG)micro-beams with general boundary conditions based on the modified strain gradient theory.To consider the effects of transverse shear and nor-mal deformations,a general displacement field is achieved by relaxing the assumption of the constant transverse displacement through the thickness.The conventional beam theories including the classical beam theory,the first-order beam theory,and the higher-order beam theory are regarded as the special cases of this model.The material proper-ties changing gradually along the thickness direction are calculated by the Mori-Tanaka scheme.The energy-based formulation is derived by a variational method integrated with the penalty function method,where the Chebyshev orthogonal polynomials are used as the basis function of the displacement variables.The formulation is validated by some comparative examples,and then the parametric studies are conducted to investigate the effects of transverse shear and normal deformations on vibration behaviors.
基金Supported by the Strategic Priority Research Program on Space Science(XDA04060801,XDA04060802,XDA04060803,XDA04060804)of Chinese Academy of Sciencesthe Specialized Research Fund for State Key Laboratory of China+1 种基金the Chinese National Science Foundation(41374175,41204129)the CAS/SAFEA international Partnership Program for Creative Research Teams
文摘The Solar Polar ORbit Telescope(SPORT) project for space weather mission has been under intensive scientific and engineering background studies since it was incorporated into the Chinese Space Science Strategic Pioneer Project in 2011.SPORT is designed to carry a suite of remote-sensing and in-situ instruments to observe Coronal Mass Ejections(CMEs),energetic particles,solar high-latitude magnetism,and the fast solar wind from a polar orbit around the Sun.The first extended view of the polar regions of the Sun and the ecliptic enabled by SPORT will provide a unique opportunity to study CME propagation through the inner heliosphere,and the solar high-latitude magnetism giving rise to eruptions and the fast solar wind.Coordinated observations between SPORT and other spaceborne/ground-based facilities within the International Living With a Star(ILWS) framework can significantly enhance scientific output.SPORT is now competing for official selection and implementation during China's 13 th Five-Year Plan period of 2016-2020.
基金the National Key Research Program of China(Grant No.2016YFC0200900)the National Natural Science Foundation of China(NSFC)(Grant No.41775023)+1 种基金the Excellent Young Scientists Program of the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR19D050001)the Fundamental Research Funds for the Central Universities,and the State Key Laboratory of Modern Optical Instrumentation Innovation Program.
文摘A method to tighten the cloud screening thresholds based on local conditions is used to provide more stringent schemes for Orbiting Carbon Observatory-2(OCO-2)cloud screening algorithms.Cloud screening strategies are essential to remove scenes with significant cloud and/or aerosol contamination from OCO-2 observations,which helps to save on the data processing cost and ensure high quality retrievals of the column-averaged CO2 dry air mole fraction(XCO2).Based on the radiance measurements in the 0.76μm O2A band,1.61μm(weak),and 2.06μm(strong)CO2 bands,the current combination of the A-Band Preprocessor(ABP)algorithm and Iterative Maximum A Posteriori(IMAP)Differential Optical Absorption Spectroscopy(DOAS)Preprocessor(IDP)algorithm passes around 20%-25%of all soundings,which means that some contaminated scenes also pass the screening process.In this work,three independent pairs of threshold parameters used in the ABP and IDP algorithms are sufficiently tuned until the overall pass rate is close to the monthly clear-sky fraction from the MODIS cloud mask.The tightened thresholds are applied to observations over land surfaces in Europe and Japan in 2016.The results show improvement of agreement and positive predictive value compared to the collocated MODIS cloud mask,especially in summer and fall.In addition,analysis indicates that XCO2 retrievals with more stringent thresholds are in closer agreement with measurements from collocated Total Carbon Column Observing Network(TCCON)sites.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.41127002,11574099,41504034,and 11474115)the National Basic Research Program of China(Grant No.2010CB832806)
文摘We investigated the sensitivities of atom interferometers in the usual fringe-scanning method （FSM） versus the fringe- locking method （FLM）. The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.
基金supported by the NSFC(Grant Nos 42130204 and 42188101)the Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the support of the Tencent Foundation.
文摘The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.
基金supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)Natural Science Foundation of Shanghai’s Science and Technology Innovation Action Plan(General Program:No.22ZR1472900)+4 种基金Study on the Environment and Dynamics of Earth’s Inner Magnetospheric Particles and the Needs of Space-based Exploration(Grant No.D-2022-09-13-001)Hong Kong-Macao-Taiwan Cooperation Funding of Shanghai Committee of Science and Technology(Grant No.19590761300)Shanghai 2022“Science and Technology Innovation Action Plan”Hong Kong,Macao and Taiwan Science and Technology Cooperation Project(Grant No.22590760900)Shanghai Postdoctoral Daily Funding(Grant No.K-2021-12-16001)。
文摘Ground and space-based observations of the geomagnetic field are usually a superposition of different sources from the Earth’s core,lithosphere,ocean,ionosphere,and magnetosphere,and also from field-aligned currents coupling the ionosphere and magnetosphere—the meridional currents that connect the two hemispheres and the induced currents due to the variations of fields over time.The fluctuation of magnetic fields generated by these highly dynamic space currents greatly limits the accuracy of the geomagnetic models.In order to better accomplish the scientific objectives of Macao Science Satellite-1(MSS-1),and to improve existing geomagnetic field models,we present here for the first time a self-consistent coupling of solar wind,magnetosphere,and ionosphere,which represents the most developed numerical simulation method for space physics research so far,making it possible to quantify the contribution of different current systems to the total observed magnetic field(B).The results show that numerical simulation can capture main magnetic disturbance characteristics with significant precision.Partial ring current is a major contributor to the latitudinal magnetic perturbation near the equator.Magnetopause and magnetotail currents affect the radial magnetic perturbation around the mid-latitudes.Field-aligned and Pedersen currents produce significant longitudinal and latitudinal magnetic perturbations at high latitudes.
基金supported by the Fundamental Research Funds for the Central Universities(No.NS2014092)the Natural Science Foundation of Jiangsu Province(No.SBK201343261)the Shanghai Aerospace Science and Technology Innovation Foundation(No.SAST2015035)
文摘Rotation modulation technique is generally used to improve the performance of aviation and marine inertial navigation system.Considering of the performance requirements from current aerospace to MEMS micro-nano inertial device,this paper proposedrotary inertial device modulation technology application methods on the satellite.Firstly,taking the advantage ofultrasonic motor,like high resolution,fast response,electromagnetic compatibility,a lowmagnetic,high-precision and appropriate for use on satellite ultrasonic motor modulation turntable was developed.Then,through theoretical modeling and simulations,the rotation modulation technology was verified to improvethe precise of satellite attitude measurementeffectively,equivalent toimprove the accuracy of MEMS gyro over an order of magnitude.This work helpsachieve the application of rotation modulation technology in aerospace and acceleratethe promotion of the MEMS gyro in satellite attitude measurement.
基金This work was financially supported by the Foundation of the Future Industry of Shenzhen(Grant No.JCYJ20170413163838640)the Research and Development Project in Key Areas of Guangdong Province(Grant No.2020B010190002).
文摘Carbon nanotube(CNT)-reinforced composites have ultra-high elastic moduli,low densities,and fibrous structures.This paper presents the multi-scale finite element modeling of CNT-reinforced polymer composites from micro-to macro-scales.The nanocomposites were modeled using representative volume elements(RVEs),and finite element code was written to simulate the modeling and loading procedure and obtain equivalent mechanical properties of the RVEs with various volume fractions of CNTs,which can be used directly in the follow-up simulation studies on the macroscopic model of CNT-reinforced nanocomposites.When using the programming to simulate the deformation and fracture process of the CNT-reinforced epoxy composites,the mechanical parameters and stress-strain curves of the composites on themacro-scale were obtained by endowing the elements of the lattice models withRVE parameters.Tensile experiments of the CNT-reinforced composites were also carried out.The validity of the finite element simulation method was verified by comparing the results of the simulations and experiments.Finite element models of functionally graded CNT-reinforced composites(FG-CNTRC)with different distributions were established,and the tensile and three-point-bending conditions for various graded material models were simulated by the methods of lattice model and birth-death element to obtain the tensile and bending parameters.In addition,the influence of the distribution and volume ratio of the CNTs on the performance of the graded composite material structures was also analyzed.
基金the National Natural Science Foundation of China(No.11872207)Aeronautical Science Foundation of China(No.20180952007)+2 种基金Foundation of National Key Laboratory on Ship Vibration and Noise(No.614220400307)Natural Science Foundation of Jiangsu Province(No.BK20200413)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘In cryogenic wind tunnel tests,piezoelectric stacks are adopted to realize the vibration control of the cantilever sting.However,the free stroke and blocking force of the piezoelectric stack would decrease dramatically as the temperature decreases.This paper proposes a convenient and effective warming structure for the piezoelectric stack,which could keep it working at operating temperatures when the ambient temperature drops.The piezoelectric stack actuator is wrapped with the heating film,and this resulting assembly is then wrapped with the aerogel material for thermal insulation.Both ends of the piezoelectric stack actuator make direct contact with the payload structure.Both one-dimensional and two-dimensional theoretical analyses of the heating conduction problem of the piezoelectric stack actuator are conducted.These analyses results are compared with those of the finite element simulation analysis.The finite element method results show a good consistency with the two-dimensional theoretical results,and a slight deviation of only 0.91 K is observed,indicating its potential for protecting piezoelectric stacks at low temperatures.
基金Supported by National Key R&D Program of China(2020YFE0202100)National Mission/Other National Mission:Research on Key Technologies of the Outer Heliospheric Space Exploration System(Y91 Z100102)National Mission/National Major Science and Technology Project:CE-7 Relay Satellite Display Neutral Atom Imager(E16504B31S)。
文摘Geosynchronous orbit is located in the ring current region,where the energetic particle emission environment challenges the ion deflection design limit of the Energetic Neutral Atom(ENA)imager.Therefore,there is no measurement record of ENA imaging in this area before.On the basis of possessing the patent of high-energy ion deflection technology,ENA imaging under different Kp index in geosynchronous orbit is simulated.The simulation images show the characteristics of low-altitude ENA emission source and the rough sketch of magnetosphere.Due to the north-south conjugation observation of geosynchronous orbit,the simulated ENA images at different positions all have north-south symmetry.Aiming at the unsolved problems,such as the input source of ring current energetic ions during geomagnetic activities and its evolution process,we analyzed the possible results of ENA imaging combined with in-situ particle measurements in the same satellite,as well as the subversion effect of any north-south asymmetry of ENA map on the inversion model.
文摘In this work,we have carried out a simulation study on the discharge process of Hall thrusters under the conditions of different neutral gas radial supply positions based on the particle-in-cell(PIC)and Monte Carlo collision(MCC)methods.This paper compares the two-dimensional(2D)distributions of neutral gas,plasma and wall erosion-related parameters under different neutral gas supply positions.The comparison results show that the change of the neutral gas supply position affects the radial distribution uniformity of the neutral gas and plasma in the channel.From the comparison of the density peaks,it can be found that the neutral gas density and the plasma density peak under the upper gas supply condition are relatively low,and the plasma density peak is 22.49%lower than the density peak under the middle gas supply condition.Meanwhile,as the radial position of the gas supply moves from the lower gas supply to the upper gas supply,the position of the ionization zone also gradually moves toward the anode.The results of erosion-related parameter distribution comparison show that the change of gas supply location has an obvious influence on erosion rate and erosion range.In terms of erosion rate,the wall erosion rate is relatively low under the upper gas supply condition,and the peak erosion rates of the inner and outer walls are 33.3%and 29.9%lower than those under the other two conditions.In terms of erosion range,as the gas supply position moves from the lower gas supply position to the upper gas supply position,the erosion range gradually increases from5 to 7.5 mm.
基金Project supported by the National Key Scientific Instrument and Equipment Development Project of China(Grnat No.2014YQ060537)the National Basic Research Program of China(Grant No.2013CB632803)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05040102)the National Natural Science Foundation of China(Grant No.41405134)
文摘A quantum cascade laser（QCL） based system for simultaneous detection of CO and CO_2 is developed.The QCL can scan over two neighboring CO（2055.40 cm^（-1）） and CO_2（2055.16 cm^（-1）） lines with a single current scan.The wavelength modulation spectroscopy（ f = 20 k Hz） is utilized to enhance the signal-to-noise ratio.A white cell with an effective optical path length of 74 m is used.The calibration of the sensor is performed and minimum detection limits of 1.3 ppb（1 × 10^（-9））for CO and 0.44 ppm（1 × 10^（-6）） for CO_2 are achieved.
基金supported by the National Key Research and Development Program of China(2016YFB0500901)the Natural Science Foundation of Shanghai(18ZR1437200)the Satellite Mapping Technology and Application National Key Laboratory of Geographical Information Bureau(KLSMTA-201709)
文摘According to the oversampling imaging characteristics, an infrared small target detection method based on deep learning is proposed. A 7-layer deep convolutional neural network(CNN) is designed to automatically extract small target features and suppress clutters in an end-to-end manner. The input of CNN is an original oversampling image while the output is a cluttersuppressed feature map. The CNN contains only convolution and non-linear operations, and the resolution of the output feature map is the same as that of the input image. The L1-norm loss function is used, and a mass of training data is generated to train the network effectively. Results show that compared with several baseline methods, the proposed method improves the signal clutter ratio gain and background suppression factor by 3–4 orders of magnitude, and has more powerful target detection performance.
基金funded by the “Integration of Space and Ground Based Instruments” project of the China National Space Administrationthe National Natural Science Foundation of China (Grant Nos. 11673012, 11533005 and 11733003)
文摘The Chinese HαSolar Explorer(CHASE)is designed to test a newly developed satellite platform and conduct solar observations.The scientific payload of the satellite is an Hαimaging spectrograph(HIS),which can,for the first time,acquire full-disk spectroscopic solar observations in the Hαwaveband.This paper briefly introduces CHASE/HIS including its scientific objectives,technical parameters,scientific application system,etc.The CHASE mission is scheduled to launch in 2021.It will complement the observations by on-orbit solar spacecraft(such as SDO,IRIS,STEREO and PSP),as well as future solar missions of the Solar Orbiter and Advanced Space-based Solar Observatory(ASO-S).
