空间科学学报

Abstract:
Chinese lunar exploration program is facing a new development situation, which raises higher demands for many aspects of the Chinese lunar exploration mission, including demonstration of plans, overall design, system development and orbital detection. Currently, Model-Based System Engineering (MBSE), concurrent engineering and other new methods and new techniques have received growing attention, both domestically and internationally. In this paper, the research status of MBSE from the aspects of processes, methods, tools and applications, are summarized to analyze the development trends of it. Integrating the project characteristic and mission demands of the Chinese lunar exploration program, the model-based demonstration framework for concurrent and collaborative design is proposed, and then the analysis is conducted on two categories of key technology of the framework. Based on a dependency graph, the consistency maintenance technology across disciplines, levels and regions is proposed. And, the component service packaging integration technology based on OSLC is proposed. The initial application has been conducted on the demonstration and design for International Lunar Research Station, in which multi-roles cooperation is realized, the full synchronization time is less than 1 minute. The designing practice of ILRS provides the instructional framework and practical exploration to comprehensively promote MBSE for further lunar exploration program.

Simulation of the Diffusion Processes of Solar Energetic Particle Events Based on the Green Functional Theory

ZHU Linling, ZHANG Xiaoxin, GU Bin

2022, 42(2): 191-198. doi: 10.11728/cjss2022.02.210326038

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Abstract:
In order to investigate the diffusion processes of Solar Energetic Particle (SEP) events, four SEP events with different coronal-foot-point longitudes are simulated based on the two-phase model proposed by Huang et al. The simulations agree with the observations from GOES satellites, indicating that the model has wide applicability. Sensitivity tests for multiple transmission parameters in the model show that the change of the longitude of the coronal foot point affects the detection time and peak value of the observations, and the change of the solar wind speed has different influencing mechanisms to the SEP events with different coronal-foot-point longitudes. Furthermore, it can be found that the transverse diffusion coefficient of the corona area is associated with the diffusion processes of SEP events along the solar surface, and mainly affects the intensity of the event. Different radial diffusion coefficients mainly change the arrival time of the events, and it plays a more effective role in the diffusion of SEP events in comparison with the lateral diffusion coefficient, since the SEP events mainly transmit along the interplanetary magnetic field. In addition, the escape time that manifests the average lifetime of the SEP source or the time window for the outflow of SEPs from the solar activity, has the least effect on the simulations in comparison with the other parameters.

Kp Index Prediction Based on Similarity Algorithm of Machine Learning

WANG Zisiyu, SHI Liqin, LIU Siqing, ZHONG Qiuzhen, CHEN Yanhong, YAN Xiaohui, SHI Yurong, HE Xinran

2022, 42(2): 199-205. doi: 10.11728/cjss2022.02.210316030

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Abstract:
The solar wind is the direct cause of the geomagnetic disturbance. In this paper, based on the feature selection and similarity algorithm of machine learning, a recommended model is established to search for cases whose characteristics are similar to the current solar wind in historical solar wind data, and to obtain the prediction of the geomagnetic Kp index. Tested on 120 solar wind cases randomly selected from 1998 to 2019, the results show that the solar wind cases which have similar geomagnetic effects to the input solar wind can be worked out successfully by proposed model . And the root mean square error between the Kp index of the optimal case recommended by the model and the actual value is 0.79, and the correlation coefficient is 0.93. Different from traditional forecast models, the proposed recommended model in this paper can not only provide a geomagnetic Kp index as a forecast, but also give a clearer and more intuitive comparison of the changes between the solar wind characteristic parameters according to the time series. Even because the historical events have already happened, we can artificially find more dimensional information of the similar historical cases, which makes forecasters better combine their own experience in Kp index forecasting.

Magnetospheric Multiscale Observation of Electromagnetic Ion Cyclotron Wave Modulated by ULF Wave in Outer Magnetosphere

LIAO Zedong, LIU Si, GAO Zhonglei, HE Qian, LI Tong, SHANG Xiongjun

2022, 42(2): 206-215. doi: 10.11728/cjss2022.02.210204018

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Abstract:
A quasi-periodic Electromagnetic Ions Cyclotron (EMIC) wave event was reported. The event was observed by the Magnetospheric Multiscale (MMS-1) at dayside (06:30 MLT) in the outer magnetosphere. EMIC waves with more than 21 wave packets occurred within L value is from 7.5 to 10.1. Ultra-Low Frequency (ULF) waves and the quasi-periodic enhancement of energy protons temperature anisotropy are simultaneously observed. Frequency analysis shows that the period of the ULF wave, the proton anisotropy period and the period of the EMIC wave packet are very close. The MMS-4 satellite passed the very close region about an hour later and found that the quasi-periodicity of the EMIC wave packet decreased as the amplitude of the ULF wave decreased. The current results provide evidences that the ULF wave can modulate the energetic proton anisotropy in the outer magnetosphere at dayside and thus generate periodic EMIC wave packets. Moreover, correlated observations by MMS-1 and MMS-4 show that the ULF-modulation of EMIC waves can occur in a spatial scale that greater than 2 R_e, and last for several hours.

Distribution of the Projection Position of the Magnetotail FAC in the Northern and Southern Hemisphere Based on Cluster Observations

CHENG Zhengwei, SHI Jiankui, WANG Guojun, WANG Zheng, SHANG Sheping, WANG Xiao

2022, 42(2): 216-224. doi: 10.11728/cjss2022.02.210111005

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Abstract:
Using the magnetic field data of Cluster 4 satellites, the density of Field-Aligned Current (FAC) was calculated and projected to the polar ionosphere, and the distribution of its projected position in the north and south hemispheres was studied. The FAC events during strong magnetic storms are removed from the statistical process (during the main phase of storm Dst<–100 nT). The results showed that: The projection locations of magnetotail FAC events in the polar region are mainly distributed in the Invariant Latitude (ILAT) between 64° and 76°. The distribution in the northern and southern hemispheres is obviously asymmetric, with a single peak structure in the northern hemisphere and a bimodal structure in the southern hemisphere. The number of FAC events that can project to lower latitudes (< 64°) in the northern hemisphere is significantly more than in the southern hemisphere, and can achieve the lowest latitude is lower; The number of FAC events that can project to higher latitudes (>74°) in the southern hemisphere is significantly more than in the northern hemisphere, and can achieve the highest latitude is higher. Distinguish the polarity of FAC, the distribution of earthward FAC and the tailward FAC in the north and south hemisphere is similar. Under quiet geomagnetic conditions (|AL|<100 nT), the current density of FAC in the magnetotail increased with the Magnetic Local Time (MLT) (from 20:00 MLT before midnight to 04:00 MLT after midnight), which was consistent with the previous detection results of Region 1 FAC by low-altitude satellites. The above results show that the latitude distribution of the projected position of the magnetotail FAC presents an obvious north-south asymmetry, which is closely related to the spatial distribution of the magnetotail FAC in the northern and southern hemispheres and the structure of the magnetic field in the magnetosphere. The distribution of the FAC density in the magnetotail with MLT is consistent with the distribution of Region 1 FAC in the polar ionosphere, which provides indirect evidence for the connection between the magnetotail FAC and Region 1 FAC, indicating that the FAC is a large-scale structure from the magnetotail to the ionosphere.

Effects of the Length-width Ratio of Current Sheet on Asymmetry Multiple X-line Reconnection

LI Lingjie

2022, 42(2): 225-231. doi: 10.11728/cjss2022.02.210113008

Abstract(364) FullText HTML (283) PDF 1131KB(18)

Abstract:
Effects of the length-width ratio of current sheet (${L_x}$) on asymmetry multiple X-line reconnection are investigated using a two-dimensional compressible resistive Magnetohydrodynamics (MHD) model. It is found that multiple-X lines induced by secondary tearing instability occur during the asymmetry reconnection processes when ${L_x}$ exceeds a critical value. Multiple X-line reconnection occurs faster as ${L_x}$ becomes larger, and percent of secondary island is also increases. For large ${L_x}$ cases, locations of the reconnection points of asymmetry multiple X-line reconnection and sizes of the secondary island are tend to stationary with the evolution of the multiple X-line reconnection, which is consistent to the Magnetospheric Multiscale (MMS) observations. The results here can be useful for understanding some observed data, even for the secondary tearing instability and multipleX-line reconnection observations.

Magnetic Signatures and Identification of Equatorial Plasma Bubbles

LI Bo, LI Lei, GOU Xiaochen, ZHOU Bin

2022, 42(2): 232-239. doi: 10.11728/cjss2022.02.210323033

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Abstract:
Equatorial Plasma Bubbles (EPBs) are density depleted structures in the equatorial ionosphere, accompanied by the enhanced magnetic field strength, and fluctuations in the directions transverse to the main field, which have Alfvenic wave signatures. Utilizing the scalar, vector magnetic field, and plasma data from the Swarm mission, the magnetic signatures related with EPB are investigated. It is found that the changes both in the magnetic field strength and the component parallel with the main field are anti-correlated with the density changes inside EPBs, suggesting both the scalar and vector magnetic field data could be used to identify EPSs. Comparing the results of EPB identification using Swarm satellite scalar and vector magnetic field data products respectively, it is confirmed using the scalar data can increase the chance to identify EPBs, especially to find EPBs with relatively lower field fluctuations, since the noise level of the Swarm scalar magnetometer is about one order of magnitude lower than that of the vector magnetometer.

A New Ionosphere Sporadic E Research Method Based on Wavelet Decomposition and Reconstruction

WANG Xixi, NIU Jun, FANG Hanxian, FAN Xin, BAO Yun

2022, 42(2): 240-245. doi: 10.11728/cjss2022.02.210127014

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Abstract:
The ionospheric irregularities have important impact on the satellite navigation, communication, radar system etc. In this paper, the numerical simulation and observation data contrast are both carried out to validate the feasibility of wavelet decomposition and reconstruction method. Taking sporadic E for example, in numerical simulation, the background of the electron density distribution is simulated by the International Reference Ionosphere (IRI). Then the horizontal total electron density (δ_ht) is used in the inversion of the ionosphere irregularities, and the results are compared with the simulated data. With the wavelet decomposition and reconstruction method of observation data, the COSMIC occultation data from 1 to 9 in July 2009 have been compared with the ground-based observation data provided by SPIDR. Both results show well accordance with the true value or observation which indicates the method is feasible for the inversion of ionosphere irregularities. This is in great significance for the research of ionosphere irregularities.

Modeling Study on the Response of the Thermospheric Vertical Winds to Geomagnetic Storm at Middle Latitudes

SU Ye, LI Jingyuan, LÜ Jianyong, WANG Ming, WEI Guanchun, SUN Meng, XIONG Shiping, LI Zheng

2022, 42(2): 246-254. doi: 10.11728/cjss2022.02.210303023

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Abstract:
Based on the simulation data of TIMEGCM, the influence of horizontal wind variations on middle-latitude vertical wind changes during the geomagnetic storms (100~650 km) on 10 September 2005 is studied. The model simulations were diagnostically analyzed, which is to investigate the causes of storm-time vertical wind changes. The results show that the vertical wind variations above 250 km depend on the changes of horizontal wind, and the vertical wind changes below 250 km are driven by the vertical wind at high altitudes. In the early initial phase of geomagnetic storms, the meridional winds have more significant influence on the vertical winds over 250 km than the zonal winds. As the storm evolves, the zonal winds contributed more to the changes of vertical wind. The responses of temperature variations to the geomagnetic storms are similar with horizontal wind changes. At the beginning of the initial phase, the temperature propagates faster along the longitude, and the meridional wind changes faster. As the storm evolves, the temperature propagates faster along the latitude, and the zonal wind changes faster.

Longitudinal Difference of Equatorial Thermospheric Zonal Wind’s Reversal Time and Speed

GAO Jie, WANG Hui, ZHANG Kedeng, ZHENG Zhichao, HE Yangfan, SUN Luyuan, ZHONG Yunfang

2022, 42(2): 255-263. doi: 10.11728/cjss2022.02.210329039

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Abstract:
Based on the Challenging Minisatellite Payload (CHAMP) satellite observations and Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations, the longitudinal variation of the reversal local time of the equatorial thermospheric zonal wind and its speed at equinoxes during solar minimum period are investigated. It is found that the zonal wind generally turns from eastward to the westward in the morning and from westward to the eastward in the afternoon. However, there are obvious longitudinal differences in the reversal time, with the maximum longitudinal difference of 1.8 h. This is mainly due to the upward-propagating non-migrating tide in the lower atmosphere. The tide can advance the reversal time about 2 h in the afternoon, which is more consistent with the observation. However, it has no obvious effect on the reversal time in the morning, which makes the simulation result different from the observation. The longitudinal wave-4 structure of the zonal wind mainly comes from the non-migrating tide, but the ion drag contributes to the wave-4 structure of the zonal wind. The quantitative analysis shows that the contribution of ion drag to the wave-4 structure is about 25%. The ion drag effect is larger in the daytime than the nighttime, and larger in the frame of the idea dipole field than the real IGRF field.

Experimental Investigation of Large Sessile Droplet Evaporation with Pinned Triple Line

ZHAO Dongdong, ZHU Zhiqiang, LIU Qiusheng, QIN Jun, TAO Yuequn

2022, 42(2): 264-269. doi: 10.11728/cjss2022.02.210123035

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Abstract:
The in-depth study on the evaporation of large sessile liquid droplets has important scientific significance and engineering application value. Using the evaporation-convection box in SJ-10 scientific experimental satellite, the scientific matching experiments of large sessile ethanol droplets evaporation on heated PTFE are conducted on the ground, in which the triple line of the liquid droplet is pinned and the contact radius is greater than capillary length. In present experiments, it is found that the volume of the large sessile droplet with pinned triple decreases linearly with time, but the CCA mode during evaporation is not observed. The average evaporation rate is also focused on, and it is found to be independent on initial volume of the large sessile pinned droplet with the same contact radius, which is similar in the tendency for small evaporating liquid drop, indicating that evaporation occurs most violently near the triple line. The instant evaporation rate is observed to increase firstly and then keep stable until the end of the lifetime. Comparisons between the present experimental results and the results predicted by the empirical models are also performed. It is deduced that the diffusion-limited evaporation model is appropriate for the small droplet, but underestimates evaporation rate of the large sessile pinned liquid droplet, while the accuracy of an empirical model considering both diffusion and natural convection depends on the experimental working medium.

Non-modal Stability Analysis of Thermocapillary Liquid Layers

ZHENG Sheng, HU Kaixin

2022, 42(2): 270-276. doi: 10.11728/cjss2022.02.201104097

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Abstract:
The sensitivity of subcritical thermocapillary liquid layers to initial disturbances and external excitations is investigated by the non-modal stability analysis. The amplifications of initial disturbances and external excitations are measured by the growth function and response function, respectively. Results show that at small Prandtl numbers (Pr), the subcritical flows are sensitive to both initial disturbances and external excitations. The maximum amplifications are approximately proportional to the square of Reynolds number (Re). At large Pr, large amplifications to external excitations are found in the return flow. The maximum response increases linearly with Re⁵ and Pr⁵. When the frequency increases, the total wave number of the optimal response decreases. The flow and temperature fields indicate that the magnitudes of output temperature and velocity are far larger than those of input, which is significantly different from the pipe flow.

Application of Atmospheric Drag Model Based on Reynolds Number in Reentry Prediction of Rocket Bodies

LIU Jinghong, XU Jin, DU Jianli, PAN Jianping

2022, 42(2): 277-283. doi: 10.11728/cjss2022.02.210222020

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Abstract:
With the increasing demand for space technology services and the realization of active space debris removal technology, space debris will frequently re-enter the atmosphere in the future with the characteristics of large quantity, high quality and difficult decomposition, causing more threats to the safety of people and property. Therefore, there is an urgent need for early warning of atmospheric reentry of large spacecraft such as rocket body. However, due to the lack of appropriate atmospheric drag coefficient model, it is difficult to achieve high-precision atmospheric reentry prediction. Therefore, an atmospheric dynamic model based on Reynolds number is introduced for simplified spacecraft model, and the prediction results are obtained by numerical integration of the differential equation of motion through RK6(7), which are compared with the prediction results of high-precision numerical orbital propagator HPOP and semi analytical orbital propagator WHU-SST. The experimental results show that using the differential equation of motion with the atmospheric dynamic model based on Reynolds number to predict the reentry of the rocket body 30 days in advance, the accuracy of prediction is significantly improved, and the prediction error of an object is reduced from 96% to 7.8%; Using the new model for ground risk assessment with TLE data only, the real decayed location can be located in the predicted statistical decayed location.

Simulation Research on Precision Digital Fluxgate Magnetometer Based on Sigma-Delta Modulation Technology

CHEN Wuxiang, WANG Jindong, LÜ Shang, LI Yunpeng, XUE Yongliang, SONG Wei

2022, 42(2): 284-293. doi: 10.11728/cjss2022.02.210121010

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Abstract:
A precision digital fluxgate magnetometer was designed based on Sigma-Delta modulation technology. Signal processing simulation model is carried out with Simulink tools in Matlab, simulation analysis of magnetometer characteristics is given, including the noise, linearity, response speed and frequency characteristic. The simulation results show that the measurement range of 1 bit digital magnetometer could reach more than ±10⁵ nT to cover Earth magnetic field, system noise is lower than 4.66 pT·Hz^–1/2 at 1 Hz which means the resolution is sufficient for deep space magnetic field exploration. The maximum nonlinear error is 0.16 nT and the dynamic response speed reaches 2×10⁶ nT·s^–1 and the efficient Bandwidth is higher than 10 Hz. The simulation results indicate that 1bit digital fluxgate magnetometer could effectively reduce the critical requirements of the accuracy on the A/D converter, simplify the analog signal processing electrical circuit and improve the system reliability. The performance of 1 bit Sigma-Delta digital magnetometer indicates its impressive advantages over traditional magnetometers and wide application prospects in the field of deep space exploration and space magnetic field measurement.

Simulations of the Antenna-shielding Effect of the Daocheng Solar Radio Telescope (DSRT)

LU Guang, WANG Bing, CHEN Yao, WU Ji, YAN Jingye, WU Zhao, YAN Fabao, WU Lin

2022, 42(2): 294-305. doi: 10.11728/cjss2022.02.210202017

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Abstract:
The Daocheng Solar Radio Telescope (DSRT) is a next-generation solar radio telescope funded by the Chinese Meridian Project–Phase II. DSRT is composed of 313 parabolic antennas with a diameter of six meters. The antennas are evenly distributed in a circle with a diameter of one kilometer. With the synthetic aperture imaging techniques, key factors determining the DSRT imaging quality are accurate calibrations of amplitude and phase of the received signals. Yet, under some circumstances, adjacent antennas of DSRT may shield each other, which will affects the amplitude and phase of the received signals and thus deteriorate imaging quality. In this study, such shielding effects of three- or two-antenna using the electromagnetic simulation software at frequencies of 300 MHz (λ=1 m) were simulated. The shielding effect in the three-antenna system is slightly worse than that in the two-antenna system. When the projected distance of adjacent antennas is taken to be –1λ, i.e., the most serious effect of shielding considered here, the horizontal and vertical gains of the system with two/three antennas decline by 0.6/0.6 dB and 0.3/0.4 dB, respectively, and the horizontal and vertical phase deviations are –3.3º/–3.871º and –1.744º/–2.244º, respectively, compared to the system with one antenna. Other situations with different projected shielding distances are also investigated. The results show that the two-antenna system can sufficiently describe the shielding effect associated with DSRT. Such effect should be properly taken into account when processing the future DSRT data so as to improve the data usage efficiency and imaging quality.

Research on the Application of ARIMA-SVR Combination Model in Satellite Telemetry Parameter Prediction

GU Xinyu, XIAO Zhigang

2022, 42(2): 306-312. doi: 10.11728/cjss2022.02.210106002

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Abstract:
In order to provide decision analysis support for assisting the in-orbit operation of satellite, combining with the time series characteristics of satellite telemetry parameters, an ARIMA-SVR combination prediction method is used to judge whether the actual telemetry data is in the normal range through the prediction of satellite telemetry parameters. In this model, ARIMA model is used to linearly fit the preprocessed data, and SVR model is used to compensate the nonlinear part of the data. Based on the telemetry data of temperature of star sensor A in KX09 satellite, the combination model was used to predict the short-term and medium-term temperature of star sensor A, and the Root Mean Square Error (RMSE) of the short-term and medium-term temperature of star sensor A was 0.768 and 0.968, respectively. Compared with the single ARIMA model, the RMSE of the short and medium-term temperature of star sensor A was 46.2% and 16.4% higher than that of the single ARIMA model respectively. In addition, the x-axis angular velocity of gyro B on the satellite is predicted in short and medium term. In the short term prediction, the RMSE of the combined model is increased by 71.2% compared with that of the single ARIMA model. In the medium prediction, the RMSE of the combination model is 64.2% higher than that of the single ARIMA model. Experimental results show that the ARIMA-SVR combination model provides effective decision analysis support for ensuring the healthy in-orbit operation of satellites.

Drone-airborne Interference Array Platform for Outfield Tests

HU Yasi, DENG Li, ZHU Yao

2022, 42(2): 313-320. doi: 10.11728/cjss2022.02.201203105

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Abstract:
As the wavelength of ultra-long band radio waves is from several meters to several hundred meters, to achieve high-resolution imaging of cosmic radio signals in the ultra-long wave band, the antenna diameter is usually required to reach hundreds or even thousands times of the wavelength. The traditional single antenna method is no longer applicable. The far side of the Moon is shielded from radio interference from Earth and has the quietest electromagnetic environment in the solar and terrestrial space, making it ideal for ultra-long-wave observations. The main idea of space-distributed passive microwave interference imaging technology is to use distributed satellite constellations to achieve oversized interferometric baselines in deep space to realize the high-resolution imaging of cosmic radio sources, instead of using large aperture antenna. In order to promote the scheme optimization, it is necessary to conduct sufficient ground tests before the satellites are deployed in-orbit to verify the key technologies of the space distributed interferometry system. The drone-airborne interference array platform is built for effectively solving the multipath effects of the communication ranging system in ground tests, supporting multi-drone formation and control, and the positioning accuracy is up to the centimeter level. By carrying payloads on drones and simulating satellites’ autonomous formation flying around the Moon, interference baselines in different scales are formed. The platform can be used in the mission of Discovering the Sky at the Longest wavelength with small satellites (DSL) to conduct principle verifications such as ranging and angle measurement. It can also be popularized for other distributed drone airborne tests, which is economically feasible and has good application prospects.

Mission Planning for Astronomical Satellite Based on Genetic Algorithm under Tiling Coverage Strategy

XU Ziling, LIU Yurong, FENG Zhun

2022, 42(2): 321-328. doi: 10.11728/cjss2022.02.210112006

Abstract(686) FullText HTML (368) PDF 1467KB(33)

Abstract:
Astronomical observation is an important means for space scientific research. ToO (Target of Opportunity), such as GW (Gravitational Wave) and GRB (Gamma Ray Burst), are significant phenomena in astronomical observation. The planning of ToO observation is an important task. Astronomy satellite planning is a complex multi-objective optimization problem. In this paper, the mission planning requirements and constraints under tiling coverage strategy are abstracted, and the ToO planning model under tiling coverage strategy is established. Based on the model, a multi-objective optimization planning algorithm TPA (ToO Planning Algorithm) based on GA (Genetic Algorithm) is designed. An example is given to illustrate the solution under different parameters, where the simulation input data is provided by JAUBERT Jean of SVOM team. The simulation result shows that the TPA can effectively solve the multi-objective task planning problem of astronomical satellites ToO under coverage strategy.

2022 Vol. 42, No. 2

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