2015 Vol. 35, No. 5

Display Method:
Simulation Of Induced Step-Transient Magnetic Field With A Lunar Homogeneous Model
ZHANG Xiangyu, ZHAO Hua
2015, 35(5): 525-532. doi: 10.11728/cjss2015.05.525
With a homogeneous model of the Moon, the induced magnetic field caused by step-transient disturbation of interplanetary magnetic field is simulated by the electromagnetic induction theory. As the range of conductivity assigned, the variation from step to calm of both the vectors and magnitudes can be obtained with a fixed permeability μ0. Then the magnetic characteristic transient response function, the field components and total field at 3 different points selected in a longitude line can all be given in different conductivities by numerical inverse Laplace transformation. The calculation provides a reasonable result that components perpendicular to the external step-transient field will disappear in a long-enough time, whereas the parallel component will become unity with it. When the external field step varies, the maximum field value which can be detected in the vicinity of the equator and the polar region are 13.65nT and 2.71nT, respectively. The processes of parallel component change are remarkably different in low latitude and polar region. This phenomenon reflects that magnetometers in different sites of lunar surface may lead to different field curves.
Analysis On The Distribution Of Geomagnetic Storm Number
LIU Yumei, CHEN Chun, SUN Shuji, BAN Panpan
2015, 35(5): 533-540. doi: 10.11728/cjss2015.05.533
Abstract(923) PDF 977KB(1617)
A geomagnetic storm is a global disturbance in Earth's magnetic field, which is caused by various solar phenomenon. Dst index is the most widely used index which denotes the intensity of magnetic storm activity. The distributions of moderate geomagnetic storms (-100<Dst≤ -50nT) and intense geomagnetic storms (Dst≤ -100nT) and their causes in 1957-2008 are identified. Moreover, annual average number of geomagnetic storm in ascending phase, maximum phase, declining phase, and minimum phase of solar activity was analyzed according to different kinds of geomagnetic storms. It is found that the total number of geomagnetic storm in maximum phase year is greater than that in minimum phase year of the same solar activity, and there is close relation between the average number of Sun spots per year and the total number of geomagnetic storm. A dominant dual-peak distribution usually exists in the solar cycle variability of intense geomagnetic storm, but a dual-peak distribution of moderate geomagnetic storm exists and a trinal-peak distribution appears in intense geomagnetic storm. The presence of the extra peak might be attributing to a typical year compared to other rising phase years. On the other hand, another possibility is that 1999 could be an unusual year, with a low rate of intense magnetic storm. The magnetic storms mainly happen in equinox, and the number of magnetic storm is obviously changed with the increased Dst index.
Cit-Based Correction Algorithm For The Ionospheric Delay In Wide Area Augmentation System
Ou Ming, Zhen Weimin, Yu Xiao, Liu Yiwen, Xu Jisheng
2015, 35(5): 541-548. doi: 10.11728/cjss2015.05.541
Ionospheric delay is one of the most important error sources in satellite navigation and positioning, many methods were adopted to mitigate the ionospheric delay for high precision navigation applications, such as local area differential GPS, wide area differential GPS, wide area augmentation differential GPS and Wide Area Augmentation System (WAAS). A new algorithm based on Computerized Ionospheric Tomography (CIT) for ionospheric delay correction in WAAS was proposed in this paper. The error of ionospheric delay can be corrected by the orthogonal combination of model-based function and Truncated Singular Value Decomposition (TSVD) for single frequency user in WAAS. The simulation results of 23 wide-area reference stations and 10 user stations in China show that the precision of ionospheric delay correction based on traditional grid-based algorithm and CIT-based algorithm have evident correlation with solar activities, local time and magnetic latitude as well. However, the performance of CIT-based algorithm is much better than that of grid-based algorithm. Both the mean error and standard deviation of CIT-based algorithm are far less than grid-based algorithm.
An Anisotropic Scattering Model Of Ionospheric Field-Aligned Irregularities
Zhang Yabin, Wu Jian, Guo Lixin, Xu Bin, Xue Kun, Zhao Haisheng, Xu Zhengwen
2015, 35(5): 549-555. doi: 10.11728/cjss2015.05.549
As influenced by geomagnetic field, electron density fluctuations of ionospheric irregularities are highly elongated in the direction of geomagnetic field, and the scattering of the irregularities are also highly directional, which could be potentially used as long-distance communication circuits in VHF band. Based on the characteristic of ionospheric Field-Aligned Irregularities Scattering (FAIS), an anisotropic scattering model of ionospheric field-aligned irregularities is proposed in the geomagnetic reference frame. The parameters such as path loss, delay spread and coherence bandwidth of forward and back scattering are calculated by the model. The results of Radar Cross Section (RCS) predicted by the model have a good agreement with data in literatures. The model given herein can be helpful to construct ionospheric irregularities scattering communication systems in VHF band.
Comparison Of Ionospheric Total Electron Content Over North America And East Asia With Eof Analysis
Yao Xin, Zhao Biqiang, Liu Libo, Wan Weixing
2015, 35(5): 556-565. doi: 10.11728/cjss2015.05.556
Abstract(1147) PDF 6969KB(1738)
In the present work, variations of ionospheric Total Electron Content (TEC) are investigated and compared with applying Empirical Orthogonal Functions (EOF) on the dataset from the Global Ionospheric Maps (GIMs) which are produced by Jet Propulsion Laboratory (JPL) over two concerned areas: the North America (30°N-50°N, 140°W-50°W) and East Asia (42.5°N-57.5°N, 65°E-140°E). The first three EOF components attribute about 99.57% and 99.79% to the total variations separately, and spatial-temporal features manifested by each EOF components are similar for the two areas: the first order EOF component for both areas represents semiannual variation which is strongly modulated by the solar activity; the second order component exhibits pronounced east-west longitude difference to the zero valued geomagnetic declination line, and these east-west longitude differences are coincidently consistent with plasma drift velocity caused by thermospheric zonal wind; the third order component demonstrates latitudinal variations possibly influenced by plasma drift velocity caused by thermospheric meridional wind. Results of the this paper are useful for understanding the physics mechanism of the ionospheric variations.
Observation Of Sporadic Sodium Layer Over Haikou Of China In 2010
Zhang Tiemin, Wang Jihong, Liu Hanjun
2015, 35(5): 566-573. doi: 10.11728/cjss2015.05.566
Abstract(1260) PDF 946KB(1382)
Sodium lidar observations of Sporadic Sodium Layers (SSL) in 2010 at a low-latitude location (Haikou, China, 20.0°N, 110.3°E) are reported in this paper. The wavelength of the dye laser is set to 589nm by a sodium fluorescence cell. The energy and divergence of the beam are about 45mJ and 1mrad, respectively. The repetition rate of Nd:YAG laser is 30Hz. The backscattered fluorescence photons from the sodium layer are collected by a telescope with a 1000mm diameter primary mirror. From 38 SSLs events detected in about 458h of observation, an SSL occurrence rate of 1 event every 12h at our location was obtained. This result, combined with previous studies at a mid-latitude location (Wuhan, China, 31°N, 114°E), and compared with the SSLs at a low-latitude location (Brazil, 23°S, 46°W), reveals that the SSL occurrence can be frequent at a low-latitude location of Haikou, China. The profiles of a peak density of the SSL were very spatial symmetry on Dec. 30, 2010. With respect to the correlation with sporadic E, the ionosphere data obtained by an ionosonde operated at Danzhou, China (19.5°N, 109.1°E), about 160km southwest of Haikou lidar station, have been examined. By statistical analysis of 13 events, when simultaneous SSL data and ionograms are available, a considerable correlation was found between sporadic E layers and the SSLs. The sporadic sodium layers have average downward vertical velocities at Haikou, China.
Design And Testing Of An Ionospheric Doppler Receiver
Chen Yanlong, Zhang Yuannong
2015, 35(5): 574-580. doi: 10.11728/cjss2015.05.574
Abstract(746) PDF 963KB(1340)
As an important part of the Earth space environment, ionosphere variations have a very important impact on the daily life and activities and living of human beings. Ionosphere disturbance always manifests itself as a complex temporal and spatial variation process. Therefore, to strengthen the real-time monitoring of ionosphere disturbance and study the physical mechanism of the ionosphere disturbance is an important topic of space physics. Software defined radio technology is deployed to design an ionosphere Doppler receiver. Consisting of PXI bus and digital chips including DSP and FPGA, the receiver uses GPS as a module to synchronize time and frequency. Its system parameters can be set flexibly. Receiving high frequency signals from the Shanxi astronomical observatory, the receiver can get real-time ionosphere Doppler shift information caused by ionosphere disturbance. A signal processing software using MATLAB language processes the received high frequency signals. Observations show that the receiver is proved to be an effective means to obtain the ionosphere disturbance information in different spatial scales by data processing since it can analyze the change in Doppler shift of the echo signal of an ionosphere as time changes.
Analysis Of High Energy Electron Environment Properties On The Middle Earth Orbit
Yang Xiaochao, Zhu Guangwu, Fu Yang, Sun Yueqiang, Liang Jinbao, Jing Tao, Chang Zheng, Shi Chunyan
2015, 35(5): 581-587. doi: 10.11728/cjss2015.05.581
Abstract(1003) PDF 5470KB(1661)
By utilizing data obtained on Chinese satellite in the middle Earth orbit from solar activity descending phase to solar activity ascending phase, the properties of high energy electron environment in the middle Earth orbit are analyzed, such as spatial distribution, flux intensity, temporal variations, and response to geomagnetic storms. The investigating results indicate that the spatial distribution of high energy electron in the middle Earth orbit is stable; the fluxes of electrons decrease with energy increasing; the high energy electron environment is a dynamical system which disturbs evidently on different timescales; the evolvement of this system is stimulated by geomagnetic storms, but the correlation between the evolvement and the storms is nonlinear.
Chang'e-3 Lander's Scientific Payloads Test
Jia Yingzhuo, Dai Shuwu, Wang Lei, Liu Mingjie
2015, 35(5): 588-595. doi: 10.11728/cjss2015.05.588
Chinese Chang'E-3 spacecraft includes a lander and a robotic rover. The scientific objectives of the Chang'E-3 mission were to examine the texture, mineralogy, and structure of the local lunar terrain; to determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites; and to operate an ultraviolet astronomy camera on the Moon and image the distribution of He+ in Earth's plasmasphere by detecting its resonantly-scattered emission at 304 Å. Four kinds of scientific instruments are chosen as the payloads for Chang'E-3 lander, which include topography camera, lunar optical telescope, extreme ultraviolet imager and descent imager, etc. This paper mainly introduces Chang'E-3 lander's scientific payloads ground test, including test schemes and results.
Dangerous Conjunction Analysis Of Space Objects Based On Random Point Simulation Method
Cang Zhongya, Xue Bingsen, Cheng Guosheng, Zhu Xiaolu
2015, 35(5): 596-602. doi: 10.11728/cjss2015.05.596
Abstract(1132) PDF 1355KB(1379)
The position, velocity and prediction error information of space objects can be obtained by using two-line element set and SGP4 model. Based on these results, a new method to calculate the collision probability is proposed, which is called the random point simulation method. There are two differences when this new method is compared with the traditional method of integral in conjunction plane. One is to concern the effects of error bias, which means the error ellipsoid no longer center on the predicted position. The other is to focus on simulating all possible conjunction situations and do not ignore error in each direction. The feasibility of this method is verified by analyzing cases, and results show that the maximum collision probability no longer appears in the time of closest approach because the error bias is not zero. Meanwhile, simulation results indicate that the positional relationship between two objects has also deviation in the direction of relative velocity, so the collision probability by random point simulation method is smaller than that of integral method. Different collision warning methods correspond to different warning thresholds, and 10-6 can be determined as the warning threshold of random point simulation method based on the case analysis in this paper.
Attitude And Translation Control For Spacecraft To Approach To A Tumbling Non-Cooperative Object During The Final Phase
LIU Hailong, HAN Xu, SHI Xiaoping
2015, 35(5): 603-610. doi: 10.11728/cjss2015.05.603
Abstract(891) PDF 940KB(1358)
This paper considers the process of motion synchronization of chaser satellite and target satellite in space. The problem of final approach to a non-cooperative tumbling target is studied in this paper. The accurate orbit and attitude dynamics model of two relative motion spacecrafts with arbitrary eccentrics is established. In order to insure the safety of final approach, the traditional linear synchronization rotating approach strategy is improved by designing an exponential decay reference trajectory to decay relative velocity with decreasing relative distance and reach zero when the chaser is hovering. The proportional-derivative-decouple relative attitude controller and relative orbit controller is proposed. The simulation shows the process of the relative velocity of the chaser decay to zero. The stability of the control law is demonstrated through Lyapunov analysis and effectiveness of controller is verified by the numerical simulation.
Using Tracking And Data Relay Satellite For Low And Middle Earth Orbit Satellite Launch And On-Orbit Control
Li Yuheng, Sun Haizhong, Zheng Jun
2015, 35(5): 611-617. doi: 10.11728/cjss2015.05.611
Abstract(1262) PDF 707KB(1511)
With successful minimization of the user terminals of Tracking and Data Relay Satellite (TDRS) and the development in higher gain and wider half-power beam of antennas, especially the upcoming multiple-access ability of TDRS, it is highly possible to control low and middle earth orbit satellites and rocket launch merely by TDRS. This paper analyzes the advantages of TDRS controlling spacecrafts, supporting rocket lunch and strengthening response ability to the emergency control call for on-orbit satellite management. The results show that only a few TDRS with multiple-access antenna could control all China low on-orbit satellites. Although a TDRSS' user terminal is generally required to install an omni-antenna to response any emergency control call, this paper proposes a method that even a satellite equipped with a TDRS user terminal of a directional antenna can response to emergency control. It will further improve the low orbit satellite control's efficiency.
Research Of Viscous Fluid Damping Isolator Used In Space Telescope
CHEN Tao, XU Zhenbang, WU Qingwen, CHEN Liheng
2015, 35(5): 618-625. doi: 10.11728/cjss2015.05.618
Abstract(1019) PDF 3091KB(1711)
In order to suppress infrared telescope astronomy disturbance caused by the satellite payload, it is needed to design vibration reduction device for the telescope. Therefor a viscous fluid damper used in space is designed, which could be sealed reliably and adapted to the space environment well. Firstly, a damping calculation model based on the theory of fluid mechanics is built. Then, the structure of the damper is designed, and parameters of the spring sheet which was a core component belonging to the damper, are optimized. A set of prototype was manufactured, and a finite element model of the vibration isolation system was created to get the system's first two models. Finally, the simulation results are compared with the experimental results. According to the analysis results, it can be seen that the damper's stiffness characteristics and damping characteristics can meet the design requirement. The theory analysis results coincide with the experimental results, which proves that the finite element model is precise and the prototype has guidance value in engineering design.
Pdqg-R Subdivision Mode And Encoding In Heliocentric Coordinate System
Hu Yasi, Shi Peng, Duan Ran
2015, 35(5): 626-633. doi: 10.11728/cjss2015.05.626
With the quick increase of space data, in order to meet the higher demand of data visualization and data access efficiency, reasonable data organization and management is needed. Based on the existing 2D subdivision models, for the ecliptic plane and meridian plane which are over the Sun centroid, a new model, PDQG-R (Plane Degradation Quad-Tree Grid), is put forward. Encoding scheme of grids is also given. Taken solar wind data as an example, the model not only resolves the problem that grids near to heliocentric are too dense, but also meets the requirement that resolution in radius is not equal to that in longitude and latitude. Besides, it provides hierarchical multi-resolution data, and can support the organization and management of massive space data effectively.
Asynchronous Differential Space-Time Block Codes Based On Spreading Techniques Over Satellite Communication
ZHANG Jianwu, ZHANG Qianhua
2015, 35(5): 634-640. doi: 10.11728/cjss2015.05.634
In satellite cooperative communication system, delay errors caused by different delay between different channels with large scale relays brings loss of BER. Traditional solutions generally use differential codes to estimate channel parameters dynamically in the receiving end of a satellite communication system. In this paper, orthogonal codes in spread spectrum technique systems are used to distinguish signals from different relay satellites. In this paper, spread spectrum codes table is used to extract signals from different relay satellites, then to carry out a space-time decoding. As can be seen in simulation results, differential space-time blocks codes with spreading has a better BER than the one without spreading. It solves the problem of random delay, so that the receiving end of the channel should not to estimate channel parameter. The complexity of the receiving end is significantly reduced.
Design Of Optical System And Analysis Of Precision Of Star And Earth Simulator
Sun Gaofei, Zhang Guoyu, Liu Shi, Wang Lingyun, Gao Yujun
2015, 35(5): 641-646. doi: 10.11728/cjss2015.05.641
In order to realize the ground calibration and accuracy testing of sensor, a star and Earth simulator is needed to achieve the star simulation accuracy of less than 10" and Earth simulation accuracy of 0.05°. The simulator utilizes a high precision collimator and a high precision UV collimator as the projection optical system. A correction method for star position simulation error and Earth graphics simulation error is proposed to improve the simulation precision of the star and the Earth. Finally, the star angular distance is measured which accuracy is better than 10", and the accuracy of the Earth graphics is better than 0.05°. The investigation result indicates that the star and Earth simulator proposed in this paper is possible to satisfy the requirements of ground calibration and accuracy testing of the sensor.
Design Of Optical And Mechanical Structure For Lunar Simulator Based On Variable Shape And Adjustable Radiance
LIU Shi, ZHANG Guoyu, SUN Gaofei, WANG Lingyun, GAO Yujuni
2015, 35(5): 647-652. doi: 10.11728/cjss2015.05.647
To simulate the different lunar phases and ensure continuous adjustability of the radiant brightness, a new broad spectrum light and frosted glass were applied and designed in the optical system for lunar simulator with the shapes and radiance being able to be adjusted. According to the engineering demand and index requirements of the optical system, three major design aspects are addressed, including the high reliability and maintainability for broad-spectrum light, heat dissipation in lunar simulator for long working hours, and bearing of the main frame under different working conditions. By designing a reasonable machine structure, and through the structure itself with the matrix arrangement of 48 axial flow fans, an effectively cooling air duct is established. Deformation and temperature were calculated by the finite element software ANSYS. The results showed that the displacement deformation reached 0.33mm and stress deformation reached 0.02MPa at the temperature of 20℃; when the main frame was in the temperature field between 20℃ and 65℃, the maximum displacement deformation reached 13.30mm and maximum stress deformation is 97.90MPa, and the amount of this deformation is very small in considering of the mechanical structure dimensions and weight of the lunar simulator.