Table of Content

    15 March 2013, Volume 33 Issue 2 Previous Issue    Next Issue
    Flow field prediction of an orbiter entering the Mars atmosphere
    LÜ Junming, Cheng Xiaoli, Wang Qiang
    2013, 33 (2):  129-134.  doi: 10.11728/cjss2013.02.129
    Abstract ( 1907 )   PDF (1168KB) ( 1185 )   Save

    Based on the hypersonic entry in the Entry-Descending-Landing procedure, the three-dimensional Navier-Stokes equations are solved by a parallel code to analyze the flow field structures, aerodynamic characteristics and their variation patterns of the Mars Science Laboratory entering the Martian atmosphere with and without the chemical reaction models. The analysis shows that parameters of the thermal dynamics and the transportation have an effect on the position and intensity of the shock wave. As a result of the chemical non-equilibrium effect, the shock layer is strongly compressed, the stagnation pressure decreases and the maximum temperature behind the shock is highly reduced where large number of CO2 is dissociated. Results of the streamlines on symmetric plane and in space reflect the complicated three-dimensional separation flows in the wake.

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    Electrostatic transportation of lunar dust: a review
    Gan Hong, Wang Shijie, Li Xiongyao
    2013, 33 (2):  135-142.  doi: 10.11728/cjss2013.02.135
    Abstract ( 2366 )   PDF (548KB) ( 1326 )   Save

    Electrostatic levitation and transportation of lunar dust had been one of the most interesting and controversial problems since the Apollo era. It is not only significant clues to study the evolution of lunar surface material, but also a key factor which should be considered in lunar mission. On lunar surface, the dust grains are electrostatically charged by electron deposition, photoemission, and secondary electron emission. With the charge processes, an electrostatic field might be formed on lunar near-surface. As a result, dust grains could be lifted. However, the electrostatic levitation and transportation process of lunar dust grains are still not clear. Shortage in comprehension of electrostatic properties of lunar dust grains, simulation of electrostatic levitation and transportation, and landing detection of lunar dust environment might be the main factors which limit the further knowledge of electrostatic levitation and transportation of lunar dust grains. To satisfy the need of lunar science and future lunar missions, development of lunar dust simulant, measurement of electrostatic properties of lunar dust, simulation of electrostatic levitation and transportation, and detection of lunar dust environment are important aspects in the study of lunar dust in the future.

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    In-flight Experiment of Solar Wind Ion Detectors on Chang'E-1 and the Solar Wind Near the Moon
    WANG Xinyue, ZHANG Aibing, KONG Linggao, ZHANG Xianguo, REN Qiongying, WANG Shijin, H. Réme
    2013, 33 (2):  143-150.  doi: 10.11728/cjss2013.02.143
    Abstract ( 2088 )   PDF (747KB) ( 1194 )   Save

    It's the first time for the two scientific instruments of Solar Wind Ion Detectors (SWID-A/B) on Chang'E-1 to explore the plasma environment in the 200km lunar polar orbit. SWIDs are primarily developed for the scientific objectives of measuring the Moon-plasma interactions, and deducing the solar wind bulk speed, density and temperature. SWIDs observe the ions fluxes which include the information of solar wind speed, density and temperature. In this paper, the algorithm of deducing the solar wind bulk speed, density and temperature by the observation results of SWID-A/B is shown. By simulating the solar wind ions injecting to the SWIDs, the algorithm is validated. The characteristics of solar wind near the Moon are studied. During the period of the Sun disturbing comparatively quiet in solar minimum, it is found that the similar trend of variation is maintained when the solar wind go through the interplanetary to the Moon. Whereas the solar wind ions speed and density are the same to those of the upstream interplanetary solar wind, the solar wind temperature near the Moon is 10^3K higher than that of the upstream interplanetary solar wind.

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    Forecasting geomagnetic activity Kp index of space environment with Hp
    Song Dan, Xue Bingsen, Cheng Guosheng
    2013, 33 (2):  151-157.  doi: 10.11728/cjss2013.02.151
    Abstract ( 1863 )   PDF (579KB) ( 1211 )   Save

    Geomagnetic disturbance can cause a series of changes for near-Earth space environment, including the ionosphere and magnetosphere, and Kp index is the important reference index for disturbance of space weather. Hp component data monitored by GOES-8 satellite of geosynchronous orbit was used in this paper. By analyzing statistical relation between Kp index and Hp component width of fluctuation, it is shown that the change of Hp component and Kp index have good correlation. Based on the change of Hp component, Kp index in the same time interval is calculated, and then Kp index forecast model is established by means of regression analysis and RBF neural networks. Monitoring results show that the prediction method has certain validity and practicability especially that Kp index calculated by artificial neural networks is quite consistent with its measured values. By using this method, it is able to forecast geomagnetic disturbance quickly, and to provide reference in time for space weather guarantee not relying on the data from geomagnetic diction. In addition, China is going to launch FY-4 satellite, on which a magnetic field detector will be carried. Hence, this research will provide the foundation for application using FY-4 data in the future.

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    Effect of ionospheric irregularities on GPS performance
    Li Jinghua, Ma Guanyi
    2013, 33 (2):  158-169.  doi: 10.11728/cjss2013.02.158
    Abstract ( 2945 )   PDF (795KB) ( 1133 )   Save

    Ionospheric irregularities may cause the amplitude and phase fluctuation of the trans-ionospheric radio signals, known as ionospheric scintillation. It can increase the tracking error of Global Positioning System (GPS) receiver, degrade the positioning accuracy and precision, and even cause loss of lock. This paper is a review of the effect of ionospheric irregularities on GPS receiver's performance. First, the parameters used to describe the ionospheric irregularities and the GPS receiver tracking loops are introduced. Based on the scintillation signal model, the results on how the ionospheric scintillation affects the performances of carrier and code tracking loops are summarized. Then the positioning errors of single frequency and dual-frequency GPS receivers are analyzed and discussed under realistic ionospheric scintillation environments. Finally, possible suggestions to future research topics are given.

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    Study on high energy electron flux enhancement events and whistler chorus wave
    He Tian, Liu Siqing, Zheng Jinlei, Gong Jiancun
    2013, 33 (2):  170-175.  doi: 10.11728/cjss2013.02.170
    Abstract ( 2245 )   PDF (751KB) ( 1292 )   Save

    The local acceleration mechanism is one of the crucial factors for the high energy electron flux enhancement events in the outer radiation belt. There are two substantial preconditions for this acceleration mechanism. The first and the most important one is the presence of enough low energy electron (on the order of tens to hundreds of keV), so-called seed electron; the other is the enhancement of plasma waves including whistler chorus waves which can contribute to the electron acceleration by wave-particle interaction. Geomagnetic field data observed by Memambetsu (L=1.57) observatory are used to extract Pi1 pulsation during 2004-2006. The linear correlation between Pi1 pulsation duration and seed electron flux (LANL 50~225keV) is greater than 0.7, which indicates that the Pi1 pulsation duration is a good indicator of seed electron flux. After the investigation of three magnetic storms events in 2005, the evidence had been found for acceleration of seed electrons to high energies by whistler chorus waves and the positive correlation between the chorus waves' spectral density and high energy electron flux.

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    A high efficiency orbit screening method for space debris collision prediction
    Yang Zhitao, Liu Lin, Liu Jing, Zhang Yao, Cheng Haowen
    2013, 33 (2):  176-181.  doi: 10.11728/cjss2013.02.176
    Abstract ( 2075 )   PDF (451KB) ( 842 )   Save

    In general, there are three prefilters for orbit screening, namely height prefilter, geometrical prefilter and time prefilter. The algorithms of the last two prefilters are slightly different in literatures. The Methods offered by references can hardly be competent in fast collision warning for three days. In this paper, a new orbit screening method is introduced, which can highly improve the screening efficiency and hence reduce the computation time for space debris collision predictions. In this method, the time prefilter algorithm is improved by giving more consideration to the first order perturbation of the target orbit. After that, a distance prefilter is added, which screens through the minimum distance between two objects. As a result, the ratio of objects excluded from the candidates can be improved from about 99% to 99.97%. The correctness and high efficiency of this method got verified through the calculation of the measured data. Therefore, this method can be treated as a theoretical basis for three-day fast collision warning.

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    Orbital evolution of high area-to-mass ratio debris under the influence of radiation pressure and gravitational effects
    Cheng Haowen, Tang Jingshi, Liu Jing, Liu Lin
    2013, 33 (2):  182-187.  doi: 10.11728/cjss2013.02.182
    Abstract ( 2551 )   PDF (400KB) ( 1071 )   Save

    Dynamical evolution of high area-to-mass ratio debris in high orbit (a > 10000km) is analyzed, especially the geosynchronous orbit. The analysis provides a formulation of eccentricity variation by Kozai's method. According to the formulation, for GEO debris with inclination bigger than the critical inclination (63°26'), large eccentricity during evolution can be caused just under the influence of third body gravity and J2 term effect. And for debris with extremely high value of area-to-mass ratio, under the influence of radiation pressure and J2 term, resonant phenomenon occurs when the secular rates of the direction of the eccentricity vector caused by J2 term effect and the direction of the solar ecliptic longitude are close, and there is a relationship between the initial direction of the perigee and maximum value of the eccentricity during the evolution.

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    Modeling and simulation of visible light scattering properties of spatial object using STK
    Li Yanjie, Jin Guang, Zhong Xing
    2013, 33 (2):  188-193.  doi: 10.11728/cjss2013.02.188
    Abstract ( 1853 )   PDF (565KB) ( 1161 )   Save

    For supplying the space-based optical observation system designer with referenced data, equivalent magnitude model of spatial object is established using STK. First, the visible light scatting characteristics of spatial object surface cell is analyzed by using BRDF five-parameter model. Second, combined with the characteristics of object shape and material property, the configuration model of space target is built, and formulation of equivalent magnitude computing model of space object is carried out by analyzing every single surface cell. Last, Satellite Tool Kit (STK) was used to provide relationship among sun, space object and observation satellite to simplify the solving of the formulation, and then, a new magnitude computing model based on STK is established. It was verified with one example and some analyses. The result displays that the new model is much more precise than the diffuse one. Besides, the results show that the best observing time and the corresponding magnitude can be easily solved with STK.

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    Autonomous orbit and attitude determination including time prediction based on XNAV and ultraviolet sensor
    Yang Chengwei, Zheng Jianhua, Gao Dong
    2013, 33 (2):  194-199.  doi: 10.11728/cjss2013.02.194
    Abstract ( 1904 )   PDF (450KB) ( 961 )   Save

    In order to improve the autonomous navigation ability of deep space spacecraft, the X-ray detector and ultraviolet sensor were applied simultaneously. The attitude angles and errors of time of pulse arrival of pulsars were measured by X-ray detector, and simultaneously the central body's barycenter line-of-sight vector, distance between spacecraft and the barycenter, and the attitude angles were measured by ultraviolet sensor. The state of the integrated navigation system includes position and velocity vectors in inertial coordinate system, attitude angles and clock error. The Federated Extended Kalman Filter (FEKF) was applied to estimate the state of the navigation system. Simulation results in Mars orbit demonstrate that this method can fulfill orbit determination, attitude determination and clock time prediction simultaneously. Moreover, this integrated navigation system can provide high navigation precision and predict clock time effectively.

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    Design of dynamic star simulator based on LCOS optical splicing technology
    Liu Shi, Zhang Guoyu, Sun Gaofei, Wang Lingyun
    2013, 33 (2):  200-206.  doi: 10.11728/cjss2013.02.200
    Abstract ( 2021 )   PDF (632KB) ( 1836 )   Save

    The technical scheme of a dynamic star simulator based on the LCOS optical splicing technology is proposed in order to meet the demands of a star sensor in spacecraft engineering. Optical system parameters of the simulator are calculated by the specification of a LCOS. The two LCOS optical splicing principle and scheme are introduced in detail, method of the dynamic star map realization is given, and its error is analyzed. The simulating results indicate that field of view is of 10.2° × 10.2°, star magnitude simulated is of 2~6.5, the single star field angle is less than 20", and the star diagonal distance error is less than 22". The experimental result can satisfy the system requirements of big field of view, wide magnitude range and update rate, etc.

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    Wideband design and thermal deformation analysis of space-borne large waveguide slots array antenna in Ku-band
    Liu Shihua, Wang Hongjian, Hao Qiyan, Yi Min, Chen Xue, Liu Guang
    2013, 33 (2):  207-212.  doi: 10.11728/cjss2013.02.207
    Abstract ( 1935 )   PDF (559KB) ( 984 )   Save

    Waveguide slots array antenna was adopted in engineering project. Though this antenna had high gain, low side lobe etc, wideband requirement was a big challenge for it. As working in the space environment, large space-borne antenna would be influenced by the thermal deformation. It was necessary to analyze the influence on electrical performance, such as radiation pattern. In order to enlarge the band, antenna was separated into four areas to feed, and the feeding point was in the center of the waveguide. Special loads were exerted in waveguide H-T and E-T junctions to meet impedance matching. An approximate computation method was provided to analyze the influence of the thermal deformation on antenna performance. Some 8×10 slots array antennas were manufactured as the first step, and these antennas were tested in our near field testing system. The bandwidth of the Voltage Standing Wave Ratio (VSWR) below 1.3 was 340MHz, and the side lobe level was -25.9dB in E plane and -27.2dB in H plane. Measurement result indicated the availability of the designe.

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    Adaptive control based on saturated velocity filter for space-based manipulator system with bounded control torques
    Xie Limin, Chen Li
    2013, 33 (2):  213-218.  doi: 10.11728/cjss2013.02.213
    Abstract ( 1704 )   PDF (470KB) ( 2321 )   Save

    The intelligent control problem of space-based manipulator system with bounded control torques and uncertain parameters is studied. According to the system's momentum conservation and Lagrange's equation, the system's dynamics equation is established. An adaptive control based on saturated velocity filter for space-based manipulator system with bounded control torques and uncertain payload parameters is developed. The proposed control scheme overcomes the influence of the uncertain parameters on the control accuracy by using adaptive controller; limits the control torques by using hyperbolic functions, which lets the control more realistic. And in the control process, it doesn't need to measure and feed back the system's velocity signal by using the velocity filter, which makes the control simpler. The simulation validates the effectiveness of the proposed control scheme.

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    An SSD-based disk cache architecture and its application to data system of data center of Meridian Project
    Guo Qingpu, Xia Junbao, Zhong Dingkun
    2013, 33 (2):  219-224.  doi: 10.11728/cjss2013.02.219
    Abstract ( 1568 )   PDF (529KB) ( 891 )   Save

    Solid-State Drivers (SSD) are integrated in server storage hierarchy as a second tier of disk cache between DRAM and disks for caching more data from disks to meet the increasingly intensive I/O demands. Unfortunately, available state-of-art hybrid storage architectures cannot fully exploit SSDs' potentials and shorten their lifetime. In this paper, RAF (Random Access First), a hybrid storage architecture that combines an SSD based disk cache and a disk drive subsystem, is proposed. RAF focuses on improving the system performance while extending the lifetime of SSD through providing priority to caching random-access data. Random-access and sequential-access data are identified by sequence detection scheme, and they will be served by SSD and Hard Disk Drive (HDD) respectively. RAF is implemented in Linux kernel The results of experiments to apply it to the simulation and real data systems of Data Center of Meridian Project show that RAF can improve the performance by an average rate of 17% and reduce the flash wear by 53% compared with the state-of-art Flash Cache architecture.

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