2008 Vol. 28, No. 6

Display Method:
Numerical Simulation for the 16 August 1999 EUV Brightenings
SHA Xiaoming, FAN Quanlin
2008, 28(6): 507-512. doi: 10.11728/cjss2008.06.507
Abstract(2289) PDF 764KB(1132)
The 16 August 1999 EUV brightenings are numerically simulated by a third-order upwind compact scheme, basing on the TRACE observation. The present simulation can give a possible explanation to its formation and evolution. The numerical results show that the initial reconnection jets at around X-point are responsible for the occurrence of EUV brightening. The strong and superposed ejections caused by the first and second coalescence of magnetic islands are possibly related to the lifted material which initially appeared as absorption features and Later EUV-emitting structures respectively. The bi-directional reconnection jets may correspond to the lifted material that either continued to move upward along the apparently open field lines or fell down to the surface.
Analysis on the Interplanetary Causes of Moderate Geomagnetic Storms During the Whole 23th Solar Cycle
Tong Yanan, Liu Siqing, Gong Jiancun
2008, 28(6): 513-521. doi: 10.11728/cjss2008.06.513
Abstract(2425) PDF 934KB(1128)
The interplanetary causes of 183 moderate geomagnetic storms ( -100 nT < Dst ≤ -50 nT) and the their distributions during the solar cycle 23 (1996--2006) are identified. Moreover, the solar cycle dependence of the interplanetary source of moderate storms was analysed comparing with that of intense geomagnetic storms (Dst ≤ -100 nT). It is found that: (1) Corotating Interaction Region (CIR) and Interplanetary Coronal Mass Ejection (ICME) are equal importance in moderate storms, moreover, in the associated ICMEs, magnetic cloud and non magnetic cloud ICME are also equal importance, while the combined sheath and ICME fields (Sh+MC and Sh+nonMC) are more important in associated moderate storms; (2) the yearly distribution of moderate storms in solar cycle 23 shows that double-peak and double-valley distribution, with the first peak appearing at solar maximum 2001 and the second peak at declining phase 2003, and the double-valley appearing at solar minimum 1996 and 2006, while the moderate storms distributed on average during the other years; (3) during the maximum phase, ICME is the main interplanetary source of moderate storm, and CIR is responsible by a larger number of moderate storms during the rising and declining phase, moreover, the number of moderate storms in the declining phase is almost two times that of the rising phase. However, for intense storms, ICME is almost the most important source during the whole solar cycle 23.
Research on the Spatial Density Algorithm of Space Debris
Li Can'an, Pang Baojun
2008, 28(6): 522-530. doi: 10.11728/cjss2008.06.522
Abstract(3447) PDF 1124KB(1228)
With the development of human's space technology and activities, the space debris environment is getting more and more deteriorated, which results in a great threat to the safety of on-orbit space vehicles. Due to the threat, it's necessary to establish an engineering model for the space debris environment to access space vehicle's impact risk. Since the spatial density is the most important component in an engineering model of space debris environment, this paper is devoted to study the algorithm of the spatial density of space debris. By introducing the orbital parameters, the paper firstly gives the conception and the mathematical definition of spatial density of space debris. According to the definition, construction of the spatial density is carried out. With the aid of probability theory and orbital mechanics, the paper theoretically derives a general analytical expression for the spatial density. Afterwards, simplification of the general expression is discussed by introducing some assumptions, i.e., uniform distribution over right ascension of the ascending node and over the perigee argument, independence of orbital parameters and of spatial coordinates. The result is a more simplified expression of the spatial density, which is suitable for computation. It turns out that the SDPA model's algorithm is just a particular case of the paper's general expression. To enlarge the simplified result's for application, the paper proposes the classification method. To verify the paper's result, application to the Two-line elements is presented, which validates the paper's result. The application also shows that the classification method can help to improve accuracy.
Space Environment Background Calculation for HXMT
LI Gang, WU Mei, ZHANG Shu, JIN Yingkang
2008, 28(6): 531-540. doi: 10.11728/cjss2008.06.531
Abstract(3145) PDF 2283KB(1182)
The Hard X-ray Modulation Telescope (HXMT) is a broad band X-ray (1~250 keV) astronomical satellite. Its core payload, High Energy X-ray Telescope (hereafter HE), operates in the hard X-ray (20~250 keV) range. HXMT/HE will perform an all-sky hard X-ray survey and focused observations with the highest sensitivity. To achieve a high sensitivity, it is important to reduce the background that caused by the interactions between the satellite and the space particles. With reference of documents and up-to-date observation data which describe the background of near earth space, a suit of self-consistent data and formulas related to background particle of near earth space are sorted out. The background of HXMT and its variation with time and orbit are also given through simulation calculation with software Geant 4.
Derivation of GPS-TEC and Instrumental Biases in the Equatorial Anomaly Region
GAO Wei, MA Guanyi, CHEN Yanhong, SHEN Hua, LI Jinghua, HUANG Wengeng, LI Zheng
2008, 28(6): 541-546. doi: 10.11728/cjss2008.06.541
Abstract(2855) PDF 1168KB(1208)
Based on least-square technique, this paper presents a method to derive GPS-TEC and instrumental biases of GPS observation in equatorial anomaly region. Applying the method to the data from 4 GPS receivers located at Fuzhou, Xiamen, Guangzhou and Nanning in 2006, the TEC is obtained for 48 meshes with size of 3°× 1° in longitude and latitude covering an area of 20~28°N, 105°~123 °E. The instrumental biases are stable in the whole year. The satellite biases are close to those published by Center for Orbit Determination in Europe. This method can be used to study the ionosphere in equatorial anomaly region.
Tidal Variability Observed by MF Radar and Comparison with GSWM Model
LIU Xiao, XU Jiyao, YUAN Wei, JIANG Guoying, MA Ruiping
2008, 28(6): 547-554. doi: 10.11728/cjss2008.06.547
Abstract(3246) PDF 925KB(1208)
The tidal variabilities are studied by using the data from the 14th July to 14th August in 2006, observed by the 3 MHz and narrow beam MF radar located at the Andoya Rocket Range (69.14ºN, 16.02ºE). The results indicate that, the intensity of the zonal and meridinal components of the diurnal and semidiurnal tides has experienced the process of weak to strong and again to weak in the height range 78~94 km. This shows that, the new tides may be produced due to the instability induced by the interactions between tides and other waves during the upward propagation of tides, and again the new tides propagated upward stably. These phenomena may also be caused by the momentum deposition due to the breaking gravity waves or other waves. The tidal amplitude varies not only with increasing height, but also with time evolution. The variability of the diurnal tidal amplitude is very strong and varies by a factor of 3 in some days. Based on the recent results, the gravity waves instability and breaking are one of the causes to induce the tidal variability. Furthermore, The comparative results between the observation and GSWM-00 model shows that, the model can forecast results for the amplitude and phase of the diurnal tide are very good, but it isn't very ideal for the semi-diurnal tide's.
Atmospheric Radiowave Propagation Effects on Spatial Resolution of Spaceborne Synthetic Aperture Radar
ZHAO Hongmei, JIANG Changyin
2008, 28(6): 555-559. doi: 10.11728/cjss2008.06.555
Abstract(2154) PDF 642KB(935)
Using the theory of synthetic aperture and atmosphere refractivity, the formulas of the azimuth resolution atmospheric error for spaceborne synthetic aperture radar are derived in this report. Using ionospheric electron density profiles and the lower atmospheric refractivity profiles of different time and places, the azimuth resolution is calculated for different frequencies. Simulation results are discussed and some conclusions are summarized that the atmospheric error of azimuth resolution is at millimeter level, and the absolute value will be reduced as frequency increases.
Analysis and Simulation of Characteristics of Space Objects for Space-borne Optical Sensor
ZENG Dexian, DU Xiaoping
2008, 28(6): 560-566. doi: 10.11728/cjss2008.06.560
Abstract(2518) PDF 998KB(1158)
The characteristics of space objects are very important for the space-borne optical sensor. This paper analyzes the characteristics of distribution and geometry of the space objects, and summarizes the reflectivity of major materials used by satellite. Visible light scattering characteristic of the space objects are discussed specially. Firstly, solar radiation is calculated. Secondly, radiation luminescence calculation models of the two basic diffuse reflection surfaces of satellites are established. The simulation program of optical characteristic of space object is proposed. The simulation system of visible light scattering characteristic of space objects is set up. The simulation system can change the observation distance, photometric magnitude and the sun light phase at real time. Then two validate methods are derived for it is difficult to get real observation data. These validate methods are preferable methods for analyzing space-borne optical sensors. At last, the characteristics of space objects observed by space-borne optical sensor is depicted. This paper provides an effective reference to space-based observation system design.
Thermal Analysis of Deployable Truss Antenna in Orbit
ZHANG Huifeng, GUAN Fuling, HOU Guoyong
2008, 28(6): 567-572. doi: 10.11728/cjss2008.06.567
Abstract(2318) PDF 822KB(989)
Using conduction-radiation theory, considering the orbit of the antenna, temperature fields of a deployable truss parabolic antenna in orbit can be calculated at different local time. Using Visual Fortran, a finite element program based on the theory above is built, and temperature fields of antennas in different orbits can be calculated at different local time. The result is useful to thermal displacement analysis and thermal control design.
Numerical Analysis of the Autonomous Navigation Principle and Method of Space Vehicle Based on X-Ray Pulsars
SUN Shouming, ZHENG Wei, TANG Guojian
2008, 28(6): 573-577. doi: 10.11728/cjss2008.06.573
Abstract(2752) PDF 713KB(984)
The method of autonomous navigation based on X-ray pulsars is steady, credible and with high- accuracy. It is an important approach in the spacecraft navigation field. In this paper, firstly, the algorithms of autonomous navigation based on X-Ray pulsars are introduced; secondly the model of the extended Kalman filter which is used in the autonomous navigation based on X-Ray pulsars is established; thirdly, taking the geosynchronous orbit for example, the accuracy of navigation with different initial error, different incline of orbit, different eccentricity of orbit and different orientation error of the pulsars are simulated. With 0.001 second accuracy of pulsar orientation and 0.1 accuracy of the time of pulse arrival, from the results, it can be seen that the position accuracy of the geosynchronous orbit can reach 1\,km, and the accuracy of navigation is immune with initial error. It is also shown that the orientation of pulsars, the accuracy of the time of pulse arrival, the position of the orbit plane and the eccentricity of orbit are the main factors which influent the accuracy of navigation.
Auxiliary Trellis Based Viterbi Decoding Algorithm Research of 4D-8PSK-TCM
HUANG Yu, a, XIONG Weiming, SUN Huixian
2008, 28(6): 578-583. doi: 10.11728/cjss2008.06.578
Abstract(3034) PDF 916KB(1754)
Four-Dimensional 8PSK Trellis-Coded Modulation (4D-8PSK-TCM) is recommended as an efficient coded modulation standard for the Earth Exploration Satellite Service (EESS) 8025-8400 MHz band by the Consultative Committee for Space Data System (CCSDS). The advantage of 4D-8PSK-TCM is that coding gains can be achieved without expanding the bandwidth relative to the un-coded signal set. In this paper, the 4D-8PSK-TCM system with the modulation efficiency of 2.5 bit/symbol and its Viterbi decoding are presented and the Viterbi decoding algorithm is implemented on Matlab Simulink. During the algorithm implementation, an auxiliary trellis is introduced to reduce greatly the number of computations of metrics of each path. In this way, there are only 64 comparisons to compute the metrics in comparing with the 2032 comparisons required in a directly computing approach.
Study on Actuators of Magnetic Suspension Platform Under Microgravity Environment in Space
CHEN Jinxin, WANG Yu
2008, 28(6): 584-591. doi: 10.11728/cjss2008.06.584
Abstract(2402) PDF 1520KB(1264)
To fulfill the microgravity level of scientific experiment payloads in space lab, vibration isolation performance of platform with experiment payloads is required. And the actuator of platform under control needs to produce active force timely to restrain the vibration of platform. This paper firstly presents the elementary parameters of actuator. Various structural forms are designed, based on the theory of magnetic suspension. Finite element simulations about magnetic circuit and coil design of the actuator are given based on various forms. To provide basis for the detailed design of actuator, the strong points and shortcomings of each form are concluded through comparisons. The parameters for comparisons mainly involve the mass, the air gap, the maximum force, the current density, the supply power, and the bandwidth of the actuator. The result of comparisons shows that each form is available due to different working conditions and system demands.
Characteristic Study on the Porous Reservoir of Liquid Lubricant in Space
WANG Yang, LIU Qiusheng, YAN Jiaping
2008, 28(6): 592-596. doi: 10.11728/cjss2008.06.592
Abstract(1978) PDF 879KB(1160)
Many moving mechanical assemblies for space mechanisms rely on liquid lubricants to provide performance. However, the loss of lubricant due to space environment may results in some moving mechanical assemblies don't work before the end of mission. So lifetime, many methods are applied to supply lubricant, one of these is porous reservoir. Porous reservoirs are widely used in small space mechanisms for their small volume, simple structure and low cost. They are desirable to maintain film thickness levels and oil distribution, so many researchers paid more attention to them. Centrifuging and heating can come into being lubricant transportation in reservoir. In this paper, the rule of lubricant transportation is analyzed on the influence of centrifuging and heating. Two experimental fixtures are designed to study the rule of lubricant transportation in porous reservoir.