2014 Vol. 34, No. 4

Display Method:
Impact of Martian Atmosphere Model Parameters on Aerodynamic Characteristics of Mars Science Laboratory
Lü Junming, Miao Wenbo, Cheng Xiaoli, Wang Qiang
2014, 34(4): 377-383. doi: 10.11728/cjss2014.04.377
Abstract(1038) PDF 2554KB(2143)
The difference between Martian atmosphere and Earth atmosphere results in the different flow field and property around the entry vehicles, and the possible change of aerodynamic characteristic on account of chemical non-equilibrium will differ from that in Earth re-entry process. The differences between Martian and Earth atmosphere include species, density and temperature. Three-dimensional Navier-Stokes equations coupling real gas model are solved by a parallel code to analyze the change of aerodynamic characteristic of Mars Science Laboratory (MSL) introduced by CO2 effect as well as the uncertainty of density and temperature in hypersonic entry phase of Entry-Descending-Landing procedure when MSL entering the Martian atmosphere. The results show that the computational data of Viking based on current Martian atmosphere model and numerical methods has a good agreement with both the flight data and LAURA results. Gas species in the model, which are mainly CO2 for Mars, have a great influence on the drag and pitching moment coefficients compared to the air model of Earth, so CO2 correction should be considered while the aerodynamic data is derived from air. Increase of the density in atmosphere model enhances chemical non-equilibrium effect, but produces no distinctness for aerodynamic characteristic; increase of the temperature improves chemical non-equilibrium effect greatly, and has a small influence on aerodynamic characteristic.
Research on the Effect of Opacity on Solar Coronal Soft X-ray OⅧ Spectral Line
Zhang Qingguo, He Jian, You Jinghan
2014, 34(4): 384-389. doi: 10.11728/cjss2014.04.384
Abstract(761) PDF 503KB(1340)
To study the effect of opacity on solar plasma X-rays in solar coronal region, using the basic theory of photon escape factor in spectral analysis, the effect of opacity on intensity ratio of solar OⅧ 1.897nm and 1.601nm spectral lines is analyzed. Under optically thick conditions, theory of the effect of photon escape factor on the intensity ratio of the solar spectral lines is discussed. In the calculation, the optically depth of OⅧ spectral lines is discussed, and finally the effective emission thickness of OⅧ ion in solar plasma is estimated. Results show that under optically thick conditions, the opacity has great effect on solar OⅧ spectral line, and the effective emission thickness of OⅧ ion is greater than that in other solar ultraviolet spectral line. This is important for plasma diagnose in solar plasma emission layer.
Pitch Angle Distribution Research of Radiation Belt Protons Based on the NOAA Data
Yang Shichao, Zhang Xianguo, Wang Yue, Wang Chunqin, Chang Zheng, Qin Murong, Wang Shijin
2014, 34(4): 390-397. doi: 10.11728/cjss2014.03.390
Abstract(899) PDF 690KB(1449)
Using the NOAA-12 satellite data, a study on the Pitch Angle Distributions (PADs) of energetic protons is performed during the quiet period of space environment in the Sun-synchronous orbit. The 90° pitch angled proton flux and the anisotropy index n are calculated based on the empirical formula. According to the n values, it's found that the distributions can be classified into three categories: 90° peaked, flattop, and butterfly. For the radiation belt protons, the three types are all existed and have a significant spatial character. The 90° peaked distributions dominate at the edge of inner radiation belt; while at the higher L values region of outer radiation belt, the 90° peaked distributions decrease obviously and the flattop distribution and butterfly distribution gradually increase with the increase of L values. For the 90° peaked distributions, relationship between the anisotropy exponent n and the L values is studied. For inner radiation belt, the n values increase rapidly with the L values increasing; for outer radiation belt, the n values decrease gradually with the L values increasing. The distributions of the radiation belt protons are also studied in two different Magnetic Local Time (MLT) regions for the 250~800keV protons. The results show that the PADs are very similar at the inner radiation belt, but have obvious differences at the higher L values region of outer radiation belt. It indicates that the PADs of radiation belt protons have little dependency on the MLT at the inner radiation belt, while have more dependency on the MLT at the higher L values region of outer radiation belt.
Long-term Ionospheric Characteristics over Urumchi
ZHAO Haisheng, WU Zhensen, XU Zhengwen, WU Jian, ZHANG Yabin, XU Bin, XUE Kun
2014, 34(4): 398-405. doi: 10.11728/cjss2014.04.398
There are important effects on the electron equipments for the variations of ionosphere, such as it can induce shortwave communications quality decline indeed interrupted, navigation signal scintilla and error increase, space craft orbit change, surface charging up and proton event etc. In a word, it is important to study ionospheric characteristic and its impaction on electronic equipments. Based on Urumchi ionospheric vertical sounders and its more than fifty years data, the daily variations, seasonal changes and long-term trends of the ionosphere over Urumchi were studied. Some meaningful conclusions are given at the end of the paper.
Modeling Study on the Coupling Effect of the Horizontal Electric Field and Winds in the Ionosphere
Xie Haiyong, Yu Tao, Wang Tiebang, Wang Le
2014, 34(4): 406-414. doi: 10.11728/cjss2014.04.406
Based on the available ionospheric dynamo theoretical model and thermospheric winds theoretical model, a coupling scheme between horizontal electric field and winds is proposed. Considering mutual feedback, the differences with and without coupling between current function and winds were analyzed. The result shows that after mutual feedback, the morphology of wind field changes less than current function. The meridional wind has a distinct change during daytime. The change at night is smaller than that of daytime. This distinct change mainly appears in mid- and high-latitude. It increases with altitude and changes little above 300km. The zonal wind is similar to meridional wind, but the change is even smaller. While the current function has a large change with coupling. The two vortexes of Sq currents both have an enhancement. With coupling, northern hemisphere vortex increases 15kA at vernal equinox which is greater than southern hemisphere. The current function at night changes little with coupling. The result shows that within the heights considered, winds control electric field obviously greater than electric field to winds. This research will deepen the understanding of the coupling mechanism between neutral atmosphere and ionospheric plasma by the momentum and dynamo equations. It improves our knowledge of the dynamic processes in ionosphere.
Wind Retrieval and Error Analysis of Ground-based Fabry-Perot Interferometer for the Middle and Upper Atmosphere
Wang Houmao, Wang Yongmei, Wang Yingjian, Li Yongzhi
2014, 34(4): 415-425. doi: 10.11728/cjss2014.04.415
Fabry-Perot Interferometer (FPI) is widely used for the wind observation of the middle and upper atmosphere. The wind retrieval algorithm of ground-based FPI has been studied globally for a few years, but a detailed analysis of retrieval precision factors has not been reported yet. Currently, in China, a few studies of FPI wind retrieval based on simulation data have been carried out. However, the studies did not make a detailed analysis of wind retrieval factors yet, such as the airglow intensity, the number of interference fringes, the fringe center and the focal length. In this paper, wind velocity retrieval of the middle and upper atmosphere is based on the ground-based observation mode (one direction at zenith and four cardinal directions with 45° zenith angle) using FPI facility from the Meridian Space Weather Monitoring Project, which included the pre-processing, the fringe center determination, the fringe radius calculation and the wind velocity retrieval. For validation, the wind parameter of 8 days (May 6-13, 2010) retrieved from observation data using ten fringes were compared with the FPI wind products with an average deviation of 2.7m·s-1 (557.7nm airglow), 5.5m·s-1 (630.0nm airglow) and 7.7m·s-1 (892.0nm airglow) respectively. Furthermore, the detailed analysis of the influencing factors mentioned above was also carried out. The results demonstrate that the stronger airglow intensity is, the higher outer fringe radius calculation precision can be obtained, and more usable fringes can be chosen. Besides, the center determination deviation with ± 2pixel (using 5 interference fringes) and ± 1pixel (using 10 interference fringes) and the focal length deviation with ± 10mm have negligible effects on wind retrieval precision, but can cause large retrieval errors when the deviations exceed the ranges mentioned above.
Research on Thermospheric Densities Derived from Two-line Element Sets
Ren Tingling, Miao Juan, Liu Siqing, Li Zhitao
2014, 34(4): 426-433. doi: 10.11728/cjss2014.04.426
Abstract(1479) PDF 617KB(1090)
Two-line Orbital Element Sets (TLEs) consist of mean orbital elements at epoch, along with the NORAD (North American Aerospace Defence Command) catalog number, international designator, epoch and additional fitting parameters. These information can be used to derive thermospheric densities through integration of differential equation for mean motion. For near-circular orbit satellites, derived thermospheric density can be seen as real density because of their stable orbit height, while for elliptical orbit satellites, thermospheric density at perigee and apogee can be different as much as several orders. So different methods were applied to derive thermospheric density according to different satellite orbits. This paper chooses CHAMP and Explorer 8 satellites, whose orbits are respectively near-circular and elliptical, as our research cases. The inverse ballistic coefficient B (B-factor) was firstly derived based on TLEs data, then thermospheric densities were derived with different methods according to different orbit characters. Finally, a comparison was made among TLEs-derived density, NRLMSISE-00 model density and observed (or reference) density. The result shows that the average error of TLEs-derived density and empirical model density with respect to observed value for CHAMP is 7.94% and 13.94% respectively, and the average error with respect to reference value for Explorer 8 is 9.04% and 14.32% respectively. This result indicates that TLEs-derived density is closer to the real density than empirical model density, and this method provides an effective way to obtain extensive and reliable atmosphere density data.
Impact of Spectral Solar Irradiance Variations on the Energy Balance of the Earth
Gao Fengling, Hua Zezhao, Tao Leren, Cui Guomin, Xu Jialiang
2014, 34(4): 434-440. doi: 10.11728/cjss2014.04.434
Abstract(1412) PDF 780KB(1522)
The total solar irradiance is usually adopted when studying the solar impact on the energy balance of the Earth at present. However, based on the Solar Radiation and Climate Experiment irradiance record, the impact of solar spectral variations on the global energy balance between December 2007 and the First Half 2010, which were in the descending and ascending solar phase respectively, is studied. The results show that the relatively larger total solar output in the First Half 2010 was mainly caused by the radiation enhancements in ultraviolet and infrared regions, with increments of 0.11% in 200~400nm and 0.05% in 760~4000nm respectively, while the radiation in visible region of 400~760nm decreased by 0.05%. According to the reanalysis of the daily ozone data from MLS Version 2.2, the concentration of stratospheric ozone also increased in the First Half 2010 at the same time. Especially, in February and March whose ultraviolet enhancements are relatively higher than those in other months, the ozone increments are also higher, with maximum of 0.6mL·m-3 and 0.62mL·m-3 respectively at altitudes of 33km and 40km. As a result, the radiation reduction in visible region and concentration increase in stratospheric ozone together contributed to the smaller solar radiation at the tropopause in the First Half 2010 as compared with that in December 2007, with the maximum reduction of 0.15W·m-2 in March 2010. The results mean that the increase in solar activity or total output may also cool the Earth-Troposphere system.
Study of Covariance Calculation in Space Objects Collision Warning
Yan Ruidong, Wang Ronglan, Liu Siqing, Liu Wei, Gong Jiancun
2014, 34(4): 441-448. doi: 10.11728/cjss2014.04.441
Collision probability is an important criterion in collision warning of space objects. The accuracy of forecast covariance calculation directly affects the accuracy of the collision probability calculation. In the paper we compute two forms of statistical forecast covariance. One is to use precision numerical forecast model and the satellite precision orbit data to forecast for a specified time period, and make statistical calculation of forecast covariance of different time period as 1~ 7 days. The other is to use SGP4/SDP4 forecasting model and TLE data to forecast, and make the statistical calculation of forecast covariance of the forecast time period as 1~ 7 days. Then the forecast accuracy through two methods with the data elements affected by orbit change and without orbit change is analyzed. Taking the 2012 risk conjunction of the satellite as example, the collision warning accuracy affected by the covariance accuracy is analyzed. This covariance calculation can provide reference for actual collision warning works.
TLE Prediction Accuracy Improvement and its Application in Collision Warning
Liu Wei, Wang Ronglan, Liu Siqing, Shi Liqin, Gong Jiancun
2014, 34(4): 449-459. doi: 10.11728/cjss2014.04.449
Two Line Elements (TLE) is the only publicly available and most complete data sets of Earth orbit objects. The prediction accuracy with SGP4/SDP4 is limited. The TLE+SGP4/SDP4 prediction error sources and improvement method with historical TLE data were analyzed. A pseudo-observation data generation method was introduced. The fitting period of TLE data and the value of Δt used in generating pseudo-observation are dependent on the orbital altitude. An effective area-to-mass ratio (A/M) determination method was obtained. GPS satellites prediction error in case of η estimated or not are also tested. The improved prediction accuracy is prominent in the application of US and Russian satellites collide event. Objects were selected and their orbit were predicted with an improved TLE-numerical method. The statistical results show that the TLE prediction accuracy is greatly improved. The application of the improved TLE and possible problems were also discussed.
Precise Orbit Determination Based on Reduced Dynamic Batch LSQ Estimation Method Using Dual-frequency GPS Observations
WANG Wenbin, LIU Rongfang
2014, 34(4): 460-467. doi: 10.11728/cjss2014.04.460
Abstract(794) PDF 629KB(1214)
The dual-frequency GPS carrier phase and pseudorange measurements have become the primary observations for accurately determining the position and velocity of satellites in low Earth orbit (LEO). Reduced dynamic batch least squares (LSQ) technique is used for LEO orbit determination using pseudorange and carrier phase ionosphere-free measurements, which combines the merits of kinematic positioning technique with pure dynamic orbit determination. In order to compensate for any unmodelling or inaccuracy of the employed dynamic model, piece-wise constant accelerations are estimated in consecutive subintervals on the basis of a precise deterministic force model in the batch LSQ method. Particularly, the paper introduces two methods for calculating the sensitive matrix related to empirical accelerations and solving for the inverse of a banded sparse matrix. GRACE-A real flight data has been used to evaluate the positioning performance of the proposed method. Positioning accuracy of less than 5cm in terms of 3D RMS was achieved. The magnitudes of empirical accelerations were all less than 40nm·s-2 in radial, along-track and cross-track directions. The extra dynamic parameters CD and CR were estimated within a reasonable range and the space-borne receiver's clock offset was linear with small periodic fluctuations.
Star Position Correction of Dynamic Star Simulator Based on Distortion Effect
Zou Yangyang, Zhang Guoyu, Sun Gaofei, Zhang Jian, Chen Qimeng
2014, 34(4): 468-473. doi: 10.11728/cjss2014.04.468
This paper presents the working principle of dynamic star simulator and the calculation of star position error. According to the working principle, a star position correction method was derived based on distortion of star simulator optical system. The correction model is established and the correction formula is deduced through correction principle. By analyzing the optical system, the fitting curve between field of optical system and correction value of star position can be attained with Matlab. After selecting the revise range by means of ascertaining the critical value of field, and revising the star position on display device using the correction formula, the original requirements were met. The proposed correction can lower the requirements of optical system designing and provide an effective method for star position correction of dynamic star simulator.
Calibration of Multiband Microwave Radiometer Used for Oceanic Calibration/Validation Site
WANG Zhenzhan, LIU Jingyi, ZHANG Yu, ZHENG Wei, LI Bin
2014, 34(4): 474-482. doi: 10.11728/cjss2014.04.474
Abstract(1090) PDF 1815KB(1215)
Oceanic Multiband Microwave Radiometer (OMMR) is a five-band and 10-channel remote sensor, which is designed for in-situ calibration and validation of HY-2 satellite's scanning microwave radiometer. It was demanded to satisfy the requirements of providing higher accuracy brightness temperature data than those of microwave radiometer during its one-year lifetime. Due to its special operating condition on the platform and some unexpected interference that might be suffered in this period, an effective calibration method is necessary and critical. In this paper, the principle of OMMR internal calibration was introduced, and attentions were paid on the analyses of calibration result of tests both in laboratory and on the platform. By using these calibration results, the data from in-situ measurements on the platform are given and evaluated.
Payload Data Transmission Link Design for the Satellite with Attitude of Inertial Space Orientation
Xiong Weiming, Cheng Xin, Ye Yunshang, Yao Ye
2014, 34(4): 483-488. doi: 10.11728/cjss2014.04.483
Abstract(1294) PDF 3157KB(1648)
Satellites whose attitude is inertial space orientation cannot keep the transmitting antenna beam accurately pointing to the ground stations when the data transmitting device in the satellite is working. As a result, a new technical challenge of transmitting the payload data from the satellite to the ground stations in a high speed is brought forward. In this paper, a method using the transmitting antenna whose beam has proper width and pointing direction to resolve the problem is dedicated. For this aim, by simulating the satellite orbit with STK software, variation of the relative attitude of such satellites to the ground stations, as well as comparison on the data transmission time from the satellite to the ground stations at different beam width of the transmitting antenna, are researched. The key research is to develop an antenna whose gain is 0dBi in 140° angle of beam, and the link is designed to ensure a sufficient margin at the transmission rate of 85Mbit·s-1. As a result, under the constraint of space avionics miniaturization (10kg of mass, 80W of power consumption), the miniaturized antenna with wide beam and the solid-state power amplifier are designed to solve the problem of payload data transmission of satellites whose attitude is inertial space orientation.
Multi-body Dynamics of Repeated Fold-unfold and Lock-unlock Solar Array
Hu Ming, Kong Fei, Chen Wenhua, Li Wenjuan, Han Yadi, Wang Qingjiu
2014, 34(4): 489-496. doi: 10.11728/cjss2014.04.489
This paper presents the dynamic characteristics of repeated fold-unfold and lock-unlock solar array, which is in a topological tree configuration. According to the first modal stiffness analysis, assumptions about solar array multi-body system are proposed. Deduced from Jourdain variation principle, dynamic model of solar array flexible multi-body system is built. Furthermore, the forward-inverse mixed dynamic model is established through forward recursive formulation and motion law of solar array hinges. In order to study the impact of flexible structures on solar array deployment, the motion parameters of solar array panels, such as rotation angle, angular velocity and angular acceleration, are obtained from numerical simulation, which is based on the structure and physical parameters of repeated fold-unfold and lock-unlock solar array prototype. The results can well predict dynamic behaviors of solar array during its deploying process. In conclusion, this study has laid a foundation for subsequent engineering applications of repeated fold-unfold and lock-unlock solar array.
Design of an ASIC Chip for Spacecraft Integrated Avionics
Zhou Li, An Junshe, Fang Qingwen, Cai Fei
2014, 34(4): 497-504. doi: 10.11728/cjss2014.04.497
Abstract(1193) PDF 886KB(1489)
It is a trend to put the common spacecraft engineering requirements into one chip, which can miniaturize spacecraft avionics and reduce the repeated work for spacecraft engineers. Based on the analysis of space application requirements, the system design of an ASIC (Application Specific Integrated Circuit) chip for spacecraft telemetry and command system is proposed. Firstly, the chip system architecture is described. Secondly, four key techniques of the ASIC chip design are presented in detail, including design of the chip working modes, design of onchip IP cores, design of reliability, and the design of low power consumption technology. 1553B RT working mode of this ASIC is different and special from other space chips. The system test results based on FPGA show the validity and reliability of the ASIC system design. Finally, some promising applications of the ASIC chip are described.