2011 Vol. 31, No. 6

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A Review of Density Holes Upstream of Earth's Bow Shock
G K Parks, E Lee, N Lin, J B Cao, S Y Fu, J K Shi
2011, 31(6): 693-704. doi: 10.11728/cjss2011.06.693
Abstract(2951) PDF 1442KB(1388)
Abstract:
Larmor size transient structures with density depletions as large as 99% of ambient solar wind density levels occur commonly upstream of Earth's collisionless bow shock. These “density holes” have a mean duration of 17.9±10.4 s but holes as short as 4 s have been observed. The average fractional density depletion (δn/n) inside the holes is 0.68±0.14. The density of the upstream edge moving in the sunward direction can be enhanced by five or more times the solar wind density. Particle distributions show the steepened edge can behave like a shock, and measured local field geometries and Mach number support this view. Similarly shaped magnetic holes accompany the density holes indicating strong coupling between fields and particles. Current densities as large as 150 nA·m-2 are observed at the leading compressed edge. The waves are elliptically polarized and rotating in the sense of ions (left hand) in the plasma frame. The waves appear to grow and steepen as the density holes convect with the solar wind toward the Earth. The transient nature of density holes suggests that the temporal features could represent the different stages of nonlinear evolutionary processes that produce a shock-like structure. The density holes are only observed with upstream particles, suggesting that back-streaming particles interacting with the solar wind are important. The significance of these observations is still being investigated.
Space Weathering Processes and Effects on the Moon
FU Xiaohui
2011, 31(6): 705-715. doi: 10.11728/cjss2011.06.705
Abstract(5152) PDF 739KB(1507)
Abstract:
Space weathering on airless bodies (including Moon, asteroids, and comets) is the physical and chemical alteration due to irradiation from solar wind particles and bombardment by micrometeorites. This paper compiles current lunar space weathering results from lunar soil studies, and ion and laser irradiation simulations. On the basis of these, hypothesizes about origin of amorphous rim and nanophase Fe0 on lunar soil particles were analyzed. In current researches, the contribution of solar wind irradiation and micrometeorite impact in lunar space weathering effects could not be completely distinguished. And it is suggested that lunar space weathering model should not be directly invoked for asteroids and other bodies. In the future, more microstructure and chemical compositions of samples from lunar, asteroids and IDP, more appropriate simulations are essential for resolving of the above problems.
Statistical Analysis of Type Ⅲ Bursts in the Centimetric-Decimetric Wavelength Region
MA Yuan, XIE Ruixiang, ZHENG Xiangmin, WANG Min, YAN Yihua
2011, 31(6): 716-724. doi: 10.11728/cjss2011.06.716
Abstract(2654) PDF 655KB(1311)
Abstract:
A statistical analysis of multi-band type Ⅲ bursts observed with the spectrographes in the ranges of 625~1500MHz, 2600~3800MHz and 5200~7600MHz during the 23rd solar cycle (from July 2000 to September 2004) is carried out in the paper. The main statistical results, e.g., distribution of type Ⅲ bursts, duration, frequency drift rate (normal and reverse slopes), degree of polarization and frequency bandwidth are given. The results indicate that the average values of the frequency drift rates and frequency bandwidths increase with the frequency. The average values of the durations and degrees of polarization are neither constant nor uniform varying over broad frequency extent. Most of type Ⅲ bursts are distributed within the range from 625 to 3800MHz, and decrease with the increase in frequency. This distribution result means that the places of electron acceleration and energy release are mainly within the decimetric range, and the characteristic of frequency range is possibly related with the magnetic configuration on decimetric wavelengths, and the position of the electron acceleration in the reconnection region of magnetic field nearby the place of the main flare. However, there are large number type Ⅲ bursts in the range of 5200~7600MHz. This diagnostic means that the place of electron acceleration is in the broad range of the corona. The radiation mechanisms of type Ⅲ bursts on centimetric-decimetric wavelengths most probably include the coherent plasma radiation or the emission processes of electron cyclotron maser.
Case Study of Interaction Between Interplanetary Magnetic Cloud and Heliospheric Current Sheet
FENG Xiang, WEI Fengsi, FENG Xueshang
2011, 31(6): 725-738. doi: 10.11728/cjss2011.06.725
Abstract(3173) PDF 1106KB(1367)
Abstract:
Based on 105 Magnetic Cloud (MC) events detected by WIND spacecraft from 1995 to 2007, according to whether the MC collided with the Heliospheric Current Sheet (HCS), the MC events are devided into two types, namely, colliding and non-colliding. The preliminary results are as follows. Firstly, there are 51 MCs which may have collided with the HCS, and that is about 49% of the total incident. Secondly, when a MC collided with the HCS, dynamic interactions tend to inhance in the region between magnetic cloud and heliospheric current sheet, such as appearance of local magnetic field directional discontinuity structures, decreased magnetic field strength, increased proton temperature, irrupt changes of some components of proton velocity, enhancement of ionacoustic waves or Langmuir waves. These phenomena are possibly related to magnetic reconnection in the colliding interaction regions. In case of non-colliding, these characteristics are not evident. Thirdly, in at least 15 cases, the magnetic polarity of the background magnetic fields in front of the magnetic cloud and the one behind the magnetic cloud are opposite, or the reverse point of magnetic polarity was inside the magnetic cloud, which means the magnetic cloud was moving cross the HCS. Lastly, bright fronts and bright cores of MCs have been observed in some events. These very preliminary results are beneficial to understanding the process of interaction between magnetic cloud and the heliospheric current sheet, however further researches are still required.
Study of the South China Ionospheric TEC Disturbances During June-July 2009
HUANG Jiang, DENG Baichang, XU Jie, HUANG Linfeng, LIU Weifeng, ZHAO Wenhua
2011, 31(6): 739-746. doi: 10.11728/cjss2011.06.739
Abstract(3151) PDF 849KB(1243)
Abstract:
There are many origins of ionospheric TEC (Total Electron Content) disturbances during June-July 2009, including several earthquakes and a total solar eclipse. In current study, using the GPS-TEC date observed during June-July 2009 in Guangzhou GPS station and processed by a sliding window with the data of prior 15 days, the characters of South China ionosphere are investigated in spatial and temporal distribution. The results indicate that there are possible relations between the South China ionospheric TEC disturbances and seismic-activities as well as total solar eclipse during June-July 2009. The characters of ionospheric TEC disturbance induced by several earthquakes are commented as follows: positive values before earthquake, positive values or negative values near and after the occurrence of earthquake, even more, that the positive values on the day of total solar eclipse (22 July 2009) may be accounted for magnetic activities, seismic activities and total solar eclipse.
Application of Analog Prediction Method on Ionospheric TEC Short-term Forecast
WENG Libin, FANG Hanxian, XIE Yanqiong, YANG Shenggao
2011, 31(6): 747-753. doi: 10.11728/cjss2011.06.747
Abstract(2826) PDF 575KB(1256)
Abstract:
Analog Deviation is introduced to evaluate the analog degree between two samples, and tests of Analog Prediction Method for 24 h ahead forecast of ionospheric TEC detected by Xiamen station in 2004 have been conducted in this paper. The results reveal that the relative error has good relationship with the geomagnetic activities, and it will be larger under geomagnetically disturbed conditions than undisturbed ones obviously, reaching 100% indeed; as a whole, the relative error is 18.022%, 44.896% and 11.676% under conditions of geomagnetic disturbances and undisturbed respectively. The cumulative proportions of relative error under 10%, 20%, 30%, 40% are 38.209%, 65.075%, 84.984% and 90.448% respectively. The Analog Prediction Method is based on the autocorrelation method, with the observed ionospheric TEC to predict, but only choosing the 24, 48, 72 h data which will have best analog with the predictions. The result of forecast will be much more better on condition of using ionospheric TEC in mid-latitude or under geomagnetic undisturbed conditions.
Validation of Global VTEC Maps Constructed Using Data Derived From COSMIC Constellation
LEI Xiaolong, FU Yang, XUE Zhengang, DU Xiaoyong, YAN Wei, LU Xu
2011, 31(6): 754-764. doi: 10.11728/cjss2011.06.754
Abstract(3134) PDF 770KB(1228)
Abstract:
The construction of reliable global maps of vertical total electron content of the Ionosphere (Vertical TEC or VTEC Maps) is a useful but challenging task. A new technological route to construct global VTEC maps has been raised by us that COSMIC RO data points are collected during the past 24 hours in the sun-fixed coordinate system (local time and geomagnetic latitude) and then vertical TEC values within height range from 110km to 750km are calculated by numerical integration of electron density profiles at these RO points after quality control. At last, ordinary Kriging method is adopted to construct Global COSMIC TEC Maps with a grid resolution of MAGLat 2.5°× 2 h. Comparisons during the interval from DOY (Day of Year) 001, 2008 to 181, 2010 between Global COSMIC TEC Maps and IGS GIMs, from DOY 194, 2008, to 181, 2010 between Global COSMIC TEC Maps and OSTM/JASON-2 observations have been made, and differences are calculated for different seasons, local time and geomagnetic latitudes. It proves that COSMIC TEC Maps have good agreements with IGS GIMs and OSTM/JASON-2 observations, so COSMIC TEC Maps are accurate enough to be used to correct the ionospheric delay in GNSS systems. With further improvement on RO theories and commencement of new RO constellations in future, the quality and quantity of ionospheric RO data will be raised greatly with no doubt. Hence, it will be a much promising technology to apply ionospheric RO data to correct the ionospheric delay for GNSS systems.
Preliminary Statistic Analysis of L-band Ionospheric Scintillation Over Nanjing Region in China
YANG Shenggao, FANG Hanxian, WENG Libin, XU Zhenzhong
2011, 31(6): 765-770. doi: 10.11728/cjss2011.06.765
Abstract(2990) PDF 598KB(1060)
Abstract:
Data recorded by a GPS ionospheric scintillation monitor installed in Nanjing has been used to study the day-to-day, month-to-month, local time and special variation characteristics of L-band ionospheric amplitude scintillation during the period between November 2008 and October 2009, which lays the foundation for grasping disciplines of the ionospheric scintillation in future. The preliminary statistical analysis shows that the amplitude scintillations were quite quiet and the scintillation activities with S4 > 0.2 occurred infrequently. Different intensities of amplitude scintillation have a common spatiotemporal variation characteristics. The occurrence rate in Jun., Aug., Sept. and Oct. is higher than that in other months, and the highest occurrence rate took place in October and the lowest in November. The occurrence rate in northern direction is higher than that in the southern direction. But the results are not approved fully. So it is necessary to analyze and certify them in future.
An OI-based Assimilation Method of Vertical Ionospheric Electron Density Profile Over Xiamen
WANG Yong, LIN Zhaoxiang, YU Tao
2011, 31(6): 771-777. doi: 10.11728/cjss2011.06.771
Abstract(2615) PDF 727KB(961)
Abstract:
By comparing the development of data assimilation in meteorology, Optimal Interpolation (OI) assimilation in one-dimension ionosphere is introduced. OI assimilation is a method that minimizes error variance of analysis by non-linear least-squares. Based on IGGCAS1D (Institute of Geology and Geophysics, Chinese Academy of Sciences 1 Dimension) model and Xiamen digital ionosonde observations, OI assimilation has been validated by simulation experiments. The detailed information of observations is that, 11:00UT 15 June, 11:00UT 22 July, 11:15UT 31 August, 2009, respectively. The results show that analysis conforms to observation even if the model background is far away from it and that OI assimilation is validated. After that, using one of the results from simulation experiments (11:15UT, 31 August 2009), a residual prediction is introduced. The result of residual prediction accords with observation very well. From the difference between prediction and observation, it can be concluded that the residual prediction is a worthy method to be verified in future.
Lidar Observations of Middle Atmospheric Density and Temperature Over Qingdao
WANG Xiaobin, SUN Shuji, CHEN Chun, CHEN Jinsong, XU Zhengwen
2011, 31(6): 778-783. doi: 10.11728/cjss2011.06.778
Abstract(3476) PDF 571KB(958)
Abstract:
The structure and performance of CRIRP (China Research Institute of Radiowave Propagation) Rayleigh backscattering lidar are introduced, the principles to derive middle atmospheric density and temperature are described, and the primary results observed over Qingdao are reported. The lidar observed temperatures are validated through comparison with a variety of observational and model data provided by satellite, radiosonde and CIRA86 respectively. The mean and seasonal variation of middle atmospheric temperature profiles is given, based on the observational data during 2008-2009. The lidar results show that stratospheric temperature over Qingdao is higher than the CIRA86 model, and that the difference is small in summer and autumn, and large in winter and spring, while the mesospheric temperature trend is opposite.
Image Data Processing of Spaceborne Fabry-Perot Interferometer Prototype
HAN Weihua, , LÜJiangong, WANG Yongmei
2011, 31(6): 784-788. doi: 10.11728/cjss2011.06.784
Abstract(2985) PDF 570KB(1194)
Abstract:
Fabry-Perot Interferometer (FPI) is one of the best detectors to explore the middle and upper atmosphere wind. A spaceborne FPI prototype with a large diameter telescope was designed and constructed and the image of interference fringe was acquired. This paper introduces the principle of FPI and a feasible inversion algorithm of the wind velocity in the middle and upper atmosphere. A technique for F-P interference fringe auto-processing is developed. The technique includes filtering, segmentation, thinning, and extracting of interferogram characteristic data. Filtering is composed of median filtering and background compensation. Binary fringe is obtained through selecting the area mean gray scale as threshold for segmentation. Mathematical morphology is fitting for restoring rupture and burr. As thinning is essential for the accuracy of inverting middle and upper atmosphere wind, thinning is discussed in details. Skeletonization thinning is put into practice. At last, characteristic data such as center of circle and radius are extracted. Visual C++ is adopted to develop the FPI interference fringe image process software, and the technique mentioned above has good performance in experimental practice.
Applications of Delta Differential One-way Ranging (ΔDOR) to Lunar Exploration Program
DING Suquan, LI Haitao
2011, 31(6): 789-793. doi: 10.11728/cjss2011.06.789
Abstract(2957) PDF 462KB(1115)
Abstract:
Delta Differential One-way Ranging (ΔDOR) is used for high precision angle measurement in many deep space exploration programs. The fundamentals of ΔDOR are introduced. Also, recommendations about ΔDOR of CCSDS (Consultative Committee for Space Data System) are presented. According to the high precision and real-time navigation requirements, the ΔDOR measurement schemes are designed for China's lunar exploration program whose current object is soft-land on the moon. The angle measurement precisions are analyzed in terms of the current performances of on-board and ground TT&C equipments. The resolution of the cycle ambiguity is presented. Research results show that the angle measurement precision is 25 nrad, which corresponds to about 10m on the moon. Further, the cycle ambiguity of DOR measurements can be resolved correctly.
Fault Detection and Isolation for Satellite Using Lipschitz Nonlinear Sliding-mode Observers
WANG Zheng, LI Yanjun, ZHANG Ke
2011, 31(6): 794-799. doi: 10.11728/cjss2011.06.794
Abstract(2784) PDF 498KB(1067)
Abstract:
Spacecrafts are nonlinear systems. But when they are orbiting in small angles, their models correspond with Lipschitz condition. Fault detection technology could be used to insure safety of the system under these circumstances. With application of the nonlinear sliding mode method, a series of multi-channel fault detection observers for the actuators was designed. The convergence of the observers was proved by choosing a proper Lyapunov function. The observers designed for the spacecraft can realize the isolation of the faults, and this was illustrated with absurdity. The parameters of the observer were derived from the application of linear matrix inequalities. Finally, modeling and simulation were conducted for a certain satellite, and it is compared with linearization method to verify the effectiveness of the proposed algorithm.
A Solution of Displacement Damage Evaluation on Silicon Chip Under Space Environment
YU Hao, WANG Zhiqiang, WANG Wenbin, LIU Wei
2011, 31(6): 800-807. doi: 10.11728/cjss2011.06.800
Abstract(2887) PDF 660KB(1078)
Abstract:
A method of displacement damage simulation under space environment is presented. This simulation of silicon lattice displacement damage rate is used for low Earth orbit satellite application. In this application, altitude was set for 375km as a typical variable. Through the simulation, displacement damage rates of different geomagnetic latitude orbital positions were given, which is useful for evaluating reliability of semiconductor devices on spacecraft. And displacement damage rates of different geomagnetic latitude orbital positions were compared, which is useful for orbit design. Diverse particles caused displacement damage are concerned, such as Gamma, electron, positron, pi+, pi?, proton, deuterium, tritium, helium and aluminum. The main displacement damage source is proton, which is part of cosmic ray or secondary particle from the shell of spacecraft. Compared with None Ionizing Energy Lost (NIEL), this result is given by “density of displacement damage in silicon crystal”, which is a useful way to evaluate defects of semiconductor device or solar cells, in turn more helpful for engineers.
Effect of an Alternating Electric Field on Dust Removal
SUN Zhibin, LIU Xuefeng, WANG Chao, YE Jingwei, JIANG Yu, a, ZHAO Qing, ZHAI Guangjie
2011, 31(6): 808-813. doi: 10.11728/cjss2011.06.808
Abstract(2542) PDF 504KB(1258)
Abstract:
Dust removal by means of an electric curtain is analyzed theoretically and demonstrated experimentally. A critical “floating” voltage criterion is introduced, above which the effect of the Vander Waals force on dust movement can be overcome. The relationship between critical voltage and frequency of the alternating field is derived. The results of numerical simulation as well as experiments show that the dependence of critical voltage on frequency is different for low and high frequencies. For high frequencies critical voltage is in direct proportion with frequency, while in low frequencies there is a lower limit of critical voltage. The experiment result coincides with our simulation conclusion. This method to remove dust does not abrade the circuit boards and has promising applications in the future exploration of deep space.
Application of DC/DC Converter in Secondary Power for Spacecraft
WANG Xiaopeng, YU Ping, LI Dongjing, QI Xinda
2011, 31(6): 814-820. doi: 10.11728/cjss2011.06.814
Abstract(3061) PDF 660KB(1211)
Abstract:
In aerospace engineering, it is demanded to design a power system of high-reliability, high performance and strong anti-interference ability, to ensure the life of the spacecraft and its reliable operation. The DC/DC converter has been widely used in the secondary power supply in aerospace engineering attributing to its reliability, high integration, small size, high efficiency. But in the DC conversion process, it is easy to introduce various forms of interference and noise, which directly affects the quality of power supply, and consequently affects the spacecraft's technical performance. To solve the interference problem and improve the reliability of the secondary power supply, a number of key techniques have been discussed on the DC/DC design applications, including: soft-start, filter, Electromagnetic Compatibility (EMC), reliability. After taking corresponding measures, reliability of the secondary power supply has been greatly improved, with surge current being reduced to 1/20 of the original level, and the output ripple being reduced to 1/4 of the original level. The measured data of the CE (Conduction emission) and RE (Radiation emission) tests in the EMC were under the limitation of GJB 151A-97. Results of the experiments and actual application show that the anti-interference design is effective.
Tracking Control for Coordinated Motion of Space Manipulator in Joint Space Based on Fuzzy Wavelet Neural Network
HUANG Dengfeng, CHEN Li
2011, 31(6): 821-828. doi: 10.11728/cjss2011.06.821
Abstract(2538) PDF 606KB(2296)
Abstract:
The trajectory tracking control for coordinated motion of free-floating space manipulator system with an attitude controlled base is discussed. According to the geometrical relationship and law of conservation of momentum, the dynamic equations of space manipulator system are constituted through Lagrange equation of the second kind. Based on the above, a fuzzy wavelet neural network scheme is designed to control the base attitude and the joint angle of manipulator to track desired trajectories synchronously in joint space on condition that system parameters are unknown. The control scheme needs neither linearly parameterize the dynamic equations of the system, nor know any system parameters. Further more, its network weights are learning online based on errors by back propagation algorithm so the self-learning and self-adapting ability of fuzzy neural network is enhanced and meantime the offline training time is saved. Numerical simulations are presented to verify the feasibility and effectiveness of the proposed control scheme.

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