2007 Vol. 27, No. 3

Display Method:
ICMEs Likely From the Same Active Region Observed by Both Helios 1 and IMP 8
DU Dan, WANG Chi
2007, 27(3): 177-181. doi: 10.11728/cjss2007.03.177
Abstract(1873) PDF 1577KB(1070)
The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in the heliosphere. On day 72 of 1975, an ICME was observed by Helios 1 at 0.3 AU, while a similar solar wind structure was observed by IMP 8 at Earth on day 70 of 1975. On the basis of comparison of the plasma signatures and the transit time from Helios 1 to IMP 8, we hypothesize the observed ICMEs by both spacecraft are resulted from the same active region on the solar surface. A one-dimensional MHD model was used to track the ICME from Helios 1 (0.3 AU) to Earth. The observed plasma profiles and timing are close to those predicted by our MHD model and thus, give the supports to the model.
The Interplanetary Causes of the Anormalous SSC Events
LI Changxing, HUANG Zhaohui, WANG Chi
2007, 27(3): 182-191. doi: 10.11728/cjss2007.03.182
Abstract(2615) PDF 4375KB(1991)
SSC is a result of the interrelation between strong solar wind dynamic pressure or interplanetary shock and the geomagnetosphere. Generally, the rise time of SSC varies from 4 minutes to 10 minutes. So, we refer to the SSC of the rise time which is more than 15 minutes as anomalous SSC event. We identified 5 anomalous SSC events from the geomagnetic index SYM-H data since the observation beginning of the geomagnetic field. Using the multipoint observations of the solar wind from the Wind, ACE, IMP 8, Goes and Geotail, the interplanetary causes of those anomalous SSC events were analyzed. It is found that: (1) all of 5 anomalous SSC events are accompanied with strong interplanetary disturbances, among which there are 4 events corresponding with the forward fast interplanetary shocks, and 3 events corresponding with multi-step solar wind dynamic pressure changes and 1 event corresponding with a sudden direction change and large amplitude variation in interplanetary electric field. (2) the rise time of those resulted from interplanetary shocks desponds on the orientation of the interplanetary shock, i.e., the bigger the angle between the interplanetary shock normal and the Sun-Earth line, the shorter the rise time, and the contribution of the orientation of the interplanetary shock is more remarkable than its speed. (3) There is no explicit relation between the rise time of the anomalous SSC events and the interplanetary field direction.
Effect of Tailward Flows From the Ionosphere on the Near-Earth Magnetic Field
ZHANG Lingqian, LIU Zhenxing, WANG Jiye, PU Zhuyin, MA Zhiwei, SHEN Chao
2007, 27(3): 192-197. doi: 10.11728/cjss2007.03.192
Abstract(1894) PDF 1274KB(1163)
Tailward flows are often observed in the near-Earth magnetotail by TC-1 satellite during quiet time and substorm active period. The statistical studies show that the perpendicular component of the tailward flow will leads to stretching of magnetic field lines. Due to the tailward flow, the Bx component of the magnetic field distinctly increases or the magnetic field geometry becomes tail-like from dipolar-like. The magnetic field is recovered and back to dipole-like structure when plasma flow is reversed. Along with magnetic field stretch, it is found that both temperature anisotropy and ion temperature decrease at the same time. During the period of the magnetic field recovering dipolar- like, the ion temperature rapidly increases and the temperature becomes anisotropy associated with the release of the magnetic energy. From the observations, it is also shown that the tailward flow causes an enhancement of By component. The results from the TC-1 satellite indicate that the tailward flow from the ionosphere has an important effect on the near-earth magnetotail.
Investigation on Properties of Ionospheric Es Layer in Hainan Region
GONG Yu, SHI Jiankui, WANG Guojun
2007, 27(3): 198-203. doi: 10.11728/cjss2007.03.198
Abstract(2578) PDF 1910KB(1179)
Using the observation data (Mar. 2002-Feb. 2005) from DPS-4 at Hainan ionospheric station, a statistic analysis for sporadic-E (Es) occurrence frequency in Hainan region in the descending phase of solar cycle has been performed. The seasonal variation and annual variation of occurrence of Es are mainly studied. The results show that, in the three years, Es occurrence in Hainan region is increasing with year. Esl and Esq occurs most frequently, next is Esr, then, Esc and Esf occurs lesser, ESh occurs least. Es occurs most frequently in Summer, secondly in Autumn and Winter, and most infrequently in Spring. Different type of Es has different properties, such as Es1 and Esq occurs almost every season, next is Esr, then, Esc, Esf and ESh occurs infrequently in any season, particularly, Esf almost disappears in Autumn. These results provide observation evidence for studying the physics mechanism of the ionospheric irregularity, it is also important to establish space weather predicting model on ionosphere.
Measurement and Analysis of Ionospheric Virtual Height With High Precision
ZHU Zhengping, NING Baiqi, WAN Weixing
2007, 27(3): 204-210. doi: 10.11728/cjss2007.03.204
Abstract(1850) PDF 2335KB(1189)
In order to improve the spacial resolution of ionospheric virtual height in vertical ionospheric sounding, a high precision virtual height measurement experiment are carried out by means of ionospheric echo's phase measurement and corresponding data analysis processing arithmetic with modern digital ionosonde. When two radio frequency pulse signals, the frequency difference of which is a fixed value are transmitted and the echo's phase difference is measured, the ionospheric virtual height with high precision can be acquired. According to this ionospheric virtual height sounding principle, the observation mode of ionospheric virtual height with high precision is realized. In this mode, the measured height resolution of the ionospheric virtual height is increased by more than ten times, that is, from 6 km to about 200 m, which can entirely satisfy the observation research demand of the ionospheric fine structure and small scale disturbances. Through a series of virtual height measurement experiments by using combinational pulses control and echo's phase measurement analysis based on CADI ionosonde, some meaningful results are obtained and some comparisons are made with TOA (Time Of Arrival) method. Experimental results reveal that the height resolution of ionospheric virtual height measurement with echo's phase method is ten times higher than that of virtual height measurement with TOA method. This is very important in that electron density profile under ionospheric peak can be accurately inversed and ionospheric fine structure can be carefully studied.
Study of Internal Gravity Waves Propagation on the Basis of the Three-Dimensional Transfer Function Model
SUN Lingfeng, WAN Weixing, DING Feng, MAO Tian
2007, 27(3): 211-217. doi: 10.11728/cjss2007.03.211
Abstract(2209) PDF 1916KB(1052)
In this paper the three-dimensional transfer function model has been developed in the atmosphere with dissipation and background winds. Then the model is used to analyze the filter characteristics in the frequency wavenumber domain and the spatial-temporal domain. Finally, we discussed the total energy of ionosphere response on the three rectangle waves with the different spatial-temporal scales on the surface. The computed results reveal that for internal gravity waves, the atmosphere behaves like a filter which only offers the easy passage to some gravity waves with periods of 15-30 min and with horizontal wave lengths of 200-400 km. The wave fronts which are like funnels in vertical profile and concentric circles in horizontal plane are distorted by the background winds when the gravity waves propagate from the earth surface to the ionospheric height. The gravity waves propagating against winds are easier than those propagating along winds. The total energy of ionosphere response can arrive at maximum when rectangle wave source's spatial scale is between 150km to 250km and temporal scale is between 20min to 30min.
Preliminary Attempt in Prediction the Geomagnetic Storm With Ground Cosmic Ray Data
XUE Bingsen, YE Zonghai, GONG Juhong
2007, 27(3): 218-222. doi: 10.11728/cjss2007.03.218
Abstract(2204) PDF 1049KB(1018)
In this paper an algorithm is introduced to use the ground cosmic ray data to prealct great geomagnetic storms. The muon measurement data from Nagoya station, Japan, was employed and the characters of cosmic ray evolvement before geomagnetic storm were revealed by analyzing the differences between the data just before the geomagnetic storms and the quiet days. It was found that fluctuations before geomagnetic storms increased due to the approaching of CME because the shock front and strong IMF induced by CME. An index to measure the fluctuation of data, Ds(t), was used in the cosmic ray data processing. The result shows that Ds(t) always increases monotonously several hours ahead the geomagnetic storm, which hopefully could become a useful factor for geomagnetic storm prediction. As it had been known that most of the large geomagnetic storms were caused by CMEs accompanying the Solar Proton Events (SPEs), the SPEs were also chosen together with Ds(t) in the prediction process. The mentioned algorithm was tested with the relative data of whole year 2001. The result turned out to be encouraging with the accuracy rate reach to 80% (8 out of 10) and false rate less than 18% (2 out of 11).
Calibration Method of Electric Field
LUO Fushan, HE Yuhui, ZHANG Huawei, ZHANG Jian, ZHUANG Hongchun, HU Shengbo
2007, 27(3): 223-226. doi: 10.11728/cjss2007.03.223
Abstract(1990) PDF 1634KB(1487)
The calibration method for the balloon-borne double-sphere electric field instrument, the micro-rocket-borne electric field instrument and the ground mill fieldmeter is introduced. The atmospheric electric field, relating with space physics and space environment, is a key parameter for studying various phenomena in earth science, such as lightning and earthquake, so the atmospheric electric field is becoming more and more important. With the lack of the national standards and military standards for the measurement and calibration of electric field, a set of calibration system is designed and developed to calibrate electric field instruments of different structures. The results are consistent with the theoretical calculation, and provides the foundation for the reliability of the electric field measurement data.
On a Tracking and Data Relay Satellite (TDRS) Tracking a Lunar satellite
LI Yuheng, ZHENG Jun, YI Kechu
2007, 27(3): 227-232. doi: 10.11728/cjss2007.03.227
Abstract(2114) PDF 1324KB(1178)
China has implemented its change engineering. The first lunar satellite will be lunched in 2007. When it is on orbit and tracked and controlled by a ground-based TTC station, the zone of exclusion caused by the earth's rotation is about 50%. Although the coverage can be improved by scattered more earth stations along the longitude, the improvement effect is limited with the restriction of Chinese territory. Obviously, an on-orbit tracking and data relay satellite can enlarge the coverage. Based on the orbital elements, an algorithm to calculate the terms for a TDRS tracking a lunar satellite is presented here. Then the space coverage of a lunar satellite tracked by an earth station or a TDRS is computed. Their results show that compared with the tracking coverage of 32% or 50% made by an earth station, a TDRS can cover a lunar satellite by 61% with lunar exclusion or 90% without lunar exclusion. When a lunar satellite is tracked by a TDRS rather than an earth satellite, some extra requirements are added to the TDRS' antenna movement. These requirements are beyond the capability of the current on-orbit TDRS, which is designed for tracking low earth satellites. Finally, with the help of an earth station and a careful scheduler, a proposal is presented to further enlarge the tracking coverage for a current on-orbit TDRS tracking a lunar satellite.
Analysis and Modeling for the in-Orbit Dynamics of Nano-Satellite's Thermal System
LI Yunze, NING Xianwen, WANG Xiaoming, SHI Xiaobo, ZHUANG Damin, WANG Jun
2007, 27(3): 233-238. doi: 10.11728/cjss2007.03.233
Abstract(1873) PDF 1510KB(1017)
Nano-satellite's thermal system is fundamental for its passive thermal control. The analysis and modeling of its in-orbit dynamical performance are necessary for nano-satellite's thermal control scheme design and evaluation. A three-dimension nonlinear dynamical model of satellite's temperature change was built up by dividing the typical passive thermal control system of nano- satellite into three representative functional node, the in-orbit temperature changes of satellite surface and indoor environment can be calculated conveniently from this model. A set of equations for the in-orbit calculations of nano-satellite's external space heat flow and flight position were also introduced. These equations are based on nano-satellite's body-reference frame and share same solving algorithm with the three-dimension nonlinear dynamical model. These provide a new transient analytical model and simplified in-orbit calculating method for the developing of advanced nano-satellite thermal control and thermal management technologies. The in-orbit dynamical performance of a sunsynchronous orbit nano-satellite thermal system had been calculated as an example. The results and its discussion were described at end of this article.
Research on Architecture Model With Autonomous Coordination for Distributed Satellite Systems
GAO Li, SHA Jichang
2007, 27(3): 239-244. doi: 10.11728/cjss2007.03.239
In a broad sense, Distributed Satellites System (DSS) refers to a multi-satellites system, which distributes over different special orbits and submits to given constraints. Generally, it is fleets of autonomous spacecraft. Some of the many advantages of using DSS include greater performance, lower cost, and improved fault tolerance, reconfigurability and upgradeability. The vision of what can be achieved from space is no longer bound by what an individual satellite can accomplish. According to characteristics of DSS, it is necessary and feasible to adopt Multiple Agent System (MAS) theory to instruct the research on autonomous control of DSS. This paper discussed the qualitative analysis and comparison of commonly-used autonomous control architectures of DSS. Based on it, a hybrid systematic hierarchical structure model with two levels is put forward to fulfill autonomous coordination demands of DSS under the dynamic and complicated uncertain circumstances. Furthmore, the study on satellite autonomy at home and abroad is still in the early stage, and there are not any guidelines or frameworks to follow till now. A novel agent model on satellite control architecture is outlined, and the components, functions and relationships of agents in the architecture are analyzed. It is designed for multi-satellites coordination and satellite self-government, thus it has generality to a certain extent.
Space-Based TTC Method of Lower Orbit Satellite
YANG Tianshe, Dong Xiaoshe, XI Zheng, LI Jisheng, HUANG Yongxuan
2007, 27(3): 245-249. doi: 10.11728/cjss2007.03.245
Abstract(2006) PDF 2239KB(2560)
Currently, TTC (Tracking, Telemetry and Command) for satellites of our country is mainly executed by Ground-Based TTC network. With the increment of requirement for different kinds of purposes, the numbers of satellites in lower orbits increase rapidly. It is very difficult to meet the requirements of the satellites only based on ground-based TTC network. To seek a new, effective and economical mode to TTC lower orbit satellites is absolutely necessary for our country and to apply space-based TTC technology is an appropriate way to solve ground-based equipment shortages. Based on analysis of Tracking and Data Relay Satellite System (TDRSS) of NASA (National Aeronautics and Space Administration of the United States), a new mode, space-ground-based TTC Mode (SGBM) for lower orbit satellites, is proposed. In this paper, the operating principle of space-ground-based TTC mode is discussed, the simulation system used to simulate space-ground-based TTC mode is designed, and the key technologies need to be solved when using space-ground-based TTC mode is analyzed. The different functions of space-ground-based TTC mode are verified based on the developed simulation system. The simulation results show that the proposed satellite TTC mode is feasible and reliable, and the requirement of lower orbit satellite can be met by using the mode.
Comprehensive Reliability Assessment of High Reliable Space Electronic Products Based on General Failure Rate
FU Hongyong, LIN Baojun, CHEN Fuen
2007, 27(3): 250-252. doi: 10.11728/cjss2007.03.250
Abstract(1963) PDF 553KB(1345)
According to the Bayes theorem, the comprehensive reliability assessment of high reliable electronic products in astronautics is studied theoretically and a method for the number of equivalent tasks is given, A calculation method from the tested and applied parameters of components is put forward. Finally a practical example for a certain space electronic product is presented.
Estimation of Satellite Signal's Propagation Delay for Fast and Direct Acquisition of Long Cycle and High Rate Pseudo-Random Code
WANG Mengli, WANG Feixue
2007, 27(3): 253-257. doi: 10.11728/cjss2007.03.253
In satellite navigation and positioning system, time is important information for fast and direct acquisition of long cycle code, one of its important aspects is the uncertainty compression of signal's propagation delay to reduce time search range. Based on coarse data of positions of user and satellite, estimation algorithms of propagation delay between different satellites and users are given. Simulation results indicate that the algorithm can reduce the delay's uncertainty range greatly, even with great position errors the uncertainty range still can be reduced to the half, and is effective for the fast acquisition of long cycle code.
Analysis on Algorithm of GPS Signal Non-Coherent Acquisition Scheme in MIMU/GPS Embedded Integrated Navigation
TANG Kanghua, HUANG Xinsheng, WU Meiping, HU Xiaoping
2007, 27(3): 258-265. doi: 10.11728/cjss2007.03.258
The signal processing for a GPS receiver is composed of the signal acquisition, the tracking, and the navigation. The goal of the acquisition is to synchronize the code phase and a carrier frequency with the income signal for a particular satellite. For the algorithm of GPS signal acquisition, the previous GPS acquisition scheme adopted not only the coherent integration acquisition technique, but also the non-coherent integration technique. Since the long coherent integration time increases the number of frequency search cells, while the non-coherent integration technique causes the squaring loss. Because of the effect of estimated Doppler frequency error and estimated code phase error on the non-coherent integration technique, this paper proposed an efficient MIMU/GPS embedded integrated navigation system to aid GPS signal non-coherent integration acquisition scheme. Expressions of detection probability and false alarm probability about GPS signal acquisition were gained in this paper. And the method of MIMU to aid GPS signal non-coherent acquisition was presented. Finally, the paper analyzed the performance of MIMU/GPS aiding GPS signal non-coherent integration acquisition.. The simulated result shows the precision of the estimated doppler frequency is better than 4 Hz. The result also shows based on MIMU/GPS integrated navigation aiding, the performance of GPS signal non-coherent integration acquisition can be improved greatly.