空间科学学报

2015 Vol. 35, No. 3

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Detecting Energetic Neutral Atoms in and out of the Heliosphere

K C Hsieh

2015, 35(3): 253-292. doi: 10.11728/cjss2015.03.253

Abstract(1878) PDF 15415KB(1186)

Abstract:
By Energetic Neutral Atoms (ENA), we mean atoms having kinetic energies >0.1keV found in and out of the heliosphere. In the regions lacking any neutral gas of temperatures >10⁶K, while abundant in ions of kinetic energies >0.1keV, surely an ENA has to be the product of charge exchange between an ion and an atom or molecule B of the local gas, i.e. A⁺+B → A+B⁺. Because energy exchange is minute during charge exchange, the newly formed ENA A and ion B⁺ can be considered keeping their respective original kinetic energies. Instantly, ion B⁺ is trapped by the local magnetic field, but ENA A is liberated and flies yonder, to be a sample of its originating plasma in mass and energy, thus providing a precious medium for remote sensing the parent plasma. The recent success of NASA's IBEX (Interstellar Boundary EXplorer) Mission in directly detecting ENA coming from the local interstellar medium greatly expanded the scope of ENA remote sensing. Here, we review the discovery of ENA in high altitudes, the basic concept and existing examples of remote sensing of ENA, recent results, and the designs and development of the necessary instruments, and also offer a prospective on ENA-sensing in the near future.

Central Radiation Model of Proton Radiation Belt

Tao Hongren, Lin Ruilin, Shi Liqin, Liu Siqing, Zhang Xiaoxin, Gong Jiancun

2015, 35(3): 293-305. doi: 10.11728/cjss2015.03.293

Abstract(1999) PDF 3288KB(1357)

Abstract:
According to the databases of AP-8 and CRRESPRO proton radiation belt models, comparison between both models on the magnetic equator is carried out and reasons for their differences are presented. The model of proton radiation belt for the peak radiation region is developed by using the analytic function, which includes the submodel for relationship between the L value corresponding to the peak value of omni-directional proton differential flux (L_c) and the proton energy, and the submodel for relationship between the peak value of omni-directional proton differential flux J_max and the proton energy. Finally, the observation of energetic proton on the magnetic equator from RBSP A satellite's REPT telescope is used to compare with the results from AP-8 model, CRRESPRO model and the central radiation model. It is found that the values of omni-directional proton differential flux for 78.9, 102.6 and 208MeV channels from RBSP A satellite are obviously larger than those from the three models, but the values of L_c from RBSP A satellite are very close to those from AP-8 model and the central radiation model, and RBSP satellite also observes the hidden secondary proton radiation belt presented by CRRESPRO Quiet model.

Characteristics of Multi-GNSS Global Gonospheric Godeling and Gnalysis of the Accuracy

Zhao Wenjiao, Wang Hu, Dang Yamin, Bai Guixia

2015, 35(3): 306-314. doi: 10.11728/cjss2015.03.306

Abstract(1511) PDF 14054KB(4102)

Abstract:
The model of ionospheric delay correction is established by only GPS and by fusing BDS, GPS and GLONASS with observations of pseudo distance smoothed by carrier phase and spherical harmonics. And some experiments of the global ionospheric inversion have been done. The variations process of ionospheric is fused daily in January, 2014 to obtain monthly comprehensive differential code bias product and did some analysis on the accuracy of the products. The fusion of the three systems not only increases the number of satellites observation but also improves the geometric distribution of the puncture point. The analysis result shows that the accuracy of inversion of global ionospheric of three system fusions is better than GPS system alone, about 5 to 10 increase in TECU. The Precision of monthly comprehensive differential code bias product of GPS is better than GLONASS, while the BDS stability is poor.

Study on Spectrum of Sprite Emissive Using Numerical Simulation

Jiang Fang, Huang Chaoyan, Zhang Hualong, Li Xiaoyin, Wang Yongmei

2015, 35(3): 315-323. doi: 10.11728/cjss2015.03.315

Abstract(1526) PDF 1816KB(19310)

Abstract:
Sprites are the transient luminous events above very active thunderstorms and are the direct evidence of the energy in troposphere coupled to the upper atmosphere. The emissive spectrum study is the important means to understand the energy injected into upper atmosphere and regional ionization, the electron energy distribution during the whole event. These parameters are useful for the study of sprites' physical mechanism, in addition as a kind of natural atmospheric luminous phenomenon, the emissive spectrum study is useful for providing important information to the research of atmospheric radiation background information. Based on the Boltzmann Equation to calculate the time evolution of the electron energy distribution function in a mixture of partially ionized gases with an applied electric field, the paper calculated the spectral intensity in typical emissive band for sprites. Simulation results show that the emissive intensity is more intensive with more intensive E/N and the emissive spectrum is from far ultraviolet to near infrared.

Multifractal Analysis of ELF Transient Events Based on MF-DFA

JIANG Su, ZHANG Qilin, HUANG Kaili, CHEN Yuan, SU Jianfeng, QIN Wei

2015, 35(3): 324-329. doi: 10.11728/cjss2015.03.324

Abstract(1290) PDF 975KB(1143)

Abstract:
In this paper, the magnetic field components totally continued 10 seconds using measured ELF global lightning activity background signal. The measuring signal sensor includes a pair of horizontal antenna which are orthogonal to each other and a spherical antenna with vertical placement. The horizontal antenna is for receiving ELF horizontal magnetic (HNS, HEW) signal of north-south and east-west directions, while the vertical antenna is for receiving ELF vertical electric field signal. By using the magnetic field component in both north-south and east-west direction of the observational extremely low frequency background signal of global lightning activity, and based on MF-DFA (Multifractal Detrended Fluctuation Analysis) multiple fractal method to analyze the long range correlation and multiple fractal characteristic of the background signal one second before the Q-burst occurs. Then, it is found that the magnetic field in the north-south, east-west direction of the maximum impulse one second before the Q-burst occurs has a long range correlation and multiple fractal characteristics. Among them, the minimum scaling exponent of the north-south direction is 0.15 < a_min < 0.22, fractal spectrum width is 1.09 < Δa < 1.51; the minimum scaling exponent of the east-west direction is 0.23 < a_min < 0.59, fractal spectrum width is 0.75 < Δa < 0.99. The multiple fractal spectrum parameters Δa, a_min can automatically identify the occurrence of Q-burst excellently.

Preliminary Studies on Collagen Fibrosis and Hydroxyapatite Crystallization under Microgravity

WANG Jing, LAN Ding, WANG Yuren, DAI Guoliang, KONG Liming

2015, 35(3): 330-335. doi: 10.11728/cjss2015.03.330

Abstract(1278) PDF 1977KB(1195)

Abstract:
Bone loss during long-term space flight is a serious problem. Collagen fibrils in bones are a key factor of Hydroxyapatite (HAP) crystal growth in its crystallization process, which is a main constituent of bones. In this paper, the changes of collagen fibrosis process under simulated microgravity and normal gravity conditions were studied, and the morphologies of HAP crystals grown on the surface of collagen fibrils were observed. Results showed that the amount and the size of pores inside collagen fibers formed under simulated microgravity condition and different concentrations of collagen were significantly larger than that under normal gravity condition and different concentrations of collagen. The distribution of the porosity under simulated microgravity condition was different with that under normal gravity condition. The morphology of HAP crystals under simulated microgravity condition was mainly cube-shaped. However, under normal gravity condition, HAP crystals were mainly plate-liked. These preliminary results will help to clarify the mechanism of bone loss in space in future.

Prototype System Used for Flame Structure Display and Temperature Measurement Technology in Microgravity Combustion Experiment

WANG Jing, SUN Zhibin, DAI Bin, DAI Guoliang, KONG Liming, WANG Baorui

2015, 35(3): 336-342. doi: 10.11728/cjss2015.03.336

Abstract(1432) PDF 5777KB(2037)

Abstract:
The facility for combustion experiments in space is lightweight, small sized and multi-functional. In this paper, a prototype system used for flame structure display and temperature measurement is presented, which combined the schlieren method, rainbow schlieren deflection method and differential interference method. It is also lightweight and small sized. As for the prototype system, the flame structure display function was checked by schlieren method in microgravity drop tower, and the temperature measurement function was checked by rainbow schlieren deflection and differential interference method under normal gravity condition. Results show that the resolution of flame structure was not less than 1mm, and temperature field measurement was accurate with relative error smaller than 2%. Such prototype system is important to the promotion of space combustion science experiment technology and will be beneficial to the future combustion experiments in space.

A Carrier Synchronization Algorithm for Autonomous Radio Receiver in Deep Space

Song Qingping, Liu Rongke

2015, 35(3): 343-349. doi: 10.11728/cjss2015.03.343

Abstract(1234) PDF 586KB(1265)

Abstract:
The carrier synchronization algorithm of the autonomous radio for deep space is studied. When the signal modulation is unknown, this paper improves the existing universal carrier synchronization loop for multiple modulations, expands the frequency tracking range of the loop, proposes a Tong detection-based M-ary Phase Shift Keying (M-PSK) signal locking detection algorithm to rapidly and effectively determine whether the current phase discrimination mode matches the modulation mode, so as to independently choose whether to switch the phase discrimination mode. Through theoretical analysis and comparison, it is described that the total detection probability of the algorithm proposed in this paper is significantly higher than the probability of single lock detection. Simulation results show that the algorithm has high detection probability and low computational complexity at a low signal to noise ratio.

Inversion Algorithms and Precision Analysis of ROPP

WANG Dazhao, BAI Weihua, SUN Yueqiang, MENG Xiangguang, WANG Dongwei, LI Wei

2015, 35(3): 350-355. doi: 10.11728/cjss2015.03.350

Abstract(1712) PDF 1861KB(1173)

Abstract:
The unique combination of global coverage, high precision, high vertical resolution, long-term stability and all-weather viewing of radio occultation will enhance the data sets of numerical weather prediction and improve the precision of Numeric Weather Prediction (NWP). And data assimilation requires preprocessing of the raw radio signals into the bending angles and refractivity. Then the atmospheric parameters such as temperature, pressure and humidity can be retrieved through data variational assimilation. The procedures for processing of radio occultation data, especially several important steps are introduced. And comparative analysis between these results and those from CDAAC shows that below the altitude of 30km, the relative errors of refractivity, pressure and humidity are within 2% and the deviation of temperature is below 2K. The results are also compared with the data from ERA-interim model of ECMWF and similar conclusion is obtained.

Study on High Precise and High Dynamic Star Simulator

Wang Lingyun, Wang Bo, Zhang Guoyu, Sun Gaofei

2015, 35(3): 356-361. doi: 10.11728/cjss2015.03.356

Abstract(1681) PDF 1795KB(1033)

Abstract:
The composition and overall structure of high precise and high dynamic star simulator system is presented, and a new method is put forward based on sub-pixel display technology to improve the dynamic star simulator to display the star point more precisely, which can reduce the position deviations of both geometric center and the energy center of the star point. Meanwhile, a new method for fast and accurate retrieval of the navigational star in the entire celestial sphere is presented by partitioning the SAO (Smithsonian Astrophysical Observatory) star catalogue, analyzing the four elements of the spacecraft attitude to determine where the visual axis points to, eliminating the search and match of navigational stars far from the visual axis so as to reduce the search area, hence decreasing the time that the whole celestial stars traversal required. Through simulation testing, results show that the speed of this quick search method to select the celestial navigational star has been increased by nearly 10 times.

External Heat Flux of the Solar Array on the Polar Lunar Orbit

SONG Xin, ZHANG Youwei, LIU Zijun, SI Dongbo

2015, 35(3): 362-367. doi: 10.11728/cjss2015.03.362

Abstract(1736) PDF 1112KB(1219)

Abstract:
Accurate lunar surface temperature distribution model is important for human lunar exploration. But there is a lack of research on how to calculate the temperature distribution of the entire lunar surface. In this paper, an entire lunar surface temperature model has been established which uses Racca model to calculate temperature of the lunar sunny side. For lunar shady side, the lunar surface is divided into several zones along the latitudinal direction whose temperature is solved by one-dimensional non-steady heat conduction equation. According to Chang'E-3 solar array temperature data, parameter values of the heat conduction equation are amended. Thermal analysis results of Chang'E-3 solar array temperature are in good agreement with the measuring data, which preliminary proves that this model is sound and feasible. Based on lunar temperature distribution calculated by this model, heat flux characteristic of the solar array on polar lunar orbit has been researched.

Analysis on Application of Real-Time Ethernet in Spacecraft

Qiu Aihua, Zhang Tao, Gu Yidong

2015, 35(3): 368-380. doi: 10.11728/cjss2015.03.368

Abstract(1618) PDF 2338KB(10493)

Abstract:
The main purpose to use Ethernet in spacecraft is to take advantage of its flexibility to meet the requirement of communication access convenience, simultaneously take into account that Ethernet has high bandwidth and data rates, and expect that it has both real-time and deterministic in control field. Looking for some real time network is the priority of the spacecraft using Ethernet. The deterministic scheduling mechanism of communication and transmission characteristics of real-time Ethernet has become a main determination of whether the Ethernet can meet the demand of spacecraft network traffic characteristics. According to the analysis of data communication characteristics in spacecraft, and comparison of real-time Ethernet communication scheduling strategy, the real-time Ethernet applied in spacecraft should has time synchronization, strong real-time, deterministic, high-bandwidth, containing multiple data types, dual redundant channels, meanwhile it is compatible with standard Ethernet.