空间科学学报

2014 Vol. 34, No. 2

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Observations of energetic particles in the upstream of a quasi-parallel collisionless shock

Zhang Weina, Wu Mingyu, Lu Quanming, Shan Lican, Hao Yufei, Gao Xinliang, Wang Shui

2014, 34(2): 137-142. doi: 10.11728/cjss2014.02.137

Abstract(1279) PDF 539KB(1774)

Abstract:
With the Cluster observations of a quasi-parallel shock on 16 March 2005, relationship between the upstream low-frequency waves and the energetic ions (about several keV) has been studied. The observation results show that there are full of waves in the upstream of the shock which can interact with the upstream plasma. The differential energy flux of energetic ions in the upstream is dependent on the magnetic field strength of these waves. The energetic ion energy flux is higher in the regions with a weaker magnetic field. The possible explanation is that the ions can be trapped by the nonlinear upstream waves. Then the energetic ions were accelerated by the electric field every time when they bounced in these nonlinear waves. Our observation results are consistent with the recent hybrid simulation results.

Comparison of diurnal, seasonal and solar cycle variations of high-latitude, mid-latitude and low-latitude ionosphere

K G Ratovsky, J K Shi, A V Oinats, E B romanova

2014, 34(2): 143-153. doi: 10.11728/cjss2014.02.143

Abstract(1248) PDF 482KB(1765)

Abstract:
Comparison of regular (diurnal, seasonal and solar cycle) variations of high-latitude,mid-latitude and low-latitude ionospheric characteristics has been provided on basis of local empirical models of the peak electron density and the peak height. The local empirical models were derived from the hand-scaled ionogram data recorded by DPS-4 digisondes located at Norilsk (69°N, 88°E), Irkutsk (52°N, 104°E) and Hainan (19°N, 109°E) for a 6-year period from December, 2002 to December, 2008. The technique used to build the local empirical model is described. The primary focus is diurnal-seasonal behavior under low solar activity and its change with increasing solar activity. Both common and specific features of the high-latitude (Norilsk), mid-latitude (Irkutsk) and low-latitude (Hainan) regular variations were revealed using their local empirical models.

Study on the Adaptability of Global Ionoshperic Scintillation Model at Low Latitude in China

Sheng Dongsheng, Zhao Zhenwei, Sun Shuji, Wang Feifei

2014, 34(2): 154-159. doi: 10.11728/cjss2014.02.154

Abstract(1313) PDF 1490KB(1587)

Abstract:
A forecast of ionospheric scintillations can provide the opportunity for radio communication system to take appropriate action to mitigate the effects and optimize service. The Global Ionospheric Scintillation Model (GISM) by Béniguel was developed to forecast the global ionospheric scintillation condition. To check the prediction accuracy of the model at low latitude in China, this paper compares the model predictions with observed L-band ionospheric scintillation data at three low-latitude stations in China from July 2011 to June 2012. The results show that the model predictions had a good correlation with the statistical characteristics of the scintillation during solar maximum. The predicted beginning time of the scintillation agreed with measurements in general, while the end time was delayed for about an hour. As to the maximum scintillation intensity, the predictions could reproduce the measurements fairly well. Under the same cumulate probability condition, the model had somewhat higher prediction precision for each given scintillation intensity. The predicted percentage of occurrence and intensity of scintillation show gradual decrease versus latitude, which is consistence with measurement.

Method for determining the critical frequency and propagation factor at the path midpoint from maximum usable frequency and its propagation delay based on oblique sounder

Wang Jian, Ji Shengyun, Wang Hongfa, Lu Dongming, Wang Xianyi

2014, 34(2): 160-167. doi: 10.11728/cjss2014.02.160

Abstract(1421) PDF 643KB(2034)

Abstract:
Accurately determining critical frequency and propagation factor of ionosphere was important to frequency forecast and management of short-wave communication. Oblique sounder provide a valid method for real-time observation of it. A new practicable method was presented for determining f₀F₂ and M(3000)F₂ at the path midpoint from the oblique sounding data, which was based on simple oblique ray theory and only rely on maximum observation frequency and its propagation delay. The inversion from oblique sounding data on the Changchun-Jingyang and Xinxiang-Chifeng path, were compared with the vertical sounding data in Beijing during October 2009. According to analysis, the stability, accuracy and practicability of the new method are validated. The results show that the root-mean-square error of the new inverse method is 0.48MHz, and the relative root-mean-square error is 10.50%. It is obvious that the new inverse method is better than Smith's method and reference ionosphere of China. Moreover, the method is simple and easy to use. It provides the basis for frequency forecast and management of short-wave communication, and help to know ionospheric variational characteristics.

Derivation of TEC and GPS hardware delay based on dual-frequency GPS observations

Wang Xiaolan, Ma Guanyi

2014, 34(2): 168-179. doi: 10.11728/cjss2014.02.168

Abstract(1571) PDF 1085KB(1936)

Abstract:
The ground-based GPS receivers and hence networks enable studies of the ionosphere on a large regional or global scale by measuring the ionospheric TEC from dual-frequency GPS observations. However, originated in the hardware delay of the GPS satellite and receivers, a systematic bias affects the accuracy of the TEC derivation greatly. For accurate estimation of TEC, satellite and receiver instrumental biases should be removed from TEC measurements properly. This paper gives a comprehensive review of the algorithms on TEC and GPS hardware delays derivations. Starting from ionospheric radio wave propagation, the paper describes how the TEC is related with hardware delays. Then the TEC derivation methods are analyzed, evaluated and categorized into 3 main types. Finally, some suggestions are provided for further research on derivation of TEC and hardware delay.

Simulation and validation of composite shielding for total ionizing dose

Hu Jianhang, Feng Ying, Han Jianwei, Cai Minghui, Yang Tao

2014, 34(2): 180-185. doi: 10.11728/cjss2014.02.180

Abstract(1216) PDF 1002KB(1557)

Abstract:
Total ionizing dose effects caused by space radiation environment will be hazards for satellite electronic devices, and radiation shielding with appropriate materials is needed. Different shielding schemes for electron have been simulated with Monte-Carlo method. Three different shielding options, i.e., pure aluminum, pure tantalum and double-layer structure constituted by these two materials, have been compared. The results indicated that, when the shielding thickness is large enough, composite shielding for electron is better than single material shielding. And through experiments using the ⁹⁰Sr-⁹⁰Y source for irradiation test, pure material shielding and composite shielding are compared. The results were consistent with those of the simulation. The research conclusions can provide valuable references to optimization design for radiation shielding.

A method for separating O wave and X wave in digital ionosonde

Wang Shun, Chen Ziwei, Zhang Feng, Gong Zhaoqian, Fang Guangyou, Wang Yungang

2014, 34(2): 186-193. doi: 10.11728/cjss2014.02.186

Abstract(1937) PDF 1868KB(1558)

Abstract:
Separation for O wave and X wave is an important job in ionosphere detection. A new digital method for separating O wave and X wave is presented in this paper, being different from using image recognition technique to separate trace O and trace X in ionograms or electrical method to synthesize circularly polarized signals to separate O wave and X wave from echoes of the ionosphere. A numerical synthesizing method is employed in the new method. By introducing phase shifters of ±90° in digital domain, circularly polarized signals are synthesized digitally within the range of 1～ 30MHz, which eliminates the nonlinearity and expands the bandwidth of the ionosonde compared with DPS-4, and there is no need to switch the analog switches continuously. The new method has been successfully applied to CAS-DIS ionosonde and testing results show that the new digital method is capable of separating O wave and X wave well.

Study on the transmission properties of plasma sheath based on transfer matrix method

Sun Xin, Liu Yanan, Liu Yimin, Wang Xianyi, Wang Jian

2014, 34(2): 194-200. doi: 10.11728/cjss2014.02.194

Abstract(1286) PDF 1633KB(1617)

Abstract:
Due to compression and pyrogenation by shock wave, plasma sheath is formed around the surface of vehicle when hypersonic aerocrafts fly in near space. Plasma sheath can absorb and reflect electromagnetic wave radiated by the antenna on the vehicle. In order to analyze transmission property of plasma sheath, transfer matrix method is introduced. Based on the typical vehicle model and fundamentals of computational fluid dynamic, the Navier-Stokes equations are solved and electron density distribution in the plasma sheath is obtained. On the basis of propagation theory of electromagnetic wave and correlative characteristics of plasma sheath, the attenuation coefficient of electromagnetic wave in plasma sheath is diagnosed. On the other hand, propagation characteristics of electromagnetic signals which mainly include refection and transmission coefficients are analyzed. Analysis results show that good agreement is achieved among numerical results of transfer matrix method, theory analysis results and simulation results of FDTD (Finite Difference Time Domain). It is proved that the proposed method dramatically decreases computation complexity and is suitable for any kind of electron density distribution and thickness of plasma sheath.

Fault detection for in-orbit satellites using an adaptive prediction model

Li Weizheng, Meng Qiao

2014, 34(2): 201-207. doi: 10.11728/cjss2014.02.201

Abstract(1484) PDF 949KB(1704)

Abstract:
Faults are unavoidable for in-orbit satellites. They are able to be detected by carefully analyzing the telemetry data from these satellites. It is obvious that a good performance of anomaly detection algorithm is very important. This paper presents a new approach which takes the advantage of the similarity of preceding telemetry data to detect current anomaly. Because of its adaptive checking criteria, it can find some faults that cannot be found by some traditional methods. Most of important thing of this algorithm is that no prior knowledge about any particular satellite is needed except telemetry data themselves. In order to prove its availability, we use this new approach to process telemetry data from a China on-orbit satellite in 2012 and a fault is detected instantaneously.

An orbital anomaly analysis method based on TLE data

Wang Ronglan, Liu Wei, Liu Siqing, Yan Ruidong, Gong Jiancun

2014, 34(2): 208-213. doi: 10.11728/cjss2014.02.208

Abstract(1653) PDF 498KB(1577)

Abstract:
Orbital Anomaly of space object is an important problem for satellite operators and users. It is very meaningful to find orbital anomaly timely and quickly. By analyzing orbital anomaly of space objects, the avoidance or collision event can be found and discriminated, further the ability of United States Space Surveillance Network (SSN) can be determined. This paper put forward a simple orbital anomaly analysis method based on TLE data called Semi-major Axis Change Method (SACM). This method is rapid and valid, and can be applied to orbital anomaly analysis of LEO operational satellites and the breakup debris produced in the Cosmos 2251 and Iridium 33 satellite collision. With this method, the discrimination accuracy rate can reach 100 percent. By analyzing the orbit anomaly of American Russian breakup debris with SACM, it is found that US SSN can steadily detect over 90 percent breakup debris.

Study of small rocket-borne SF₆ active releaser

Cai Minghui, Feng Ying, Wu Fengshi, Huang Wengeng, Li Hongwei, Yang Tao, Han Jianwei

2014, 34(2): 214-218. doi: 10.11728/cjss2014.02.214

Abstract(1294) PDF 543KB(1692)

Abstract:
Chemical release at ionospheric altitudes is one of the most important ways to carry out active experiments for investigation of ionosphere features. A new rocket-borne SF₆ releaser is studied. This releaser has many advantages such as small size, light weight, low requirements for the launch platform, and when the device weight is 6kg, 2kg SF₆ can be released. By means of simulation, the diffusion process of neutral gas and relevant chemical reactions in ionosphere are calculated, and the effect of SF₆ releases is investigated．Results showed that the designs scheme of the SF₆ releaser is feasible and consistent with domestic rocket-borne platform and conditions in China, hence has high application value.

Chang’E-3 Lander’s scientific payloads

Jia Yingzhuo, Dai Shuwu, Wu Ji, Sun Huixian, Liu Enhai, Wei Jianyan, Chen Bo, Huang Changning, Chen Xiaomin

2014, 34(2): 219-225. doi: 10.11728/cjss2014.02.219

Abstract(2583) PDF 2769KB(2019)

Abstract:
Four kinds of scientific instruments are chosen as the payloads on Chinese Chang'E-3 Lander, including topography camera, lunar astronomical optical telescope, extreme ultraviolet imager and descending camera. Topography camera is to acquire the optical image of lunar surface topography around the landing area, and observe the rover moving process on the lunar surface. Lunar astronomical optical telescope operates in the near ultraviolet spectrum, which can observe the brightness variations of various stars. Extreme ultraviolet imager works on the wavelength of 30.4nm, and the observation target is the resonance scattering between Earth's plasma He⁺ layer and 30.4nm solar radiation. Descending camera is to acquire the lunar optical image in the landing region during descending. In this paper, Chang'E-3 Lander's scientific exploration missions, as well as the payloads' system design are introduced. Each payload's design and main technical specifications are also described in detail.

Polarimetric mode of full polarization interferometric radiometer

Yang Xiaocheng, Yan Jingye, Wu Ji

2014, 34(2): 226-234. doi: 10.11728/cjss2014.02.226

Abstract(1447) PDF 1137KB(2056)

Abstract:
Demonstrator of Full Polarization Interferometric Radiometer (FPIR) is a one dimensional microwave interferometric radiometer with high resolution, light weight and low power consumption at X-band. The theory of polarimetry is analyzed to deduce the polarimetric visibility function in FPIR. To obtain the full polarimetric information, two kinds of different antenna arrays are designed in the FPIR system. Corresponding optimal polarization switching sequence for each sparse antenna array is also designed. The minimum degradation in sensitivity is achieved and sensitivities of the horizontal, vertical, and complex cross brightness temperatures are the same in the polarimetric mode of FPIR with the polarization switching sequence.

A method of in-orbit calibration of fluxgate magnetometer based on the measurement of absolute scalar magnetometer

Zhang Zhenqi, Li Lei, Zhou Bin, Zhang Yiteng

2014, 34(2): 235-241. doi: 10.11728/cjss2014.02.235

Abstract(1659) PDF 838KB(1865)

Abstract:
High precision measurement of the magnetic field is required for in-orbit magnetic field monitoring and mapping. Due to the restrictions of processing technology and installation, the three axes of fluxgate magnetometer cannot be strictly orthogonal and the offsets in three directions are unknown in actual measurement. To solve this problem, it is necessary to determine the alignment and offset of the fluxgate magnetometer in-orbit instead of on the ground. According to the method of calibrating with scalar magnetometer, a method for calibrating the alignment, sensitivity, and offset by an improved least square calibration algorithm is proposed. Results show that considering the noise of detector itself, the error of fluxgate magnetometer can be reduced from about 100nT to less than 0.2nT. This calibration algorithm offers a feasible way of in-orbit high-precision measurements.

Simulation of 3D X-ray imaging for space material science experiments

Yu Qiang, Tong Fangyuan, Zhou Binghong

2014, 34(2): 242-248. doi: 10.11728/cjss2014.02.242

Abstract(1357) PDF 653KB(1584)

Abstract:
Developing X-ray observation facility has been planned in the Chinese space station. Simulating the process of three-dimensional X-ray imaging can offer valuable reference for the facility development. The simulation process can be divided into three steps. Firstly, to use the cone beam X-ray to scan an object, and rotate the object to obtain projection images at enough number of views; Secondly, to reconstruct the scanned object according to the projection images and the geometrical information; Finally, to visualize the reconstruction object. By employing a 3D Shepp-Logan model consisting of 10 interlapped ellipsoids with different linear attenuation coefficients as the object, the processes of projection, back projection and 3D visualization are realized by simulation, and through image reconstruction, the stereo structure of the scanned object can be well displayed.