空间科学学报

2017 Vol. 37, No. 3

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Research on Characteristics of X-class Solar Proton Flare

ZHANG Ye, SHI Liqin, CUI Yanmei, LIU Siqing

2017, 37(3): 249-261. doi: 10.11728/cjss2017.03.249

Abstract(1146) PDF 1833KB(1508)

Abstract:
Solar Proton Events (SPE) often accompany with solar flares, and the probability that solar proton events triggered by X-class flares is larger than that triggered by other types of flares. In order to improve the forecast accuracy of solar proton events triggered by X-class flares, the relation between proton/non-proton flares and space environmental parameters, including X-ray integrated flux, source region, CME speed, CME angle width, ambient solar wind speed, and ambient X-ray flux, are analyzed statistically. The results show that the distributions of X-ray integrated flux, heliolongitude, CME speed, and CME angle width are different for non-proton and proton flares. Non-proton flares are mostly located at eastern part, where X-ray integrated flux is less than 0.3J·m^-2 and CME speed is less than 1300km·s^-1. While proton flares are mostly located at central and western part, where X-ray integrated flux is greater than 0.3J·m^-2 and CME speed is greater than 1300km·s^-1. Furthermore, halo CMEs are often associated with proton flares, while angle width distribution of CMEs that accompanied with non-proton flares is relatively disperse. For proton and non-proton flares, the distribution of their ambient solar wind speed and ambient X-ray flux are similar. According to the different characteristics of the SPEs for proton and non-proton flares, the accuracy of SPE forecast can be improved.

Study on the Short to Medium Term Forecast Model of Solar Proton Event

CUI Yanmei, SHI Liqin, LIU Siqing

2017, 37(3): 262-269. doi: 10.11728/cjss2017.03.262

Abstract(1180) PDF 2724KB(1342)

Abstract:
Solar proton event forecast is very important to guarantee the security of spacecrafts and astronauts. According to the short to medium term space mission, the solar proton fluences whose energy are greater than 10MeV, 30MeV and 60MeV are statistically analyzed. It is found that the probability of solar proton fluences has a normal distribution, and their standard deviations and expectations are logarithmic functions over different time period from Day 1 to 365. Consequently, a short to medium term forecast model of solar proton fluences is built, which can forecast the solar proton fluences whose energy are greater than 10MeV, 30MeV and 60MeV with certain confidence levels for different time period. Therefore, this model is very helpful to safely carry out the space mission which task period is less than 1 year.

Ionospheric Weather Disturbance Indices Based on Spectral Whitening

ZHAO Yuxin, MAO Tian, CHEN Zhou, WANG Jingsong

2017, 37(3): 270-276. doi: 10.11728/cjss2017.03.270

Abstract(1088) PDF 4240KB(1813)

Abstract:
A Spectral Whitening Method (SWM) is introduced and applied in the study of ionospheric weather disturbances to calculate J_s, J_r and J_p indices on the basis of Total Electron Content (TEC) data provided by IGS. These indices can reflect the disturbances of ionospheric weather of single station, latitude circle (integral along longitude) and the whole planet separately. During a geomagnetic storm in March 2015, all three indices well reflect the ionospheric disturbances. The correlation coefficient between J_p and Dst indices reaches -0.72, and the 2D images of ionospheric disturbances can be well captured by J_s map. The correlation coefficient between J_p index and Dst index, from 2011 to 2014, reaches -0.67 if J_p is greater than or equal to 2, and the correlation coefficient can reach -0.87 if J_p is greater than or equal to 3. By analyzing the frequencies of different levels of geomagnetic storms under different threshold values of J_p index, the results suggest that J_p index, as a possible characterization parameter of ionospheric weather condition, can well reflect planetary ionospheric disturbances during geomagnetic storms.

Advances in the Study of Transionospheric Propagation of VLF Waves

LIAO Li, ZHAO Shufan, ZHANG Xuemin

2017, 37(3): 277-283. doi: 10.11728/cjss2017.03.277

Abstract(1273) PDF 1021KB(1178)

Abstract:
Very Low Frequency (VLF) electromagnetic wave (3~30kHz) mainly radiated by lightening and ground-based VLF transmitters, which plays a very important role on controlling the distribution of high energy particles in the magnetosphere. VLF radiation can penetrate into the ionosphere, and propagate in whistler mode in the ionosphere, and interact with high energy particles in the magnetosphere. In this paper, the development of the calculation model of VLF wave penetrating into the ionosphere, the validation of the model and the application of the model in the study of the ionospheric phenomena are reviewed, and a preliminary outlook for future work has also been made.

Observations and Simulations of the Mean Winds in Mesosphere and Lower Thermosphere over Langfang of China

YANG Junfeng, XIAO Cunying, HU Xiong, XU Qingchen

2017, 37(3): 284-290. doi: 10.11728/cjss2017.03.284

Abstract(940) PDF 1717KB(1045)

Abstract:
By use of the observations of the meteor radar located at Langfang, China (39.4°N, 116.7°E), the seasonal variation of mean winds in the Mesospheric and Lower Thermospheric (MLT) layer at 80~100km altitude over Langfang are studied. The time range of the observations is from 1 April 2012 to 31 March 2013. The results show that both the mean zonal winds and the mean meridional winds have obvious seasonal variations. In winter, westward winds prevail in the MLT, which are strongest in mesopause and decrease with increasing altitude. In summer, eastward winds dominate in mesosphere and decrease with increasing altitude, then turn to the strong westward winds at 82km altitude in lower thermosphere. Usually, the mean meridional winds are southward in summer and northward in winter. The wind evolutions have the transition features in spring and autumn. The above main seasonal variations of mean winds are captured largely by the simulation of WACCM4 model and HWM93 model. However, WACCM overestimates the wind velocities, and HWM93 underestimates the winds velocities.

Optimizing the NRLMSISE-00 Model by a New Solar EUV Proxy

XUE Bingsen, CANG Zhongya

2017, 37(3): 291-297. doi: 10.11728/cjss2017.03.291

Abstract(1495) PDF 1289KB(1216)

Abstract:
Solar EUV radiation is one of the sources for atmospheric density variation in thermosphere. NRLMSISE-00 model is widely used to simulate the density variation in the satellite orbit. However, this model always exhibits large density errors compared with satellite observations．In this work, the model output is compared with CHAMP satellite observation on the same position, and an ideal value of proxy for solar EUV (F^*) is chosen through changing the input F_10.7. Further investigation shows that F^* is closely related to another solar EUV index MgII. By using of neuron network technique, the correspondence relationship between the new proxy of solar EUV (F_euv) and F_10.7 and MgII. The target parameter is F^*. The new proxy substitutes F_10.7, and is input into NRLMSISE-00 model. The results show the difference of thermosphere density between those detected by CHAMP and GRACE-A satellite and that calculated by the NRLMSISE-00 model is dropped significantly.

Dynamic Prediction Model of Relativistic Electron Differential Fluxes at the Geosynchronous Orbit

LI Sheng, HUANG Wengeng, LIU Siqing, ZHONG Qiuzhen

2017, 37(3): 298-311. doi: 10.11728/cjss2017.03.298

Abstract(1074) PDF 9420KB(1202)

Abstract:
The Empirical Orthogonal Function (EOF) analysis is applied to develop an empirical model to predict relativistic electron fluxes at the geostationary orbit. This model uses the solar wind parameters and geomagnetic index to forecast the EOF-coefficient, and then gives the 5min prediction results of relativistic electron differential fluxes during the coming day according to the EOF base function. By comparing with the original relativistic electron data obtained by GOES 10 from January 2003 to June 2006, it is found that the model is capable of approximately reconstructing the real changes of relativistic electron fluxes and of effectively forecasting their 5min variations. The mean prediction efficiency of this model is 67%.

Analysis on Determining Warning Threshold of Space Objects

ZHOU Weiping, SHEN Ming, GUO Xiaozhong, GAO Pengqi, ZHAO You

2017, 37(3): 312-321. doi: 10.11728/cjss2017.03.312

Abstract(1362) PDF 1196KB(1369)

Abstract:
The method of collision probability is usually used to realize the work of collision assessment and warning of space objects, thus improving accuracy of collision assessment and warning is very important. The collision probability criterion is collision probability threshold. By investigating and analyzing the related bibliography from both domestic and international researchers, a comprehensive description on determination of collision probability threshold of space objects is presented. The determination of covariance matrix, the calculation of collision probability and the flux calculation of debris are introduced in detail. Taking International Space Station (ISS) for instance, of which, the debris flux was calculated and the incidence from space environment was analyzed. The conclusion that collision probability threshold of ISS may be overrated is reached by comparing with previous results.

Comparison of Adaptive Filter for Celestial Navigation during Approach Phase

NING Xiaolin, LI Zhuo, HUANG Panpan, YANG Yuqing

2017, 37(3): 322-331. doi: 10.11728/cjss2017.03.322

Abstract(1094) PDF 1625KB(1105)

Abstract:
Celestial navigation is an autonomous navigation method for deep space mission, which has been wildly researched. In celestial navigation, nonlinear Kalman filters such as Unscented Kalman Filter (UKF) are usually used. However, for traditional nonlinear Kalman filter, the system model errors should be Gaussian noise and their statistical characteristics should be known. However, the information is usually unknown and the system model errors are usually time-varying in real system. Hence, many adaptive filters have been studied to solve this problem. In this paper, three adaptive filters based on adjusting the predicted state covariance matrix are compared by simulation. Before this, the system model errors of celestial navigation are also analyzed for the approach phase.

Application of LQR Algorithm with Pole Placement in TEA Control for Space Station

LI Xinfeng, ZHANG Tao

2017, 37(3): 332-337. doi: 10.11728/cjss2017.03.332

Abstract(1370) PDF 1007KB(1063)

Abstract:
While designing the Torque Equilibrium Attitude (TEA) controller, a plant model for space station control, including attitude dynamics and momentum management, is concatenated with rejection filters to counteract the attitude undulation due to specified frequency disturbances. A modified Least Quadratic Regulator (LQR) algorithm with pole placement is adopted for the linearized motion model. This approach places close-looped poles in a margined fan-like region with its span angle defined by a specified integer and margin distance to the imaginary axis by a positive scalar. One pair of algebra Riccati equations can be solved with two-stage iterations, and the state weight matrix as well as the feedback gain matrix is calculated during the procedure. Desirable dynamic and stable performance can be obtained when this approach is tried upon this coupled model.

Design of Physical Simulation System for Satellite Flexible Rotating Panels Based on Flotation

YIN Meng, XU Zhigang, BAI Xinlin, LIU Zhe

2017, 37(3): 338-343. doi: 10.11728/cjss2017.03.338

Abstract(1068) PDF 2037KB(1096)

Abstract:
The elastic vibration is the main reason that affects the pointing accuracy and control performance of the space vehicle. It is of great interest to verify the ability of the control system to suppress vibration. Because the natural vibration frequency of solar panel is very low and its scale is large, the difficulty and cost to construct a spatial microgravity environment in ground are great. A flexible simulator based on equivalent principal axis inertia and flexible frequency is presented. Based on flotation technique, the physical simulation system of low friction and micro gravity environment is designed, and the dynamic model of the simulator is established, which realizes the effective and high economic test of the control algorithm. The results verify that the vibration characteristics of the simulator is consistent with those of the real solar panel, and its performance meets the test requirements. The simulator can change the parameters smoothly through a simple operation to simulate various flexible satellite rotating panel with different parameter and structure.

Experimental Research on Solar Array Drive Assembly Internal Charging Effects

SHI Liang, LIU Qing, CHEN Yifeng, YANG Shengsheng, QIN Xiaogang, LI Detian, WANG Jun

2017, 37(3): 344-349. doi: 10.11728/cjss2017.03.344

Abstract(1296) PDF 1948KB(1348)

Abstract:
Solar Array Drive Assembly (SADA) is a crucial component of the electrical transfer sub-assembly of the modern long life and large power satellite. The internal discharging and secondary arc in SADA, which happened under the high-energy electron environment, can lead to spacecraft abnormity and malfunction. Experimental platform has been built by using the two-beam accelerator. In the experiment, the electron energy is 2MeV, the beam density is 5pA·cm^-2, the working voltage of SADA is from 50 to 150V, and the working current is from 0.5 to 1.5A. The charging potential of test sample can reach equilibrium after 5 hours of irradiation. The electric field can reach about 5×10⁶V·m^-1. The time of discharge increases apparently with the increase of the working voltage at the same operating current. It shows that the electric field formed by the working voltage and the electric field formed by the high energy electron deposition will be superposed, which leads to the increase of the risk of SADA discharge. According the experiment results, the design of SADA anti-internal electricity can be improved by adopting the following methods. By reducing the bulk resistivity of SADA dielectric disk and improving the design of conducting ring structure, the electric field on the dielectric disk formed by the voltage between the conductive rings can be reduced.

Optical Prototype and Experimental Results of Geosynchronous Orbit Dynamic Monitoring System

LUO Hao, MAO Yindun, YU Yong, ZHANG Huiyan, TANG Zhenghong

2017, 37(3): 350-360. doi: 10.11728/cjss2017.03.350

Abstract(1192) PDF 3613KB(1295)

Abstract:
There are a large number of Geosynchronous Orbit (GEO) targets with variable motion form. In order to protect space activities and master the space activities happened in our exclusive orbit space, it is necessary to develop the dynamic monitoring of GEO. In December 2015, an optical prototype of GEO dynamic monitoring system was set up in Gaomeigu observation site of Lijiang observatory. Observation experiments were carried out by use of the prototype from December 2015 to February 2016. The results show that 27 GEO targets can be continuously monitored, and 2 of them are uncatalogued by North American Aerospace Defense Command (NORAD). The observation precision for GEO targets of the prototype is derived as well as 4" in azimuth and 1" in elevation. The target orbit is improved according to the multi-cycle observations, and in the absence of orbit control occurring, the precision of 24-hour and 48-hour position forecast is better than 9" in azimuth and 2" in elevation. Taking 3 GEO targets as examples, the preliminarily analysis and verification of the orbit variation events are carried out by use of the observation data.

Solar Energetic Neutral-atom Code Mask Imager

YANG Chuibai, ZHANG Binquan, CAO Guangwei, LIANG Jinbao, LU Li, ZHANG Shenyi

2017, 37(3): 361-368. doi: 10.11728/cjss2017.03.361

Abstract(1054) PDF 1795KB(1039)

Abstract:
A general design of Solar Neutral Atom code mask Imager (SNAI) is proposed for the Kuafu space weather exploring plan. The instrument is designed to measure the solar Energetic Neutral Atoms (ENA) emitted from the solar flare or CME. The differential energy spectrum of ENA is between 0.5MeV and 6MeV, and the FOV of ENA is 360° × 10°. This instrument combines innovative sensor geometry, an m sequence coding mask modulation aperture, and a combination of high voltage deflecting plate of active and passive shielding charging particles to obtain ENA in space flight. The coded imaging scheme and its simulation have laid the technical foundation for the coronal neutral atom imaging observation, which will provide the technical supports for the study of space weather.