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Atmospheric density determination using high-accuracy satellite GPS data

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Science China(Technological Sciences) 2018年第2期61卷 204-211页

作者： REN TingLing MIAO Juan liu siqing National Space Science Center Chinese Academy of SciencesBeijing 100190China College of Earth Sciences University of Chinese Academy of SciencesBeijing 100049China

Atmospheric drag is the main source of error in the determination and prediction of the orbit of low Earth orbit （LEO） satellites; however, empirical models that are used to account for this often have density errors of around 15%-30%. Atmospheric density determination has thus become an important topic for researchers. Based on the relationship between file atmospheric drag force and the decay of the semi-major axis of the orbit, we derived atmospheric density along the trajectory of challenging mini-satellite payload （CHAMP） satellite with its rapid science orbit （RSO） data. Three primary parameters--the ratio of cross-sectional area to mass, the drag coefficient, and the decay of the semi-major axis caused by atmospheric drag--were calculated. We also analyse the source of the error and made a comparison between the GPS-derived and reference density. The result for December 2, 2008, showed that the mean error of the GPS-derived density could be decreased from 29.21% to 9.20%, if the time span adopted for the process of computation was increased from 10 min to 50 min. The result for the entire month of December indicated that a density precision of 10% could be achieved, when the time span meets the condition that the amplitude of the decay of the semi-major axis is much greater than its standard deviation.

关键词： atmospheric density determination high-accuracy GPS data drag coefficient orbit decay

基于神经网络的未来3天Kp指数预报建模与可解释AI应用

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空间科学学报 2024年第3期44卷 437-445页

作者：王听雨罗冰显陈艳红石育榕王晶晶刘四清中国科学院国家空间科学中心空间天气学国家重点实验室中国科学院大学

当前业务中对未来3天Kp指数预报需求强烈.但地磁暴中多参数耦合导致难以量化各预报因子对Kp值的贡献,制约了预报精度提升.本文构建了神经网络3天Kp指数预报模型,并使用人工智能(AI)可解释性算法定量化各因子贡献.结果显示,行星际磁场南... 详细信息

当前业务中对未来3天Kp指数预报需求强烈.但地磁暴中多参数耦合导致难以量化各预报因子对Kp值的贡献,制约了预报精度提升.本文构建了神经网络3天Kp指数预报模型,并使用人工智能(AI)可解释性算法定量化各因子贡献.结果显示,行星际磁场南向分量在提前3 h对Kp指数的贡献为37.15%,为主要因子,说明模型能捕捉符合物理特征的主要预报因子. Kp指数历史特征贡献随提前量逐渐增加,提前3天总体贡献占68.06%,验证了对冕洞高速流引起的地磁暴事件的预报能力.对2015和2017年特大地磁暴进行贡献分析,模型准确捕捉了地磁暴多参数耦合的复杂特性.研究表明,可解释AI算法在一定程度上能定量化各预报因子对Kp指数的预报贡献,有助于改进未来3天Kp指数AI预报模型.

关键词：地磁暴未来3天Kp指数预报神经网络可解释性AI算法

Verification of SPE probability forecasts at the Space Environment Prediction Center(SEPC)

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Science China Earth Sciences 2016年第6期59卷 1292-1298页

作者： CUI YanMei liu siqing A Er Cha ZHONG QiuZhen LUO BingXian AO XianZhi National Space Science Center Chinese Academy of Sciences

In space weather forecasting, forecast verification is necessary so that the forecast quality can be assessed. This paper provides an example of how to choose and devise verification methods and techniques according to different space weather forecast products. Solar proton events(SPEs) are hazardous space weather events, and forecasting them is one of the major tasks of the Space Environment Prediction Center(SEPC) at the National Space Science Center of the Chinese Academy of Sciences. Through analyzing SPE occurrence characteristics, SPE forecast properties, and verification requirements at SEPC, verification methods for SPE probability forecasts are identified, and verification results obtained. Overall, SPE probability forecasts at SEPC exhibit good accuracy, reliability, and discrimination. Compared with climatology and persistence forecasts, the SPE forecasts are more accurate. However, the forecasts for SPE onset days are substantially underestimated and need to be considerably improved.

关键词： Forecast verification SPE forecast SPE onset days Space weather forecasting

Prediction of the smoothed monthly mean sunspot numbers for solar cycle 24

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Science China(Physics,Mechanics & Astronomy) 2008年第12期51卷 1938-1946页

作者： WANG JiaLong MIAO Juan liu siqing GONG JianCun ZHU CuiLian National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China Center for Space Science and Applied Research Chinese Academy of SciencesBeijing 100080China

The prediction for the smoothed monthly mean sunspot numbers (hereafter SMSNs) of solar cycle 23, which was given with a similar cycle method proposed by us at the beginning time of cycle 23, is analyzed and verified in this paper. Using our predicted maximum SMSN and the ascending length for solar cycle 24, and as- suming their relative errors to be respectively 20% and ± 7 months, solar cycles 2, 4, 8, 11, 17, 20 and 23 are selected to be the similar cycles to cycle 24. The selected solar cycles are divided into two groups. The first group consists of all the selected cycles; while the second group consists of only cycles 11, 17, 20 and 23. Two SMSN time profiles then may be obtained, respectively, for the two similar cycle groups. No significant difference is found between the two predicted time profiles. Consid- ering the latest observed sunspot number so far available for cycle 23 and the pre- dictions for the minimum SMSN of cycle 24, a date calibration is done for the ob- tained time profiles, and thus, SMSNs for 127 months of cycle 24, from October 2007 to April 2018, are predicted.

关键词： solar cycle sunspot numbers prediction of cycle 24

Comparison of a new model with previous models for the low-latitude magnetopause size and shape

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Chinese Science Bulletin 2010年第2期55卷 179-187页

作者： LIN RuiLin ZHANG XiaoXin liu siqing WANG YongLi GONG JianCun Centerfor Space Science and Applied Research Chinese Academy of Sciences Beijing 100190 China Graduate University of Chinese Academy of Sciences Beijing 100049 China National Center for Space Weather China Meteorological Administration Beijing 100081 China NASA/Goddard Space Flight Center Greenbelt Maryland 20771 USA

In this study, the advantages and the limitations of previous low-latitude magnetopause empirical models are discussed. In order to overcome their limitations and inherit their advantages, a new continuous function for the influence of the interplanetary magnetic field (IMF) Bz on the magnetopause, the Shue model function and the 613 low-latitude magnetopause crossings are used to construct a new low-latitude magnetopause model parameterized by the solar wind dynamic pressure (Dp) and IMF Bz. In comparison with the previous low-latitude magnetopause models, it is found that the new model improves the prediction capability and has a large range of validity for the low-latitude magnetopause. In addition, it is also demonstrated that the new model and the previous low-latitude magnetopause models are not appropriate for predicting the high-latitude magnetopause.

关键词：磁层顶低纬度国际货币基金组织型号形状行星际磁场经验模型连续函数

A regional ionospheric TEC mapping technique over China and adjacent areas: GNSS data processing and DINEOF analysis

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Science China(Information Sciences) 2015年第10期58卷 168-178页

作者： A Ercha HUANG WenGeng liu siqing SHI LiQin GONG JianCun CHEN YanHong SHEN Hua National Space Science Center Chinese Academy of Sciences

A technique is developed to derive two-dimensional maps of total electron content(TEC) over China and adjacent areas using Global Navigation Satellite System(GNSS) data from the Crustal Movement Observation Network of China(CMONOC) and the International Global Navigation Satellite System Service(IGS). A revised self-calibration of pseudo-range errors(SCORE) algorithm is used to derive the TEC and to determine the Differential Code Biases(DCBs) simultaneously. The accuracy and validity of this technique is verified in two ways. Firstly, the estimated TEC is compared with the results derived using DCBs from Center for Orbit Determination of Europe(CODE) under different solar activity conditions and seasons; secondly, sample TEC along the receiver-to-satellite ray paths are simulated by Ne Quick model and are reprocessed by this TEC derivation technique to make the accuracy test. Two-dimensional maps of vertical TEC of ionospheric pierce points(IPPs) are obtained accordingly with a time resolution of 30 s. The data interpolating empirical orthogonal functions(DINEOF) technique is then used to make the extrapolation for the unknown or missing data points. The optimal EOF modes for data reconstruction are specified via cross-validation method. The regional TEC distribution over China and adjacent areas is scaled into grid size of 1? × 1? for each 5 min, which can well reflect the characteristic of large-scale regional variations and temporal evolution as well as the small-scale local features of ionosphere.

关键词： TEC mapping GNSS processing SCORE algorithm DINEOF technique Ne Quick

Rabies surveillance and control in China over the last twenty years

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Biosafety and Health 2021年第3期3卷 142-147页

作者： Xiaoyan Tao siqing liu Wuyang Zhu Simon Rayner Key Laboratory of Biosafety National Health and Family Planning CommissionNational Institute for Viral Disease Control and PreventionChinese Center for Disease Control and PreventionBeijing 102206China Center for Biosafety Mega-Science Chinese Academy of SciencesWuhan 430071China Department of Medical Genetics Oslo University Hospital and University of OsloOslo 0424Norway

Globally,rabies remains a serious threat to public *** particular,large number of cases continue to be detected in Africa and *** has experienced three major outbreaks with the current epizootic starting in 1990s,peaking in 2007 with 3,300 cases,and consistently decreasing since this point.A key factor of the success in keeping the rabies outbreak under control is the National Public Health Reporting Program that was introduced to coordinate surveillance at provincial and regional *** this program,it is possible to obtain an integrated overview of how rabies was spreading and how various factors were contributing to the *** the same time,samples have been collected from suspected rabies cases and a subset of positive samples selected for *** this way,it is possible to investigate the outbreak from a phylogenetic perspective,providing the comprehensive description of a rabies outbreak to *** thiswork,we review rabies control efforts over the last 20 years,and showhowthis integrated approach has led to a deeper characterization of the outbreak and a better understanding of the factors driving the spread of the disease.

关键词： Rabies Rabies virus China Surveillance Lineage

Development and characterization of a clinical strain of Coxsackievirus A16 and an eGFP infectious clone

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Virologica Sinica 2015年第4期30卷 269-276页

作者： Chenglin Deng Xiaodan Li siqing liu Linlin Xu Hanqing Ye Cheng-Feng Qin Bo Zhang Key Laboratory of Special Pathogens and Biosafety Wuhan Institute of Virology Chinese Academy of Sciences University of Chinese Academy of Sciences State Key Laboratory of Pathogen and Biosecurity Beijing Institute of Microbiology and Epidemiology

Coxsackievirus A16(CA16) is one of the major causes of hand, foot, and mouth disease(HFMD) worldwide, which is a common illness that affects children. The frequent occurrence of HFMD outbreaks has become a serious public health problem in Asia. Therefore, it is important to understand the pathogenesis and replication of CA16. In this study, a stable infectious c DNA clone of an epidemic strain of Coxsackievirus A16(CA16) was assembled, and subsequently a reporter virus(e GFP-CA16) was constructed by inserting the e GFP gene between the 5'-UTR and the N-terminus of VP4, with the addition of a 2A protease cleavage site(ITTLG) at its C-terminus. This was transfected into Vero cells to generate infectious recombinant viruses. The growth characteristics and plaque morphology, in vitro, in mammalian cells were found to be indistinguishable between the parental and recombinant viruses. Although the e GFP-CA16 showed smaller plaque size as compared to recombinant CA16, both were found to exhibit similar growth trends and EC50 of NITD008. In summary, this stable infectious c DNA clone should provide a valuable experimental system to study CA16 infection and host response. The e GFP-CA16 is expected to provide a powerful tool to monitor e GFP expression in infected cells and to evaluate the antiviral activity of potential antiviral agents in the treatment of CA16 infections.

关键词： Coxsackievirus A16(CA16) infectious cDNA clone rep

Space Environment Prediction for SZ-4 and SZ-5

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空间科学学报 2004年第Z1期24卷 10-14页

作者： liu siqing liu Jing SHI Liqin HAN Jianwei ZANG Zhenqun Center for Space Science and Applied Research The Chinese Academy of Sciences Beijing 100080 China

The Space Environment Prediction Center (SEPC) of the Center for Space Science and Applied Research of the Chinese Academy of Sciences (CSSAR, CAS)took on the mission of offering the space environment parameters which may be of use to the safety of manned spacecraft. In order to complete the space environment safety guarantee mission for SZ-4 and SZ-5, SEPC improved the space environment monitoring system, database system, prediction result display system, prediction implementation system, etc. For guaranteeing the safety of the airship and cosmonaut in the first manned SZ-5, flying experiment mission,SEPC developed the software for analyzing radiation dose and early-warning software for large debris collision with SZ-5. Three months before the flights of SZ-4 and SZ-5, SEPC began to predict the safe launch period in view of the space environment, and offered timely and valid reference opinions for selecting the safety period. Especially during the mission of SZ-5, SEPC analyzed the space high-energy environment in a pre-arranged orbit and abnormal orbit andevaluated the radiation dose which cosmonauts may encounter in space. The evaluation offered an important reference for cosmonaut safety and decisionmaking in the SZ-5 mission. The calculation of the distribution of large debris and the collision risk assessment at different orbit entry times for SZ-5 provided an important base for the superior department to make flight decisions.

关键词： Space environment Prediction