One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang’E-3 lander and station on the Earth were collecte...One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang’E-3 lander and station on the Earth were collected from the beginning of the Chang’E-3 lunar mission in 2013.These observation data,taken together with the existing lunar laser ranging data,provide a new approach to extend research on the Earth-Moon system.The high precision of current observation data imposes exacting demands,making it necessary to include previously neglected factors.In this paper,motivated by progress of the Chinese lunar exploration project and to use its data in the near future,two lunar models:a one-layer model and a two-layer model with a fluid core,were applied to the rotational equations based on our implemented algorithm of the Moon’s motion.There was a difference of about 0.5′′in φ and ψ,but 0.2′′in θ between the two models.This result confirms that stratification of the inner structure of the Moon can be inferred from rotation data.We also added precise Earth rotation parameters in our model;the results show that this factor is negligible at present,due to the limited precision of the existing data.These results will help us understand the rotational process clearly and build a more realistic Earth-Moon model when we combine Lunar Laser Ranging data with high precision radio data to fit lunar motion in the near future.展开更多
Time series of Earth rotation parameters were estimated from range data measured by the satellite laser ranging technique to the Laser Geodynamics Satellites（LAGEOS）-1/2 through 2005 to 2010 using the dynamic method...Time series of Earth rotation parameters were estimated from range data measured by the satellite laser ranging technique to the Laser Geodynamics Satellites（LAGEOS）-1/2 through 2005 to 2010 using the dynamic method. Compared with Earth orientation parameter（EOP）C04, released by the International Earth Rotation and Reference Systems Service, the root mean square errors for the measured X and Y of polar motion（PM） and length of day（LOD）were 0.24 and 0.25 milliarcseconds（mas）, and 0.068 milliseconds（ms）, respectively.Compared with ILRSA EOP, the X and Y of PM and LOD were 0.27 and 0.30 mas, and 0.054 ms, respectively. The time series were analyzed using the wavelet transformation and least squares methods. Wavelet analysis showed obvious seasonal and interannual variations of LOD, and both annual and Chandler variations of PM; however, the annual variation could not be distinguished from the Chandler variation because the two frequencies were very close. The trends and periodic variations of LOD and PM were obtained in the least squares sense, and PM showed semi-annual, annual, and Chandler periods.Semi-annual, annual, and quasi-biennial cycles for LOD were also detected. The trend rates of PM in the X and Y directions were 3.17 and 1.60 mas per year, respectively, and the North Pole moved to 26.8E relative to the crust during 2005—2010. The trend rate of the LOD change was 0.028 ms per year.展开更多
Based on four intra-technique combined solutions in SINEX format, we tried at first to assess the accuracy of each single-technique Earth Orientation Parameters(EOPs) series over a past time interval of at least 15 ye...Based on four intra-technique combined solutions in SINEX format, we tried at first to assess the accuracy of each single-technique Earth Orientation Parameters(EOPs) series over a past time interval of at least 15 years by comparison with IERS EOP 08C04 combined solution as the reference in this paper. The EOPs studied here mainly consist of four elements, i.e. polar motion(XPO, YPO), Universal Time(UT1-UTC) and length-of-day(LOD). We combined these intra-technique EOP series, each of them associated with a given space geodetic technique by taking advantage of the relationship of the first three EOP components and three rotational parameters which carry the orientation of technique-related reference frame with respect to the estimated weekly inter-technique combined reference frame. Results indicated that the discrepancy between the pole coordinates(XPO, YPO) series, extracted from the intra-SLR combined loose-constraint solutions and the IERS EOP 08C04, seemed to be clearly characterized by systematic errors. Although both the XPO and YPO series determined by intra-VLBI combination had no significant characteristic of system error, they had relatively large difference values at some point with respect to the IERS EOP 08C04, which may be limited by the quantity of observation stations. Since the number of GPS stations is on the increase aimed at better global coverage, the accuracy of pole coordinates provided by IGS was superior to that derived from other space-geodetic techniques. As for DORIS XPO and YPO series from intra-DORIS combined minimal-constraint solutions, the discrepancy range of the former with respect to IERS EOP 08C04 was a little smaller than that of the latter. The objective of this study is twofold: on the one hand to analysis individual EOP series derived from the various space-geodetic techniques, on the other hand to present the new inter-technique combined EOP solution consistent with weekly inter-technique combined reference frame.展开更多
介绍了国际测地/天体测量学甚长基线干涉测量服务(International Very Long Baseline Interferometry(VLBI)Service for Geodesy and Astrometry,IVS)组织机构及下属分析中心概况.系统归纳了目前IVS发布的地球定向参数(Earth Orientatio...介绍了国际测地/天体测量学甚长基线干涉测量服务(International Very Long Baseline Interferometry(VLBI)Service for Geodesy and Astrometry,IVS)组织机构及下属分析中心概况.系统归纳了目前IVS发布的地球定向参数(Earth Orientation Parameters,EOP)产品类型及不同观测类型的用途.利用2010—2019年公开发布的观测资料,对IVS不同分析中心的EOP日常监测和服务能力进行了评估.通过构造观测台站所构成的几何体积,分析了EOP精度与测站数量、测站网分布的关系,统计了IVS不同观测类型的EOP解算精度.此外,综合公开发布的美国、欧洲等区域网观测数据,分析了不同地区区域网的常规及加强观测结果与IVS结果的差异.结果表明:EOP的解算精度与观测台站的分布密切相关,IVS常规观测确定的极移分量的外符合精度优于0.2 mas,世界时(Universal Time,UT1)与协调世界时(Coordinated Universal Time,UTC)之差(UT1-UTC)的精度在0.015 ms左右,加强观测的UT1-UTC值与国际自转服务组织(International Earth Rotation Service,IERS)的C04之间存在0.02–0.03 ms的差异.区域观测网的精度受观测网形和基线长度制约,总体劣于IVS观测精度,其中,美国甚长基线干涉阵列(Very Long Baseline Array,VLBA)的常规及加强观测结果与IVS全球观测结果最接近.展开更多
PRLSENTLY there are three kinds of realization of conventional celestial reference frames (CCRFs), i. e. the optical frame, the planetary frame and the extragalactic radio frame. 'Though the CCRFs are high in prec...PRLSENTLY there are three kinds of realization of conventional celestial reference frames (CCRFs), i. e. the optical frame, the planetary frame and the extragalactic radio frame. 'Though the CCRFs are high in precision, due to the difference in (ⅰ) the constants, parameters, formulae and force models used to define the frames; (ⅱ) the methods and techniques展开更多
基金supported by LIESMARS Special Research Fundingthe National Natural Science Foundation of China(U1831132,41590851,11373060,10973030 and 10778635)+3 种基金the State Key Project for Science and Technology(2015CB857101)National Astronomical Observatories,Chinese Academy of Sciences,a grant from the Hubei Province Natural Science(2018CFA087)Open Project of Lunar and Planetary Science Laboratory,Macao University of Science and Technology(FDCT 119/2017/A3)Open Funding of Guizhou Provincial Key Laboratory of Radio Astronomy and Data Processing(KF201813)
文摘One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang’E-3 lander and station on the Earth were collected from the beginning of the Chang’E-3 lunar mission in 2013.These observation data,taken together with the existing lunar laser ranging data,provide a new approach to extend research on the Earth-Moon system.The high precision of current observation data imposes exacting demands,making it necessary to include previously neglected factors.In this paper,motivated by progress of the Chinese lunar exploration project and to use its data in the near future,two lunar models:a one-layer model and a two-layer model with a fluid core,were applied to the rotational equations based on our implemented algorithm of the Moon’s motion.There was a difference of about 0.5′′in φ and ψ,but 0.2′′in θ between the two models.This result confirms that stratification of the inner structure of the Moon can be inferred from rotation data.We also added precise Earth rotation parameters in our model;the results show that this factor is negligible at present,due to the limited precision of the existing data.These results will help us understand the rotational process clearly and build a more realistic Earth-Moon model when we combine Lunar Laser Ranging data with high precision radio data to fit lunar motion in the near future.
基金supported by the National Natural Science Foundation of China(41374009)International Science and Technology Cooperation Program of China(2009DFB00130)+2 种基金Public Benefit Scientific Research Project of China(201412001)Shandong Natural Science Foundation of China(ZR2013DM009)the SDUST Research Fund(2014TDJH1010)
文摘Time series of Earth rotation parameters were estimated from range data measured by the satellite laser ranging technique to the Laser Geodynamics Satellites（LAGEOS）-1/2 through 2005 to 2010 using the dynamic method. Compared with Earth orientation parameter（EOP）C04, released by the International Earth Rotation and Reference Systems Service, the root mean square errors for the measured X and Y of polar motion（PM） and length of day（LOD）were 0.24 and 0.25 milliarcseconds（mas）, and 0.068 milliseconds（ms）, respectively.Compared with ILRSA EOP, the X and Y of PM and LOD were 0.27 and 0.30 mas, and 0.054 ms, respectively. The time series were analyzed using the wavelet transformation and least squares methods. Wavelet analysis showed obvious seasonal and interannual variations of LOD, and both annual and Chandler variations of PM; however, the annual variation could not be distinguished from the Chandler variation because the two frequencies were very close. The trends and periodic variations of LOD and PM were obtained in the least squares sense, and PM showed semi-annual, annual, and Chandler periods.Semi-annual, annual, and quasi-biennial cycles for LOD were also detected. The trend rates of PM in the X and Y directions were 3.17 and 1.60 mas per year, respectively, and the North Pole moved to 26.8E relative to the crust during 2005—2010. The trend rate of the LOD change was 0.028 ms per year.
基金supported by the National Natural Science Foundation of China (grants 11773058)
文摘Based on four intra-technique combined solutions in SINEX format, we tried at first to assess the accuracy of each single-technique Earth Orientation Parameters(EOPs) series over a past time interval of at least 15 years by comparison with IERS EOP 08C04 combined solution as the reference in this paper. The EOPs studied here mainly consist of four elements, i.e. polar motion(XPO, YPO), Universal Time(UT1-UTC) and length-of-day(LOD). We combined these intra-technique EOP series, each of them associated with a given space geodetic technique by taking advantage of the relationship of the first three EOP components and three rotational parameters which carry the orientation of technique-related reference frame with respect to the estimated weekly inter-technique combined reference frame. Results indicated that the discrepancy between the pole coordinates(XPO, YPO) series, extracted from the intra-SLR combined loose-constraint solutions and the IERS EOP 08C04, seemed to be clearly characterized by systematic errors. Although both the XPO and YPO series determined by intra-VLBI combination had no significant characteristic of system error, they had relatively large difference values at some point with respect to the IERS EOP 08C04, which may be limited by the quantity of observation stations. Since the number of GPS stations is on the increase aimed at better global coverage, the accuracy of pole coordinates provided by IGS was superior to that derived from other space-geodetic techniques. As for DORIS XPO and YPO series from intra-DORIS combined minimal-constraint solutions, the discrepancy range of the former with respect to IERS EOP 08C04 was a little smaller than that of the latter. The objective of this study is twofold: on the one hand to analysis individual EOP series derived from the various space-geodetic techniques, on the other hand to present the new inter-technique combined EOP solution consistent with weekly inter-technique combined reference frame.
文摘介绍了国际测地/天体测量学甚长基线干涉测量服务(International Very Long Baseline Interferometry(VLBI)Service for Geodesy and Astrometry,IVS)组织机构及下属分析中心概况.系统归纳了目前IVS发布的地球定向参数(Earth Orientation Parameters,EOP)产品类型及不同观测类型的用途.利用2010—2019年公开发布的观测资料,对IVS不同分析中心的EOP日常监测和服务能力进行了评估.通过构造观测台站所构成的几何体积,分析了EOP精度与测站数量、测站网分布的关系,统计了IVS不同观测类型的EOP解算精度.此外,综合公开发布的美国、欧洲等区域网观测数据,分析了不同地区区域网的常规及加强观测结果与IVS结果的差异.结果表明:EOP的解算精度与观测台站的分布密切相关,IVS常规观测确定的极移分量的外符合精度优于0.2 mas,世界时(Universal Time,UT1)与协调世界时(Coordinated Universal Time,UTC)之差(UT1-UTC)的精度在0.015 ms左右,加强观测的UT1-UTC值与国际自转服务组织(International Earth Rotation Service,IERS)的C04之间存在0.02–0.03 ms的差异.区域观测网的精度受观测网形和基线长度制约,总体劣于IVS观测精度,其中,美国甚长基线干涉阵列(Very Long Baseline Array,VLBA)的常规及加强观测结果与IVS全球观测结果最接近.
文摘PRLSENTLY there are three kinds of realization of conventional celestial reference frames (CCRFs), i. e. the optical frame, the planetary frame and the extragalactic radio frame. 'Though the CCRFs are high in precision, due to the difference in (ⅰ) the constants, parameters, formulae and force models used to define the frames; (ⅱ) the methods and techniques
