IERS1996规范中地球引力势模型和测量模型的改进

简要而系统地介绍ＩＥＲＳ１９９６规范采用的地球引力势模型和各种测量模型,着重叙述了其与ＩＥＲＳ１９９２标准相比所作的改进。规范用ＪＧＭ－３地球引力势模型取代ＧＥＭ－Ｔ３模型,在计算地球潮汐形变产生的附加势时展开到３阶,并考虑了地幔的滞弹效应。在测站位移的计算中,规范引入了３倍洛夫数,计及地幔的滞弹性,引入了计算冰后期回弹的ＩＣＥ－４Ｇ模型,列出了改正ＶＬＢＩ观测中天线形变改正的公式。关于地球自转和     

1979-1999全球天测与测地VLBI观测资料处理结果与讨论

采用国际地民服务（ＩＥＲＳ）１９９６年规范和上海天文台甚长基线干涉测量（ＶＬＢＩ）资料分析软件,对自１９７９年８月以来全球约２９００次天测与测地ＶＩＢＬ实验进行了综合归算,得到６０１颗河外射电源在Ｊ２０００．０的坐标、１０１台站在Ｊ１９９７．０的坐标和运动速度、以及约２０年地地球定向参数序列。与国际相关结果的比较表明,归算结果不存在显著系统差。通过对归算结果的分析,指出目前国际上评估天球参考架局部     

国际天球参考系

阐述了１９９８年１月４日起ＩＡＵ采用的天球参考系的定义,以及它与以往采用的光学天球参考架ＦＫ５的关系。介绍了国际天球参考系在射电波段的实现过程,其稳定性的维持方法和它与依巴谷星表之间的关系。重点描述了影响国际天球参考架稳定性的物理因素－河外射电源的结构及其变化,射电源喷流的视超光速现象和由银河系盘星和大质量致密晕的引力透镜效应引起的视自行等。     

N－Cat系列综合河外射电源表

本文利用弧长差选源方法和共同基本源指向维持模型，并参照当今各河外射电源观测表之间的相互独立性，组建了１９８８至１９９３各年度的综合河外射电源表，即Ｎ－Ｃａｔ系列综合表。检验结果表明，Ｎ－Ｃａｔ系列表中坐标系是统一的，其指向维持精度高于０．１ｍａｓ，明显好于Ａ－Ｃａｔ系列表和ＩＥＲＳ系列表，这充分肯定了弧长差选源方法和共同基本源指向维持模型的优越性。文中部分结果显示，１９９２年与１９９３年的ＩＥＲＳ综合表之间存在显著指向差异，对此应予以重视。     

依巴谷星(104297)相对于伽里略卫星Callisto的CCD位置测量

１９９７年１１月１４日晚，在中国科学院云南天文台１米望远镜上用新安装的１０２４２ＣＣＤ观测到了木星的两颗伽里略卫星；Ｅｕｒｏｐａ和Ｃａｌｌｉｓｔｏ及一颗依巴谷星（星号为 １０４２９７）．当采用新的 ＪＰＬ ＤＥ４０５和 Ｓａｍｐｓｏｎ－Ｌｉｅｓｋｅ理论（Ｇ５）计算卫星的理论位置并相对于Ｃａｌｌｉｓｔｏ测量恒星位置时，视位置的观测值与计算值之差的平均值在赤经和赤纬方向分别为△α＝－０″０２９±０．″０１２，△δ＝０．″００５± ０．″０１１．这对应于平均观测历元（ＵＴ）：１９９７年１１月１４日１３时４３分５０秒．这一试验结果与 Ｃａｓａｓ等在同一时期内ＣＣＤ观测的结果有着很好的一致性 它反映了依巴谷星表体现的光学参考系与ＤＥ４０５体现的动力学参考系在观测历元具有较好的一致性．单次位置测定的标准误差在赤经赤纬方向分别为±０．″０５２和０．″０４７．这一精度明显优于 Ｃａｓａｓ等人发表的 Ｃａｌｌｉｓｔｏ的处理精度，并与目前国际上最好的伽里略卫星观测精度相当     

PUBLICATIONS OF THE YUNNAN OBSERVATORY 2001 CONTENTS

ＳｔａｒＰｈｙｓｉｃｓＰｒｏｇｒｅｓｓｉｎｔｈｅＳｔｕｄｙｏｆＡｂｕｎｄａｎｃｅｓｏｆＨｅａｖｙＥｌｅｍｅｎｔｓｉｎＭｅｔａｌ-ＰｏｏｒＳｔａｒｓＺＨＯＵＧｕｉ-ｄｅ ( 4) . 7……………………………………………………………………ＳｏｌａｒＰｈｙｓｉｃｓ　ＲａｄｉｏＡｓｔｒｏｎｏｍｙＴｈｅＤｙｎａｍｉｃａｌＦｅａｔｕｒｅｏｆＦｉｌａｍｅｎｔｓｉｎＡＲ750 0ＪＩＡＮＧＹｕｎ -ｃｈｕｎ ,ＬＵＡＮＤｉ ( 1 ) . 1 8………ＳｏｌａｒＲａｄｉｏＭｅｔｒｉｃＷａｖｅＥｖｅｎｔｓＦｒｏｍＡｃｔｉｖｅＲｅｇｉｏｎ 653 8…     

利用地球定向参数确定依巴谷输入星表与射电天球参考架之间的旋转

通过比较地球定向参数（ＥＯＰ）序列和对应的地固参考架，本文得到了依巴谷输入星表（ＨＩＣ）和国际地球自转服务（ＩＥＲＳ）基于甚长基线干涉测量（ＶＬＢＩ）建立的河外天球参考架（ＩＣＲＦ）之间的旋转参数，在Ｊ２０００．０历元，前者至后者的旋转参数为［８．４±１．１ｍａｓ，４６．７±１．１ｍａｓ，４５．５±１．５ｍａｓ］，其时间变率为［－０．１４±０．０５ｍａｓ／ａ，３．２２±０．０５ｍａｓ／ａ，５．７０±０．０７ｍａｓ／ａ］。依巴谷输入星表是完全基于ＦＫ５系统的，本文得到的旋转参数与ＩＣＲＦ和ＦＫ５之间的系统差异情况相符     

1988至1992各年度IERS综合河外射电源表的重新归算

鉴于ＩＥＲＳ综合河外射电源表在建立ＩＡＵ协议天球参考架方面的重要意义和它们的不足之处，本文重新组建了１９８８至１９９２各年度的综合河外射电源表，称之为Ｃａｔ称列表，并依据综合表的组建原理，对重新计算得到的Ｃａｔ系列表进行了检验，结果表明Ｃａｔ系列表克服了ＩＥＲＳ系列表中坐标系不统一的缺点，指向的定义及维持亦较之ＩＥＲＳ系列表有较大程度地改观。比较结果显示，ＩＥＲＳ系列表中部分源的坐标存在毫角秒量级     

1988至1992各年度IERS综合河外射电源表的重新归算

鉴于ＩＥＲＳ综合河外射电源表在建立ＩＡＵ协议天球参考架方面的重要意义和它们的不足之处，本文重新组建了１９８８至１９９２各年度的综合河外射电源表，称之为Ｃａｔ系列表。并依据综合表的组建原理，对重新计算得到的Ｃａｔ系列表进行了检验，结果表明Ｃａｔ系列表克服了ＩＥＲＳ系列表中坐标系不统一的缺点，指向的定义及维持亦较之ＩＥＲＳ系列表有较大程度地改观。比较结果显示，ＩＥＲＳ系列表中部分源的坐标存在毫角秒量级的偏差，各年度综合表的指向与ＩＥＲＳ预期指向亦有不同程度的偏离，个别轴的最大指向偏差至０．６ｍａｓ。同时指出，１９９３年ＩＥＲＳ综合表的指向亦有待讨论。     

5个新发现的X选BL Lac天体

利用ＲＯＳＡＴ－ＶＬＡ方法筛选，从ＲＯＰＳＡＴ Ｘ射线源中选出了一批新的ＢＬ Ｌａｃ天体和类星体的候选体。１９９６年１２月８日至１７日，利用北京天文台２．１６ｍ望远镜和新从美国引进的ＯＭＲ摄谱仪，对这批新候选体进行了光谱认证。经ＳＵＮ工作站处理，又发现了５个新的Ｘ选ＢＬ Ｌａｃ天体。     

Accurate analytical nutation series

In this letter we present the first accurate analytical nutation series, deduced from the Hamiltonian theory by the authors. They provide the highest accuracy ever obtained by any analytical nutation series, since the deviation in CEP (celestial ephemeris pole) offsets with respect to that of the IERS Conventions 1996 is kept below 1 mas in the time domain, in spite of still lacking ocanic corrections.     

Orientation of the hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 ephemerides based on asteroid observations

Highly accurate observations of 116 asteroids are used to determine the orientation of the Hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 majorplanet ephemerides. These observations include the photographic observations of 15 asteroids obtained as part of the programs for observing selected asteroids and reduced to the Hipparcos frame using dependences, the space observations of 48 asteroids obtained by the Hipparcos satellite, and the presentday observations of 116 asteroid performed in the frame of the ACT catlog. The total number of observations used is more than 50 000 in the interval 1949–2007. Processing this series has yielded the following estimates of the orientation parameters: ω _x = 0.12 ± 0.08 mas yr^?1, ω _y = 0.66 ± 0.09 mas yr^?1, and ω _z = ?0.56 ± 0.16 mas yr^?1. This rotation may be attributable to a peculiarity of the transition from the reference frame of the DE200/LE200 ephemerides to that of DE403/LE403 ephemerides (since October 1, 1988, to J2000) that consists in the the assumption that the former reference frame has no rotation relative to the ICRF.     

Toward the construction of a new precession-nutation theory of nonrigid Earth

The accuracy of the rigid Earth solution SMART97 is 2?μ as over the time interval (1968, 2023), accuracy showed by the comparison with a numerical integration using the positions of the Moon, the Sun, and the planets given by DE403. To obtain a nonrigid Earth solution, we use the transfer function of Mathews et al. (2000) and , to keep the precision of our rigid Earth solution in the computation of the geophysical effects, we apply this transfer function to the Earth's angular velocity vector in order to avoid the inherent approximations of the classical methods. Moreover the perturbations of the third component of the angular velocity vector are taken into account. Lastly, we take into account, in an iterative process, the second order perturbations due to the geophysical effects. The results are compared with the Herring solution (1996) published in the IERS Conventions.     

Modern Numerical Ephemerides of Planets and the Importance of Ranging Observations for Their Creation

The JPL planetary and lunar ephemerides – DE200/LE200, DE403/LE403, DE405/LE405 and the planetary and lunar ephemerides, EPM87, EPM98, and EPM2000, constructed in the Institute of Applied Astronomy of RAS are described. Common properties and differences of the various ephemerides are given. Graphical comparisons of the DE ephemerides with each other and with the EPM ephemerides are presented. A fairly good agreement of planetary orbits is between DE403, DE405 and EPM98, EPM2000, respectively, over the interval of 120 years (1886–2006) covered by EPM98 and EPM2000. Some differences are explained by a slight disagreement in representing the orbits of Ceres, Pallas, and Vesta as they affect the planets. The accurate radar observations of planets and spacecraft make it possible not only to improve the orbital elements of planets but to determine a broad set of astronomical constants as well: km/AU, parameters of Mars rotation including its precessional rate, the masses of Jupiter, Ceres, Pallas, and Vesta, relativistic parameters of the PPN formalism, the variability of the gravitational constant G. These have been obtained in the fitting process of the DE405 and EPM2000 ephemerides to observational data, including nearly 80000 American and Russian radar observations of planets (1961–1997), ranging and doppler to the Viking and Pathfinder landers, and other miscellaneous measurements from various sources and spacecraft.     

1988年至1995年IERS天球参考架的指向维持

本文分析了１９９２年至１９９５年期间国际地球自转服务（ＩＥＲＳ）天球参考架的指向维持情况，结合１９８８年至１９９２年的指向维持情况指出，该参考架在１９８８年至１９９５年期间历年的指向均存在显著变化，赤经零点和天极的最大年度漂移约为０．４ｍａｓ。至１９９５年，ＩＥＲＳ天球参考架的赤经零点和天极与各自预期位置的偏差不于０．４ｍａｓ。１９９４年和１９９５年的ＩＥＲＳ天球参考架基本上维持了１９９３年的ＩＥＲＳ天球参考指向，但是其实际维持精度约为０．０５ｍａｓ，并非０．００５ｍａｓ。０．００５ｍａｓ的维持精度只是数学上的平均效果，相当一部分基本源在相邻年度的ＩＥＲＳ天球参考架中的坐标差大于０．５ｍａｓ，这说明只有采用恰当的消除局部相对形变的方法，才能将天球参考架的指向真正维持在较高水平。     

关于RSC(IERS)88 C01实现中的几个问题的讨论

本文讨论了IERS的RSC 88C01实现过程中在有关基本源选取和参考架定向确定等方面存在的问题,分析了它们对IERS天球参考架的影响,提出了建立和维持高精度天球参考架的几点建议。     

天球参考系实现中的问题评述

本文评述了在建立历表参考架和恒星参考架过程中所面临的问题和困难，回顾了建立河外射电天球参考架的发展历史，并介绍了其目前状况，讨论了河外射电天球参考架在与其他天球参考架连接过程中所遇到的问题及其可能的解决途径。