共查询到20条相似文献，搜索用时 531 毫秒
1.
赵铭 《中国科学院上海天文台年刊》1992,(13):7-23
有些文献中关于UT0和UT1的关系的概念不够明确，甚至有明显的错误。本文论述了UT0和UT1关系的准确概念，指出：1、UT1是地球自转参数之一，它正比于地球绕暧时历书轴的自转角。UT1的数值与地球坐标系的参考的选取无关，也就是与地极坐标的原点的选取无关。因此，各服务机构得到的UT1序列之间除观测误差外不存在其他系统误差，它们是直接可比的。2、UT0不是地球自转参数，它仅是用单台站观测资料归算UT1过程中人为赋予的暂定值，因此没有独立的天文意义。一个具体UT0序列只对一特定台站有意义，它不具有全球意义。UT0的数值与地球坐标系的参考极的选取有关，即与极坐标原点的选取有关。 相似文献
2.
本文讨论了新天球参考系对测时测纬结果的影响,指出,若要求在1984年初,我国系统不发生跳动,在修正测时系统差的同时,要修改纬度地方项改正。考虑到新天球参考系的优越性,建议我国UT1系统不修正FK 5对FK 4的系统差。这样,我国UT1系统将在1984年初有一跳动。 相似文献
3.
Pierre Kaufmann Gérard Trottet C. Guillermo Giménez de Castro Jean-Pierre Raulin Säm Krucker Albert Y. Shih Hugo Levato 《Solar physics》2009,255(1):131-142
The presence of a solar burst spectral component with flux density increasing with frequency in the sub-terahertz range, spectrally
separated from the well-known microwave spectral component, bring new possibilities to explore the flaring physical processes,
both observational and theoretical. The solar event of 6 December 2006, starting at about 18:30 UT, exhibited a particularly
well-defined double spectral structure, with the sub-THz spectral component detected at 212 and 405 GHz by the Solar Submilimeter
Telescope (SST) and microwaves (1 – 18 GHz) observed by the Owens Valley Solar Array (OVSA). Emissions obtained by instruments
onboard satellites are discussed with emphasis to ultra-violet (UV) obtained by the Transition Region And Coronal Explorer
(TRACE), soft X-rays from the Geostationary Operational Environmental Satellites (GOES) and X- and γ-rays from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The sub-THz impulsive component had its closer temporal
counterparts only in the higher energy X- and γ-rays ranges. The spatial positions of the centers of emission at 212 GHz for the first flux enhancement were clearly displaced
by more than one arc-minute from positions at the following phases. The observed sub-THz fluxes and burst source plasma parameters
were difficult to be reconciled with a purely thermal emission component. We discuss possible mechanisms to explain the double
spectral components at microwaves and in the THz ranges. 相似文献
4.
本用自回归谱的Marplc算法，对1990年发表的IERS新UT1－UTC序列进行了分析，得到了与理论值非常接近的潮汐短周期项Mf、Mm波的谱峰及财年项、半年项的谱峰，还用最小二乘法对它们进行了振幅估计，并解算了Love数K值，结果为KMf=0.305±0.040,KMm=0.303±0.062。 相似文献
5.
本主要讨论了利用激光测月资料解算UT的两种方法：一种方法为仅仅解算世界时TU，另一种方法是同时求解UT和纬度变化△φ。经过实际计算和分析比较，结果表明：就目前的观测资料而言，只解UT的方案对解算UT值较有利。本着重讨论了在逐步回归解算中，自变量之间的相关性问题，这种情况下采用岭回归法解算，结果会有所改善。 相似文献
6.
G. Contopoulos 《Celestial Mechanics and Dynamical Astronomy》1981,24(4):355-366
We study the resonance 12 = 41 and some near-resonance cases. The main peculiarity of this resonance is that for 12 < 4 the characteristic of the central periodic orbits is broken into two and each part is joined with a resonant characteristic. This behaviour is described theoretically by means of the third integral. It seems that there are infinite families of simple periodic orbits near the escape region. Finally, a comparison is made with the cases near the 12 = 21 resonance. 相似文献
7.
利用IVS加强观测确定UT1的分析研究 总被引：1，自引：0，他引：1
首先对IVS(International VLBI Service for Astrometry and Geodesy)UT1加强观测的历史发展和总体情况进行了比较详细的介绍,对目前加强观测中存在的问题进行了比较全面的分析;在此基础上对IVS从1984年2月到2011年8月全部的加强观测数据进行了综合处理,进一步分析了加强观测解算UT1的历史改进和目前的解算能力,对比分析不同类型加强观测的UT1结果,发现不同观测网之间存在数十微秒水平的差异;并着重分析了上海佘山站参与的加强观测的解算结果,分析表明上海佘山站在IVS加强观测中与其他参与台站具有相同的测量能力.总体而言,目前IVS加强观测确定的UT1与IERS(International Earth Rotaion Service)C04之间存在约10μs水平的不确定性. 相似文献
8.
对2021年VLBI (Very Long Baseline Interferometry)全球观测系统(VLBI Global Observing System,VGOS)单基线开展的1 h世界时(Universal Time, UT1)加强观测数据进行分析,结果表明, VGOS单基线测得的UT1与IERS (International Earth Rotation Service) C04序列提供的UT1之差的RMS (Root Mean Square)为25.3μs,优于传统S/X双频段UT1加强观测(Intensive observation, INT1)试验的28.2μs,且UT1的平均形式精度提高1倍.因VGOS单基线1 h观测数目比INT1多1倍,其测得的UT1受极移误差的影响更加稳定,每100μas的极移误差将对UT1引入2.8μs的偏移.此外分析了VGOS 30 min观测数据,除平均形式精度变差外, UT1测量结果与1 h结果相当,表明VGOS单基线30 min观测可用于UT1的超快速服务.同时分析和评估了2021年国内佘山与南山13 m VGOS基线的UT1加强观... 相似文献
9.
Jan-Cees Van Der Meer 《Celestial Mechanics and Dynamical Astronomy》1982,27(2):131-149
Consider a Hamiltonian system of two degrees of freedom at an equilibrium. Suppose that the linearized vectorfield has eigenvaluesi,i,–i,–i ( , >0) and is not semisimple. In this paper we discuss the real normalization of the Hamiltonian function of such a system. We normalize the Hamiltonian up to 4th order and show how to compute its coefficients. For the planar restricted three body problem atL
4 the coefficient that plays an important role in the investigation of the qualitative behaviour of periodic solutions near the equilibrium is explicitly calculated. 相似文献
10.
现有UT1-UTC预报模式在进行周期项与残差项拟合分离时,通常没有考虑最小二乘拟合序列的端部效应,预报精度难以取得较大提高。针对最小二乘拟合存在的端部效应,首先采用灰色模型在UT1-UTC序列的两端进行数据延拓,形成一个新序列,然后对新序列进行最小二乘拟合,最后再联合最小二乘和神经网络(LS+NN)模型对UT1-UTC原始序列进行外推。结果表明,对UT1-UTC序列进行端点数据延拓再进行最小二乘拟合,能够有效地改善最小二乘拟合序列的端部效应;相对于常规LS+NN模型,端部效应改善的LS+NN模型的UT1-UTC预报精度有一定提高,尤其对中长期预报精度提高更为明显。 相似文献
11.
本文研究了1986－1988年美国喷气推进实验室、法国地球动力学中心和上海天文台用激光测月资料推算的UT1－UTC值，并与国际地球自转参数服务给出的UT1－UTC值作比较，得到各分析中心推算UT1－UTC值的内符和外符。 相似文献
12.
13.
现有的UT1-UTC预报模式在进行周期项与残差项拟合分离时,通常没有考虑最小二乘拟合序列的端部畸变现象(数据处理中称为端部效应),预报精度难以取得较大改善。针对最小二乘拟合存在的端部畸变现象,首先采用时序分析方法在UT1-UTC序列两端进行数据延拓,形成一个新序列,然后用新序列求解最小二乘外推模型系数,最后再联合最小二乘外推模型及神经网络对UT1-UTC序列进行预测。结果表明,在UT1-UTC序列端部增加延拓数据,可以有效地抑制最小二乘拟合序列的端部畸变,相对于常规的最小二乘外推模型,基于端部效应改善的最小二乘(Edge-effect Corrected Least Squares,ECLS)外推模型的UT1-UTC中长期预报精度改善明显。 相似文献
14.
R.R. Reddy Y. Nazeer Ahammed K. Rama Gopal P. Abdul Azeem S. Anjaneyulu 《Astrophysics and Space Science》1998,262(2):223-240
The potential energy curves for the electronic ground states of astrophysically important YO, CrO, BN, ScO, SiO and AlO molecules are constructed techniques using the five-parameter Hulburt-Hirschfelder function. The estimated dissociation energies are 7.235±0.15, 4.337 ± 0.09, 3.917 ± 0.09, 6.899 ± 0.14, 8.181 ± 0.17 and 5.202 ± 0.11 eV for YO, CrO, BN, ScO, SiO and AlO, respectively. The estimated D0 values are in reasonably good agreement with literature values. The r-Centroids and Franck-Condon factors for the bands of B2 + – X2 + of YO, B5 –X5 > of CrO, A3 – X3 of BN, B2 + –X2 + of ScO, E1 + – X1 + of SiO and D2 + – X2 + and B2 + –X2 + of AlO molecules have been determined. The Franck-Condon factors are evaluated by the approximate analytical method of Jarmain and Fraser. The absence of the bands in these systems is explained. 相似文献
15.
Kathleen Connor Howell 《Celestial Mechanics and Dynamical Astronomy》1984,32(1):53-71
A largely numerical study was made of families of three-dimensional, periodic, halo orbits near the collinear libration points in the restricted three-body problem. Families extend from each of the libration points to the nearest primary. They appear to exist for all values of the mass ratio , from 0 to 1. More importantly, most of the families contain a range of stable orbits. Only near L1, the libration point between the two primaries, are there no stable orbits for certain values of . In that case the stable range decreases with increasing , until it disappears at =0.0573. Near the other libration points, stable orbits exist for all mass ratios investigated between 0 and 1. In addition, the orbits increase in size with increasing . 相似文献
16.
G.W. Lockwood 《Icarus》1977,32(4):413-430
The brightnesses of Titan, Uranus, and Neptune in b (4718 ÅA) and y (5508 ÅA) have increased linearly since 1972 at rates ranging from 0.005 to 0.025 mag yr?1. The observations were made differentially on a number of nights each season with respect to a network of comparison stars whose relative magnitudes were determined by independent measurements. Solar phase coefficients were derived for each object, and all observations have been normalized to zero solar phase angle and mean heliocentric distances. No explanation for the changes has been found, but a possible influence of solar activity upon planetary albedo is suggested by the fact that all of the objects observed have brightened during the declining half of the solar cycle. 相似文献
17.
Bonnie J. BurattiMichael D. Hicks Kimberly A. TrykaMicah S. Sittig Ray L. Newburn 《Icarus》2002,155(2):375-381
New high-resolution spectra in the 0.33 to 0.92 μm range of Iapetus, Hyperion, Phoebe, Dione, Rhea, and three D-type asteroids were obtained on the Palomar 200-inch telescope and the double spectrograph. The spectra of Hyperion and the low-albedo hemisphere of Iapetus can both be closely matched by a simple model that is the linear admixture of the spectrum of a medium-sized, high-albedo icy saturnian satellite and D-type material. Our results support an exogenous origin to the dark material on Iapetus; furthermore, this material may share a common origin and a similar means of transport with material on the surface of Hyperion. The recently discovered retrograde satellites of Saturn (Gladman et al., Nature412, 163-166) may be the source of this material. The leading sides of Callisto and the Uranian satellites may be subjected to a similar alteration mechanism as that of Iapetus: accretion of low-albedo dust originating from outer retrograde satellites. Phoebe does not appear to be related to either Iapetus or Hyperion. Separate spectra of the two hemispheres of Phoebe show no identifiable global compositional differences. 相似文献
18.
, , , , . , , . , , - - ( , ..). - . 相似文献
19.
20.
. , , . , ( ) . ( =2) ( ) . 相似文献