共查询到20条相似文献，搜索用时 15 毫秒
1.
郭俊义 《武汉大学学报(信息科学版)》2000,25(5):393-395
通过引进章动坐标系相对惯性参照系的转动角速度随时间的变化 ,导出了一个可同时解出章动和极移的地球自转方程 ,用这个方程可同时研究地球的强迫和自由转动。与现行研究地球自转的惯用方法相比 ,该方法综合性强 ,易于理解。 相似文献
2.
GUO Junyi 《地球空间信息科学学报》2001,4(3):6-8
1 ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｍｏｄｅｒｎＥａｒｔｈｒｏｔａｔｉｏｎｔｈｅｏｒｙ ,ｔｈｒｅｅｒｅｆｅｒｅｎｃｅｆｒａｍｅｓａｒｅｕｓｕａｌｌｙｕｓｅｄ ,ｉ.ｅ .,ｔｈｅｓｐａｔｉａｌ (ｉｎｅｒｔｉａｌ)ｆｒａｍｅＯξ1 ξ2 ξ3,ｔｈｅｔｅｒｒｅｓｔｒｉａｌｆｒａｍｅＯｘ1 ｘ2 ｘ3ａｎｄｔｈｅｎｕｔａｔｉｏｎｆｒａｍｅＯｘ01 ｘ02 ｘ03.Ｔｈｅｎｕｔａｔｉｏｎｆｒａｍｅｄｅｆｉｎｅｓａｃｅｌｅｓｔｉａｌｅｐｈｅｍｅｒｉｓｐｏｌｅ .Ｔｈｅｍｏｔｉｏｎｏｆｔｈｉｓｃｅｌｅｓｔｉａｌｅｐｈｅｍｅｒｉｓｐｏｌｅｗ… 相似文献
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The temporal change of the rotation vector of a rotating body is, in the first order, identical in a space-fixed system and
in a body-fixed system. Therefore, if the motion of the rotation axis of the earth relative to a space-fixed system is given
as a function of time, it should be possible to compute its motion relative to an earth-fixed system, and vice versa. This
paper presents such a transformation. Two models of motion of the rotation axis in the space-fixed system are considered:
one consisting only of a regular (i.e., strictly conical) precession and one extended by circular nutation components, which
are superimposed upon the regular precession. The Euler angles describing the orientation of the earth-fixed system with respect
to the space-fixed system are derived by an analytical solution of the kinematical Eulerian differential equations. In the
first case (precession only), this is directly possible, and in the second case (precession and nutation), a solution is achieved
by a perturbation approach, where the result of the first case serves as an approximation and nutation is regarded as a small
perturbation, which is treated in a linearized form. The transformation by means of these Euler angles shows that the rotation
axis performs in the earth-fixed system retrograde conical revolutions with small amplitudes, namely one revolution with a
period of one sidereal day corresponding to precession and one revolution with a period which is slightly smaller or larger
than one sidereal day corresponding to each (prograde or retrograde) circular nutation component. The peculiar feature of
the derivation presented here is the analytical solution of the Eulerian differential equations. 相似文献
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The purpose of this paper is to develop a canonical formulation of the rotational motion for an elastic Earth model. We have
obtained the canonical equations for the precession and nutation motion in an inertial frame, and from this we have deduced
the equations in an Earth-fixed frame. The linearized equations deduced for polar motion are equivalent to those obtained
using Liouville's equations. 相似文献
8.
Recent research in the department has involved determining the value of lunar observations in the determination of geodetic
and selenodetic control.
A fundamental consideration in the research is the determination of the orientation of the Earth in the celestial coordinate
system. Classical reductions for precession and nutation can be expected to be consistent with the present day observations,
however, corrections to the classical theory are difficult to model due to the large number of coefficients involved. Consequently,
a portion of the research has been devoted to numerically integrating the Eulerian equations of motion for a rigid Earth and
considering the six initial conditions of the integration as unknowns.
Comparison of the three adjusted Eulerian angles from the numerical integration over 1000 daysindicates agreement with classical theory to within 0.003 seconds ofarc.
This work was performed under NASA Contract No. NAS 9-13093.
Presented at the International Symposium on Computational Methods in Geometrical Geodesy, Oxford, September 2–8, 1973. 相似文献
9.
We compare nutation time series determined by several International VLBI Service for geodesy and astrometry (IVS) analysis centers. These series were made available through the International Earth Rotation and Reference Systems Service (IERS). We adjust the amplitudes of the main nutations, including the free motion associated with the free core nutation (FCN). Then, we discuss the results in terms of physics of the Earth’s interior. We find consistent FCN signals in all of the time series, and we provide corrections to IAU 2000A series for a number of nutation terms with realistic errors. It appears that the analysis configuration or the software packages used by each analysis center introduce an error comparable to the amplitude of the prominent corrections. We show that the inconsistencies between series have significant consequences on our understanding of the Earth’s deep interior, especially for the free inner core resonance: they induce an uncertainty on the FCN period of about 0.5 day, and on the free inner core nutation (FICN) period of more than 1000 days, comparable to the estimated period itself. Though the FCN parameters are not so much affected, a 100 % error shows up for the FICN parameters and prevents from geophysical conclusions. 相似文献
10.
陈光华 《测绘与空间地理信息》2009,32(2)
假定地球是一个三轴刚性体,在Euclid空间中做自由旋转.在设定主惯性矩A小于B小于C的情况下,求解欧拉运动方程,得到数值解.计算结果表明:地球在除了自转和自由进动之外,同时还存在着自由章动.章动角会随着时间做周期性变化.重点讨论的是章动角的变化. 相似文献
11.
本根据现代空间技术测定地球引力场变化的进展，提出了用实测的地球自转参数和实测的低阶重力场变化结合的方法以研究地球角动量变化。其突出的优点是可以使引起地球角动量变化的质量项和速度场项解耦，使原来较复杂的问题简化。作为本提出的方法的实例，我们用Lageos-1和Lageos-2两颗卫星的SLR资料求解ΔC20，计算出ΔLOD序列，与（ΔLOD－Wind)残差序列相比，有较好的一致性，显示出本方法的有效性。 相似文献
12.
Rotation of the Earth as a Triaxial Rigid Body 总被引：2，自引：6，他引：2
SHEN Wenbin CHEN Wei WANG Wenjun LIANG Yiqiang 《地球空间信息科学学报》2007,10(2):85-90
The Earth is taken as a triaxial rigid body, which rotates freely in the Euclidian space. The starting equations are the Euler dynamic equations, with A smaller than B and B smaller than C. The Euler equations are solved, and the numerical results are provided. In the calculations, the following parameters are used: (C-B)/A=0.003 273 53; (B-A)/C=0.000 021 96; (C-A)/B=0.003 295 49, and the mean angular velocity of the Earth's rotation, ω =0.000 072 921 15 rad/s. Calculations show that, besides the self-rotation of the Earth and the free Euler procession of its rotation, there exists the free nutation: the nutation angle, or the angle between the Earth's momentary rotation axis and the mean axis that periodically change with time. The free nutation is investigated. 相似文献
13.
Natalia Panafidina Urs Hugentobler Manuela Seitz Hana Krásná 《Journal of Geodesy》2017,91(12):1503-1512
This paper studies the connection between the subdaily model for polar motion used in the processing of very long baseline interferometry (VLBI) observations and the estimated nutation offsets. By convention accepted by the International Earth Rotation Service, the subdaily model for polar motion recommended for routine processing of geodetic observations does not contain any daily retrograde terms due to their one-to-one correlation with the nutation. Nevertheless, for a 24-h VLBI solution a part of the signal contained in the polar motion given by the used subdaily model is numerically mistaken for a retrograde daily sidereal signal. This fictitious retrograde daily signal contributes to the estimated nutation, leading to systematic differences between the nutation offsets from VLBI solutions computed with different subdaily polar motion models. We demonstrate this effect using solutions for all suitable 24-h VLBI sessions over a time span of 11 years (2000–2011). By changing the amplitudes of one tidal term in the underlying subdaily model for polar motion and comparing the estimated parameters to the solutions computed with the unchanged subdaily model, the paper shows and explains theoretically the effects produced by the individual subdaily terms on the VLBI nutation estimates. 相似文献
14.
A 29-year time-series of four-times-daily atmospheric effective angular momentum (EAM) estimates is used to study the atmospheric
influence on nutation. The most important atmospheric contributions are found for the prograde annual (77 μas), retrograde
annual (53 as), prograde semiannual (45 as), and for the constant offset of the pole (δψsinɛ0=−86 as, δɛ=77 as). Among them only the prograde semiannual component is driven mostly by the wind term of the EAM function,
while in all other cases the pressure term is dominant. These are nonnegligible quantities which should be taken into account
in the new theory of nutation. Comparison with the VLBI corrections to the IAU 1980 nutation model taking into account the
ocean tide contribution yields good agreement for the prograde annual and semiannual nutations. We also investigated time
variability of the atmospheric contribution to the nutation amplitudes by performing the sliding-window least-squares analysis
of both the atmospheric excitation and VLBI nutation data. Almost all detected variations of atmospheric origin can be attributed
to the pressure term, the biggest being the in-phase annual prograde component (about 30 as) and the retrograde one (as much
as 100200 as). These variations, if physical, limit the precision of classical modeling of nutation to the level of 0.1 mas.
Comparison with the VLBI data shows significant correlation for the retrograde annual nutation after 1989, while for the prograde
annual term there is a high correlation in shape but the size of the atmospherically driven variations is about three times
less than deduced from the VLBI data. This discrepancy in size can be attributed either to inaccuracy of the theoretical transfer
function or the frequency-dependent ocean response to the pressure variations. Our comparison also yields a considerably better
agreement with the VLBI nutation data when using the EAM function without the IB correction for ocean response, which indicates
that this correction is not adequate for nearly diurnal variations.
Received: 10 September 1997 / Accepted: 5 March 1998 相似文献
15.
Changes in the oceanic current system and in the oceanic mass distribution alter, together with other processes, the state
of the Earth’s rotation. This state is characterized by the length of day (LOD) and the tilt of the pole-to-pole axis. The
aim of our study was to derive the respective governing physical mechanisms in the ocean. Therefore, Earth rotation observations
were assimilated into a global circulation model of the ocean. Although assimilation is a well-established tool in climate
science, the assimilation of Earth rotation observations into a global ocean model was done here for the first time. Prior
to the assimilation, the Earth rotation observations were projected onto the angular momentum of the ocean. Non-oceanic contributions
were removed. The result of the subsequent assimilation procedure is a time varying ocean model state that reproduces the
projected Earth rotation observations well. This solution was studied to understand the oceanic generation of Earth rotation
deviations and to identify governing physical mechanisms. This paper focuses on LOD anomalies although polar motion was assimilated
simultaneously. Our results indicate that changes in the oceanic LOD excitation are mostly attributed to changes in total
ocean mass. Changes in the spatial distribution of ocean mass turned out to have a minor contribution to the LOD deviations.
The same applies to changes in the current system. 相似文献
16.
Foreword The International Earth Rotation Service (IERS) was organized by the International Union of Geodesy and Geophysics and the International Astronomical Union. It started
operation on 1988 January 1. Its responsabilities and activities are described in the Geodesist's Handbook (1988). The Central
Bureau ofIERS is operated by a scientific team established in cooperation by Observatoire de Paris, Institut Géographique National and
Bureau des Longitudes. This team was selected in 1987 on the basis of the present document which describes in some detail
the concepts and methods for establishing and maintaining celestial and terrestrial reference frames for Earth orientation
monitoring (polar motion, universal time, precession/nutation). The work of the Central Bureau is based on these concepts
and methods, not withstanding future evolution made possible by the improvements in observations and theories. 相似文献
17.
Methodology for the combination of sub-daily Earth rotation from GPS and VLBI observations 总被引：3，自引：3，他引：0
A combination procedure of Earth orientation parameters from Global Positioning System (GPS) and Very Long Baseline Interferometry
(VLBI) observations was developed on the basis of homogeneous normal equation systems. The emphasis and purpose of the combination
was the determination of sub-daily polar motion (PM) and universal time (UT1) for a long time-span of 13 years. Time series
with an hourly resolution and a model for tidal variations of PM and UT1-TAI (dUT1) were estimated. In both cases, 14-day
nutation corrections were estimated simultaneously with the ERPs. Due to the combination procedure, it was warranted that
the strengths of both techniques were preserved. At the same time, only a minimum of de-correlating or stabilizing constraints
were necessary. Hereby, a PM time series was determined, whose precision is mainly dominated by GPS observations. However,
this setup benefits from the fact that VLBI delivered nutation and dUT1 estimates at the same time. An even bigger enhancement
can be seen for the dUT1 estimation, where the high-frequency variations are provided by GPS, while the long term trend is
defined by VLBI. The estimated combined tidal PM and dUT1 model was predominantly determined from the GPS observations. Overall,
the combined tidal model for the first time completely comprises the geometrical benefits of VLBI and GPS observations. In
terms of root mean squared (RMS) differences, the tidal amplitudes agree with other empirical single-technique tidal models
below 4 μas in PM and 0.25 μs in dUT1. The noise floor of the tidal ERP model was investigated in three ways resulting in about 1 μas for diurnal PM and 0.07 μs for diurnal dUT1 while the semi-diurnal components have a slightly better accuracy. 相似文献
18.
The rotational motion for an elastic Earth model with a homogeneous liquid core has been obtained using Hamilton's equations. From the canonical equations for the precessional and nutational motions in an inertial frame, the corresponding equations in an Earth fixed frame are deduced. The linearized equations obtained for polar motion and liquid core motion are equivalent to the Sasao-Okubo-Saito equations. 相似文献
19.
Atmospheric Angular Momentum Time-Series: Characterization of their Internal Noise and Creation of a Combined Series 总被引：1，自引：0，他引：1
The atmosphere induces variations in Earth rotation. These effects are classically computed using the “angular momentum approach”. In this method, the variations in Earth rotation are estimated from the variations in the atmospheric angular momentum (AAM). Several AAM time-series are available from different meteorological centers. However, the estimation of atmospheric effects on Earth rotation differs when using one atmospheric model or the other. The purpose of this work is to build an objective criterion that justifies the use of one series in particular. Because the atmosphere is not the only cause of Earth rotation variations, this criterion cannot rely only on a comparison of AAM series with geodetic data. Instead, we determine the quality of each series by making an estimation of their noise level, using a generalized formulation of the “three-cornered hat method”. We show the existence of a link between the noise of the AAM series and their correlation with geodetic data: a noisy series is usually less correlated with Earth orientation data. As the quality of the series varies in time, we construct a combined AAM series, using time-dependent weights chosen so that the noise level of the combined series is minimal. To determine the influence of a minimal noise level on the correlation with geodetic data, we compute the correlation between the combined series and Earth orientation data. We note that the combined series is always amongst the best correlated series, which confirms the link established before. The quality criterion, while totally independent of Earth orientation observations, appears to be physically convincing when atmospheric and geodetic data are compared 相似文献
20.
The rotational motion for an elastic Earth model with a homogeneous liquid core has been obtained using Hamilton's equations.
From the canonical equations for the precessional and nutational motions in an inertial frame, the corresponding equations
in an Earth fixed frame are deduced. The linearized equations obtained for polar motion and liquid core motion are equivalent
to the Sasao-Okubo-Saito equations. 相似文献