Corrections to the IAU 1980 Nutation Series from LAGEOS Observations

1990 ◽  
pp. 155-155
Author(s):  
V. K. Tarady
Keyword(s):  
Nutation Series

scholarly journals A New Nutation Model Of Nonrigid Earth With Ocean And Atmosphere

2000 ◽  
Vol 180 ◽  
pp. 242-247
Author(s):  
Cheng-li Huang ◽  
Wen-jing Jin ◽  
Xing-hao Liao
Keyword(s):  
Transfer Functions ◽  
Second Order ◽  
Earth Model ◽  
Surface Boundary ◽  
Complex Frequency ◽  
Order Accuracy ◽  
Complex Scalar ◽  
Motion Equations ◽  
Surface Boundary Conditions ◽  
Nutation Series

AbstractBy integrating the truncated complex scalar gravitational motion equations for an anelastic, rotating, slightly elliptical Earth, the complex frequency dependent Earth transfer functions are computed directly. Unlike the conventional method, the effects of both oceanic loads and tidal currents are included via outer surface boundary conditions, all of which are expanded to second order in ellipticity. A modified ellipticity profile in second order accuracy for the non-hydrostatic Earth is obtained from Clairaut’s equation and the PREM Earth model by adjusting both the ellipticity of the core-mantle boundary and the global dynamical ellipticity to modern observations. The effects of different Earth models, anelastic models, and ocean models are computed and compared. The atmospheric contributions to prograde annual, retrograde annual and retrograde semiannual nutation are also included as oceanic effects. Finally, a complete new nutation series of more than 340 periods, including in-phase and out-of-phase parts of longitude and obliquity terms, for a more realistic Earth, is obtained and compared with other available nutation series and observations.

scholarly journals Dynamical adjustments in IAU 2000A nutation series arising from IAU 2006 precession

2017 ◽  
Vol 604 ◽  
pp. A92 ◽  
Author(s):  
A. Escapa ◽  
J. Getino ◽  
J. M. Ferrándiz ◽  
T. Baenas
Keyword(s):  
Nutation Series

scholarly journals VLBI studies of the nutations of the earth

1988 ◽  
Vol 129 ◽  
pp. 371-375
Author(s):  
T. A. Herring
Keyword(s):  
Truncation Error ◽  
Very Long Baseline Interferometry ◽  
Long Baseline ◽  
The Earth ◽  
Vlbi Data ◽  
One Year ◽  
Nutation Series ◽  
Theoretical Considerations ◽  
Active Investigation

The application of very–long–baseline interferometry (VLBI) to the study of the nutations of the earth has yielded unprecedented accuracy for the experimental determination of the coefficients of the nutation series. The analysis of six years of VLBI data has yielded corrections to the coefficients of the seven largest terms in the IAU 1980 nutation series with periods of one year or less, with accuracies approaching the truncation error of this nutation series (0.1 mas). The nutation series coefficients computed from the VLBI data, and those obtained from theoretical considerations (the IAU 1980 nutation series), are in excellent agreement. The largest corrections are to the coefficients of the retrograde annual nutation [2.0 ± 0.1 mas], the prograde semiannual nutation [(0.5 - ι 0.4) ±0.1 mas], and the prograde 13.7 day nutation [−0.4 ± 0.1 mas]. (The imaginary term for the semiannual nutation represents a term 90° out–of–phase with the arguments of the nutation series.) The geophysical implications of these results are currently under active investigation. We discuss the methods used to extract the nutation information from the VLBI data, the calculations of the uncertainties of the resultant corrections to the coefficients of the nutation series, and the current research into the nutations of the earth.

scholarly journals The ZMOA-1990 Nutation Series

1991 ◽  
Vol 127 ◽  
pp. 157-166 ◽  
Author(s):  
T.A. Herring
Keyword(s):  
Outer Core ◽  
Geophysical Model ◽  
Long Baseline ◽  
The Earth ◽  
Vlbi Data ◽  
Rigid Earth ◽  
Nutation Series ◽  
Two Parameters ◽  
Annual Period ◽  
Better Than

AbstractWe present a new nutation series for the Earth (ZMOA-1990) based on (1) the rigid Earth nutation series developed by Zhu and Groten [1989], (2) the normalized response for an elastic, elliptical Earth with fluid-outer and solid-inner cores developed by Mathews et al. [1990], and (3) corrections for the effects of ocean tides and anelasticity, computed to be consistent with the Mathews et al. [1990] normalized response function. In deriving this series, only two parameters of the geophysical model for the Earth have been modified from their values computed with PREM: the dynamic ellipticities of the whole Earth, e, and of the fluid outer core, ef. The adopted values for these parameters, determined from the analysts of very long baseline interferometry (VLSI) data, are e=0.00328915 which is about 1% higher than the value obtained from PREM and 6×10−5 times larger than the IAU adopted value, and ef=0.002665 which is 4.6% higher than the PREM value. The above values were obtained from an adjustment of −0.3 ʺ/cent to the IAU-1976 luni-solar precession constant for e, and from the amplitude of the retrograde annual nutation for ef. The ZMOA-1990 nutation series agrees with estimates of the in-phase and the out-of-phase nutation amplitudes obtained from VLBI data to within 0.5 mas for the terms with 18.6 year period, and to better than 0.1 mas for terms at all other periods except for the out-of-phase terms with annual period (differences 0.39 mas, retrograde, and 0.13 mas, prograde), and for the in-phase term with prograde 13.66 day period (difference −0.25 mas).

scholarly journals Improved Models for Precession and Nutation

2000 ◽  
Vol 180 ◽  
pp. 212-222 ◽  
Author(s):  
P.M. Mathews
Keyword(s):  
Theoretical Background ◽  
Precession Rate ◽  
The Past ◽  
Vlbi Data ◽  
Geophysical Information ◽  
Nutation Series

AbstractThe modeling of nutations and precession has advanced to the point where the rms of residuals between theory and the observational estimates from the VLBI data of the past decade is only 0.16 mas in Δψ sin є0 as well as in Δє. Such a fit is provided by the MHB2000 nutation series (Mathews et al., 2000) based on geophysical theory with a few basic Earth parameters estimated by a fit to nutation-precession data, and its accompanying precession rate. A brief account of the series is presented, along with an outline of the theoretical background and of the geophysical information of interest obtained in the process of constructing the series. A series due to Shirai and Fukushima (2000) also gives a somewhat comparable fit to data, improving on the IERS 1996 series, but it is essentially empirical and provides no geophysical insights.

scholarly journals Deficiencies in the Nutation Model from VLBI Observations

1993 ◽  
Vol 156 ◽  
pp. 381-386
Author(s):  
Y. F. Xia ◽  
J. Gao
Keyword(s):  
Least Squares ◽  
Periodic Variation ◽  
Mantle Boundary ◽  
Core Mantle Boundary ◽  
The Core ◽  
Vlbi Observations ◽  
Amplitude Spectra ◽  
Celestial Pole ◽  
Free Mode ◽  
Nutation Series

A VLBI series of celestial pole offsets has been used for deriving the corrections to the main terms of the IAU 1980 nutation series using the least squares solution and amplitude spectra method. The results are compared with current geophysical models. The discrepancies between observations and theory are largely due to deficiencies in the nutation models. A retrograde periodic variation (at a period of 420.0 days) has been revealed. The free mode will give us futher information on the core-mantle boundary.

scholarly journals Improvement of Nonrigid-Earth Nutation Theory by Adding a Model Free Core Nutation Term

2000 ◽  
Vol 180 ◽  
pp. 223-229 ◽  
Author(s):  
Toshimichi Shirai ◽  
Toshio Fukushima
Keyword(s):  
Transfer Function ◽  
Free Core Nutation ◽  
Model Free ◽  
Naval Observatory ◽  
Vlbi Data ◽  
Damped Oscillation ◽  
Rigid Earth ◽  
The Time Domain ◽  
Nutation Series ◽  
Oscillatory Period

AbstractFrom the analysis of VLBI observational data compiled by USNO (U.S. Naval Observatory) from MJD 44089.994 to 51618.250 (McCarthy, 2000), we showed that a strong peak around –400 sidereal days in the spectrum of its differences from the IERS96 nutation theory could be explained by adding a model Free Core Nutation (FCN) term in the form of a single damped oscillation. Then we developed a new analytical theory of the nonrigid-Earth nutation including the derived FCN model. We adopted RDAN98 (Roosbeek and Dehant, 1998) as the rigid Earth nutation theory. It was convolved with a transfer function using numerical convolution in the time domain (Shirai and Fukushima, 2000). The form of the transfer function was the same as that of Herring (1995). However, its free parameters such as the complex amplitude and frequency of the FCN were readjusted by fitting to the above VLBI data. Even after truncating the forced nutation series so as to contain only 180 terms, the WRMS (Weighted Root Mean Square) of the complex residuals for the new nutation series is 0.312 mas, which is significantly smaller than 0.325 mas, that of the IERS96 nutation theory. As for the FCN term, we estimated its oscillatory period as –430.8±0.6 sidereal days, and its Q-value as 16200 ± 1600. Also we estimated the correction of the precession constants as −0.29297±0.00047”/cy in longitude and −0.02430±0.00019”/cy in obliquity, respectively.

scholarly journals A New Nutation Series for a Rigid Earth Model

1997 ◽  
Vol 165 ◽  
pp. 287-293 ◽  
Author(s):  
Torsten Hartmann ◽  
Michael Soffel
Keyword(s):  
Angular Momentum ◽  
Order Theory ◽  
Second Order ◽  
Earth Model ◽  
Tidal Potential ◽  
Rigid Earth ◽  
Nutation Series

AbstractA new nutation series for a rigid Earth model was derived from a new and highly accurate tidal potential series. A new second order theory for the nutational amplitudes of rotation-, figure- and angular momentum-axis based on tidal amplitudes is formulated. Amplitudes larger than 0.45μas are taken into account leading to a series with 699 terms. The new series may serve as test of other ones that were recently published in the literature.

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