scholarly journals Impact of Jason-2/T2L2 Ultra-Stable-Oscillator Frequency Model on DORIS stations coordinates and Earth Orientation Parameters

2020 ◽  
Author(s):  
Alexandre Belli ◽  
Nikita P. Zelensky ◽  
Frank G. Lemoine ◽  
Douglas S. Chinn
Keyword(s):  
Frequency Model ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Oscillator Frequency ◽  
Orientation Parameters

Effect of non-tidal station loading on Lunar Laser Ranging observatories and on the estimation of Earth orientation parameters

2021 ◽  
Author(s):  
Vishwa Vijay Singh ◽  
Liliane Biskupek ◽  
Jürgen Müller ◽  
Mingyue Zhang
Keyword(s):  
Research Centre ◽  
Laser Ranging ◽  
The Moon ◽  
Lunar Laser Ranging ◽  
Earth Orientation Parameters ◽  
Tidal Station ◽  
Earth Orientation ◽  
The Earth ◽  
Lunar Laser ◽  
Orientation Parameters

<p>The distance between the observatories on Earth and the retro-reflectors on the Moon has been regularly observed by the Lunar Laser Ranging (LLR) experiment since 1970. In the recent years, observations with bigger telescopes (APOLLO) and at infra-red wavelength (OCA) are carried out, resulting in a better distribution of precise LLR data over the lunar orbit and the observed retro-reflectors on the Moon, and a higher number of LLR observations in total. Providing the longest time series of any space geodetic technique for studying the Earth-Moon dynamics, LLR can also support the estimation of Earth orientation parameters (EOP), like UT1. The increased number of highly accurate LLR observations enables a more accurate estimation of the EOP. In this study, we add the effect of non-tidal station loading (NTSL) in the analysis of the LLR data, and determine post-fit residuals and EOP. The non-tidal loading datasets provided by the German Research Centre for Geosciences (GFZ), the International Mass Loading Service (IMLS), and the EOST loading service of University of Strasbourg in France are included as corrections to the coordinates of the LLR observatories, in addition to the standard corrections suggested by the International Earth Rotation and Reference Systems Service (IERS) 2010 conventions. The Earth surface deforms up to the centimetre level due to the effect of NTSL. By considering this effect in the Institute of Geodesy (IfE) LLR model (called ‘LUNAR’), we obtain a change in the uncertainties of the estimated station coordinates resulting in an up to 1% improvement, an improvement in the post-fit LLR residuals of up to 9%, and a decrease in the power of the annual signal in the LLR post-fit residuals of up to 57%. In a second part of the study, we investigate whether the modelling of NTSL leads to an improvement in the determination of EOP from LLR data. Recent results will be presented.</p>

scholarly journals Geodetic VLBI Analysis at the National Geographic Institute of Spain

Proceedings ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 2
Author(s):  
Víctor Puente ◽  
Esther Azcue ◽  
Susana García-Espada ◽  
Yaiza Gómez-Espada
Keyword(s):  
Earth Orientation Parameters ◽  
Technical Aspects ◽  
National Geographic ◽  
Earth Orientation ◽  
Geodetic Vlbi ◽  
Software Packages ◽  
Station Coordinates ◽  
Set Up ◽  
Orientation Parameters ◽  
Troposphere Delays

National Geographic Institute of Spain has a strong background concerning technical aspects of geodetic VLBI. As a step forward in this field, a VLBI analysis team has been set up and tests with different software packages have been carried out. In this sense, two VLBI software packages have been used for experimentation activities in order to compare and validate IGE capability to produce accurate and consistent geodetic products, specifically Earth Orientation Parameters, station coordinates and troposphere delays. The purpose of this contribution is to present the results of these analyses, including some tests to use GNSS-based troposphere delay in VLBI processing and the study of gravitational deformation in Yebes radiotelescope.

Overview and Proposition for a Modern Definition of the CEP

2000 ◽  
Vol 178 ◽  
pp. 571-584
Author(s):  
Nicole Capitaine
Keyword(s):  
Working Group ◽  
Polar Motion ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Conventional Models ◽  
Definition Of ◽  
Orientation Parameters ◽  
Observational Procedure

AbstractThe current IAU conventional models for precession and nutation are referred to the Celestial Ephemeris Pole (CEP). However, the concept corresponding to the CEP is not clear and cannot easily be extended to the most recent models and observations. Its realization is actually dependent both on the model used for precession, nutation and polar motion and on the observational procedure for estimating the Earth orientation parameters. A new definition of the CEP should therefore be given in order to be in agreement with modern models and observations at a microarsecond level. This paper reviews the various realizations of the pole according to the models and observations and discusses the proposals for a modern definition of the CEP that are under consideration within the work of the subgroup T5 entitled “Computational Consequences” of the “ICRS” IAU Working Group.

scholarly journals Estimation of EOP from VLBI: Direct Approach

2000 ◽  
Vol 180 ◽  
pp. 254-258 ◽  
Author(s):  
L. Petrov
Keyword(s):  
Time Series ◽  
Harmonic Component ◽  
Segment Length ◽  
Physical Parameters ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Alternative Approach ◽  
Two Stages ◽  
Orientation Parameters ◽  
Raw Earth

AbstractThe currently adopted strategy of EOP estimation from VLBI is to estimate six parameters: UT1, UT1 rate, pole positions and nutation offsets for each 24-hour session independently. Then the resulting time series of raw Earth orientation parameters are filtered and a regression analysis is performed in order to obtain nutation coefficients, polhode of the pole and other physical parameters. Thus, the latter parameters are obtained indirectly in two stages. An alternative approach of direct estimation of the final Earth orientation parameters is presented. Pole coordinates and UT1 are considered as a sum of three components: the low-period component which is modeled by a cubic spline, the harmonic component which includes forced nutation, precession and sub-daily variations of EOP, and the stochastic component which is modeled by a linear spline with segment length 1-2 hours. All parameters are obtained in a single LSQ solution using all available data.

scholarly journals Consistency of CDP and IRIS VLBI Earth orientation results

1988 ◽  
Vol 128 ◽  
pp. 187-192 ◽  
Author(s):  
A. Mallama ◽  
T. A. Clark ◽  
J. W. Ryan
Keyword(s):  
Data Centers ◽  
Reference Frames ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Past ◽  
The Earth ◽  
Formal Error ◽  
Orientation Parameters ◽  
Iris Data

This study compares the earth orientation results obtained by the NASA CDP and the NGS IRIS experiments. The results agree at about one combined formal error (two milliarcseconds) after small biases (one to three milliarcseconds) have been removed from each component. Furthermore the biases are found to correspond to small rotations between the reference frames, principally the terrestrial frame, for the two sets of experiments. In the past the CDP data has not been used in combined solutions of earth orientation parameters prepared by the data centers at the U.S.N.O. and the B.I.H. The authors propose that these data should be included because they are distinct from the IRIS data and represent an important supplement to those data. We also point out that the total number of observations is about equal in the CDP and IRIS experiment sets.

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