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Self-consistent determination of the Earth’s GM, geocenter motion and figure axis orientation / Alexandre Couhert in Journal of geodesy, vol 94 n° 12 (December 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 12 (December 2020) . - n° 113 Titre : Self-consistent determination of the Earth’s GM, geocenter motion and figure axis orientation Type de document : Article/Communication Auteurs : Alexandre Couhert, Auteur ; Christian Bizouard, Auteur ; F. Mercier, Auteur ; Kristel Chanard , Auteur ; Marianne Greff-Lefftz, Auteur ; Pierre Exertier, Auteur Année de publication : 2020 Projets : 1-Pas de projet / Article en page(s) : n° 113 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] données Ajisai [Termes IGN] données Jason [Termes IGN] données Lageos [Termes IGN] données LARES [Termes IGN] données Starlette [Termes IGN] données Stella [Termes IGN] données TLS (télémétrie) [Termes IGN] erreur de modèle [Termes IGN] harmonique sphérique [Termes IGN] incertitude géométrique [Termes IGN] mouvement du géocentre [Termes IGN] surface de la mer Résumé : (auteur) The very low-degree Earth’s gravity coefficients, associated with the largest-scale mass redistribution in the Earth’s fluid envelope (atmosphere, oceans and continental hydrology), are the most poorly known. In particular, the first three degree geopotential terms are important, as they relate to intrinsic Earth’s mass references: gravitational coefficient (GM) of the Earth (degree 0), geocenter motion (degree 1), Earth’s figure axis orientation (degree 2). This paper presents a self-consistent determination of these three properties of the Earth. The main objective is to deal with the remaining sources of altimetry satellite orbit uncertainties affecting the fundamental record of sea surface height measurements. The analysis identifies the modeling errors, which should be mitigated when estimating the geocenter coordinates from Satellite Laser Ranging (SLR) observations. The long-term behavior of the degree-0 and -2 spherical harmonics is also observed over the 34-year period 1984–2017 from the long-time history of satellite laser tracking to geodetic spherical satellites. From the analysis of the evolution of these two coefficients, constraints regarding the Earth’s rheology and uncertainties in the value of GM could be inferred. Overall, the influence of the orbit characteristics, SLR station ranging/position biases and satellite signature effects, measurement modeling errors (tropospheric corrections, non-tidal deformations) are also discussed. Numéro de notice : A2020-330 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01450-z Date de publication en ligne : 18/11/2020 En ligne : https://doi.org/10.1007/s00190-020-01450-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96858 [article]

Elliptic polarisation of the polar motion excitation / Christian Bizouard in Journal of geodesy, vol 90 n° 2 (February 2016)  

Public [article]  inJournal of geodesy > vol 90 n° 2 (February 2016) . - pp 179 - 188 Titre : Elliptic polarisation of the polar motion excitation Type de document : Article/Communication Auteurs : Christian Bizouard, Auteur Année de publication : 2016 Article en page(s) : pp 179 - 188 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] mouvement du pôle [Termes IGN] rotation de la Terre Résumé : (auteur) Because of its geophysical interpretation, Earth’s polar motion excitation is generally decomposed into prograde (counter-clockwise) and retrograde (clockwise) circular terms at fixed frequency. Yet, these later are commonly considered as specific to the frequency and to the underlying geophysical process, and no study has raised the possibility that they could share features independent from frequency. Complex Fourier Transform permits to determine retrograde and prograde circular terms of the observed excitation and of its atmospheric, oceanic and hydrological counterparts. The total prograde and retrograde parts of these excitations are reconstructed in time domain. Then, complex linear correlation between retrograde and conjugate prograde parts is observed for both the geodetic excitation and the matter term of the hydro-atmospheric excitation. In frequency domain, the ratio of the retrograde circular terms with their corresponding conjugate prograde terms favours specific values: the amplitude ratio follows a probabilistic gamma distribution centred around 1.5 (maximum for 1), and the argument ratio obeys a distribution close to a normal law centred around 2α=160∘. These frequency and time domain characteristics mean an elliptical polarisation towards α=∼80∘ East with an ellipticity of 0.8, mostly resulting from the matter term of the hydro-atmospheric excitation. Whatsoever the frequency band above 0.4 cpd, the hydro-atmospheric matter term tends to be maximal in the geographic areas surrounding the great meridian circle of longitude ∼80∘ or ∼260∘ East. The favoured retrograde/prograde amplitude ratio around 1.5 or equivalently the ellipticity of 0.8 can result from the amplification of pressure waves propagating towards the west by the normal atmospheric mode Ψ13 around 10 days. Numéro de notice : A2016-034 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0864-7 Date de publication en ligne : 12/11/2015 En ligne : https://doi.org/10.1007/s00190-015-0864-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=79510 [article]

A first step for the French Geodetic and Fundamental Astronomy Virtual Observatory / Christophe Barache (2006)    

Public Titre : A first step for the French Geodetic and Fundamental Astronomy Virtual Observatory Type de document : Article/Communication Auteurs : Christophe Barache, Auteur ; Philippe Berio, Auteur ; Christian Bizouard, Auteur ; S. Bouquillon, Auteur ; Xavier Collilieux , Auteur ; David Coulot , Auteur ; Florent Deleflie, Auteur ; et al., Auteur Editeur : Société française d'astronomie et d'astrophysique SF2A Année de publication : 2006 Conférence : SF2A 2006, annual meeting of the French Society of Astronomy & Astrophysics 26/06/2006 30/06/2006 Paris France OA Proceedings Note générale : bibliographie Langues : Anglais (eng) Résumé : (auteur) Activities linked to VO within the french geodetic and fundamental astronomy community started in 2005, through two pilot projects, led at OCA-GRGS and OP-GRGS. They are based on visualisation and analysis software of geodetic products -Earth Orientation Parameters, polar motion, station positions, in particular- to make a new science be possible. We present the tools, which will help, we hope, the whole french geodetic community to organize its databases in VO-format. Because of the wide spectrum of its activities, among various common fields between Astronomy and Geophysics (terrestrial and celestial reference frames, gravity field, hydrosphere, ...), geodetic studies can strongly benefit from the VO-concept. Numéro de notice : C2006-035 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésNat DOI : sans En ligne : http://sf2a.eu/proceedings/2006/2006sf2a.conf..0593D.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102710

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Remaining error sources in the nutation at the submilliarc second level / Véronique Dehant in Journal of geophysical research : Solid Earth, vol 108 n° 5 (May 2003)  

Public [article]  inJournal of geophysical research : Solid Earth > vol 108 n° 5 (May 2003) . - pp 13-1 Titre : Remaining error sources in the nutation at the submilliarc second level Type de document : Article/Communication Auteurs : Véronique Dehant, Auteur ; Martine Feissel-Vernier , Auteur ; Olivier de Viron, Auteur ; C. Ma, Auteur ; D.T. Yseboodt, Auteur ; Christian Bizouard, Auteur Année de publication : 2003 Article en page(s) : pp 13-1 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] interférométrie à très grande base [Termes IGN] nutation Résumé : (auteur) Earth's precession and nutations are mainly generated by the luni-solar tidal torque. Diurnal retrograde variations in the atmospheric and oceanic angular momenta in an Earth-fixed reference system induce some additional nutation motions. Observed precession and nutations are derived from very long baseline interferometry (VLBI) data, assuming that the direction of the observed quasars are fixed in space. In this study, we consider the effects of two possible causes for explaining discrepancies between the observed nutations and those modeled in MHB2000 (model adopted by the International Astronomical Union): (1) the time variations in the atmospheric (and potentially oceanic) forcing of the nutations, of the free core nutation (FCN), and of the free inner core nutation (FICN), and (2) the possible contamination of VLBI-derived nutation amplitudes by apparent changes in the directions of the extragalactic radio sources. The robustness of MHB2000 is tested by perturbing some of the parameters and assessing the validity of the resulting nutation amplitudes against realistic estimations. We show that even allowing for large discrepancies related to atmospheric forcing, the ranges of the possible changes in the FCN and FICN periods and damping factors are small. Numéro de notice : A2003-472 Affiliation des auteurs : IGN+Ext (1940-2011) Thématique : POSITIONNEMENT Nature : Article DOI : 10.1029/2002JB001763 Date de publication en ligne : 24/05/2003 En ligne : https://doi.org/10.1029/2002JB001763 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102730 [article]