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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)
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 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 merRésumé : (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
in Journal of geodesy > vol 94 n° 12 (December 2020) . - n° 113[article]
Titre : Assessment of geocenter motion estimates from the IGS second reprocessing Type de document : Article/Communication Auteurs : Yifang Ma Année de publication : 2020 Projets : 3-projet - voir note / Article en page(s) : n° 55 Note générale : bibliographie
This study is supported by the National Science Fund for Distinguished Young Scholars (No. 41525014) and the National Key R&D Program of China (No. 2018YFC15036).Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux
[Termes IGN] analyse comparative
[Termes IGN] données TLS (télémétrie)
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] mouvement du géocentre
[Termes IGN] série temporelle
[Termes IGN] variation saisonnière
[Termes IGN] variation temporelleRésumé : (auteur) We investigate geocenter motion time series derived from the combined solutions and six individual analysis center (AC) solutions of the International GNSS Service (IGS) second reprocessing campaign using the network shift approach, in terms of noise content, long-term trends, periodic and aperiodic variations. We assess these GNSS geocenter motion estimates by comparison with independent estimates from satellite laser ranging (SLR). The GNSS geocenter time series exhibit correlated noise which is better represented by a white plus power–law noise model in the X and Y directions, and by a white plus first-order autoregressive (or generalized Gauss–Markov) noise model in the Z direction. The GNSS geocenter time series include expected seasonal variations, but also spurious draconitic signals, particularly in the Z direction. GNSS annual geocenter motion estimates are in reasonable agreement with SLR estimates in the X and Y directions. In the Z direction, however, the annual signals derived from the IGS solutions disagree with SLR estimates, except for three particular ACs. This suggests that the different orbit modeling strategies used by these ACs may constitute an improvement over the conventional strategy employed by the other ACs. The background noise in GNSS and SLR geocenter time series finally appears to be correlated, suggesting that it might partly reflect real, aperiodic geocenter motion. Numéro de notice : A2020-838 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s10291-020-0968-2 Date de publication en ligne : 10/03/2020 En ligne : https://doi.org/10.1007/s10291-020-0968-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98264
in GPS solutions > vol 24 n° 2 (April 2020) . - n° 55[article]
Titre : ITRF2014, Earth figure changes, and geocenter velocity: Implications for GIA and recent ice melting Type de document : Article/Communication Auteurs : Laurent Métivier Année de publication : 2020 Projets : 2-Pas d'info accessible - article non ouvert / Article en page(s) : n° e2019JB018333 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] figure de la Terre
[Termes IGN] fonte des glaces
[Termes IGN] harmonique sphérique
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] manteau terrestre
[Termes IGN] mouvement du géocentre
[Termes IGN] rebond post-glaciaire
[Termes IGN] vitesse de déplacementRésumé : (auteur) Using a selection of Global Navigation Satellite System vertical velocities from the latest solution of the International Terrestrial Reference Frame (ITRF) ITRF2014, we calculate the degree-1 and degree-2 spherical harmonics coefficients (SHC) of the solid Earth figure changes at different dates, with realistic errors that take into account the inhomogeneity of the network. We find that the SHC are globally close to zero except the zonal coefficients, which show values notably larger than those derived from different glacial isostatic adjustment (GIA) models and which have tended to increase during the time span of observations. We show that these differences are most probably due to global recent ice melting (RIM). Assuming elastic RIM deformation, we then investigate the Earth's geocenter velocity and the geoid oblateness time evolution (J2-rate) derived from our SHC estimations. The obtained geocenter velocity reaches 0.9 ± 0.5 mm/year in 2013 with a z-component of 0.8 ± 0.4 mm/year, which is slightly larger than previous estimations. We compare our J2-rate estimations with observations. Our estimations show a similar acceleration in J2 after 2000. However, our estimates are notably larger than the observations. This indicates either that the J2-rate due to GIA processes is lower than expected (as proposed by Nakada et al., 2015, 2016) or that the deformation induced by RIM is not purely elastic, or both. Finally, we show that viscous relaxation or phase transitions in the mantle transition zone may only partly explain this discrepancy. This raises the question of the accuracy of current mass estimations of RIM and GIA models. Numéro de notice : A2020-363 Affiliation des auteurs : UMR IPGP-Géod (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2019JB018333 Date de publication en ligne : 02/01/2020 En ligne : https://doi.org/10.1029/2019JB018333 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98263
in Journal of geophysical research : Solid Earth > vol 125 n° 2 (February 2020) . - n° e2019JB018333[article]
Titre : Influence of subdaily model for polar motion on the estimated GPS satellite orbits Type de document : Article/Communication Auteurs : Natalia Panafidina, Auteur ; Urs Hugentobler, Auteur ; Manuela Seitz, Auteur Année de publication : 2019 Article en page(s) : pp 229 - 240 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse diachronique
[Termes IGN] élément orbital
[Termes IGN] erreur systématique
[Termes IGN] International Terrestrial Reference Frame
[Termes IGN] marée océanique
[Termes IGN] mouvement du géocentre
[Termes IGN] mouvement du pôle
[Termes IGN] orbite
[Termes IGN] positionnement par GPS
[Termes IGN] rotation de la Terre
[Termes IGN] satellite GPS
[Termes IGN] traitement du signalRésumé : (auteur) In this contribution, it is shown that GPS orbits are able to absorb some diurnal signals in polar motion. The arising implications for the influence of the subdaily pole model on GPS solutions are discussed. Two signals in polar motion can be absorbed by GPS orbits: a retrograde signal with a period of a sidereal day (23 h 56 min 4 s) and a prograde signal with a period matching the revolution period of the GPS satellites in the terrestrial reference frame (23 h 55 min 56 s). We show that the retrograde signal contributes to the absolute orientation of the orbital planes in space and the prograde signal, due to coincidence of its period with the period of revolution of the GPS satellites, contributes to the position of the geocenter for each individual satellite. It is known from previous studies that there are systematic differences between orbital parameters from GPS solutions computed with different subdaily pole models. We show in this paper that this behavior can be explained by the absorption effects in 1-day GPS orbits. Diurnal signals cannot be spectrally separated over a time interval of 1 day. Adjustment of any diurnal prograde or retrograde signal to a subdaily pole time series given by a subdaily model over 24 h will lead to an estimated signal with a nonzero amplitude. Thus, any subdaily pole model used in the processing of space geodetic observations contains a part which corresponds numerically to the discussed prograde signal and a part which corresponds to the retrograde diurnal signal. Different pole models show different amplitudes of the diurnal signals which will be absorbed by the orbits. As a result, GPS orbits computed with different subdaily pole models have systematically different orientation and position in space. Using 1-day GPS solutions over a time span of 13 years (1994–2007), we show that the systematic variations in orbit position and orientation caused by individual tidal terms in polar motion can be well predicted and explained by the suggested mechanism. Numéro de notice : A2019-080 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-018-1153-z Date de publication en ligne : 24/05/2018 En ligne : https://doi.org/10.1007/s00190-018-1153-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92198
in Journal of geodesy > vol 93 n° 2 (February 2019) . - pp 229 - 240[article]
Titre : GPS-derived geocenter motion from the IGS second reprocessing campaign Type de document : Article/Communication Auteurs : Liansheng Deng, Auteur ; Zhao Li, Auteur ; Na Wei, Auteur ; Yifang Ma Année de publication : 2019 Article en page(s) : n° 74 Note générale : bibloigraphie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] campagne d'observations
[Termes IGN] mouvement du géocentre
[Termes IGN] télémétrie laser sur satelliteRésumé : (auteur) GPS data processing methods and theories are under continuous refinement in the past 30 years. Using the latest products is supposed to provide more stable and reliable geocenter estimates. In this paper, geocenter estimates from deformation inversion approach with new observations of IGS second data reprocessing campaign (IG2) are investigated. Results indicate that our IG2-derived geocenter motion estimates agree well with solutions from network approach for SLR. The truncated degree 5 exhibits the highest consistency between GPS-inverted geocenter estimates and the SLR results in both annual amplitudes and phases. Then, the GPS-derived geocenter motions are compared with results from other different approaches. We find that except for a discrepancy in the annual phase estimates of Z component, geocenter motions predicted with the IG2 data are in line with those based on other techniques. In addition, the effects of the translational parameters and the comparison with the IGS first data reprocessing campaign (IG1)-estimated geocenter motions are investigated, and results demonstrate that the translation parameters should be estimated when inversing the geocenter motion with the newly IG2 solutions and the advantage of the IG2 data reprocessing over the previous IG1 efforts. Finally, we address the impacts of post-seismic effects and the missing ocean data on the IG2-derived solutions. After removing the stations affected by large earthquakes, the amplitudes of Y component become higher, but the annual phases of the Y component become far away from the SLR solutions. Comparisons of the equivalent water height from the IG2-estimated coefficients and the solutions from the estimation of the circulation and climate of the ocean indicate that the differences between the two types of solutions vary with different truncated degrees, and the consistency is getting worse and worse with the truncated degree grows. Further researches still need to be done to invert surface mass variation coefficients from various combinations of GPS observations, ocean models and other datasets. Numéro de notice : A2019-669 Affiliation des auteurs : Géodésie+Ext (mi2018-2019) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1186/s40623-019-1054-2 Date de publication en ligne : 05/07/2019 En ligne : https://doi.org/10.1186/s40623-019-1054-2 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99940
in Earth, Planets and Space > vol 71 (2019) . - n° 74[article]GPS, DORIS and SLR combined geocenter motion from reference frame time series analysis / Patrick Sillard (1999)
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