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Mass evolution of Mediterranean, Black, Red, and Caspian Seas from GRACE and altimetry : accuracy assessment and solution calibration / B. D. Loomis in Journal of geodesy, vol 91 n° 2 (February 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 2 (February 2017) . - pp 195 - 206 Titre : Mass evolution of Mediterranean, Black, Red, and Caspian Seas from GRACE and altimetry : accuracy assessment and solution calibration Type de document : Article/Communication Auteurs : B. D. Loomis, Auteur ; Scott B. Luthcke, Auteur Année de publication : 2017 Article en page(s) : pp 195 - 206 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Caspienne, mer [Termes IGN] données altimétriques [Termes IGN] données GRACE [Termes IGN] étalonnage des données [Termes IGN] masse d'eau [Termes IGN] Méditerranée, mer [Termes IGN] Noire, mer [Termes IGN] résidu [Termes IGN] Rouge, mer [Termes IGN] série temporelle Résumé : (Auteur) We present new measurements of mass evolution for the Mediterranean, Black, Red, and Caspian Seas as determined by the NASA Goddard Space Flight Center (GSFC) GRACE time-variable global gravity mascon solutions. These new solutions are compared to sea surface altimetry measurements of sea level anomalies with steric corrections applied. To assess their accuracy, the GRACE- and altimetry-derived solutions are applied to the set of forward models used by GSFC for processing the GRACE Level-1B datasets, with the resulting inter-satellite range-acceleration residuals providing a useful metric for analyzing solution quality. We also present a differential correction strategy to calibrate the time series of mass change for each of the seas by establishing the strong linear relationship between differences in the forward modeled mass and the corresponding range-acceleration residuals between the two solutions. These calibrated time series of mass change are directly determined from the range-acceleration residuals, effectively providing regionally-tuned GRACE solutions without the need to form and invert normal equations. Finally, the calibrated GRACE time series are discussed and combined with the steric-corrected sea level anomalies to provide new measurements of the unmodeled steric variability for each of the seas over the span of the GRACE observation record. We apply ensemble empirical mode decomposition (EEMD) to adaptively sort the mass and steric components of sea level anomalies into seasonal, non-seasonal, and long-term temporal scales. Numéro de notice : A2017-063 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0952-3 En ligne : http://dx.doi.org/10.1007/s00190-016-0952-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=84277 [article]

Simulation study of a follow-on gravity mission to GRACE / B. Loomis in Journal of geodesy, vol 86 n° 5 (May 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 5 (May 2012) . - pp 319 - 335 Titre : Simulation study of a follow-on gravity mission to GRACE Type de document : Article/Communication Auteurs : B. Loomis, Auteur ; R. Nerem, Auteur ; Scott B. Luthcke, Auteur Année de publication : 2012 Article en page(s) : pp 319 - 335 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] crénelage [Termes IGN] données GRACE [Termes IGN] masse de la Terre [Termes IGN] simulation Résumé : (Auteur) The gravity recovery and climate experiment (GRACE) has been providing monthly estimates of the Earth’s time-variable gravity field since its launch in March 2002. The GRACE gravity estimates are used to study temporal mass variations on global and regional scales, which are largely caused by a redistribution of water mass in the Earth system. The accuracy of the GRACE gravity fields are primarily limited by the satellite-to-satellite range-rate measurement noise, accelerometer errors, attitude errors, orbit errors, and temporal aliasing caused by un-modeled high-frequency variations in the gravity signal. Recent work by Ball Aerospace & Technologies Corp., Boulder, CO has resulted in the successful development of an interferometric laser ranging system to specifically address the limitations of the K-band microwave ranging system that provides the satellite-to-satellite measurements for the GRACE mission. Full numerical simulations are performed for several possible configurations of a GRACE Follow-On (GFO) mission to determine if a future satellite gravity recovery mission equipped with a laser ranging system will provide better estimates of time-variable gravity, thus benefiting many areas of Earth systems research. The laser ranging system improves the range-rate measurement precision to ~0.6 nm/s as compared to ~0.2 ?m/s for the GRACE K-band microwave ranging instrument. Four different mission scenarios are simulated to investigate the effect of the better instrument at two different altitudes. The first pair of simulated missions is flown at GRACE altitude (~480 km) assuming on-board accelerometers with the same noise characteristics as those currently used for GRACE. The second pair of missions is flown at an altitude of ~250 km which requires a drag-free system to prevent satellite re-entry. In addition to allowing a lower satellite altitude, the drag-free system also reduces the errors associated with the accelerometer. All simulated mission scenarios assume a two satellite co-orbiting pair similar to GRACE in a near-polar, near-circular orbit. A method for local time variable gravity recovery through mass concentration blocks (mascons) is used to form simulated gravity estimates for Greenland and the Amazon region for three GFO configurations and GRACE. Simulation results show that the increased precision of the laser does not improve gravity estimation when flown with on-board accelerometers at the same altitude and spacecraft separation as GRACE, even when time-varying background models are not included. This study also shows that only modest improvement is realized for the best-case scenario (laser, low-altitude, drag-free) as compared to GRACE due to temporal aliasing errors. These errors are caused by high-frequency variations in the hydrology signal and imperfections in the atmospheric, oceanographic, and tidal models which are used to remove unwanted signal. This work concludes that applying the updated technologies alone will not immediately advance the accuracy of the gravity estimates. If the scientific objectives of a GFO mission require more accurate gravity estimates, then future work should focus on improvements in the geophysical models, and ways in which the mission design or data processing could reduce the effects of temporal aliasing. Numéro de notice : A2012-241 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0521-8 Date de publication en ligne : 28/10/2011 En ligne : https://doi.org/10.1007/s00190-011-0521-8 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31687 [article]

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DORIS/SLR POD modeling improvements for Jason-1 and Jason-2 / Nikita P. Zelensky in Advances in space research, vol 46 n° 12 (15/12/2010)  

Public [article]  inAdvances in space research > vol 46 n° 12 (15/12/2010) . - pp 1541 - 1558 Titre : DORIS/SLR POD modeling improvements for Jason-1 and Jason-2 Type de document : Article/Communication Auteurs : Nikita P. Zelensky, Auteur ; Franck G. Lemoine, Auteur ; Marek Ziebart, Auteur ; Ant Sibthorpe, Auteur ; Pascal Willis , Auteur ; Brian D. Beckley, Auteur ; Steven M. Klosko, Auteur ; Douglas S. Chinn, Auteur ; David D. Rowlands, Auteur ; Scott B. Luthcke, Auteur ; Despina E. Pavlis, Auteur ; Vincenza Luceri, Auteur Année de publication : 2010 Article en page(s) : pp 1541 - 1558 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] analyse de sensibilité [Termes IGN] données TLS (télémétrie) [Termes IGN] Jason [Termes IGN] orbitographie [Termes IGN] positionnement par DORIS [Termes IGN] résidu [Termes IGN] retard troposphérique [Termes IGN] télémétrie laser sur satellite Résumé : (auteur) The long-term stability and the precision of the satellite orbit is a critical component of the Jason-1 and Jason-2 (OSTM) Missions, providing the reference frame for ocean mapping using altimeter data. DORIS tracking in combination with SLR has provided orbits, which are both highly accurate and consistent across missions using the latest and most accurate POD models. These models include GRACE-derived static and time varying gravity fields and a refined Terrestrial Reference Frame based on SLR and DORIS data yielding a uniform station complement. Additional improvements have been achieved based on advances in modeling the satellite surface forces and the tropospheric path delay for DORIS measurements. This paper presents these model improvements for Jason-1 and Jason-2, including a description of DORIS sensitivity to error in tropospheric path delay. We show that the detailed University College London (UCL) radiation pressure model for Jason-1, which includes self-shadowing and thermal re-radiation, is superior to the use of a macromodel for radiation pressure surface force modeling. Improvements in SLR residuals are seen over all Beta-prime angles for both Jason-1 and Jason-2 using the UCL model, with the greatest improvement found over regimes of low Beta-prime where orbit Earth shadowing is maximum. The overall radial orbit improvement for Jason-1 using the UCL model is 3 mm RMS, as corroborated by the improvement in the independent altimeter crossover data. Special attention is paid to Jason-2 POD to assess improvements gained with the latest advances in DORIS receiver technology. Tests using SLR and altimeter crossover residuals suggest the Jason-2 reduced-dynamic DORIS-only, SLR/DORIS, and GPS orbits have all achieved 1-cm radial accuracy. Tests using independent SLR data acquired at high elevation show an average fit value of 1.02 cm for the DORIS-only and 0.94 cm for the GPS reduced-dynamic orbits. Orbit differences suggest that the largest remaining errors in the Jason-2 dynamic orbit solutions are due to radiation pressure mis-modeling and variations in the geopotential not captured in the GRACE-derived annual terms. Numéro de notice : A2010-652 Affiliation des auteurs : IGN+Ext (1940-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2010.05.008 Date de publication en ligne : 13/05/2010 En ligne : https://doi.org/10.1016/j.asr.2010.05.008 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91722 [article]

Towards development of a consistent orbit series for TOPEX, Jason-1, and Jason-2 / Franck G. Lemoine in Advances in space research, vol 46 n° 12 (15/12/2010)  

Public [article]  inAdvances in space research > vol 46 n° 12 (15/12/2010) . - pp 1513 - 1540 Titre : Towards development of a consistent orbit series for TOPEX, Jason-1, and Jason-2 Type de document : Article/Communication Auteurs : Franck G. Lemoine, Auteur ; Nikita P. Zelensky, Auteur ; Douglas S. Chinn, Auteur ; Marek Ziebart, Auteur ; Despina E. Pavlis, Auteur ; David D. Rowlands, Auteur ; Brian D. Beckley, Auteur ; Scott B. Luthcke, Auteur ; Pascal Willis , Auteur ; et al., Auteur Année de publication : 2010 Article en page(s) : pp 1513 - 1540 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] cohérence des données [Termes IGN] données altimétriques [Termes IGN] données DORIS [Termes IGN] force de gravitation [Termes IGN] International Terrestrial Reference Frame [Termes IGN] Jason [Termes IGN] niveau moyen des mers [Termes IGN] orbitographie [Termes IGN] série temporelle [Termes IGN] surcharge océanique [Termes IGN] télémétrie laser sur satellite [Termes IGN] TOPEX-Poseidon Résumé : (Auteur) The TOPEX/Poseidon, Jason-1 and Jason-2 set of altimeter data now provide a time series of synoptic observations of the ocean that span nearly 17 years from the launch of TOPEX in 1992. The analysis of the altimeter data including the use of altimetry to monitor the global change in mean sea level requires a stable, accurate, and consistent orbit reference over the entire time span. In this paper, we describe the recomputation of a time series of orbits that rely on a consistent set of reference frames and geophysical models. The recomputed orbits adhere to the IERS 2003 standards for ocean and earth tides, use updates to the ITRF2005 reference frame for both the SLR and DORIS stations, apply GRACE-derived models for modeling of the static and time-variable gravity, implement the University College London (UCL) radiation pressure model for Jason-1, use improved troposphere modeling for the DORIS data, and apply the GOT4.7 ocean tide model for both dynamical ocean tide modeling and for ocean loading. The new TOPEX orbits have a mean SLR fit of 1.79 cm compared to 2.21 cm for the MGDR-B orbits. These new TOPEX orbits agree radially with independent SLR/crossover orbits at 0.70 cm RMS, and the orbit accuracy is estimated at 1.5–2.0 cm RMS over the entire TOPEX time series. The recomputed Jason-1 orbits agree radially with the Jason-1 GDR-C orbits at 1.08 cm RMS. The GSFC SLR/DORIS dynamic and reduced-dynamic orbits for Jason-2 agree radially with independent orbits from the CNES and JPL at 0.70–1.06 cm RMS. Applying these new orbits, and using the latest altimeter corrections for TOPEX, Jason-1, and Jason-2 from September 1992 to May 2009, we find a global rate in mean sea level of 3.0 + 0.4 mm/yr. Numéro de notice : A2010-564 Affiliation des auteurs : IGN+Ext (1940-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2010.05.007 Date de publication en ligne : 13/05/2010 En ligne : https://doi.org/10.1016/j.asr.2010.05.007 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30756 [article]

Sub-centimeter SLR precision with the SLRF2005/LPOD2005 network / Nikita P. Zelensky (2008) 

Public contenu dans Proceedings of the 16th International Workshop on Laser Ranging / Stanisław Schillak (2009)   Titre : Sub-centimeter SLR precision with the SLRF2005/LPOD2005 network Type de document : Article/Communication Auteurs : Nikita P. Zelensky, Auteur ; Franck G. Lemoine, Auteur ; David D. Rowlands, Auteur ; Scott B. Luthcke, Auteur ; Douglas S. Chinn, Auteur ; J.W. Beall, Auteur ; Brian D. Beckley, Auteur ; Steven M. Klosko, Auteur ; Pascal Willis , Auteur ; Vincenza Luceri, Auteur Editeur : Varsovie : Polish Academy of Sciences Année de publication : 2008 Conférence : IWLR 2008, 16th International Laser Ranging Workshop 13/10/2008 17/10/2008 Poznan Pologne OA Proceedings Importance : pp 215 - 222 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] précision centimétrique [Termes IGN] télémétrie laser sur satellite Résumé : (auteur) Satellite Laser Ranging (SLR) offers the only unambiguous sub-centimeter range measurement to orbiting satellites. This capability finds many applications in addition to precision orbit determination (POD), which include a unique absolute measure of orbit accuracy, accurate altimeter range calibration, accurate definition of the Earth‘s center of mass, the most accurate definition of the geocentric gravitational coefficient (GM) and scale of a terrestrial reference network. Achieving sub-centimeter precision requires appropriate modeling of the satellite laser retro-reflector array (LRA) coupled in some cases with appropriate modeling of the satellite-dependant station detector characteristics, a highly accurate terrestrial reference frame, and appropriate attention to possible bias modeling of individual stations. We have processed Jason1/2, Lageos1/2, and TOPEX SLR tracking using the latest and most accurate POD models which include a GRACE-based static gravity, time varying gravity, and the highly accurate ILRS update of the rescaled ITRF2005 SLR complement, SLRF2005. SLRF2005 has been further updated, based on recommendations for the rescaling of ITRF2005, producing LPOD2005. Our analysis evaluates individual SLR station performance and systematic signals as observed from all four satellites. Several primary stations are identified as having significant range biases, which if untreated could lead to degradation in current levels of POD accuracy, and possibly degrade the results for other applications of the SLR measurement. Numéro de notice : C2008-031 Affiliation des auteurs : LAREG (1991-2011) Thématique : POSITIONNEMENT Nature : Communication nature-HAL : ComAvecCL&ActesPubliésIntl DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102414

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