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High-frequency signal and noise estimates of CSR GRACE RL04 / J.A. Bonin in Journal of geodesy, vol 86 n° 12 (December 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 12 (December 2012) . - pp 1165 - 1177 Titre : High-frequency signal and noise estimates of CSR GRACE RL04 Type de document : Article/Communication Auteurs : J.A. Bonin, Auteur ; S. Bettadpur, Auteur ; B. Tapley, Auteur Année de publication : 2012 Article en page(s) : pp 1165 - 1177 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] bruit (théorie du signal) [Termes descripteurs IGN] données GRACE [Termes descripteurs IGN] erreur [Termes descripteurs IGN] filtrage du bruit [Termes descripteurs IGN] force de gravitation [Termes descripteurs IGN] levé gravimétrique [Termes descripteurs IGN] rapport signal sur bruit [Termes descripteurs IGN] traitement du signal Résumé : (Auteur) A sliding window technique is used to create daily-sampled Gravity Recovery and Climate Experiment (GRACE) solutions with the same background processing as the official CSR RL04 monthly series. By estimating over shorter time spans, more frequent solutions are made using uncorrelated data, allowing for higher frequency resolution in addition to daily sampling. Using these data sets, high-frequency GRACE errors are computed using two different techniques: assuming the GRACE high-frequency signal in a quiet area of the ocean is the true error, and computing the variance of differences between multiple high-frequency GRACE series from different centers. While the signal-to-noise ratios prove to be sufficiently high for confidence at annual and lower frequencies, at frequencies above 3 cycles/year the signal-to-noise ratios in the large hydrological basins looked at here are near 1.0. Comparisons with the GLDAS hydrological model and high frequency GRACE series developed at other centers confirm CSR GRACE RL04’s poor ability to accurately and reliably measure hydrological signal above 3–9 cycles/year, due to the low power of the large-scale hydrological signal typical at those frequencies compared to the GRACE errors. Numéro de notice : A2012-651 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0572-5 date de publication en ligne : 03/06/2012 En ligne : https://doi.org/10.1007/s00190-012-0572-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=32097 [article]

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Reducing errors in the GRACE gravity solutions using regularization / H. Save in Journal of geodesy, vol 86 n° 9 (September 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 9 (September 2012) . - pp 695 - 711 Titre : Reducing errors in the GRACE gravity solutions using regularization Type de document : Article/Communication Auteurs : H. Save, Auteur ; S. Bettadpur, Auteur ; B. Tapley, Auteur Année de publication : 2012 Article en page(s) : pp 695 - 711 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] champ de pesanteur terrestre [Termes descripteurs IGN] données GRACE [Termes descripteurs IGN] gravimétrie [Termes descripteurs IGN] harmonique sphérique [Termes descripteurs IGN] levé gravimétrique [Termes descripteurs IGN] régularisation de Tychonoff Résumé : (Auteur) The nature of the gravity field inverse problem amplifies the noise in the GRACE data, which creeps into the mid and high degree and order harmonic coefficients of the Earth’s monthly gravity fields provided by GRACE. Due to the use of imperfect background models and data noise, these errors are manifested as north-south striping in the monthly global maps of equivalent water heights. In order to reduce these errors, this study investigates the use of the L-curve method with Tikhonov regularization. L-curve is a popular aid for determining a suitable value of the regularization parameter when solving linear discrete ill-posed problems using Tikhonov regularization. However, the computational effort required to determine the L-curve is prohibitively high for a large-scale problem like GRACE. This study implements a parameter-choice method, using Lanczos bidiagonalization which is a computationally inexpensive approximation to L-curve. Lanczos bidiagonalization is implemented with orthogonal transformation in a parallel computing environment and projects a large estimation problem on a problem of the size of about 2 orders of magnitude smaller for computing the regularization parameter. Errors in the GRACE solution time series have certain characteristics that vary depending on the ground track coverage of the solutions. These errors increase with increasing degree and order. In addition, certain resonant and near-resonant harmonic coefficients have higher errors as compared with the other coefficients. Using the knowledge of these characteristics, this study designs a regularization matrix that provides a constraint on the geopotential coefficients as a function of its degree and order. This regularization matrix is then used to compute the appropriate regularization parameter for each monthly solution. A 7-year time-series of the candidate regularized solutions (Mar 2003–Feb 2010) show markedly reduced error stripes compared with the unconstrained GRACE release 4 solutions (RL04) from the Center for Space Research (CSR). Post-fit residual analysis shows that the regularized solutions fit the data to within the noise level of GRACE. A time series of filtered hydrological model is used to confirm that signal attenuation for basins in the Total Runoff Integrating Pathways (TRIP) database over 320 km radii is less than 1 cm equivalent water height RMS, which is within the noise level of GRACE. Numéro de notice : A2012-467 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-012-0548-5 date de publication en ligne : 10/03/2012 En ligne : https://doi.org/10.1007/s00190-012-0548-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31913 [article]

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Geocenter variations derived from GPS tracking of the GRACE satellites / Z. Kang in Journal of geodesy, vol 83 n° 10 (October 2009)

Public [article]  inJournal of geodesy > vol 83 n° 10 (October 2009) . - pp 895 - 901 Titre : Geocenter variations derived from GPS tracking of the GRACE satellites Type de document : Article/Communication Auteurs : Z. Kang, Auteur ; B. Tapley, Auteur ; J. Chen, Auteur ; John Ries, Auteur ; S. Bettadpur, Auteur Année de publication : 2009 Article en page(s) : pp 895 - 901 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] géocentre [Termes descripteurs IGN] GRACE [Termes descripteurs IGN] orbite basse [Termes descripteurs IGN] orbitographie par GNSS [Termes descripteurs IGN] poursuite de satellite Résumé : (Auteur) Two 4.5-year sets of daily geocenter variations have been derived from GPS-LEO (Low-Earth Orbiter) tracking of the GRACE (Gravity Recovery And Climate Experiment) satellites. The twin GRACE satellites, launched in March 2002, are each equipped with a BlackJack global positioning system (GPS) receiver for precise orbit determination and gravity recovery. Since launch, there have been significant improvements in the background force models used for satellite orbit determination, most notably the model for the geopotential, which has resulted in significant improvements to the orbit determination accuracy. The purpose of this paper is to investigate the potential for determining seasonal (annual and semiannual) geocenter variations using GPS-LEO tracking data from the GRACE twin satellites. Internal comparison between the GRACE-A and GRACE-B derived geocenter variations shows good agreement. In addition, the annual and semiannual variations of geocenter motions determined from this study have been compared with other space geodetic solutions and predictions from geophysical models. The comparisons show good agreement except for the phase of the z-translation component. Copyright Springer Numéro de notice : A2009-428 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30059 [article]

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A simulation study of the errors of omission and commission for GRACE RL01 gravity fields / B. Gunter in Journal of geodesy, vol 80 n° 7 (October 2006)

Public [article]  inJournal of geodesy > vol 80 n° 7 (October 2006) . - pp 341 - 351 Titre : A simulation study of the errors of omission and commission for GRACE RL01 gravity fields Type de document : Article/Communication Auteurs : B. Gunter, Auteur ; John Ries, Auteur ; S. Bettadpur, Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 341 - 351 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes descripteurs IGN] champ de pesanteur terrestre [Termes descripteurs IGN] erreur [Termes descripteurs IGN] estimation statistique [Termes descripteurs IGN] GRACE [Termes descripteurs IGN] modèle de géopotentiel [Termes descripteurs IGN] simulation Résumé : (Auteur) This paper examines the influence that certain omission and commission errors can have on the gravity field models estimated from the initial release of data (RL01) from the Gravity Recovery And Climate Experiment (GRACE) satellite mission. The effects of omission errors were analyzed by limiting the degree and order to which the GPS and K-band range-rate (KBR) measurement partials were extended in the solution process. The commission error studies focused on the impact of an imperfect mean reference gravity field model on the solution. Combinations of both of these error sources were also explored. The nature of these errors makes them difficult to distinguish from the true gravity signal, so the exploration of these error sources was performed using simulations; however, comparisons to real-data solutions are provided. The results show how each of the specific error sources investigated influences the gravity field solution. The simulations also show how all of the errors examined can be sufficiently mitigated through the appropriate choice of processing parameters. Copyright Springer Numéro de notice : A2006-449 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28173 [article]

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Precise orbit determination for the GRACE mission using only GPS data / Z. Kang in Journal of geodesy, vol 80 n° 6 (September 2006)

Public [article]  inJournal of geodesy > vol 80 n° 6 (September 2006) . - pp 322 - 331 Titre : Precise orbit determination for the GRACE mission using only GPS data Type de document : Article/Communication Auteurs : Z. Kang, Auteur ; B. Tapley, Auteur ; S. Bettadpur, Auteur ; et al., Auteur Année de publication : 2006 Article en page(s) : pp 322 - 331 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes descripteurs IGN] GRACE [Termes descripteurs IGN] orbitographie par GNSS [Termes descripteurs IGN] positionnement par GPS [Termes descripteurs IGN] télémétrie laser sur satellite Résumé : (Auteur) The GRACE (gravity recovery and climate experiment) satellites, launched in March 2002, are each equipped with a BlackJack GPS onboard receiver for precise orbit determination and gravity field recovery. Since launch, there have been significant improvements in the background force models used for satellite orbit determination, most notably the model for the geopotential. This has resulted in significant improvements to orbit accuracy for very low altitude satellites. The purpose of this paper is to investigate how well the orbits of the GRACE satellites (about 470 km in altitude) can currently be determined using only GPS data and based on the current models and methods. The orbit accuracy is assessed using a number of tests, which include analysis of orbit fits, orbit overlaps, orbit connecting points, satellite Laser ranging residuals and K-band ranging (KBR) residuals. We show that 1-cm radial orbit accuracy for the GRACE satellites has probably been achieved. These precise GRACE orbits can be used for such purposes as improving gravity recovery from the GRACE KBR data and for atmospheric profiling, and they demonstrate the quality of the background force models being used. Copyright Springer Numéro de notice : A2006-417 Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=28141 [article]

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