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Gravity field processing towards LL-SST satellite missions / Ilias Daras (2016)  

Public Titre : Gravity field processing towards LL-SST satellite missions Type de document : Thèse/HDR Auteurs : Ilias Daras, Auteur ; Roland Pail, Directeur de thèse Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2016 Collection : DGK - C, ISSN 0065-5325 num. 770 Importance : 153 p. ISBN/ISSN/EAN : 978-3-7696-5182-9 Note générale : bibliographie PhD Dissertation Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] accéléromètre [Termes IGN] champ de pesanteur terrestre [Termes IGN] crénelage [Termes IGN] filtrage du bruit [Termes IGN] gravimétrie spatiale [Termes IGN] interféromètre au laser [Termes IGN] poursuite de satellite [Termes IGN] résidu [Termes IGN] satellite d'observation de la Terre Résumé : (auteur) This study focuses on important aspects concerning gravity field processing of future LL-SST [Low-Low Satellite-to-Satellite Tracking] satellite missions. Closed-loop simulations taking into account error models of new generation instrument technology are used to estimate the gravity field accuracy that future missions could provide. Limiting factors are identified, and methods for their treatment are developed. The contribution of all error sources to the error budget is analyzed. It is shown that gravity field processing with double precision may be a limiting factor for exploiting the nm-level accuracy of a laser interferometer. An enhanced numerical precision processing scheme is proposed instead, where double and quadruple precision is used in different parts of the processing chain. It is demonstrated that processing with enhanced precision can efficiently handle laser measurements and take full advantage of their accuracy, while keeping the computational times within reasonable levels. However, error sources of considerably larger impact are expected to affect future missions, with the accelerometer instrument noise and temporal aliasing effects being the most significant ones. The effect of time-correlated noise such as the one present in accelerometer measurements, can be efficiently handled by frequency dependent data weighting. Residual time series that contain the effect of system errors and propagated accelerometer and laser noise, is considered as a noise realization with stationary stochastic properties. The weight matrix is constructed from the auto-correlation functions of these residuals. Applying the weight matrix to a noise case considering all error sources leads to reduction of the error level over the complete spectral bandwidth. Co-estimation of empirical accelerations does not show the same efficiency in reducing the propagated noise with the applied processing strategy. Temporal aliasing effects are reduced essentially by adding a second pair of satellites at an inclined orbit. Compared to a GRACE-type near-polar pair, such a Bender-type constellation delivers solutions with major improvements in terms of de-aliasing potential and recovery performance. When the integrated effect of all geophysical processes is recovered, the maximum spatial resolution of 11-day solutions can be increased from 715 to 315 km half-wavelength. A further reduction of temporal aliasing errors is possible by co-parameterizing low resolution gravity fields at short time intervals, together with the higher resolution gravity field which is sampled at a longer time interval. One day was found to be the optimal sampling period for reducing the error levels in the solutions. A uniform sampling at the co-parameterized short periods, is a prerequisite for an efficient reduction of aliasing errors. High frequency atmospheric signals are captured by daily solutions to a large extent. Hence co-parameterization at daily basis results in significant reduction of aliasing caused by their under-sampling. This enables future gravity satellite missions to deliver the complete spectrum of Earth's geophysical processes. The corresponding by-products of daily gravity field solutions are expected to be very useful to atmospheric science and open doors to new fields of application. Note de contenu : 1. Introduction 1.1. Background 1.2. Motivation and objectives of this study 1.3. Outline 2. Earth's gravity field determination form satellite observations 2.1. Pertubing forces acting on a satellite 2.2. Geopotential and its functionals 2.3. Dedicated gravity satellite missions 2.4. Concepts for future satellite gravity missions 3. Description of the simulation environment for the gravity fields recovery 3.1. Outline of the simulation environment 3.2. Coordinate and time systems 3.3. Simulation if the satellite orbits 3.4. Functional model 3.5. Formulation of the NEQ system 3.6. Solution of the NEQ system 4. Design aspects and error budget of future dedicated gravity satellite missions 4.1. Orbit design 4.2. Satellite formation flights 4.3. Selected orbits for the simulations 4.4. Science and mission requirements 4.5. Noise models for the performance of the instruments 4.6. Error budget analysis 7. Treatment of temporal aliasing effects 7.1. Temporal aliasing for NGGLs 7.2. Co-parameterization of low spatial resolution gravity fiels solutions at higher frequencies 7.3. Retrieval content of NGGM gravity fiels solutions 8. Conclusions Numéro de notice : 19791 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Note de thèse : PhD Dissertation : Geodesy : Stuttgart : 2016 DOI : sans En ligne : http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20160211-1279854-1-3 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85011

Subseasonal GNSS positioning errors / Jim Ray in Geophysical research letters, vol 40 n° 22 (November 2013)    

Public [article]  inGeophysical research letters > vol 40 n° 22 (November 2013) . - pp 5854 - 5860 Titre : Subseasonal GNSS positioning errors Type de document : Article/Communication Auteurs : Jim Ray, Auteur ; Jake Griffiths, Auteur ; Xavier Collilieux , Auteur ; Paul Rebischung , Auteur Année de publication : 2013 Article en page(s) : pp 5854 - 5860 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] bruit rose [Termes IGN] coordonnées GNSS [Termes IGN] crénelage [Termes IGN] données GLONASS [Termes IGN] élément d'orientation externe [Termes IGN] variation saisonnière [Vedettes matières IGN] Traitement de données GNSS Résumé : (auteur) Global Navigation Satellite System (GNSS) station coordinate errors over seasonal and longer time scales are known to be spatially and temporally correlated with flicker noise spectra. Overlaying this are strong annual and semiannual variations that cannot be explained by any single phenomenon. Next most prominent are harmonics of the GPS draconitic year with periods of (351.4/N) days. One explanation is that errors in the standard model for Earth orientation parameter (EOP) tidal variations near 12 and 24 h periods are absorbed into the resonant GPS orbit and daily EOP estimates, resulting mainly in draconitic and fortnightly alias signatures for 24 h product sampling. With the change in International GNSS Service (IGS) station coordinates from weekly to daily resolution in August 2012, it is now possible to study subseasonal performance. All IGS Analysis Centers (ACs) show fortnightly signals, but the resolution will not be sufficient to distinguish direct from aliased subdaily tidal error sources till two more years of data are available. Nevertheless, aliased errors from the subdaily EOP tide model are expected. All but one of the ACs that includes GLONASS data have signals at ~8 day periods, the ground repeat period for GLONASS orbits. This most likely arises from larger geographically correlated orbit errors for GLONASS. Two ACs possess unique short-period features that appear to be caused by peculiarities of their analysis strategies. Numéro de notice : A2013-795 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Thématique : POSITIONNEMENT Nature : Article DOI : 10.1002/2013GL058160 Date de publication en ligne : 08/11/2013 En ligne : http://dx.doi.org/10.1002/2013GL058160 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=80235 [article]

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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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Entwicklung eines Kalman-Filters zur Bestimmung kurzzeitiger Variationen des Erdschwerefeldes aus daten der Satellitenmission GRACE / E. Kurtenbach (2012) 

Public Titre : Entwicklung eines Kalman-Filters zur Bestimmung kurzzeitiger Variationen des Erdschwerefeldes aus daten der Satellitenmission GRACE Titre original : Development of a Kalman filter to derive short-term variations of the Earth's gravity field from GRACE data Type de document : Thèse/HDR Auteurs : E. Kurtenbach, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2012 Collection : DGK - C Sous-collection : Dissertationen num. 683 Importance : 120 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-5095-2 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] corrélation automatique de points homologues [Termes IGN] crénelage [Termes IGN] données GRACE [Termes IGN] filtre de Kalman [Termes IGN] série temporelle [Termes IGN] variation temporelle Résumé : (Auteur) The gravitational field and its temporal variations represent an important observable for the monitoring of the Earth's system. The satellite mission GRACE (Gravity Recovery And Climate Experiment) is, for the first time, able to measure gravity field variations with homogeneous global coverage. Nevertheless, the predicted GRACE accuracy has not been reached yet, partly due to the insufficient representation of the temporal variations in terms of monthly mean fields. In this thesis, an approach is presented which allows the calculation of daily GRACE solutions with the goal of modeling short-term gravity field variations. This time series can on the one hand be used to improve the knowledge of the underlying geophysical processes. On the other hand the daily GRACE solutions can also be used to improve the monthly mean fields. Increasing the temporal resolution is accompanied by a loss of accuracy due to insufficient data coverage. Therefore, additional information in terms of temporal and spatial correlations of the expected gravity signal is introduced into the analysis process. The combination of the GRACE observations and the correlation patterns is then performed within a Kalman filter framework. In a simulation study, the performance of the approach at hand is investigated and, in a second step, applied to real GRACE LIB data. Comparisons to independent data sets, i.e. vertical displacements of GPS stations and ocean bottom pressure time series, reveal that the daily GRACE time series contains geophysically interpretable signal. Furthermore, the daily GRACE time series can be used to significantly reduce the effects of temporal aliasing in the processing of monthly mean gravity field solutions. Numéro de notice : 14619 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62670

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Strategies to mitigate aliasing of loading signals while estimating GPS frame parameters / Xavier Collilieux in Journal of geodesy, vol 86 n° 1 (January 2012)  

Public [article]  inJournal of geodesy > vol 86 n° 1 (January 2012) . - pp 1 - 14 Titre : Strategies to mitigate aliasing of loading signals while estimating GPS frame parameters Type de document : Article/Communication Auteurs : Xavier Collilieux , Auteur ; Tonie M. van Dam, Auteur ; Jim Ray, Auteur ; David Coulot , Auteur ; Laurent Métivier , Auteur ; Zuheir Altamimi , Auteur Année de publication : 2012 Projets : TOSCA / Article en page(s) : pp 1 - 14 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes IGN] crénelage [Termes IGN] effet de charge [Termes IGN] estimation statistique [Termes IGN] géocentre [Termes IGN] International Terrestrial Reference Frame [Termes IGN] positionnement par GPS Résumé : (Auteur) Although GNSS techniques are theoretically sensitive to the Earth center of mass, it is often preferable to remove intrinsic origin and scale information from the estimated station positions since they are known to be affected by systematic errors. This is usually done by estimating the parameters of a linearized similarity transformation which relates the quasi-instantaneous frames to a long-term frame such as the International Terrestrial Reference Frame (ITRF). It is well known that non-linear station motions can partially alias into these parameters. We discuss in this paper some procedures that may allow reducing these aliasing effects in the case of the GPS techniques. The options include the use of well-distributed sub-networks for the frame transformation estimation, the use of site loading corrections, a modification of the stochastic model by downweighting heights, or the joint estimation of the low degrees of the deformation field. We confirm that the standard approach consisting of estimating the transformation over the whole network is particularly harmful for the loading signals if the network is not well distributed. Downweighting the height component, using a uniform sub-network, or estimating the deformation field perform similarly in drastically reducing the amplitude of the aliasing effect. The application of these methods to reprocessed GPS terrestrial frames permits an assessment of the level of agreement between GPS and our loading model, which is found to be about 1.5 mm WRMS in height and 0.8 mm WRMS in the horizontal at the annual frequency. Aliased loading signals are not the main source of discrepancies between loading displacement models and GPS position time series. Numéro de notice : A2012-117 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0487-6 Date de publication en ligne : 08/11/2011 En ligne : https://doi.org/10.1007/s00190-011-0487-6 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31565 [article]

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Automatic and precise orthorectification, coregistration, and subpixel correlation of satellite images: application to ground deformation measurements / S. Leprince in IEEE Transactions on geoscience and remote sensing, vol 45 n° 6 Tome 1 (June 2007)  

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Angular resolution of terrestrial laser scanners / Derek D. Lichti in Photogrammetric record, vol 21 n° 114 (June - August 2006)  

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Kaiser filter for antialiasing in digital photogrammetry / Kourosh Khoshelham in Photogrammetric record, vol 19 n° 105 (March - May 2004)  

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Pan-shapering of very high-resolution multispectral images via generalised Laplacian pyramid fusion / S. Baronti in Bulletin [Société Française de Photogrammétrie et Télédétection], n° 169 (Janvier 2003)

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A study of the aliasing effect on gravitational potential coefficients as determined from gravity data / G.A. Desrochers (1971)

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