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

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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

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