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The impact of common versus separate estimation of orbit parameters on GRACE gravity field solutions / U. Meyer in Journal of geodesy, vol 89 n° 7 (July 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 7 (July 2015) . - pp 685 - 696 Titre : The impact of common versus separate estimation of orbit parameters on GRACE gravity field solutions Type de document : Article/Communication Auteurs : U. Meyer, Auteur ; Adrian Jäggi, Auteur ; Gerhard Beutler, Auteur ; Heike Bock, Auteur Année de publication : 2015 Article en page(s) : pp 685 - 696 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] données GRACE [Termes IGN] élément orbital [Termes IGN] orbitographie [Termes IGN] paramètre de temps [Termes IGN] propagation du signal [Termes IGN] traitement du signal Résumé : (auteur) Gravity field parameters are usually determined from observations of the GRACE satellite mission together with arc-specific parameters in a generalized orbit determination process. When separating the estimation of gravity field parameters from the determination of the satellites’ orbits, correlations between orbit parameters and gravity field coefficients are ignored and the latter parameters are biased towards the a priori force model. We are thus confronted with a kind of hidden regularization. To decipher the underlying mechanisms, the Celestial Mechanics Approach is complemented by tools to modify the impact of the pseudo-stochastic arc-specific parameters on the normal equations level and to efficiently generate ensembles of solutions. By introducing a time variable a priori model and solving for hourly pseudo-stochastic accelerations, a significant reduction of noisy striping in the monthly solutions can be achieved. Setting up more frequent pseudo-stochastic parameters results in a further reduction of the noise, but also in a notable damping of the observed geophysical signals. To quantify the effect of the a priori model on the monthly solutions, the process of fixing the orbit parameters is replaced by an equivalent introduction of special pseudo-observations, i.e., by explicit regularization. The contribution of the thereby introduced a priori information is determined by a contribution analysis. The presented mechanism is valid universally. It may be used to separate any subset of parameters by pseudo-observations of a special design and to quantify the damage imposed on the solution. Numéro de notice : A2015-354 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-015-0807-3 Date de publication en ligne : 29/03/2015 En ligne : https://doi.org/10.1007/s00190-015-0807-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76777 [article]

GOCE: assessment of GPS-only gravity field determination / Adrian Jäggi in Journal of geodesy, vol 89 n° 1 (January 2015)  

Public [article]  inJournal of geodesy > vol 89 n° 1 (January 2015) . - pp 33 - 48 Titre : GOCE: assessment of GPS-only gravity field determination Type de document : Article/Communication Auteurs : Adrian Jäggi, Auteur ; Heike Bock, Auteur ; U. Meyer, Auteur ; et al., Auteur Année de publication : 2015 Article en page(s) : pp 33 - 48 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] champ géomagnétique [Termes IGN] données GOCE [Termes IGN] données GPS [Termes IGN] erreur systématique [Termes IGN] ionosphère [Termes IGN] orbite précise [Termes IGN] positionnement cinématique Résumé : (auteur) The GOCE satellite was orbiting the Earth in a Sun-synchronous orbit at a very low altitude for more than 4 years. This low orbit and the availability of high-quality data make it worthwhile to assess the contribution of GOCE GPS data to the recovery of both the static and time-variable gravity fields. We use the kinematic positions of the official GOCE precise science orbit (PSO) product to perform gravity field determination using the Celestial Mechanics Approach. The generated gravity field solutions reveal severe systematic errors centered along the geomagnetic equator. Their size is significantly coupled with the ionospheric density and thus generally increasing over the mission period. The systematic errors may be traced back to the kinematic positions of the PSO product and eventually to the ionosphere-free GPS carrier phase observations used for orbit determination. As they cannot be explained by the current higher order ionospheric correction model recommended by the IERS Conventions 2010, an empirical approach is presented by discarding GPS data affected by large ionospheric changes. Such a measure yields a strong reduction of the systematic errors along the geomagnetic equator in the gravity field recovery, and only marginally reduces the set of useable kinematic positions by at maximum 6 % for severe ionosphere conditions. Eventually it is shown that GOCE gravity field solutions based on kinematic positions have a limited sensitivity to the largest annual signal related to land hydrology. Numéro de notice : A2015-328 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-014-0759-z Date de publication en ligne : 10/09/2014 En ligne : https://doi.org/10.1007/s00190-014-0759-z Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=76653 [article]

GPS-derived orbits for the GOCE satellite / Heike Bock in Journal of geodesy, vol 85 n° 11 (November /2011)  

Public [article]  inJournal of geodesy > vol 85 n° 11 (November /2011) . - pp 807 - 818 Titre : GPS-derived orbits for the GOCE satellite Type de document : Article/Communication Auteurs : Heike Bock, Auteur ; Adrian Jäggi, Auteur ; U. Meyer, Auteur ; P. Visser, Auteur ; et al., Auteur Année de publication : 2011 Article en page(s) : pp 807 - 818 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes IGN] antenne GPS [Termes IGN] GOCE [Termes IGN] orbite basse [Termes IGN] orbitographie [Termes IGN] orbitographie par GNSS [Termes IGN] positionnement cinématique [Termes IGN] série temporelle [Termes IGN] télémétrie laser sur satellite Résumé : (Auteur) The first ESA (European Space Agency) Earth explorer core mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) was launched on 17 March 2009 into a sun-synchronous dusk–dawn orbit with an exceptionally low initial altitude of about 280 km. The onboard 12-channel dual-frequency GPS (Global Positioning System) receiver delivers 1 Hz data, which provides the basis for precise orbit determination (POD) for such a very low orbiting satellite. As part of the European GOCE Gravity Consortium the Astronomical Institute of the University of Bern and the Department of Earth Observation and Space Systems are responsible for the orbit determination of the GOCE satellite within the GOCE High-level Processing Facility. Both quick-look (rapid) and very precise orbit solutions are produced with typical latencies of 1 day and 2 weeks, respectively. This article summarizes the special characteristics of the GOCE GPS data, presents POD results for about 2 months of data, and shows that both latency and accuracy requirements are met. Satellite Laser Ranging validation shows that an accuracy of 4 and 7 cm is achieved for the reduced-dynamic and kinematic Rapid Science Orbit solutions, respectively. The validation of the reduced-dynamic and kinematic Precise Science Orbit solutions is at a level of about 2 cm. Numéro de notice : A2011-469 Affiliation des auteurs : non IGN Thématique : IMAGERIE/POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0484-9 Date de publication en ligne : 26/05/2011 En ligne : https://doi.org/10.1007/s00190-011-0484-9 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31363 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2011111	RAB	Revue	Centre de documentation	En réserve L003	Disponible

The celestial mechanics approach : theoretical foundations / Gerhard Beutler in Journal of geodesy, vol 84 n° 10 (October 2010)  

Public [article]  inJournal of geodesy > vol 84 n° 10 (October 2010) . - pp 605 - 624 Titre : The celestial mechanics approach : theoretical foundations Type de document : Article/Communication Auteurs : Gerhard Beutler, Auteur ; Adrian Jäggi, Auteur ; L. Mervart, Auteur ; U. Meyer, Auteur Année de publication : 2010 Article en page(s) : pp 605 - 624 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] antenne GPS [Termes IGN] champ de pesanteur terrestre [Termes IGN] constellation GPS [Termes IGN] mécanique orbitale [Termes IGN] orbitographie Résumé : (Auteur) Gravity field determination using the measurements of Global Positioning receivers onboard low Earth orbiters and inter-satellite measurements in a constellation of satellites is a generalized orbit determination problem involving all satellites of the constellation. The celestial mechanics approach (CMA) is comprehensive in the sense that it encompasses many different methods currently in use, in particular so-called short-arc methods, reduced-dynamic methods, and pure dynamic methods. The method is very flexible because the actual solution type may be selected just prior to the combination of the satellite-, arc- and technique-specific normal equation systems. It is thus possible to generate ensembles of substantially different solutions - essentially at the cost of generating one particular solution. The article outlines the general aspects of orbit and gravity field determination. Then the focus is put on the particularities of the CMA, in particular on the way to use accelerometer data and the statistical information associated with it. Numéro de notice : A2010-417 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-010-0401-7 Date de publication en ligne : 24/08/2010 En ligne : https://doi.org/10.1007/s00190-010-0401-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30610 [article]

Exemplaires(1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
266-2010101	SL	Revue	Centre de documentation	Revues en salle	Disponible