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Mission design, operation and exploitation of the gravity field and steady-state ocean circulation explorer mission / R. Floberghagen in Journal of geodesy, vol 85 n° 11 (November /2011)  

Public [article]  inJournal of geodesy > vol 85 n° 11 (November /2011) . - pp 749 - 758 Titre : Mission design, operation and exploitation of the gravity field and steady-state ocean circulation explorer mission Type de document : Article/Communication Auteurs : R. Floberghagen, Auteur ; M. Fehringer, Auteur ; D. Lamarre, Auteur ; D. Muzi, Auteur ; et al., Auteur Année de publication : 2011 Article en page(s) : pp 749 - 758 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] circulation océanique [Termes IGN] données GOCE [Termes IGN] géoïde terrestre [Termes IGN] GOCE [Termes IGN] gradient de gravitation [Termes IGN] gradiomètre [Termes IGN] gravimétrie spatiale Résumé : (Auteur) The European Space Agency’s Gravity field and steady-state ocean circulation explorer mission (GOCE) was launched on 17 March 2009. As the first of the Earth Explorer family of satellites within the Agency’s Living Planet Programme, it is aiming at a better understanding of the Earth system. The mission objective of GOCE is the determination of the Earth’s gravity field and geoid with high accuracy and maximum spatial resolution. The geoid, combined with the de facto mean ocean surface derived from twenty-odd years of satellite radar altimetry, yields the global dynamic ocean topography. It serves ocean circulation and ocean transport studies and sea level research. GOCE geoid heights allow the conversion of global positioning system (GPS) heights to high precision heights above sea level. Gravity anomalies and also gravity gradients from GOCE are used for gravity-to-density inversion and in particular for studies of the Earth’s lithosphere and upper mantle. GOCE is the first-ever satellite to carry a gravitational gradiometer, and in order to achieve its challenging mission objectives the satellite embarks a number of world-first technologies. In essence the spacecraft together with its sensors can be regarded as a spaceborne gravimeter. In this work, we describe the mission and the way it is operated and exploited in order to make available the best-possible measurements of the Earth gravity field. The main lessons learned from the first 19 months in orbit are also provided, in as far as they affect the quality of the science data products and therefore are of specific interest for GOCE data users. Numéro de notice : A2011-467 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0498-3 Date de publication en ligne : 18/10/2011 En ligne : https://doi.org/10.1007/s00190-011-0498-3 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31361 [article]

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GOCE gravitational gradients along the orbit / Johannes Bouman in Journal of geodesy, vol 85 n° 11 (November /2011)  

Public [article]  inJournal of geodesy > vol 85 n° 11 (November /2011) . - pp 791 - 805 Titre : GOCE gravitational gradients along the orbit Type de document : Article/Communication Auteurs : Johannes Bouman, Auteur ; S. Fiorot, Auteur ; M. Fuchs, Auteur ; Thomas Gruber, Auteur Année de publication : 2011 Article en page(s) : pp 791 - 805 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] GOCE [Termes IGN] gradient de gravitation Résumé : (Auteur) GOCE is ESA’s gravity field mission and the first satellite ever that measures gravitational gradients in space, that is, the second spatial derivatives of the Earth’s gravitational potential. The goal is to determine the Earth’s mean gravitational field with unprecedented accuracy at spatial resolutions down to 100 km. GOCE carries a gravity gradiometer that allows deriving the gravitational gradients with very high precision to achieve this goal. There are two types of GOCE Level 2 gravitational gradients (GGs) along the orbit: the gravitational gradients in the gradiometer reference frame (GRF) and the gravitational gradients in the local north oriented frame (LNOF) derived from the GGs in the GRF by point-wise rotation. Because the V XX , V YY , V ZZ and V XZ are much more accurate than V XY and V YZ , and because the error of the accurate GGs increases for low frequencies, the rotation requires that part of the measured GG signal is replaced by model signal. However, the actual quality of the gradients in GRF and LNOF needs to be assessed. We analysed the outliers in the GGs, validated the GGs in the GRF using independent gravity field information and compared their assessed error with the requirements. In addition, we compared the GGs in the LNOF with state-of-the-art global gravity field models and determined the model contribution to the rotated GGs. We found that the percentage of detected outliers is below 0.1% for all GGs, and external gravity data confirm that the GG scale factors do not differ from one down to the 10-3 level. Furthermore, we found that the error of V XX and V YY is approximately at the level of the requirement on the gravitational gradient trace, whereas the V ZZ error is a factor of 2–3 above the requirement for higher frequencies. We show that the model contribution in the rotated GGs is 2–35% dependent on the gravitational gradient. Finally, we found that GOCE gravitational gradients and gradients derived from EIGEN-5C and EGM2008 are consistent over the oceans, but that over the continents the consistency may be less, especially in areas with poor terrestrial gravity data. All in all, our analyses show that the quality of the GOCE gravitational gradients is good and that with this type of data valuable new gravity field information is obtained. Numéro de notice : A2011-468 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0464-0 Date de publication en ligne : 18/10/2011 En ligne : https://doi.org/10.1007/s00190-011-0464-0 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31362 [article]

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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]

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Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons / Thomas Gruber in Journal of geodesy, vol 85 n° 11 (November /2011)  

Public [article]  inJournal of geodesy > vol 85 n° 11 (November /2011) . - pp 845 - 860 Titre : Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons Type de document : Article/Communication Auteurs : Thomas Gruber, Auteur ; P. Visser, Auteur ; C. Ackermann, Auteur ; M. Hosse, Auteur Année de publication : 2011 Article en page(s) : pp 845 - 860 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] analyse comparative [Termes IGN] analyse de variance [Termes IGN] champ de pesanteur terrestre [Termes IGN] données GOCE [Termes IGN] données GRACE [Termes IGN] géoïde gravimétrique [Termes IGN] géoïde terrestre [Termes IGN] harmonique sphérique [Termes IGN] limite de résolution géométrique [Termes IGN] orbitographie [Termes IGN] résidu Résumé : (Auteur) Three GOCE-based gravity field solutions have been computed by ESA’s high-level processing facility and were released to the user community. All models are accompanied by variance-covariance information resulting either from the least squares procedure or a Monte-Carlo approach. In order to obtain independent external quality parameters and to assess the current performance of these models, a set of independent tests based on satellite orbit determination and geoid comparisons is applied. Both test methods can be regarded as complementary because they either investigate the performance in the long wavelength spectral domain (orbit determination) or in the spatial domain (geoid comparisons). The test procedure was applied to the three GOCE gravity field solutions and to a number of selected pre-launch models for comparison. Orbit determination results suggest, that a pure GOCE gravity field model does not outperform the multi-year GRACE gravity field solutions. This was expected as GOCE is designed to improve the determination of the medium to high frequencies of the Earth gravity field (in the range of degree and order 50 to 200). Nevertheless, in case of an optimal combination of GOCE and GRACE data, orbit determination results should not deteriorate. So this validation procedure can also be used for testing the optimality of the approach adopted for producing combined GOCE and GRACE models. Results from geoid comparisons indicate that with the 2 months of GOCE data a significant improvement in the determination of the spherical harmonic spectrum of the global gravity field between degree 50 and 200 can be reached. Even though the ultimate mission goal has not yet been reached, especially due to the limited time span of used GOCE data (only 2 months), it was found that existing satellite-only gravity field models, which are based on 7 years of GRACE data, can already be enhanced in terms of spatial resolution. It is expected that with the accumulation of more GOCE data the gravity field model resolution and quality can be further enhanced, and the GOCE mission goal of 1–2 cm geoid accuracy with 100 km spatial resolution can be achieved. Numéro de notice : A2011-470 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-011-0486-7 Date de publication en ligne : 08/06/2011 En ligne : https://doi.org/10.1007/s00190-011-0486-7 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=31364 [article]

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