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Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground networks / Wen Huang in Journal of geodesy, vol 94 n°10 (October 2020)  

Public [article]  inJournal of geodesy > vol 94 n°10 (October 2020) . - 13 p. Titre : Integrated processing of ground- and space-based GPS observations: improving GPS satellite orbits observed with sparse ground networks Type de document : Article/Communication Auteurs : Wen Huang, Auteur ; Benjamin Männel, Auteur ; Pierre Sakic-Kieffer, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : 13 p. Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes descripteurs IGN] modèle d'orbite [Termes descripteurs IGN] orbite basse [Termes descripteurs IGN] orbite précise [Termes descripteurs IGN] orbitographie [Termes descripteurs IGN] orbitographie par GNSS [Termes descripteurs IGN] récepteur GPS [Termes descripteurs IGN] station GPS Résumé : (auteur) The precise orbit determination (POD) of Global Navigation Satellite System (GNSS) satellites and low Earth orbiters (LEOs) are usually performed independently. It is a potential way to improve the GNSS orbits by integrating LEOs onboard observations into the processing, especially for the developing GNSS, e.g., Galileo with a sparse sensor station network and Beidou with a regional distributed operating network. In recent years, few studies combined the processing of ground- and space-based GNSS observations. The integrated POD of GPS satellites and seven LEOs, including GRACE-A/B, OSTM/Jason-2, Jason-3 and, Swarm-A/B/C, is discussed in this study. GPS code and phase observations obtained by onboard GPS receivers of LEOs and ground-based receivers of the International GNSS Service (IGS) tracking network are used together in one least-squares adjustment. The POD solutions of the integrated processing with different subsets of LEOs and ground stations are analyzed in detail. The derived GPS satellite orbits are validated by comparing with the official IGS products and internal comparison based on the differences of overlapping orbits and satellite positions at the day-boundary epoch. The differences between the GPS satellite orbits derived based on a 26-station network and the official IGS products decrease from 37.5 to 23.9 mm (34% improvement) in 1D-mean RMS when adding seven LEOs. Both the number of the space-based observations and the LEO orbit geometry affect the GPS satellite orbits derived in the integrated processing. In this study, the latter one is proved to be more critical. By including three LEOs in three different orbital planes, the GPS satellite orbits improve more than from adding seven well-selected additional stations to the network. Experiments with a ten-station and regional network show an improvement of the GPS satellite orbits from about 25 cm to less than five centimeters in 1D-mean RMS after integrating the seven LEOs. Numéro de notice : A2020-630 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01424-1 date de publication en ligne : 10/10/2020 En ligne : https://doi.org/10.1007/s00190-020-01424-1 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=96049 [article]

Orbit and clock analysis of BDS-3 satellites using inter-satellite link observations / Xin Xie in Journal of geodesy, vol 94 n° 7 (July 2020)  

Public [article]  inJournal of geodesy > vol 94 n° 7 (July 2020) . - n° 64 Titre : Orbit and clock analysis of BDS-3 satellites using inter-satellite link observations Type de document : Article/Communication Auteurs : Xin Xie, Auteur ; Tao Geng, Auteur ; Qile Zhao, Auteur ; et al., Auteur Année de publication : 2020 Article en page(s) : n° 64 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] constellation BeiDou [Termes descripteurs IGN] horloge du satellite [Termes descripteurs IGN] orbite géostationnaire [Termes descripteurs IGN] orbite terrestre [Termes descripteurs IGN] orbitographie [Termes descripteurs IGN] variance d'Allan Résumé : (auteur) China is currently focusing on the establishment of its BDS-3 system, and a BDS-3 constellation with 18 satellites in medium Earth orbit (MEO) and one satellite in geostationary Earth orbit (GEO) has been able to provide preliminary global services since the end of 2018. These BDS-3 satellites feature the inter-satellite link (ISL) and new high-quality onboard clocks. In this study, we present the analysis of BDS-3 orbits and clocks determined by Ka-band ISL measurements from 18 MEO satellites and one GEO satellite. The ISL data of 43 days from 1 January to 12 February 2019 are used. The BDS-3 ISL measurement is described by a dual one-way ranging model. After converting bidirectional observations to the same epoch, Ka-band clock-free and geometry-free observables are obtained by the addition and subtraction of dual one-way observations, respectively. One anchor station with Ka-band bidirectional observations is introduced into the orbit determination to provide the orientation constraints. Using Ka-band clock-free observables, BDS-3 satellite orbits are determined. The ISL hardware delays are estimated together with orbits, and the resulting hardware delay estimates are quite stable with STD of about 0.03 ns. The Ka-band orbits are evaluated by orbit overlap differences, comparison with L-band precise orbits, and satellite laser ranging validation. The results indicate that the radial orbit errors are on the 2–4 cm level for MEO satellites and 8–10 cm for the GEO satellite. In addition, we investigate the ground anchoring capability by adding one anchor station and reducing the amount of data of the anchor station. Using Ka-band geometry-free observables, BDS-3 satellite clocks are estimated and the RMS of post-fit ISL residuals is about 5 cm. The Ka-band clock offsets are analyzed and compared with L-band precise clocks. Independent of orbit errors, the Allan deviation of Ka-band clocks for averaging interval longer than 5000 s is superior to that of L-band clocks. Furthermore, a pronounced bump, which appears in the Allan deviation of L-band clocks, almost vanishes in Ka-band clocks. Finally, the periodic variations are detected for L-band and Ka-band clocks. Numéro de notice : A2020-534 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-020-01394-4 date de publication en ligne : 08/07/2020 En ligne : https://doi.org/10.1007/s00190-020-01394-4 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95724 [article]

Impact of thermospheric mass density on the orbit prediction of LEO satellites / Changyong He in Space weather, vol 18 n° 1 (January 2020)  

Public [article]  inSpace weather > vol 18 n° 1 (January 2020) . - n° e2019SW002336 Titre : Impact of thermospheric mass density on the orbit prediction of LEO satellites Type de document : Article/Communication Auteurs : Changyong He , Auteur ; Yang Yang, Auteur ; Brett Carter, Auteur ; Kefei Zhang, Auteur ; Andong Hu, Auteur ; Wang Li, Auteur ; Florent Deleflie, Auteur ; Robert Norman, Auteur ; Suqin Wu, Auteur Année de publication : 2020 Projets : 1-Pas de projet / Article en page(s) : n° e2019SW002336 Note générale : bibliographie This study was supported by the Cooperative Research Centre for Space Environment Management (SERCLimited) through the Australian Government's Cooperative Research Centre Programme and partially supported by the National Natural Science Foundation of China(41874040) and the CUMT Independent Innovation Project of “Double-First Class” Construction (2018ZZCX08) Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Techniques orbitales [Termes descripteurs IGN] masse d'air [Termes descripteurs IGN] orbite basse [Termes descripteurs IGN] orbitographie Résumé : (auteur) Many thermospheric mass density (TMD) variations have been recognized in observations and physical simulations; however, their impact on the low‐Earth‐orbit satellites has not been fully evaluated. The present study investigates the quantitative impact of periodic spatiotemporal TMD variations modulated by the empirical DTM2013 model. Also considered are two small‐scale variations, that is, the equatorial mass anomaly and the midnight density maximum, which are reproduced by the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model. This investigation is performed through a 1‐day orbit prediction (OP) simulation for a 400‐km circular orbit. The results show that the impact of TMD variations during solar maximum is 1 order of magnitude larger than that during solar minimum. The dominant impact has been found in the along‐track direction. Semiannual and semidiurnal variations in TMD exert the most significant impact on OP among the intra‐annual and intradiurnal variations, respectively. The zero mean periodic variations in TMD may not significantly affect the predicted orbit but increase the orbital uncertainty if their periods are shorter than the time span of OP. Additionally, the equatorial mass anomaly creates a mean orbit difference of 50 m (5 m) with a standard deviation of 30 m (3 m) in 1‐day OP during high (low) solar activity. The midnight density maximum exhibits a stronger impact in the order of 150±30 and 15±6 m during solar maximum and solar minimum, respectively. This study makes clear that careful selection of TMD variations is of great importance to balance the trade‐off between efficiency and accuracy in OP problems. Numéro de notice : A2020-467 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2019SW002336 date de publication en ligne : 06/11/2019 En ligne : https://doi.org/10.1029/2019SW002336 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95553 [article]

Real-time GPS satellite orbit and clock estimation based on OpenMP / Kaifa Kuang in Advances in space research, vol 63 n° 8 (15 April 2019)  

Public [article]  inAdvances in space research > vol 63 n° 8 (15 April 2019) . - pp 2378 - 2386 Titre : Real-time GPS satellite orbit and clock estimation based on OpenMP Type de document : Article/Communication Auteurs : Kaifa Kuang, Auteur ; Shoujian Zhang, Auteur ; Jian Cheng Li, Auteur Année de publication : 2019 Article en page(s) : pp 2378 - 2386 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] estimation statistique [Termes descripteurs IGN] filtre de Kalman [Termes descripteurs IGN] horloge du satellite [Termes descripteurs IGN] modèle mathématique [Termes descripteurs IGN] Open Multi-Processing [Termes descripteurs IGN] orbite [Termes descripteurs IGN] temps réel Résumé : (Auteur) Real-time precise GNSS satellite orbit and clock products are the prerequisite of real-time GNSS-based applications. To obtain real-time GNSS satellite orbit and clock, three approaches exist currently, namely, the prediction-estimation approach, the prediction-correction approach and the estimation approach. Different from the former two approaches, which are based on the predicted orbit, the last approach estimates orbit and clock in an integrated way, thus it is the most rigorous one. However, the simultaneously estimation of both orbit and clock parameters makes it very time-consuming. In this contribution, the extended Kalman filter with parallel computation proposed for real-time GPS satellite clock estimation (Gao et al., 2017) is introduced to improve the computational efficiency. In the introduced method, the epoch observations are processed sequentially and the covariance update process is accelerated with the Open Multi-Processing. With observation data from about 70 globally distributed stations spanning days 001–003 of 2018, the real-time GPS orbit and clock are estimated for validation. The epoch average processing time of the introduced method achieves around 2.9 s on average with 16 CPU cores, while that of the traditional method without Open Multi-Processing is about 4.1 s. When compare the estimated orbit and clock to the IGS final products, the daily constellation-mean RMS of orbit achieve 2.7, 5.7, 4.9 cm for the radial, along-track and cross-track respectively, while the daily constellation-mean STD of the clock is about 0.10 ns. The numerical experiments indicate that the introduced method is able to provide real-time sub-decimeter GPS orbit and clock within 10.0 s considering the time for data collection and corrections broadcast. Numéro de notice : A2019-170 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.asr.2019.01.009 date de publication en ligne : 19/01/2019 En ligne : https://doi.org/10.1016/j.asr.2019.01.009 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92619 [article]

Impact of predicting real-time clock corrections during their outages on precise point positioning / Ahmed El-Mowafy in Survey review, vol 51 n° 365 (March 2019)  

Public [article]  inSurvey review > vol 51 n° 365 (March 2019) . - pp 183 - 192 Titre : Impact of predicting real-time clock corrections during their outages on precise point positioning Type de document : Article/Communication Auteurs : Ahmed El-Mowafy, Auteur Année de publication : 2019 Article en page(s) : pp 183 - 192 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale [Termes descripteurs IGN] décalage d'horloge [Termes descripteurs IGN] données GNSS [Termes descripteurs IGN] orbite [Termes descripteurs IGN] positionnement ponctuel précis [Termes descripteurs IGN] temps réel Résumé : (Auteur) Real-time precise point positioning (RT-PPP) is a popular positioning method for natural hazard warning systems (NHWS) such as for monitoring tsunami and earthquakes. PPP relays on the use of precise orbits and clock corrections. Hence, the positioning accuracy of RT-PPP will significantly deteriorate when experiencing a discontinuity in receiving these corrections, for instance due to a temporary modem failure. The best available approach in this case would be to use the International Global Navigation Satellite Systems Service ultra-rapid (IGU) orbits and clocks that would result in a low positioning accuracy. In this paper, we present a simplified approach to a method that we recently proposed to bridge outages in the corrections and improve the RT-PPP accuracy compared with the use of IGU. In this method, the most recent IGU orbits are used as they are compatible with the RT orbits; however, the clock corrections are predicted as a time series using a linear model with four sinusoidal terms. The prediction errors resulting from this method, age of the model and its validity period are discussed. The impact of using the proposed approach is evaluated at a number of sites of known positions by comparing its performance to using IGU orbits and clocks. Moreover, the impact of using predicted corrections is assessed in different scenarios. The experimental results proved validity of the presented approach where positioning mean RMSE of less than 20 cm was maintained during the outage period. Numéro de notice : A2019-191 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1080/00396265.2017.1405155 date de publication en ligne : 26/11/2017 En ligne : https://doi.org/10.1080/00396265.2017.1405155 Format de la ressource électronique : URL Article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=92635 [article]

Combined orbits and clocks from IGS second reprocessing / Jake Griffiths in Journal of geodesy, vol 93 n° 2 (February 2019)  

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Influence of subdaily model for polar motion on the estimated GPS satellite orbits / Natalia Panafidina in Journal of geodesy, vol 93 n° 2 (February 2019)  

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Estimation of antenna phase center offset for BDS IGSO and MEO satellites / Guanwen Huang in GPS solutions, vol 22 n° 2 (April 2018)  

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Validation of Galileo orbits using SLR with a focus on satellites launched into incorrect orbital planes / Krzysztof Sosnica in Journal of geodesy, vol 92 n° 2 (February 2018)  

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Dependency of geodynamic parameters on the GNSS constellation / Stefano Scaramuzza in Journal of geodesy, vol 92 n° 1 (January 2018)  

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Precise orbit determination of the Fengyun-3C satellite using onboard GPS and BDS observations / Min Li in Journal of geodesy, vol 91 n° 11 (November 2017)  

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Comparison of precise orbit determination methods of zero-difference kinematic, dynamic and reduced-dynamic of GRACE-A satellite using SHORDE software / Kai Li in Journal of applied geodesy, vol 11 n° 3 (September 2017)  

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Precision on board : orbit determination of LEO satellites with real-time corrections / André Hauschild in GPS world, vol 28 n° 4 (April 2017)

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Eléments de géodésie et de la théorie des moindres carrés / Abdelmajid Ben Hadj Salem (2017)

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Ionosphere probing with simultaneous GNSS radio occultations / Viet-Cuong Pham in GPS solutions, vol 21 n° 1 (January 2017)  

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