GRGS and CLS teams process regularly GPS data from a worldwide network of IGS permanent stations.... more GRGS and CLS teams process regularly GPS data from a worldwide network of IGS permanent stations. We compute precise GPS orbits together with Earth rotation parameters and stations coordinates at the highest level of precision using the CNES-GRGS GINS software. Our solutions are being submitted to the International Earth Rotation Service since January 2004 and to the IGS since July 2007. This poster gives a summary of our processing strategy as well as the status of the quality of our products. In addition, the source of a systematic scale factor between our orbit solution and the IGS ones is discussed. Special interest is paid on the radiation pressure modelization which includes in our case the Earth albedo contribution. The processing of SLR tracking data from GPS satellite SVN35 and 36 is included in this study.
The DORIS system was developed for precise orbit determination and precise positioning on Earth. ... more The DORIS system was developed for precise orbit determination and precise positioning on Earth. In continuation of the DORIS Pilot Experiment initiated in 1999, the International DORIS Service (IDS) officially started on July 1, 2003 as an IAG Service after the decision of the IAG Executive Committee at the IUGG General Assembly in Sapporo. Following this decision, the IERS Directing board accepted the DORIS Service as a new IERS external service. Six satellites fitted out with DORIS receivers are currently flying, permanently observed by 56 well distributed stations. Among them, three satellites equipped with new DORIS receivers (Jason-1, ENVISAT and SPOT5) have been successfully launched between Dec. 2001 and May 2002. All of them host a navigation function, called DIODE. Two new stations have been added to the permanent network in 2003: Crozet (French Southern Indian Ocean territories) and Jiufeng (China). In response to proposals submitted by candidate host agencies in the fram...
1] In the framework of the activities of the Combination Research Centers (CRC) of the Internatio... more 1] In the framework of the activities of the Combination Research Centers (CRC) of the International Earth Rotation and Reference Systems Service (IERS), the French Groupe de Recherche en Géodésie Spatiale (GRGS) studies the benefit of combining space-geodetic techniques (Doppler orbitography and radiopositioning integrated by satellite, GPS, satellite laser ranging, and very long baseline interferometry) at the observational level. This combination aims to produce a global and consistent solution for Earth orientation parameters (EOPs), polar motion x p and y p , and universal time UT1 with a 1-day or a 6-hour sampling, as well as weekly station positions. In this paper we present a methodology for multitechnique combination at the observational level. We process the measurements of the four techniques over a 1-year period (the year 2002) in order to illustrate and validate our method. All techniques are processed with the same computational framework, thus with the same models and a priori values for parameters. By using the same software and conventions, we avoid inconsistencies in individual computations. We process each technique individually and inside the combination. The comparison between these solutions is a way of analyzing the power of our method even if the actual status of our software does not reproduce the state-of-the-art analyses of each technique. However, we produce an analysis of the quality of our individual computations so that readers can get an informed appreciation of the current capabilities of our software. Finally, we present the capability of such combinations in terms of accuracy and precision, we underline the main issues of our method and propose solutions to solve them in the future. Citation: Coulot, D., P. Berio, R. Biancale, S. Loyer, L. Soudarin, and A.-M. Gontier (2007), Toward a direct combination of spacegeodetic techniques at the measurement level: Methodology and main issues,
DORIS is a French precise orbit determination system. However, in the past four years, through th... more DORIS is a French precise orbit determination system. However, in the past four years, through the creation of the International DORIS Service, a larger international cooperation was involved. Furthermore, the precision of its scientific applications (geodesy, geophysics) gradually improved and expanded to new fields (atmospheric sciences), leading, for example, to the publication of a special issue of the Journal of Geodesy. The goal of this manuscript is to present and explain these changes and to put them in perspective with current results obtained with other space geodetic techniques, such as GPS or Satellite Laser Ranging. To cite this article: P. Willis et al., C. R. Geoscience 339 . # 2007 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
ABSTRACT The International DORIS Service (IDS), in operation since 2003, submitted three sets of ... more ABSTRACT The International DORIS Service (IDS), in operation since 2003, submitted three sets of solutions to ITRF2005 from the IGN/JPL, LEGOS/CLS, and INASAN analysis centers, but no DORIS technique combination. Since that time new analysis centers, have become operational, including the Geodetic Observatory Pecny (GOP), and the European Space Operations Center (ESOC). Other analysis centers who have made SINEX submissions for inclusion in ITRF2008, including Geoscience Australia (GAU), the University of Newcastle (NCL), and the Goddard Space Flight Center (GSC). These analysis centers run different software, including Gypsy (IGN & INASAN), GINS (LCA), Bernese (GOP), NAPEOS (ESOC), GEODYN (Geoscience Australia and NASA GSFC) and FAUST (NCL). Each center applies own analysis strategy in the preparation of their SINEX contribution. The objective is to combine these analysis center contributions into a single IDS combination. The SINEX submissions are processed using the CATREF software, and we describe the results in comparison to ITRF2005. For example, preliminary results already obtained for the period from 1999 to 2008 show a strong improvement in the scale agreement between the analysis centers. We also describe the results of detailed intercenter orbit comparisons using DORIS satellite orbits, which allow us to diagnose potential anomalies in the processing and implement improvements in the future DORIS/IDS ITRF submission.
In this study, we apply Genetic Algorithms (GAs) in order to optimize the referencing (and conseq... more In this study, we apply Genetic Algorithms (GAs) in order to optimize the referencing (and consequently the precision - stability - and the accuracy) of the EOPs with respect to ITRF2005. These EOPs are derived from SLR or DORIS data at a daily sampling, simultaneously with weekly station positions. GAs are evolutionary algorithms, i.e. stochastic algorithms based on the evolution
DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing... more DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing System (GGOS), particularly to maintain and disseminate the Terrestrial Reference Frame as determined by International Earth rotation and Reference frame Service (IERS). A few years ago, under the umbrella of the International Association of Geodesy, a DORIS International Service (IDS) was created in order to foster
For Precise Orbit Determination of altimetry missions, we have computed a data set of DORIS stati... more For Precise Orbit Determination of altimetry missions, we have computed a data set of DORIS station coordinates defined for specific time intervals called DPOD2005. This terrestrial reference set is an extension of ITRF2005. However, it includes all new DORIS stations and is more reliable, as we disregard stations with large velocity formal errors as they could contaminate POD computations in the near future. About 1/4 of the station coordinates need to be defined as they do not appear in the original ITRF2005 realization. These results were verified with available DORIS and GPS results, as the integrity of DPOD2005 is almost as critical as its accuracy. Besides station coordinates and velocities, we also provide additional information such as periods for which DORIS data should be disregarded for specific DORIS stations, and epochs of coordinate and velocity discontinuities (related to either geophysical events, equipment problem or human intervention). The DPOD model was tested for orbit determination for TOPEX/Poseidon (T/P), Jason-1 and Jason-2. Test results show DPOD2005 offers improvement over the original ITRF2005, improvement that rapidly and significantly increases after 2005. Improvement is also significant for the early T/P cycles indicating improved station velocities in the DPOD2005 model and a more complete station set. Following 2005 the radial accuracy and centering of the ITRF2005-original orbits rapidly degrades due to station loss.
GRGS and CLS teams process regularly GPS data from a worldwide network of IGS permanent stations.... more GRGS and CLS teams process regularly GPS data from a worldwide network of IGS permanent stations. We compute precise GPS orbits together with Earth rotation parameters and stations coordinates at the highest level of precision using the CNES-GRGS GINS software. Our solutions are being submitted to the International Earth Rotation Service since January 2004 and to the IGS since July 2007. This poster gives a summary of our processing strategy as well as the status of the quality of our products. In addition, the source of a systematic scale factor between our orbit solution and the IGS ones is discussed. Special interest is paid on the radiation pressure modelization which includes in our case the Earth albedo contribution. The processing of SLR tracking data from GPS satellite SVN35 and 36 is included in this study.
The DORIS system was developed for precise orbit determination and precise positioning on Earth. ... more The DORIS system was developed for precise orbit determination and precise positioning on Earth. In continuation of the DORIS Pilot Experiment initiated in 1999, the International DORIS Service (IDS) officially started on July 1, 2003 as an IAG Service after the decision of the IAG Executive Committee at the IUGG General Assembly in Sapporo. Following this decision, the IERS Directing board accepted the DORIS Service as a new IERS external service. Six satellites fitted out with DORIS receivers are currently flying, permanently observed by 56 well distributed stations. Among them, three satellites equipped with new DORIS receivers (Jason-1, ENVISAT and SPOT5) have been successfully launched between Dec. 2001 and May 2002. All of them host a navigation function, called DIODE. Two new stations have been added to the permanent network in 2003: Crozet (French Southern Indian Ocean territories) and Jiufeng (China). In response to proposals submitted by candidate host agencies in the fram...
1] In the framework of the activities of the Combination Research Centers (CRC) of the Internatio... more 1] In the framework of the activities of the Combination Research Centers (CRC) of the International Earth Rotation and Reference Systems Service (IERS), the French Groupe de Recherche en Géodésie Spatiale (GRGS) studies the benefit of combining space-geodetic techniques (Doppler orbitography and radiopositioning integrated by satellite, GPS, satellite laser ranging, and very long baseline interferometry) at the observational level. This combination aims to produce a global and consistent solution for Earth orientation parameters (EOPs), polar motion x p and y p , and universal time UT1 with a 1-day or a 6-hour sampling, as well as weekly station positions. In this paper we present a methodology for multitechnique combination at the observational level. We process the measurements of the four techniques over a 1-year period (the year 2002) in order to illustrate and validate our method. All techniques are processed with the same computational framework, thus with the same models and a priori values for parameters. By using the same software and conventions, we avoid inconsistencies in individual computations. We process each technique individually and inside the combination. The comparison between these solutions is a way of analyzing the power of our method even if the actual status of our software does not reproduce the state-of-the-art analyses of each technique. However, we produce an analysis of the quality of our individual computations so that readers can get an informed appreciation of the current capabilities of our software. Finally, we present the capability of such combinations in terms of accuracy and precision, we underline the main issues of our method and propose solutions to solve them in the future. Citation: Coulot, D., P. Berio, R. Biancale, S. Loyer, L. Soudarin, and A.-M. Gontier (2007), Toward a direct combination of spacegeodetic techniques at the measurement level: Methodology and main issues,
DORIS is a French precise orbit determination system. However, in the past four years, through th... more DORIS is a French precise orbit determination system. However, in the past four years, through the creation of the International DORIS Service, a larger international cooperation was involved. Furthermore, the precision of its scientific applications (geodesy, geophysics) gradually improved and expanded to new fields (atmospheric sciences), leading, for example, to the publication of a special issue of the Journal of Geodesy. The goal of this manuscript is to present and explain these changes and to put them in perspective with current results obtained with other space geodetic techniques, such as GPS or Satellite Laser Ranging. To cite this article: P. Willis et al., C. R. Geoscience 339 . # 2007 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.
ABSTRACT The International DORIS Service (IDS), in operation since 2003, submitted three sets of ... more ABSTRACT The International DORIS Service (IDS), in operation since 2003, submitted three sets of solutions to ITRF2005 from the IGN/JPL, LEGOS/CLS, and INASAN analysis centers, but no DORIS technique combination. Since that time new analysis centers, have become operational, including the Geodetic Observatory Pecny (GOP), and the European Space Operations Center (ESOC). Other analysis centers who have made SINEX submissions for inclusion in ITRF2008, including Geoscience Australia (GAU), the University of Newcastle (NCL), and the Goddard Space Flight Center (GSC). These analysis centers run different software, including Gypsy (IGN & INASAN), GINS (LCA), Bernese (GOP), NAPEOS (ESOC), GEODYN (Geoscience Australia and NASA GSFC) and FAUST (NCL). Each center applies own analysis strategy in the preparation of their SINEX contribution. The objective is to combine these analysis center contributions into a single IDS combination. The SINEX submissions are processed using the CATREF software, and we describe the results in comparison to ITRF2005. For example, preliminary results already obtained for the period from 1999 to 2008 show a strong improvement in the scale agreement between the analysis centers. We also describe the results of detailed intercenter orbit comparisons using DORIS satellite orbits, which allow us to diagnose potential anomalies in the processing and implement improvements in the future DORIS/IDS ITRF submission.
In this study, we apply Genetic Algorithms (GAs) in order to optimize the referencing (and conseq... more In this study, we apply Genetic Algorithms (GAs) in order to optimize the referencing (and consequently the precision - stability - and the accuracy) of the EOPs with respect to ITRF2005. These EOPs are derived from SLR or DORIS data at a daily sampling, simultaneously with weekly station positions. GAs are evolutionary algorithms, i.e. stochastic algorithms based on the evolution
DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing... more DORIS is one of the four space-geodetic techniques participating in the Global Geodetic Observing System (GGOS), particularly to maintain and disseminate the Terrestrial Reference Frame as determined by International Earth rotation and Reference frame Service (IERS). A few years ago, under the umbrella of the International Association of Geodesy, a DORIS International Service (IDS) was created in order to foster
For Precise Orbit Determination of altimetry missions, we have computed a data set of DORIS stati... more For Precise Orbit Determination of altimetry missions, we have computed a data set of DORIS station coordinates defined for specific time intervals called DPOD2005. This terrestrial reference set is an extension of ITRF2005. However, it includes all new DORIS stations and is more reliable, as we disregard stations with large velocity formal errors as they could contaminate POD computations in the near future. About 1/4 of the station coordinates need to be defined as they do not appear in the original ITRF2005 realization. These results were verified with available DORIS and GPS results, as the integrity of DPOD2005 is almost as critical as its accuracy. Besides station coordinates and velocities, we also provide additional information such as periods for which DORIS data should be disregarded for specific DORIS stations, and epochs of coordinate and velocity discontinuities (related to either geophysical events, equipment problem or human intervention). The DPOD model was tested for orbit determination for TOPEX/Poseidon (T/P), Jason-1 and Jason-2. Test results show DPOD2005 offers improvement over the original ITRF2005, improvement that rapidly and significantly increases after 2005. Improvement is also significant for the early T/P cycles indicating improved station velocities in the DPOD2005 model and a more complete station set. Following 2005 the radial accuracy and centering of the ITRF2005-original orbits rapidly degrades due to station loss.
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Papers by L. Soudarin