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1.
Pascal Willis Claude Boucher Hervé Fagard Zuheir Altamimi 《Comptes Rendus Geoscience》2005,337(7):653-662
IGN is in charge of the installation and maintenance of the DORIS orbit determination network. More recently, in collaboration with JPL, precise geodetic computations were performed. The goal of this paper is to recall the various historic contributions of IGN to the DORIS system in their international context and then to describe a new estimation technique developed for a multi-satellite mode, making full profit of a better modeling for satellites and ground clocks as well as tropospheric correction parameters. Derived geodetic results demonstrate a precision in the order of 1 cm for station positions. To cite this article: P. Willis et al., C. R. Geoscience 337 (2005). 相似文献
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We examine the contribution of the Doppler Orbit determination and Radiopositioning Integrated by Satellite (DORIS) technique to the International Terrestrial Reference Frame (ITRF2005) by evaluating the quality of the submitted solutions as well as that of the frame parameters, especially the origin and the scale. Unlike the previous versions of the ITRF, ITRF2005 is constructed with input data in the form of time-series of station positions (weekly for satellite techniques and daily for VLBI) and daily Earth orientation parameters (EOPs), including full variance–covariance information. Analysis of the DORIS station positions’ time-series indicates an internal precision reaching 15 mm or better, at a weekly sampling. A cumulative solution using 12 years of weekly time-series was obtained and compared to a similar International GNSS Service (IGS) GPS solution (at 37 co-located sites) yielding a weighted root mean scatter (WRMS) of the order of 8 mm in position (at the epoch of minimum variance) and about 2.5 mm/year in velocity. The quality of this cumulative solution resulting from the combination of two individual DORIS solutions is better than any individual solution. A quality assessment of polar motion embedded in the contributed DORIS solutions is performed by comparison with the results of other space-geodetic techniques and in particular GPS. The inferred WRMS of polar motion varies significantly from one DORIS solution to another and is between 0.5 and 2 mas, depending on the strategy used and in particular estimating or not polar motion rate by the analysis centers. This particular aspect certainly needs more investigation by the DORIS Analysis Centers. 相似文献
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Strategies to mitigate aliasing of loading signals while estimating GPS frame parameters 总被引：7，自引：5，他引：2
Xavier?CollilieuxEmail author Tonie?van?Dam Jim?Ray David?Coulot Laurent?Métivier Zuheir?Altamimi 《Journal of Geodesy》2012,86(1):1-14
Although GNSS techniques are theoretically sensitive to the Earth center of mass, it is often preferable to remove intrinsic
origin and scale information from the estimated station positions since they are known to be affected by systematic errors.
This is usually done by estimating the parameters of a linearized similarity transformation which relates the quasi-instantaneous
frames to a long-term frame such as the International Terrestrial Reference Frame (ITRF). It is well known that non-linear
station motions can partially alias into these parameters. We discuss in this paper some procedures that may allow reducing
these aliasing effects in the case of the GPS techniques. The options include the use of well-distributed sub-networks for
the frame transformation estimation, the use of site loading corrections, a modification of the stochastic model by downweighting
heights, or the joint estimation of the low degrees of the deformation field. We confirm that the standard approach consisting
of estimating the transformation over the whole network is particularly harmful for the loading signals if the network is
not well distributed. Downweighting the height component, using a uniform sub-network, or estimating the deformation field
perform similarly in drastically reducing the amplitude of the aliasing effect. The application of these methods to reprocessed
GPS terrestrial frames permits an assessment of the level of agreement between GPS and our loading model, which is found to
be about 1.5 mm WRMS in height and 0.8 mm WRMS in the horizontal at the annual frequency. Aliased loading signals are not
the main source of discrepancies between loading displacement models and GPS position time series. 相似文献
5.
Xavier Collilieux Laurent Métivier Zuheir Altamimi Tonie van Dam Jim Ray 《GPS Solutions》2011,15(3):219-231
The International GNSS Service (IGS) contributes to the construction of the International Terrestrial Reference Frame (ITRF)
by submitting time series of station positions and Earth Rotation Parameters (ERP). For the first time, its submission to
the ITRF2008 construction is based on a combination of entirely reprocessed GPS solutions delivered by 11 Analysis Centers
(ACs). We analyze the IGS submission and four of the individual AC contributions in terms of the GNSS frame origin and scale,
station position repeatability and time series seasonal variations. We show here that the GPS Terrestrial Reference Frame
(TRF) origin is consistent with Satellite laser Ranging (SLR) at the centimeter level with a drift lower than 1 mm/year. Although
the scale drift compared to Very Long baseline Interferometry (VLBI) and SLR mean scale is smaller than 0.4 mm/year, we think
that it would be premature to use that information in the ITRF scale definition due to its strong dependence on the GPS satellite
and ground antenna phase center variations. The new position time series also show a better repeatability compared to past
IGS combined products and their annual variations are shown to be more consistent with loading models. The comparison of GPS
station positions and velocities to those of VLBI via local ties in co-located sites demonstrates that the IGS reprocessed
solution submitted to the ITRF2008 is more reliable and precise than any of the past submissions. However, we show that some
of the remaining inconsistencies between GPS and VLBI positioning may be caused by uncalibrated GNSS radomes. 相似文献
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ITRF2008 is a refined version of the International Terrestrial Reference Frame based on reprocessed solutions of the four space geodetic techniques: VLBI, SLR, GPS and DORIS, spanning 29, 26, 12.5 and 16?years of observations, respectively. The input data used in its elaboration are time series (weekly from satellite techniques and 24-h session-wise from VLBI) of station positions and daily Earth Orientation Parameters (EOPs). The ITRF2008 origin is defined in such a way that it has zero translations and translation rates with respect to the mean Earth center of mass, averaged by the SLR time series. Its scale is defined by nullifying the scale factor and its rate with respect to the mean of VLBI and SLR long-term solutions as obtained by stacking their respective time series. The scale agreement between these two technique solutions is estimated to be 1.05 ± 0.13 ppb at epoch 2005.0 and 0.049 ± 0.010?ppb/yr. The ITRF2008 orientation (at epoch 2005.0) and its rate are aligned to the ITRF2005 using 179 stations of high geodetic quality. An estimate of the origin components from ITRF2008 to ITRF2005 (both origins are defined by SLR) indicates differences at epoch 2005.0, namely: ?0.5, ?0.9 and ?4.7?mm along X, Y and Z-axis, respectively. The translation rate differences between the two frames are zero for Y and Z, while we observe an X-translation rate of 0.3?mm/yr. The estimated formal errors of these parameters are 0.2?mm and 0.2?mm/yr, respectively. The high level of origin agreement between ITRF2008 and ITRF2005 is an indication of an imprecise ITRF2000 origin that exhibits a Z-translation drift of 1.8?mm/yr with respect to ITRF2005. An evaluation of the ITRF2008 origin accuracy based on the level of its agreement with ITRF2005 is believed to be at the level of 1?cm over the time-span of the SLR observations. Considering the level of scale consistency between VLBI and SLR, the ITRF2008 scale accuracy is evaluated to be at the level of 1.2?ppb (8?mm at the equator) over the common time-span of the observations of both techniques. Although the performance of the ITRF2008 is demonstrated to be higher than ITRF2005, future ITRF improvement resides in improving the consistency between local ties in co-location sites and space geodesy estimates. 相似文献
7.
IGS reference frames: status and future improvements 总被引：7，自引：0，他引：7
The hierarchy of reference frames used in the International GPS Service (IGS) and the procedures and rationale for realizing them are reviewed. The Conventions of the International Earth Rotation and Reference Systems Service (IERS) lag developments in the IGS in a number of important respects. Recommendations are offered for changes in the IERS Conventions to recognize geocenter motion (as already implemented by the IGS) and to enforce greater model consistency in order to achieve higher precision for combined reference frame products. Despite large improvements in the internal consistency of IGS product sets, defects remain which should be addressed in future developments. If the IGS is to remain a leader in this area, then a comprehensive, long-range strategy should be formulated and pursued to maintain and enhance the IGS reference frame, as well as to improve its delivery to users. Actions should include the official designation of a high-performance reference tracking network whose stations are expected to meet the highest standards possible.Also published in the proceedings of the workshop and symposium Celebrating a Decade of the International GPS Service, Astronomical Institute, University of Bern, Switzerland. 相似文献
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C. Abbondanza Z. Altamimi T. M. Chin R. S. Gross M. B. Heflin J. W. Parker X. Wu 《Journal of Geodesy》2015,89(4):313-329
9.
Sara Bruni Paul Rebischung Susanna Zerbini Zuheir Altamimi Maddalena Errico Efisio Santi 《Journal of Geodesy》2018,92(4):383-399
The realization of the international terrestrial reference frame (ITRF) is currently based on the data provided by four space geodetic techniques. The accuracy of the different technique-dependent materializations of the frame physical parameters (origin and scale) varies according to the nature of the relevant observables and to the impact of technique-specific errors. A reliable computation of the ITRF requires combining the different inputs, so that the strengths of each technique can compensate for the weaknesses of the others. This combination, however, can only be performed providing some additional information which allows tying together the independent technique networks. At present, the links used for that purpose are topometric surveys (local/terrestrial ties) available at ITRF sites hosting instruments of different techniques. In principle, a possible alternative could be offered by spacecrafts accommodating the positioning payloads of multiple geodetic techniques realizing their co-location in orbit (space ties). In this paper, the GNSS–SLR space ties on-board GPS and GLONASS satellites are thoroughly examined in the framework of global reference frame computations. The investigation focuses on the quality of the realized physical frame parameters. According to the achieved results, the space ties on-board GNSS satellites cannot, at present, substitute terrestrial ties in the computation of the ITRF. The study is completed by a series of synthetic simulations investigating the impact that substantial improvements in the volume and quality of SLR observations to GNSS satellites would have on the precision of the GNSS frame parameters. 相似文献
10.
IGS contribution to the ITRF 总被引：2，自引：0，他引：2
We examine the contribution of the International GNSS Service (IGS) to the International Terrestrial Reference Frame (ITRF) by evaluating the quality of the incorporated solutions as well as their major role in the ITRF formation. Starting with the ITRF2005, the ITRF is constructed with input data in the form of time series of station positions (weekly for satellite techniques and daily for VLBI) and daily Earth Orientation Parameters. Analysis of time series of station positions is a fundamental first step in the ITRF elaboration, allowing to assess not only the stations behavior, but also the frame parameters and in particular the physical ones, namely the origin and the scale. As it will be seen, given the poor number and distribution of SLR and VLBI co-location sites, the IGS GPS network plays a major role by connecting these two techniques together, given their relevance for the definition of the origin and the scale of the ITRF. Time series analysis of the IGS weekly combined and other individual Analysis Center solutions indicates an internal precision (or repeatability) <2 mm in the horizontal component and <5 mm in the vertical component. Analysis of three AC weekly solutions shows generally poor agreement in origin and scale, with some indication of better agreement when the IGS started to use the absolute model of antenna phase center variations after the GPS week 1400 (November 2006). 相似文献