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GENESIS: integracja technik geodezji satelitarnej w przestrzeni kosmicznej

Nowak Adrian, Sośnica Krzysztof

Przegląd Geodezyjny

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2023

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R. 95, nr 4

21--23

PL

W 2022 roku Europejska Agencja Kosmiczna podjęła decyzję o sfinansowaniu GENESIS - pierwszej misji satelitarnej dedykowanej w całości geodezji. Misja ta będzie posiadała na pokładzie instrumenty do łączenia czterech technik geodezyjnych, które zostaną skorygowane względem siebie za pomocą starannie skalibrowanych centrów fazowych celem wyznaczenia wektorów wiążących w przestrzeni kosmicznej (ang. space ties). Integracja różnych technik geodezyjnych w przestrzeni kosmicznej pozwoli na rozwiązanie problemów związanych z niespójnościami i błędami pomiędzy nimi, a także otworzy nowe możliwości realizacji układów odniesienia. Dzięki temu społeczność naukowa zbliży się do wypełnienia celów Globalnego Geodezyjnego Systemu Obserwacyjnego, czyli dokładności układów geodezyjnych na poziomie 1 mm oraz ich stabilności w czasie o wartości nieprzekraczającej 0.1 mm/rok. Niniejszy artykuł opisuje nowości technologiczne misji GENESIS oraz ich znaczenie w realizacji globalnych ziemskich układów odniesienia w kontekście różnic względem dotychczasowych rozwiązań.

EN

In 2022, the European Space Agency has decided to fund GENESIS, the first satellite mission dedicated entirely to geodesy. The mission will have instruments onboard to integrate four geodetic techniques, which will be corrected against each other using carefully calibrated phase centers to determine space ties. The integration of different space geodetic techniques will resolve inconsistencies and errors between them, and open up new possibilities for realizing reference frames. As a result, the scientific community will come closer to realizing the goals of the Global Geodetic Observing System, i.e. the accuracy of geodetic frames at the level of 1 mm and their temporal stability of no more than 0.1 mm/year. This article describes the technological innovations of the GENESIS mission and their significance in the realization of the global terrestrial reference frames in the context of their differences from existing solutions.

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Global Geodetic Observing System 2015–2018

Sośnica Krzysztof, Bosy Jarosław

Geodesy and Cartography

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2019

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Vol. 68, no. 1

121--144

EN

Global Geodetic Observing System (GGOS) was established in 2003 by the International Association of Geodesy (IAG) with the main goal to deepen understanding of the dynamic Earth system by quantifying human-induced Earth’s changes in space and time. GGOS allows not only for advancing Earth Science, including solid Earth, oceans, ice, atmosphere, but also for better understanding processes between different constituents forming the system Earth, and most importantly, for helping authorities to make intelligent societal decisions. GGOS comprises different components to provide the geodetic infrastructure necessary for monitoring the Earth system and global changes. The infrastructure spreads from the global scale, through regional, to national scales. This contribution describes the GGOS structure, components, and goals with the main focus on GGOS activities in Poland, including both the development of the geodetic observing infrastructure as well as advances in processing geodetic observations supporting GGOS goals and providing high-accuracy global geodetic parameters.

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Testing impact of the strategy of VLBI data analysis on the estimation of Earth Orientation Parameters and station coordinates

Wielgosz A., Tercjak M., Brzeziński A.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 101

1--15

EN

Very Long Baseline Interferometry (VLBI) is the only space geodetic technique capable to realise the Celestial Reference Frame and tie it with the Terrestrial Reference Frame. It is also the only technique, which measures all the Earth Orientation Parameters (EOP) on a regular basis, thus the role of VLBI in determination of the universal time, nutation and polar motion and station coordinates is invaluable. Although geodetic VLBI has been providing observations for more than 30 years, there are no clear guidelines how to deal with the stations or baselines having significantly bigger post-fit residuals than the other ones. In our work we compare the common weighting strategy, using squared formal errors, with strategies involving exclusion or down-weighting of stations or baselines. For that purpose we apply the Vienna VLBI Software VieVS with necessary additional procedures. In our analysis we focus on statistical indicators that might be the criterion of excluding or down-weighting the inferior stations or baselines, as well as on the influence of adopted strategy on the EOP and station coordinates estimation. Our analysis shows that in about 99% of 24-hour VLBI sessions there is no need to exclude any data as the down-weighting procedure is sufficiently efficient. Although results presented here do not clearly indicate the best algorithm, they show strengths and weaknesses of the applied methods and point some limitations of automatic analysis of VLBI data. Moreover, it is also shown that the influence of the adopted weighting strategy is not always clearly reflected in the results of analysis.

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Sub-diurnal Earth rotation variations observed by VLBI

Nilsson T., Böhm J., Schuh H.

Artificial Satellites : Journal of Planetary Geodesy

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2010

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Vol. 45, No. 2

49--55

EN

We analyse sub-diurnal Earth rotation variations obtained from the continuous VLBI experiments CONT02, CONT05, and CONT08. We find that the Earth rotation parameters estimated from these campaigns contain signals with periods ±12 hours, +24 hours, and in CONT02 also -8 hours, which cannot be explained by the current IERS sub-diurnal pole model. We investigate if these signals could be caused by atmospheric excitations, but find that these excitations are too small.

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Status and prospects for combined GPS LOD and VLBI UT1 measurements

Senior K., Kouba J., Ray .

Artificial Satellites : Journal of Planetary Geodesy

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2010

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Vol. 45, No. 2

57--73

EN

A Kalman filter was developed to combine VLBI estimates of UT1-TAI with biased length of day (LOD) estimates from GPS. The VLBI results are the analyses of the NASA Goddard Space Flight Center group from 24-hr multi-station observing sessions several times per week and the nearly daily 1-hr single-baseline sessions. Daily GPS LOD estimates from the International GNSS Service (IGS) are combined with the VLBI UT1-TAI by modeling the natural excitation of LOD as the integral of a white noise process (i.e., as a random walk) and the UT1 variations as the integration of LOD, similar to the method described by Morabito et al. (1988). To account for GPS technique errors, which express themselves mostly as temporally correlated biases in the LOD measurements, a Gauss-Markov model has been added to assimilate the IGS data, together with a fortnightly sinusoidal term to capture errors in the IGS treatments of tidal effects. Evaluated against independent atmospheric and oceanic axial angular momentum (AAM + OAM) excitations and compared to other UT1/LOD combinations, ours performs best overall in terms of lowest RMS residual and highest correlation with (AAM + OAM) over sliding intervals down to 3 d. The IERS 05C04 and Bulletin A combinations show strong high-frequency smoothing and other problems. Until modified, the JPL SPACE series suffered in the high frequencies from not including any GPS-based LODs. We find, surprisingly, that further improvements are possible in the Kalman filter combination by selective rejection of some VLBI data. The best combined results are obtained by excluding all the 1-hr single-baseline UT1 data as well as those 24-hr UT1 measurements with formal errors greater than 5 μs (about 18% of the multi-baseline sessions). A rescaling of the VLBI formal errors, rather than rejection, was not an effective strategy. These results suggest that the UT1 errors of the 1-hr and weaker 24-hr VLBI sessions are non-Gaussian and more heterogeneous than expected, possibly due to the diversity of observing geometries used, other neglected systematic effects, or to the much shorter observational averaging interval of the single-baseline sessions. UT1 prediction services could benefit from better handling of VLBI inputs together with proper assimilation of IGS LOD products, including using the Ultra-rapid series that is updated four times daily with 15 hr delay.

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Russian State Time and Earth Rotation Service: observations, EOP series, prediction

Kaufman M., Pasynok S.

Artificial Satellites : Journal of Planetary Geodesy

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2010

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Vol. 45, No. 2

81--86

EN

Russian State Time, Frequency and Earth Rotation Service provides the official EOP data and time for use in scientific, technical and metrological works in Russia. The observations of GLONASS and GPS on 30 stations in Russia, and also the Russian and worldwide observations data of VLBI (35 stations) and SLR (20 stations) are used now. To these three series of EOP the data calculated in two other Russian analysis centers are added: IAA (VLBI, GPS and SLR series) and MCC (SLR). Joint processing of these 7 series is carried out every day (the operational EOP data for the last day and the predicted values for 50 days). The EOP values are weekly refined and systematic errors of every individual series are corrected. The combined results become accessible on the VNIIFTRI server (ftp.imvp.ru) approximately at 6h UT daily.

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User Interaction and Workflow Management in Grid enabled e-VLBI Experiments

Dolata Ł., Okoń M., Stokłosa D., Trocha Sz., Meyer N., Stroiński M., Kaliszan D., Rajtar T., Lawenda M.

Computational Methods in Science and Technology

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2009

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Vol. 15, nr 1

95-104

EN

The purpose of this paper is to present the design of the integration of radio-astronomical VLBI experiments with the Grid environment. The current status of the VLBI process is described, and the main part of this document presents the proposed architecture for the development of the next generation e-VLBI system. This design was created for the purpose of the EXPReS project [12], partially funded by the European Commission (FP6 – IST).

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CoCoS: a new SINEX combination software

Lytvyn M.

Artificial Satellites : Journal of Planetary Geodesy

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2008

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Vol. 43, No. 1

15--24

EN

A simple and flexible algorithm for combination of space geodesy observations is presented. The CoCoS software that implements this algorithm is described in details. The combined GPS-VLBI solution for the CONT02 VLBI experiment data and observations from co-located GPS sites is obtained and discussed.