Geodetic Datum Realization Using SLR‐GNSS Co‐Location Onboard Galileo and GLONASS

Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław; Strugarek, Dariusz; Hugentobler, Urs

doi:10.1029/2021jb022211

Cited by 9 publications

(3 citation statements)

References 49 publications

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“…Therefore, Galileo satellites integrate both GNSS and SLR techniques, which formed the basis for different studies on the combination of U. Hugentobler Institute for Astronomical and Physical Geodesy, TU München, München, Germany Fig. 1 Illustration of observations to satellites and quasars with VLBI telescopes these observations (Thaller et al 2011), using the satellite co-locations for determining precise Galileo orbits (Bury et al 2021a) and realizing the geodetic datum (Bury et al 2021b).…”

Section: Introductionmentioning

confidence: 99%

Dilution of Precision (DOP) Factors for Evaluating Observations to Galileo Satellites with VLBI

Wolf

Böhm

Schartner

et al. 2022

International Association of Geodesy Symposia

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Installing a VLBI transmitter on Galileo satellites will allow observing satellites in parallel to quasars with Very Long Baseline Interferometry (VLBI) telescopes. This offers a variety of new applications such as the direct determination of the absolute orientation of the satellite constellation with respect to the International Celestial Reference Frame (ICRF) and the improvement of the Terrestrial Reference Frame (TRF) exploiting the possibilities of direct high precision tying of the different space geodetic equipment. In preparation of these observations by enhancing the capabilities of the VLBI scheduling program VieSched++, we perform an evaluation study of observations of a Galileo satellite employing Dilution of Precision (DOP) factors. The idea is to introduce DOP factors in the decision process of VieSched++ after a thorough assessment of DOP factors for individual parameters. In our study, we choose an existing network of VLBI Global Observing System (VGOS) type telescopes for observing Galileo satellite GSAT0212 within a 24 h arbitrary session. Preparing the DOP factor analysis, we first carry out a theoretical study to investigate the VLBI sensitivity to satellite orbit displacements in the local orbital frame with normal (radial), tangential and cross-track direction. This analysis shows that the highest sensitivity of a satellite observation is that of the tangential component if the direction of the satellite track is parallel to the direction of the observing baseline. A satellite observation is most sensitive towards the cross-track component if these two directions are orthogonal to each other. The DOP factor analysis itself is performed separating the satellite position again into its three components and adding a separate DOP factor for the UT1-UTC (dUT1) parameter. The periods, where satellite observations are possible, were determined using VieSched++. At a later stage, these DOP factors will be used as an optimization criterion for the scheduling process. The DOP factors of potential observations from the chosen VGOS network to GSAT0212 reach minimum DOP values of 27.13 in normal, 1.49 in tangential, and 1.67 in cross-track direction and 0.45 for determining dUT1. With these results, which have confirmed intuitive considerations on the relative magnitudes, we have laid the groundwork for using DOP factors as driving criteria in the scheduling process of Galileo satellites embedded in regular VLBI observations of quasars.

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Section: Introductionmentioning

confidence: 99%

Dilution of Precision (DOP) Factors for Evaluating Observations to Galileo Satellites with VLBI

Wolf

Böhm

Schartner

et al. 2022

International Association of Geodesy Symposia

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“…Furthermore, it enables the performance of independent GNSS orbit solutions based solely on laser observations (Pavlis 1995;Bury et al 2019b), or the combination of both SLR and GNSS observations (Thaller et al 2011;Hackel et al 2015;Bury et al 2020a;Delva et al 2023). Finally, the SLR observations of GNSS satellites can be used for determining global geodetic parameters and terrestrial reference frame realization (Sośnica et al 2018(Sośnica et al , 2019Bury et al 2021;Strugarek et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Satellite laser ranging to BeiDou-3 satellites: initial performance and contribution to orbit model improvement

Zajdel,

Nowak,

Sośnica

2024

GPS Solut

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In January 2023, the International Laser Ranging Service (ILRS) approved the tracking of 20 additional BeiDou-3 Medium Earth Orbit (BDS-3 MEO) satellites, integrating them into the ILRS tracking network. Before that, only 4 BDS-3 MEO satellites had been tracked. BDS satellites employ highly advanced GNSS components and technological solutions; however, microwave-based orbits still contain systematic errors. Satellite Laser Ranging (SLR) tracking is thus crucial for better identification and understanding of orbit modeling issues. Orbit improvements are necessary to consider BDS in future realizations of terrestrial reference frames, supporting the determination of global geodetic parameters and utilizing them for the co-location of GNSS and SLR in space. In this study, we summarize the first 6 months of SLR tracking 24 BDS-3 MEO satellites. The study indicates that the ILRS network effectively executed the request to track the entire BDS-3 MEO constellation. The number of observations is approximately 1300 and 450 for high- and low-priority BDS-3 satellites, respectively, over the 6 months. More than half of the SLR observations to BDS-3 MEO satellites were provided by 5 out of the 24 laser stations, which actively measured GNSS targets. For 14 out of 24 BDS-3 MEO satellites, the standard deviation of SLR residuals is at the level of 19–20 mm, which is comparable with the quality of the state-of-the-art Galileo orbit solutions. However, the SLR validation of the individual satellites revealed that the BDS-3 MEO constellation consists of more ambiguous groups of satellites than originally reported in the official metadata files distributed by the BDS operators. For 8 BDS-3 satellites, the quality of the orbits is noticeably inferior with a standard deviation of SLR residuals above 100 mm. Therefore, improving orbit modeling for BDS-3 MEO satellites remains an urgent challenge for the GNSS community.

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“…Range biases are calculated using various strategies, i.e., station-specific range biases from 1-week SLR data to spherical geodetic LAGEOS-1/2 satellites (Appleby et al 2016), a set of individual station coordinate and range bias corrections based on 1-year data from different LEOs by fixing GPS-derived LEO orbits (Arnold et al 2019a), or a set of particular station-satellite specific range bias corrections based on 1-year data to spherical geodetic satellites, and fixed GNSS-based orbits of LEO and Galileo satellites (Strugarek et al 2019(Strugarek et al , 2021bBury et al 2021). Time biases are introduced for time synchronization between clocks used at SLR stations (Exertier et al 2017) by using the time transfer technique (Samain et al 2008), by calculating timing offsets from a long period of SLR residuals to LEO satellites using GPS-based orbit solutions (Arnold et al 2019a), or by calculating time biases from each satellite pass (Otsubo et al 2019).…”

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confidence: 99%

Satellite laser ranging to GNSS-based Swarm orbits with handling of systematic errors

et al. 2022

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Satellite laser ranging (SLR) retroreflectors along with GNSS receivers are installed onboard numerous active low earth orbiters (LEOs) for the independent validation of GNSS-based precise orbit determination (POD) products. SLR validation results still contain many systematic errors that require special handling of various biases. For this purpose, we derive methods of reducing systematic effects affecting the SLR residuals to LEO Swarm satellites. We test solutions incorporating the estimation of range biases, station coordinate corrections, tropospheric biases, and horizontal gradients of the troposphere delays. When estimating range biases once per day, the standard deviation (STD) of Swarm-B SLR residuals is reduced from 10 to 8 mm for the group of high-performing SLR stations. The tropospheric biases estimated once per day, instead of range biases, further reduce the STD of residuals to the level of 6 mm. The systematic errors that manifest as dependencies of SLR residuals under different measurement conditions, e.g., elevation angle, are remarkably diminished. Furthermore, introducing troposphere biases allows for the comparison of the orbit quality between kinematic and reduced-dynamic orbits as the GPS-based orbit errors become more pronounced when SLR observations are freed from elevation-dependent errors. Applying tropospheric biases in SLR allows obtaining the consistency between the POD solution and SLR observations that are two times better than when neglecting to model of systematic effects and by 29% better when compared with solutions considering present methods of range bias handling.

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Geodetic Datum Realization Using SLR‐GNSS Co‐Location Onboard Galileo and GLONASS

Cited by 9 publications

References 49 publications

Dilution of Precision (DOP) Factors for Evaluating Observations to Galileo Satellites with VLBI

Dilution of Precision (DOP) Factors for Evaluating Observations to Galileo Satellites with VLBI

Satellite laser ranging to BeiDou-3 satellites: initial performance and contribution to orbit model improvement

Satellite laser ranging to GNSS-based Swarm orbits with handling of systematic errors

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