Combination of GNSS and VLBI data for consistent estimation of Earth Rotation Parameters

2021 ◽  
Author(s):  
Lisa Lengert ◽  
Claudia Flohrer ◽  
Anastasiia Girdiuk ◽  
Hendrik Hellmers ◽  
Daniela Thaller
Keyword(s):  
Time Series ◽  
Earth Rotation ◽  
Polar Motion ◽  
Normal Equation ◽  
Station Coordinates ◽  
Earth Rotation Parameters ◽  
Vlbi Data ◽  
Rotation Parameters ◽  
Gnss Data ◽  
The Impact

<p>We present the current activities of the Federal Agency for Cartography and Geodesy (BKG) towards a combined processing of VLBI and GNSS data.  The main goal of the combined analyses of the two different space-geodetic techniques is the improvement of the consistency between the techniques through common parameters, i.e., mainly Earth Rotation Parameters (ERPs), but also station coordinates and tropospheric parameters through local ties and atmospheric ties, respectively.</p><p>Based on our previous combination studies using GNSS data and VLBI Intensive sessions on a daily and multi-day level, we generate a consistent, low-latency ERP time series with a regular daily resolution for polar motion and dUT1. We achieved in this way a significant accuracy improvement of the dUT1 time series and a slight improvement of the pole coordinates time series, comparing ERPs from the combined processing with the individual technique-specific ERPs.</p><p>In our recent studies, we extend the combination of GNSS and VLBI Intensive sessions by adding VLBI 24-hour sessions in order to exploit the benefit of the combination to its maximum extend. We analyse the impact of the combination on the global parameters of interest, i.e., mainly dUT1, polar motion and LOD, but also on station coordinates.</p><p>BKG’s primary interest is the combination of GNSS and VLBI data on the observation level. However, the current combination efforts are based on the normal equation level using technique-specific SINEX files as a starting point.</p>

Combination of GNSS and VLBI data for consistent estimation of Earth Orientation Parameters

2020 ◽  
Author(s):  
Lisa Lengert ◽  
Hendrik Hellmers ◽  
Claudia Flohrer ◽  
Daniela Thaller ◽  
Alexander Kehm
Keyword(s):  
Normal Equation ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
Starting Point ◽  
Station Coordinates ◽  
Space Geodetic Techniques ◽  
Vlbi Data ◽  
Gnss Data ◽  
The Impact ◽  
Orientation Parameters

<p>We present the current activities of the Federal Agency for Cartography and Geodesy (BKG) towards a combined processing of VLBI and GNSS data.  The main goal of the combined analyses of the two different space-geodetic techniques is the improvement of the consistency between the techniques through common parameters, as Earth Orientation Parameters (EOPs), but also station coordinates and tropospheric parameters through local ties and atmospheric ties, respectively.</p><p>The combination of GNSS data with VLBI 24-hour sessions and VLBI Intensive sessions is studied in detail w.r.t. EOPs to exploit he combination benefit to its maximum extend. We analyse the impact of the combination on the technique-specific parameters (e.g. dUT1), but also on common parameters (e.g. LOD, polar motion, station coordinates). When using GNSS data in combination with VLBI Intensive sessions, we can demonstrate an accuracy improvement of the dUT1 time series.</p><p>We also study the combination of troposphere parameters, focusing first on the validation of the technique-specific troposphere parameters at VLBI-GNSS co-located sites and on the modelling of the corresponding atmospheric ties.</p><p>BKGs primary interest is the combination of GNSS and VLBI data on the observation level. However, the current combination efforts are based on the normal equation level using technique-specific SINEX files as a starting point.</p>

scholarly journals Combination of VLBI Intensive Sessions with GNSS for generating Low latency Earth Rotation Parameters

2019 ◽  
Vol 50 ◽  
pp. 49-56
Author(s):  
Hendrik Hellmers ◽  
Daniela Thaller ◽  
Mathis Bloßfeld ◽  
Alexander Kehm ◽  
Anastasiia Girdiuk
Keyword(s):  
Time Series ◽  
Earth Rotation ◽  
Normal Equation ◽  
Laser Ranging ◽  
Low Latency ◽  
Lunar Laser Ranging ◽  
Earth Orientation ◽  
The Earth ◽  
Earth Rotation Parameters ◽  
Rotation Parameters

Abstract. The Earth Orientation Parameters (EOPs) are published by the Earth Orientation Centre of the International Earth Rotation and Reference Systems Service (IERS). They are provided as the low-latency Bulletin A and the 30 d latency long-term EOP time series IERS 14 C04. The EOPs are a combined product derived from different geodetic space techniques, namely Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR), Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) and Very Long Baseline Interferometry (VLBI). Since not all techniques are equally sensitive to every EOP, several parameters rely on specific observation techniques. As an example, dUT1 can only be estimated from VLBI observations. This means VLBI is an essential part of the estimation procedure for consistent EOPs. Within this paper, we are performing a combination of two low-latency space geodetic techniques as they enable the estimation of the full set of Earth Rotation Parameters (ERPs; polar motion, dUT1 and the corresponding rates). In particular, we focus on the development of a robust combination scheme of 1 h VLBI Intensive sessions with so-called GNSS Rapid solutions on the normal equation level of the Gauß-Markov model. The aim of the study is to provide highly accurate low-latency ERPs. So far, a latency of approximately only 1–3 d cold be reached since the main limiting factor is still the latency of the input data. The mathematical background of the applied algorithm is discussed in detail and evaluated by numerical results of empirical investigations. The combination yields a numerical stabilization of the equation system as well as an improvement (reduction) of the corresponding root mean square deviation of the epoch-wise estimated parameters w.r.t. the IERS 14 C04 reference time series.

On the potential of single-satellite space ties to achieve the Global Geodetic Observing System goals

2021 ◽  
Author(s):  
Patrick Schreiner ◽  
Nicat Mammadaliyev ◽  
Susanne Glaser ◽  
Rolf König ◽  
Karl Hans Neumayer ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Research Collaboration ◽  
Precise Orbit Determination ◽  
Added Value ◽  
Station Coordinates ◽  
Earth Rotation Parameters ◽  
German Research ◽  
Rotation Parameters ◽  
The Impact ◽  
Space Ties

<p>GGOS-SIM-2, funded by the German Research Foundation (DFG), is a research collaboration project between the German Research Center for Geosciences (GFZ) and the Technische Universität Berlin (TUB). Simulations are utilized to examine the potential of co-location in space, called space ties, of the four main space geodetic techniques, i.e. DORIS, GNSS, SLR and VLBI to achieve the requirements of the Global Geodetic Observing System (GGOS) for a global terrestrial reference frame (TRF), 1 mm accuracy and 1 mm / decade long-term stability. The simulations are performed for six fictional orbit scenarios, including proposed missions GRASP (USA) and E-GRASP (EU), and expanded by a variation of the E-GRASP orbit with lower eccentricity as well as three higher orbiting circular orbits with different inclination over a time span of seven years. For most realistic simulations, we first evaluated real DORIS, GPS and SLR observations to the satellites LAGEOS 1 und 2, Ajisai, LARES, Starlette, Stella, ENVISAT, Jason 1 und 2, Sentinel 3A and B using Precise Orbit Determination (POD), to get detailed information about the individual station and receiver accuracy, availability and further technique-specific effects. Then, we generate simulated single-technique TRF solutions based on existing missions and add the co-location-in-space satellite in the six orbit scenarios. In order to quantify the effects of the different scenarios, we examine the added value w.r.t. the existing missions in terms of origin and scale and of formal errors of the station coordinates and Earth rotation parameters. We also investigate the impact of systematic errors on the derived orbits on the final TRF. The different techniques show individual advantages regarding the respective orbit parameters. For instance, a higher eccentricity of the orbit seems to lead to improved accuracy of length-of-day (LOD) from SLR. The results will help to find the best trade-off for a satellite that co-locates all four techniques in space towards a GGOS-compliant TRF and Earth rotation parameters.</p>

scholarly journals Procedure for VLBI Estimates of Earth Rotation Parameters Referred to the Nonrotating Origin

1991 ◽  
Vol 127 ◽  
pp. 77-84 ◽  
Author(s):  
N. Capitaine ◽  
A.M. Gontier
Keyword(s):  
Earth Rotation ◽  
Partial Derivatives ◽  
The Earth ◽  
Earth Rotation Parameters ◽  
Vlbi Data ◽  
Rotation Parameters ◽  
Derivatives Of ◽  
Rotational Transformation

AbstractThis paper investigates the practical use of the nonrotating origin (NRO) (Guinot 1979) for estimating the Earth Rotation Parameters from VLBI data, which is based on the rotational transformation between the geocentric celestial and terrestrial frames as previously derived by Capitaine (1990). Numerical checks of consistency show that the transformation referred to the NRO is equivalent to the classical one referred to the equinox and considering the complete “equation of the equinoxes” (Aoki & Kinoshita 1983). The paper contains the expressions for the partial derivatives of the VLBI geometric delay to be used for the adjustment of the pole coordinates, UT1 and deficiencies in the two celestial coordinates of the Celestial Ephemeris Pole (CEP) in the multiparameters fits to VLBI data. The use of the NRO is shown to simplify the estimates of these parameters and to free the estimated UT1 parameter from the model for precession and nutation.

scholarly journals SLR Contribution to Investigation of Polar Motion

2000 ◽  
Vol 178 ◽  
pp. 267-276
Author(s):  
Zinovy Malkin
Keyword(s):  
Earth Rotation ◽  
Polar Motion ◽  
Satellite Laser Ranging ◽  
Laser Ranging ◽  
International Earth Rotation Service ◽  
Global Tracking ◽  
International Earth Rotation ◽  
Earth Rotation Parameters ◽  
Rotation Parameters

AbstractThe Satellite Laser Ranging (SLR) technique has been used to determine Earth Rotation Parameters (ERP) for over twenty years. Most of results contributed to the International Earth Rotation Service (IERS) are based on analysis of observations of Lageos 1 & 2 satellites collected by the global tracking network of about 40 stations. Now five analysis centers submit operational (with 2–15 days delay) solutions and about ten analysis centers contribute yearly final (up to 23 years) ERP series. Some statistics related to SLR observations and analysis are presented and analyzed. Possible problems in SLR observations and analysis and ways of its solution are discussed.

scholarly journals Stability of Determining the Earth Rotation Parameters (ERP) with VLBI

1988 ◽  
Vol 129 ◽  
pp. 417-420
Author(s):  
Shifang Luo ◽  
Dawei Zheng
Keyword(s):  
Earth Rotation ◽  
Polar Motion ◽  
Systematic Errors ◽  
Geometric Effect ◽  
The Earth ◽  
Geometric Uncertainty ◽  
Earth Rotation Parameters ◽  
Rotation Parameters ◽  
The Stability

By using the observations of IRIS network, the stability of determinang ERP with VLBI is studied. It is concluded that the uncertainties from initial values of ERP, the errors of other parameters are at the same level as the formal errors in determination of ERP. The geometric effect on determination of ERP is important and appears as systematic errors. Geometric uncertainty on polar motion is greater than that on UT1. and specially much worse for the continenal network. The stability of determining ERP with VLBI can be improved either by increasing new stations at reasonable location in a VLBI network or by increasing new networks.

scholarly journals Combination of data from different space geodetic systems for the determination of Earth rotation parameters

1988 ◽  
Vol 128 ◽  
pp. 233-239
Author(s):  
Brent A. Archinal
Keyword(s):  
Earth Rotation ◽  
Normal Equation ◽  
Laser Ranging ◽  
Weighted Mean ◽  
Lunar Laser Ranging ◽  
Long Baseline ◽  
Lunar Laser ◽  
Earth Rotation Parameters ◽  
Vlbi Data

Simulation experiments have been performed in order to compare the Earth Rotation Parameter (ERP) results obtained from a) individual observational systems, b) the weighted mean of the results from a), and c) all of the observational data, via the combination of the normal equations obtained in a). These experiments included the use of 15 days of simulated Lunar Laser Ranging (LLR), Satellite Laser Ranging (SLR) to Lageos, and Very Long Baseline Interferometry (VLBI) data using realistic station positions and accuracies. Under the assumptions chosen, the normal equation combination solutions usually provide the best ERP over recovery periods of 6 and 12 hours, and 1, 2, and 5 days. However, solutions by the weighted mean (and even by VLBI alone) provide results that are nearly as good, i.e., within a factor of one to two in accuracy. Complete details are presented in [Archinal, 1987].

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