scholarly journals Impact of network constraining on the terrestrial reference frame realization based on SLR observations to LAGEOS

2019 ◽  
Vol 93 (11) ◽  
pp. 2293-2313 ◽  
Author(s):  
R. Zajdel ◽  
K. Sośnica ◽  
M. Drożdżewski ◽  
G. Bury ◽  
D. Strugarek
Keyword(s):  
Reference Frame ◽  
A Priori ◽  
Terrestrial Reference Frame ◽  
Laser Ranging ◽  
Potential Core ◽  
North East ◽  
The North ◽  
Station Coordinates ◽  
Earth Rotation Parameters ◽  
Variable List

Abstract The Satellite Laser Ranging (SLR) network struggles with some major limitations including an inhomogeneous global station distribution and uneven performance of SLR sites. The International Laser Ranging Service (ILRS) prepares the time-variable list of the most well-performing stations denoted as ‘core sites’ and recommends using them for the terrestrial reference frame (TRF) datum realization in SLR processing. Here, we check how different approaches of the TRF datum realization using minimum constraint conditions (MCs) and the selection of datum-defining stations affect the estimated SLR station coordinates, the terrestrial scale, Earth rotation parameters (ERPs), and geocenter coordinates (GCC). The analyses are based on the processing of the SLR observations to LAGEOS-1/-2 collected between 2010 and 2018. We show that it is essential to reject outlying stations from the reference frame realization to maintain a high quality of SLR-based products. We test station selection criteria based on the Helmert transformation of the network w.r.t. the a priori SLRF2014 coordinates to reject misbehaving stations from the list of datum-defining stations. The 25 mm threshold is optimal to eliminate the epoch-wise temporal deviations and to provide a proper number of datum-defining stations. According to the station selection algorithm, we found that some of the stations that are not included in the list of ILRS core sites could be taken into account as potential core stations in the TRF datum realization. When using a robust station selection for the datum definition, we can improve the station coordinate repeatability by 8%, 4%, and 6%, for the North, East and Up components, respectively. The global distribution of datum-defining stations is also crucial for the estimation of ERPs and GCC. When excluding just two core stations from the SLR network, the amplitude of the annual signal in the GCC estimates is changed by up to 2.2 mm, and the noise of the estimated pole coordinates is substantially increased.

Simulation studies on single-satellite space ties and their potential to achieve the Global Geodetic Observing System goals.

2020 ◽  
Author(s):  
Patrick Schreiner ◽  
Nicat Mammadaliyev ◽  
Susanne Glaser ◽  
Rolf Koenig ◽  
Karl Hans Neumayer ◽  
...  
Keyword(s):  
Reference Frame ◽  
Precise Orbit Determination ◽  
Terrestrial Reference Frame ◽  
German Research Foundation ◽  
Station Coordinates ◽  
Earth Rotation Parameters ◽  
German Research ◽  
Space Geodetic Techniques ◽  
The Impact ◽  
Space Ties

<p>The German Research Foundation (DFG) project GGOS-SIM-2, successor of project GGOS-SIM, is a collaboration between the Helmholtz Center Potsdam - German Research Center for Geosciences (GFZ) and the Technische Universität Berlin (TUB). The project aims at investigating the feasibility of meeting the requirements specified by the Global Geodetic Observing System (GGOS) for a global terrestrial reference frame (TRF) with the help of simulations. In GGOS-SIM-2 the potential of so-called space ties is examined in relation to the GGOS targets, 1 mm accuracy in position and 1 mm / decade long-term stability, which have not yet been achieved by the recent International Terrestrial Reference Frame (ITRF). Space ties are provided by a satellite that carries two, three or all the four main space-geodetic techniques, i.e. DORIS, GPS, SLR and VLBI. This allows for a quantification of the impact of systematic errors on the derived orbits and subsequent results of the dynamic method as the TRF. Proposed co-location in space missions such as GRASP and E-GRASP anticipate such a scenario. We therefor simulate the space-geodetic observations based on Precise Orbit Determination (POD) with real observations from various missions and evaluate their potential for determining a TRF. So far, we simulated DORIS and SLR observations to six orbit scenarios, including a GRASP-like and an E-GRASP-like one, and generated TRFs based on each scenario either technique-wise or combined via the space-ties or in combination with ground data. We quantify the effect on the TRF in terms of changes of origin and scale and of formal errors of the ground station coordinates and of the Earth rotation parameters.</p>

GPS z-PCO and GNSS-based scale determined by integrated processing with LEOs and Galileo

2021 ◽  
Author(s):  
Wen Huang ◽  
Benjamin Männel ◽  
Andreas Brack ◽  
Harald Schuh
Keyword(s):  
Reference Frame ◽  
A Priori ◽  
Terrestrial Reference Frame ◽  
International Gnss Service ◽  
Satellite Transmitter ◽  
Ground Station ◽  
Station Coordinates ◽  
Integrated Processing ◽  
Current Constellation ◽  
The Impact

<p>The Global Positioning System (GPS) satellite transmitter antenna phase center offsets (PCOs) in z-direction and the scale of the terrestrial reference frame are highly correlated when neither of them is constrained to an a priori value in a least-squares adjustment. The commonly used PCO values offered by the International GNSS Service (IGS) are estimated in a global adjustment by constraining the ground station coordinates to the current International Terrestrial Reference Frame (ITRF). As the scale of the ITRF is determined by other techniques, the estimated GPS z-PCOs are not independent. Consequently, the z-PCOs transfer the scale to any subsequent GNSS solution. To get a GNSS-based scale that can contribute to a future ITRF realization, two methods are proposed to determine scale-independent GPS z-PCOs. One method is based on the gravitational constraint on Low Earth Orbiters (LEOs) in an integrated processing of the GPS satellites and LEOs. The correlation coefficient between the GPS PCO-z and the scale is reduced from 0.85 to 0.3 by supplementing a 54-ground-station network with seven LEOs. The impact of individual LEOs on the estimation is discussed by including different subsets of the LEOs. The accuracy of the z-PCOs of the LEOs is very important for the accuracy of the solution. In another method, the GPS z-PCOs and the scale are determined in a GPS+Galileo processing where the PCOs of Galileo are fixed to the values calibrated on ground from the released metadata. The correlation between the GPS PCO-z and the scale is reduced to 0.13 by including the current constellation of Galileo with 24 satellites. We use the whole constellation of Galileo and the three LEOs of the Swarm mission to perform a direct comparison and cross-check of the two methods. The two methods provide mean GPS z-PCO corrections of -186±25 mm and -221±37 mm with respect to the IGS values, and +1.55±0.22 ppb (part per billion) and +1.72±0.31 ppb in the terrestrial scale with respect to the IGS14 reference frame. The results of both methods agree with each other with only small differences. Due to the larger number of Galileo observations, the Galileo-PCO-fixed method leads to more precise and stable results. In the joint processing of GPS+Galileo+Swarm in which both methods are applied, the constraint on Galileo dominates the results. We also discuss how fixing either the Galileo transmitter antenna z-PCO or the Swarm receiver antenna z-PCOs in the GPS+Galileo+Swarm processing propagates to the respective freely estimated z-PCOs of Swarm or Galileo.</p>

scholarly journals Determination of Global Geodetic Parameters Using Satellite Laser Ranging Measurements to Sentinel-3 Satellites

2019 ◽  
Vol 11 (19) ◽  
pp. 2282 ◽  
Author(s):  
Dariusz Strugarek ◽  
Krzysztof Sośnica ◽  
Daniel Arnold ◽  
Adrian Jäggi ◽  
Radosław Zajdel ◽  
...  
Keyword(s):  
Land Surface ◽  
Earth Rotation ◽  
Terrestrial Reference Frame ◽  
Satellite Laser Ranging ◽  
Laser Ranging ◽  
Station Coordinates ◽  
Geocenter Motion ◽  
Earth Rotation Parameters ◽  
Rotation Parameters

Sentinel-3A/3B (S3A/B) satellites are equipped with a number of precise instruments dedicated to the measurement of surface topography, sea and land surface temperatures and ocean and land surface color. The high-precision orbit is guaranteed by three instruments: Global Positioning System (GPS) receiver, laser retroreflector dedicated to Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) antenna. In this article, we check the possibility of using SLR observations and GPS-based reduced-dynamic orbits of active S3A/B satellites for the determination of global geodetic parameters, such as geocenter motion, Earth rotation parameters (ERPs) and the realization of the terrestrial reference frame, based on data from 2016-2018. The calculation process was preceded with the estimation of SLR site range biases, different network constraining tests and a different number of orbital arcs in the analyzed solutions. The repeatability of SLR station coordinates based solely on SLR observations to S3A/B is at the level of 8-16 mm by means of interquartile ranges even without network constraining in 7-day solutions. The combined S3A/B and LAGEOS solutions show a consistency of estimated station coordinates better than 13 mm, geocenter coordinates with a RMS of 6 mm, pole coordinates with a RMS of 0.19 mas and Length-of-day with a RMS of 0.07 ms/day when referred to the IERS-14-C04 series. The altimetry observations have to be corrected by the geocenter motion to obtain unbiased estimates of the mean sea level rise. The geocenter motion is typically derived from SLR measurements to passive LAGEOS cannonball-like satellites. We found, however, that SLR observations to active Sentinel satellites are well suited for the determination of global geodetic parameters, such as Earth rotation parameters and geocenter motion, which even further increases the potential applications of Sentinel missions for deriving geophysical parameters.

scholarly journals Realization of the Primary Terrestrial Reference Frame

1991 ◽  
Vol 127 ◽  
pp. 108-115
Author(s):  
W. Kosek ◽  
B. Kołaczek
Keyword(s):  
Reference Frame ◽  
Geographic Distribution ◽  
Terrestrial Reference Frame ◽  
Mean Square ◽  
Minimum Value ◽  
Collocation Points ◽  
Station Coordinates ◽  
The Mean ◽  
Transformation Parameters ◽  
Mean Square Errors

AbstractThe PTRF is based on 43 sites with 64 SSC collocation points with the optimum geographic distribution, which were selected from all stations of the ITRF89 according to the criterion of the minimum value of the errors of 7 parameters of transformation. The ITRF89 was computed by the IERS Terrestrial Frame Section in Institut Geographique National - IGN and contains 192 VLBI and SLR stations (points) with 119 collocation ones. The PTRF has been compared with the ITRF89. The errors of the 7 parameters of transformation between the PTRF and 18 individual SSC as well as the mean square errors of station coordinates are of the same order as those for the ITRF89. The transformation parameters between the ITRF89 and the PTRF are negligible and their errors are of the order of 3 mm.

scholarly journals Geocentric Terrestrial Reference Frame Accuracy: DSN Spacecraft Tracking and VLBI/Lunar Laser Ranging

1988 ◽  
Vol 128 ◽  
pp. 115-120 ◽  
Author(s):  
A. E. Niell
Keyword(s):  
Reference Frame ◽  
Terrestrial Reference Frame ◽  
Spin Axis ◽  
Laser Ranging ◽  
Lunar Laser Ranging ◽  
Deep Space Network ◽  
Long Baseline ◽  
Lunar Laser ◽  
Spacecraft Tracking ◽  
Geocentric Coordinates

From a combination of 1) the location of McDonald Observatory from Lunar Laser Ranging, 2) relative station locations obtained from Very Long Baseline Interferometry (VLBI) measurements, and 3) a short tie by traditional geodesy, the geocentric coordinates of the 64 m antennas of the NASA/JPL Deep Space Network are obtained with an orientation which is related to the planetary ephemerides and to the celestial radio reference frame. Comparison with the geocentric positions of the same antennas obtained from tracking of interplanetary spacecraft shows that the two methods agree to 20 cm in distance off the spin axis and in relative longitude. The orientation difference of a 1 meter rotation about the spin axis is consistent with the error introduced into the tracking station locations due to an error in the ephemeris of Jupiter.

scholarly journals Drift of the Earth’s Principal Axes of Inertia from GRACE and Satellite Laser Ranging Data

2020 ◽  
Vol 12 (2) ◽  
pp. 314
Author(s):  
José M. Ferrándiz ◽  
Sadegh Modiri ◽  
Santiago Belda ◽  
Mikhail Barkin ◽  
Mathis Bloßfeld ◽  
...  
Keyword(s):  
Reference Frame ◽  
Terrestrial Reference Frame ◽  
Satellite Laser Ranging ◽  
Laser Ranging ◽  
Navigation Systems ◽  
Time Varying ◽  
Stationary Case ◽  
Principal Axes ◽  
Initial Location ◽  
Gravity Recovery

The location of the Earth’s principal axes of inertia is a foundation for all the theories and solutions of its rotation, and thus has a broad effect on many fields, including astronomy, geodesy, and satellite-based positioning and navigation systems. That location is determined by the second-degree Stokes coefficients of the geopotential. Accurate solutions for those coefficients were limited to the stationary case for many years, but the situation improved with the accomplishment of Gravity Recovery and Climate Experiment (GRACE), and nowadays several solutions for the time-varying geopotential have been derived based on gravity and satellite laser ranging data, with time resolutions reaching one month or one week. Although those solutions are already accurate enough to compute the evolution of the Earth’s axes of inertia along more than a decade, such an analysis has never been performed. In this paper, we present the first analysis of this problem, taking advantage of previous analytical derivations to simplify the computations and the estimation of the uncertainty of solutions. The results are rather striking, since the axes of inertia do not move around some mean position fixed to a given terrestrial reference frame in this period, but drift away from their initial location in a slow but clear and not negligible manner.

scholarly journals Unconstrained Estimation of VLBI Global Observing System Station Coordinates

2021 ◽  
Vol 55 ◽  
pp. 23-31
Author(s):  
Markus Mikschi ◽  
Johannes Böhm ◽  
Matthias Schartner
Keyword(s):  
Reference Frame ◽  
Terrestrial Reference Frame ◽  
Baseline Length ◽  
Radio Telescopes ◽  
Earth Orientation Parameters ◽  
The Earth ◽  
Station Coordinates ◽  
International Vlbi Service ◽  
Orientation Parameters

Abstract. The International VLBI Service for Geodesy and Astrometry (IVS) is currently setting up a network of smaller and thus faster radio telescopes observing at broader bandwidths for improved determination of geodetic parameters. However, this new VLBI Global Observing System (VGOS) network is not yet strongly linked to the legacy S/X network and the International Terrestrial Reference Frame (ITRF) as only station WESTFORD has ITRF2014 coordinates. In this work, we calculated VGOS station coordinates based on publicly available VGOS sessions until the end of 2019 while defining the geodetic datum by fixing the Earth orientation parameters and the coordinates of the WESTFORD station in an unconstrained adjustment. This set of new coordinates allows the determination of geodetic parameters from the analysis of VGOS sessions, which would otherwise not be possible. As it is the concept of VGOS to use smaller, faster slewing antennas in order to increase the number of observations, shorter estimation intervals for the zenith wet delays and the tropospheric gradients along with different relative constraints were tested and the best performing parametrization, judged by the baseline length repeatability, was used for the estimation of the VGOS station coordinates.

scholarly journals Plate Motion and Earth Orientation

1988 ◽  
Vol 129 ◽  
pp. 363-364
Author(s):  
A. Mallama ◽  
M. Kao
Keyword(s):  
A Priori ◽  
Terrestrial Reference Frame ◽  
North American Plate ◽  
Plate Motion ◽  
Earth Orientation ◽  
Root Mean Square Residual ◽  
The North ◽  
Tectonic Motion ◽  
Analysis System ◽  
Simple Rotation

Earth orientation series are linked to the terrestrial reference frame in which the observing site locations are measured. The effect of tectonic motion is a simple rotation for any given plate, but the overall effect depends on the distribution of sites. The magnitude of this motion is large enough to be evident in the data. For example, the coefficient of rotation for the North American plate around the Earth's Y-axis is −0.8 millarcseconds per year in the AMO-2 plate motion model of Minster and Jordan. The VLBI analysis system at NASA/GSFC for computing earth orientation series has recently been enhanced by including the Minster and Jordan model for a priori tectonic effects. Tests indicate that the weighted-root-mean-square residual of observations to the solution is decreased by using this model.

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