GNSS zenith delays and gradients in the analysis of VLBI Intensive sessions

Teke, Kamil; Boehm, J.; Madzak, Matthias; Kwak, Younghee; Steigenberger, Peter

doi:10.1016/j.asr.2015.07.032

Cited by 12 publications

(18 citation statements)

References 35 publications

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“…Boehm et al (2010) showed that the use of a priori values from direct raytracing or linear horizontal gradients on the TsukubaWettzell baseline (INT2) did not significantly decrease the empirical standard deviations of UT1-UTC, but length-of-day (LOD) comparisons show a possibility to improve the results with direct ray-tracing. In Teke et al (2015), the use of GNSS-derived gradients showed only small improvement in UT1-UTC accuracy. Additionally, in Nilsson et al (2011), daily 2-h segments from the 15-day CONT08 campaign in August 2008 were used to emulate single-baseline experiments corresponding to INT1 and INT2 sessions.…”

Section: Analysis Of Intensive Vlbi Sessionsmentioning

confidence: 99%

“…However, it is possible to compute a priori values for the gradients with external data from, e.g., numerical weather models or by estimating the gradients using observations from co-located GNSS sites. The effect of this additional information to the UT1-UTC estimation has been investigated in, e.g., Boehm et al (2010) and Teke et al (2015). Boehm et al (2010) showed that the use of a priori values from direct raytracing or linear horizontal gradients on the TsukubaWettzell baseline (INT2) did not significantly decrease the empirical standard deviations of UT1-UTC, but length-of-day (LOD) comparisons show a possibility to improve the results with direct ray-tracing.…”

Section: Analysis Of Intensive Vlbi Sessionsmentioning

confidence: 99%

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Automated analysis of Kokee–Wettzell Intensive VLBI sessions—algorithms, results, and recommendations

2015

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The time-dependent variations in the rotation and orientation of the Earth are represented by a set of Earth Orientation Parameters (EOP). Currently, Very Long Baseline Interferometry (VLBI) is the only technique able to measure all EOP simultaneously and to provide direct observation of universal time, usually expressed as UT1-UTC. To produce estimates for UT1-UTC on a daily basis, 1-h VLBI experiments involving two or three stations are organised by the International VLBI Service for Geodesy and Astrometry (IVS), the IVS Intensive (INT) series. There is an ongoing effort to minimise the turn-around time for the INT sessions in order to achieve near real-time and high quality UT1-UTC estimates. As a step further towards true fully automated real-time analysis of UT1-UTC, we carry out an extensive investigation with INT sessions on the Kokee-Wettzell baseline. Our analysis starts with the first versions of the observational files in S-and X-band and includes an automatic group delay ambiguity resolution and ionospheric calibration. Several different analysis strategies are investigated. In particular, we focus on the impact of external information, such as meteorological and cable delay data provided in the station log-files, and a priori EOP information. The latter is studied by extensive Monte Carlo simulations. Our main findings are that it is easily possible to analyse the INT sessions in a fully automated mode to provide UT1-UTC with very low latency. The information found in the station log-files is important for the accuracy of the UT1-UTC results, provided that the data in the station log-files are reliable. Furthermore, to guarantee UT1-UTC with an accuracy of less than 20 μs, it is necessary to use predicted a priori polar motion data in the analysis that are not older than 12 h.

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Section: Analysis Of Intensive Vlbi Sessionsmentioning

confidence: 99%

Section: Analysis Of Intensive Vlbi Sessionsmentioning

confidence: 99%

Automated analysis of Kokee–Wettzell Intensive VLBI sessions—algorithms, results, and recommendations

2015

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“…A single-technique solution where tropospheric gradients are provided as a priori information and ZWD is estimated online, has been described as the most precise formulation for the processing of intensive sessions (Teke et al 2015). We validate this assumption and evaluate the performance of COL against it.…”

Section: Comparison To Single-technique Analyses With a Priori Gradientsmentioning

confidence: 97%

“…The tropospheric gradients, and in particular the one that lies on the east-west direction, have been shown to have a significant impact in the quality of (UT1-UTC) (Böhm and Schuh 2007) and can amount to some tens of μs (Böhm et al 2010). In fact, previous research points towards including a priori determined gradients, and estimating ZWD, as the preferred analysis scheme for VLBI intensive sessions (Teke et al 2015), and the effect of ray-traced gradients on (UT1-UTC) has also been explored (Landskron and Böhm 2019).…”

Section: Tropospheric Gradientsmentioning

confidence: 99%

Combining VGOS, legacy S/X and GNSS for the determination of UT1

Diamantidis

Haas

Schartner

et al. 2022

J Geod

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We perform a combination on the observation level (COL) between VLBI and co-located GNSS in the context of VLBI intensive sessions. Our approach revolves around an estimation procedure which uses 3 h of GNSS data that uniformly encapsulate the 1-h VLBI data, in order to provide consistent troposphere information. We test this approach on both VGOS and Legacy S/X using the VGOS-B and concurrently observed INT1 sessions. The COL strategy is found to increase the precision by 15 % over both session types and leads to an increase of 65 % in the agreement between the sessions when estimating tropospheric gradients every 3 h. A more frequent estimation of the gradients every 1 h, which can be rigorously pursued with the utilization of multi-GNSS, results in a further convergence of the two session types by 30 %. The COL-aided length-of-day (LOD) products also show a 55 % better agreement to external GNSS-derived LOD. In the light of the increasing precision of broadcast GNSS orbits and clocks, this COL strategy can be used to derive rapid UT1-UTC products.

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“…Results worsen if GNSS-based ZTDs are used as a priori value and not estimated. Nevertheless, the evolution of the software presented could be used in the frame of VLBI intensive sessions analysis, since GNSS-based gradients improve UT1 estimation [11].…”

Section: Troposhere Estimationmentioning

confidence: 99%

Geodetic VLBI Analysis at the National Geographic Institute of Spain

Puente

Azcue

Garcia-Espada

et al. 2019

The II Geomatics Engineering Conference

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National Geographic Institute of Spain has a strong background concerning technical aspects of geodetic VLBI. As a step forward in this field, a VLBI analysis team has been set up and tests with different software packages have been carried out. In this sense, two VLBI software packages have been used for experimentation activities in order to compare and validate IGE capability to produce accurate and consistent geodetic products, specifically Earth Orientation Parameters, station coordinates and troposphere delays. The purpose of this contribution is to present the results of these analyses, including some tests to use GNSS-based troposphere delay in VLBI processing and the study of gravitational deformation in Yebes radiotelescope.

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GNSS zenith delays and gradients in the analysis of VLBI Intensive sessions

Cited by 12 publications

References 35 publications

Automated analysis of Kokee–Wettzell Intensive VLBI sessions—algorithms, results, and recommendations

Automated analysis of Kokee–Wettzell Intensive VLBI sessions—algorithms, results, and recommendations

Combining VGOS, legacy S/X and GNSS for the determination of UT1

Geodetic VLBI Analysis at the National Geographic Institute of Spain

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