Earth orientation parameters estimated from VLBI during the CONT11 campaign

Nilsson, Tobias; Heinkelmann, Robert; Karbon, Maria; Raposo-Pulido, Virginia; Soja, Benedikt; Schuh, Harald

doi:10.1007/s00190-014-0700-5

Cited by 27 publications

(20 citation statements)

References 18 publications

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“…As a first index of the solution appropriateness we used the variance scaling factor, as it is commonly used in statistic and in VLBI data analysis (eg. (Nilsson et al, 2014)). For each step and for each session the variance scaling factors of session, stations and baselines were computed to indicate the possible source of inappropriateness.…”

Section: Analysis and Resultsmentioning

confidence: 99%

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

Wielgosz

Tercjak

Brzeziński

2016

Reports on Geodesy and Geoinformatics

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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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Section: Analysis and Resultsmentioning

confidence: 99%

“…Nevertheless, the process of VLBI data analysis still depends, to a certain extent, on experience of an analyst, especially when incorrect data negatively affect results (e.g. (Nilsson et al, 2014)). In such cases, the analyst has to decide between removing, down-weighting or leaving these data unchanged.…”

Section: Introductionmentioning

confidence: 99%

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

Wielgosz

Tercjak

Brzeziński

2016

Reports on Geodesy and Geoinformatics

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“…The CONT campaigns are outstanding compared to standard VLBI sessions by having observations scheduled continuously for 15 days, featuring a larger station network and recording data at a higher rate. As a result, the number of observations per day is larger than for normal 24-h VLBI sessions and thus the overall quality of results is better (e.g., Nilsson et al 2014). Due to the efforts in organizing such campaigns, they have only been scheduled once every 3 years since 2002.…”

Section: Datamentioning

confidence: 99%

Tropospheric delay determination by Kalman filtering VLBI data

et al. 2015

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The troposphere is one of the most important error sources for space geodetic techniques relying on radio signals. Since it is not possible to model the wet part of the tropospheric delay with sufficient accuracy, it needs to be estimated from the observational data. In the analysis of very long baseline interferometry (VLBI) data, the parameter estimation is routinely performed using a least squares adjustment. In this paper, we investigate the application of a Kalman filter for parameter estimation, specifically focusing on the tropospheric delays. The main advantages of a Kalman filter are its real-time capability and stochastic approach. We focused on the latter and derived stochastic models for VLBI zenith wet delays, taking into account temporal and location-based differences. Compared to a static noise model, the quality of station coordinates, also estimated in the Kalman filter, increased as a result. In terms of baseline length and station coordinate repeatabilities, this improvement amounted to 2.3 %. Additionally, we compared the Kalman filter and least squares results for VLBI with zenith wet delays derived from GPS (Global Positioning System), water vapor radiometers, and ray tracing in numerical weather models. The agreement of the Kalman filter VLBI solution with respect to water vapor radiometer data was larger than that of the least squares solution by 6-15 %. Our investigations are based on selected VLBI data (CONT campaigns) that are closest to how future VLBI infrastructure is designed to operate. With the aim for continuous and near real-time parameter estimation and the promising results which we have achieved in this study, we expect Kalman filtering to grow in importance in VLBI analysis.

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“…The antennas monitor the emitted wavefront by a distant quasar. Using a global VLBI network antennas and measuring many time differences, the VLBI it is able to determine an inertial reference frame which is defined by the quasars, and also to determine with high precision the antennas position (Nilsson et al 2014).…”

Section: Intruductionmentioning

confidence: 99%

Scheduling And Simulation Of VLBI Measurements For The Determination Of Earth Orientation Parameters

Nistor

Buda

2015

Journal of Applied Engineering Sciences

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The article aims to present the results obtain from the scheduling and simulation of VLBI measurements in October 2010 for a period of three days for 24 hour continuous observations. To be sure that we will obtain good VLBI observation we have to do an optimization of the network. This can be done quite accurately by using the new modules that are part of the VLBI processing software’s, the modules scheduling and simulation. This can be considered the first step in preparation of the VLBI experiment. Very Long Baseline Interferometry (VLBI) it is a primary space-geodetic technique that it is able to determine precise coordinates on the Earth, by monitoring the variable of Earth orientation parameters (EOP) with high precision. Also Very Long Baseline Interferometry plays an important role for determination of celestial and terrestrial reference frame. It is also a technique that each year is more developed form a software and hardware point of view. To obtain the scans we used a set of eight different VLBI antennas and as a source we used different quasars. In the scheduling we used the source based strategy contrary to the station based approach and the radio sources where from updated catalogues according to the requirements of the VLBI2010 system, which means that we are able to obtain a best coverage of the celestial sphere. The results show that scheduling and simulation are very good tools in preparing real VLBI experiments.

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Earth orientation parameters estimated from VLBI during the CONT11 campaign

Cited by 27 publications

References 18 publications

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

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

Tropospheric delay determination by Kalman filtering VLBI data

Scheduling And Simulation Of VLBI Measurements For The Determination Of Earth Orientation Parameters

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