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Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates

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Abstract

The very long baseline interferometry (VLBI) Intensive sessions are typically 1-h and single-baseline VLBI sessions, specifically designed to yield low-latency estimates of UT1-UTC. In this work, we investigate what accuracy is obtained from these sessions and how it can be improved. In particular, we study the modeling of the troposphere in the data analysis. The impact of including external information on the zenith wet delays (ZWD) and tropospheric gradients from GPS or numerical weather prediction models is studied. Additionally, we test estimating tropospheric gradients in the data analysis, which is normally not done. To evaluate the results, we compared the UT1-UTC values from the Intensives to those from simultaneous 24-h VLBI session. Furthermore, we calculated length of day (LOD) estimates using the UT1-UTC values from consecutive Intensives and compared these to the LOD estimated by GPS. We find that there is not much benefit in using external ZWD; however, including external information on the gradients improves the agreement with the reference data. If gradients are estimated in the data analysis, and appropriate constraints are applied, the WRMS difference w.r.t. UT1-UTC from 24-h sessions is reduced by 5% and the WRMS difference w.r.t. the LOD from GPS by up to 12%. The best agreement between Intensives and the reference time series is obtained when using both external gradients from GPS and additionally estimating gradients in the data analysis.

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Notes

  1. http://itrf.ign.fr/ITRF_solutions/2014/.

  2. ftp://maia.usno.navy.mil/ser7/finals.daily.

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Acknowledgements

We are grateful to the IVS for providing the data from the Intensive sessions (Nothnagel et al. 2015), the IGS for providing the GPS data and the LOD series, and Jan Douša for providing the gradients. We are also grateful to the three anonymous reviewers for their comments which helped us in improving the paper.

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Authors and Affiliations

  1. Department 1: Geodesy and Remote Sensing, Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, 14473, Potsdam, Germany

    Tobias Nilsson, Benedikt Soja, Maria Karbon, Robert Heinkelmann, Zhiguo Deng & Harald Schuh

  2. Institute of Geodesy and Geoinformation Science, Technische Universität Berlin, Straße des 17. Juni 135, 10623, Berlin, Germany

    Kyriakos Balidakis & Harald Schuh

Authors
  1. Tobias Nilsson
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  2. Benedikt Soja
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  3. Kyriakos Balidakis
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  4. Maria Karbon
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  5. Robert Heinkelmann
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  6. Zhiguo Deng
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  7. Harald Schuh
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Corresponding author

Correspondence to Tobias Nilsson.

Additional information

This work was supported by the Austrian Science Fund (FWF), project number P24187-N21 (VLBI-ART).

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Nilsson, T., Soja, B., Balidakis, K. et al. Improving the modeling of the atmospheric delay in the data analysis of the Intensive VLBI sessions and the impact on the UT1 estimates. J Geod 91, 857–866 (2017). https://doi.org/10.1007/s00190-016-0985-7

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  • DOI: https://doi.org/10.1007/s00190-016-0985-7

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