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Baseline vector repeatability at the sub-millimeter level enabled by radio interferometer phase delays of intra-site baselines
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  • Ming Hui Xu,
  • Tuomas Savolainen,
  • Sergei Bolotin,
  • Simone Bernhart,
  • Christian Plötz,
  • Rüdiger Haas,
  • Eskil Varenius,
  • Guangli Wang,
  • Jamie N McCallum,
  • Robert Heinkelmann,
  • Susanne Lunz,
  • Harald Schuh,
  • Nataliya Zubko,
  • Niko Kareinen
Ming Hui Xu
Aalto University

Corresponding Author:minghui.xu@aalto.fi

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Tuomas Savolainen
Aalto University
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Sergei Bolotin
NVI,Inc.
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Simone Bernhart
Reichert GmbH / BKG
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Christian Plötz
Geodetic Observatory Wettzell, Federal Agency for Cartography and Geodesy
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Rüdiger Haas
Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology
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Eskil Varenius
Department of Space, Earth and Environment, Onsala Space Observatory, Chalmers University of Technology
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Guangli Wang
Shanghai Astronomical Observatory (CAS)
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Jamie N McCallum
University of Tasmania
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Robert Heinkelmann
GFZ Potsdam
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Susanne Lunz
GFZ German Research Centre for Geosciences
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Harald Schuh
GFZ
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Nataliya Zubko
Finnish Geospatial Research Institute
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Niko Kareinen
Finnish Geospatial Research Institute
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Abstract

We report the results of position ties for short baselines at eight geodetic sites based on phase delays that are extracted from global geodetic very-long-baseline interferometry (VLBI) observations rather than dedicated short-baseline experiments. An analysis of phase delay observables from two antennas at the Geodetic Observatory Wettzell, Germany, extracted from 107 global 24-hour VLBI sessions since 2019 yields weighted root-mean-square scatters about the mean baseline vector of 0.3, 0.3, and 0.8 mm in the east, north, and up directions, respectively. Position ties are also obtained for other short baselines between legacy antennas and nearby, newly built antennas. They are critical for maintaining a consistent continuation of the realization of the terrestrial reference frame, especially when including the new VGOS network. The phase delays of the baseline WETTZ13N–WETTZELL enable an investigation of sources of error at the sub-millimeter level. We found that a systematic variation of larger than 1 mm can be introduced to the up estimates of this baseline vector when atmospheric delays were estimated. Although the sub-millimeter repeatability has been achieved for the baseline vector WETTZ13N–WETTZELL, we conclude that long term monitoring should be conducted for more short baselines to assess the instrumental effects, in particular the systematic differences between phase delays and group delays, and to find common solutions for reducing them. This will be an important step towards the goal of global geodesy at the 1 mm level.