Journal of Geodesy

, Volume 84, Issue 5, pp 319–325 | Cite as

Asymmetric tropospheric delays from numerical weather models for UT1 determination from VLBI Intensive sessions on the baseline Wettzell–Tsukuba

  • Johannes Böhm
  • T. Hobiger
  • R. Ichikawa
  • T. Kondo
  • Y. Koyama
  • A. Pany
  • H. Schuh
  • K. Teke
Original Article

Abstract

One-baseline 1-h Very Long Baseline Interferometry (VLBI) Intensive sessions are carried out every day to determine Universal Time (UT1). Azimuthal asymmetry of tropospheric delays around the stations is usually ignored and not estimated because of the small number of observations. In this study we use external information about the asymmetry for the Intensive sessions between Tsukuba (Japan) and Wettzell (Germany), which are carried out on Saturdays and Sundays (1) from direct ray-tracing for each observation at Tsukuba and (2) in the form of linear horizontal north and east gradients every 6 h at both stations. The change of the UT1 estimates is at the 10 μs level with maximum differences of up to 50 μs, which is clearly above the formal uncertainties of the UT1 estimates (between 5 and 20 μs). Spectral analysis reveals that delays from direct ray-tracing for the station Tsukuba add significant power at short periods (1–2 weeks) w.r.t. the state-of-the-art approach, and comparisons with length-of-day (LOD) estimates from Global Positioning System (GPS) indicate that these ray-traced delays slightly improve the UT1 estimates from Intensive sessions.

Keywords

VLBI Intensive sessions Universal Time 1 Troposphere gradients 

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Johannes Böhm
    • 1
  • T. Hobiger
    • 2
  • R. Ichikawa
    • 2
  • T. Kondo
    • 2
    • 3
  • Y. Koyama
    • 2
  • A. Pany
    • 1
  • H. Schuh
    • 1
  • K. Teke
    • 1
    • 4
  1. 1.Institute of Geodesy and GeophysicsVienna University of TechnologyViennaAustria
  2. 2.Space-Time Standards GroupNational Institute of Information and Communications Technology (NICT)TokyoJapan
  3. 3.Ajou UniversitySuwonKorea
  4. 4.Department of Geodesy and Photogrammetry EngineeringHacettepe UniversityAnkaraTurkey

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