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

Boehm J., Hobiger T., Ichikawa R., Kondo T., Koyama Y., Pany A., ...Daha Fazla

JOURNAL OF GEODESY, cilt.84, sa.5, ss.319-325, 2010 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 84 Sayı: 5
  • Basım Tarihi: 2010
  • Doi Numarası: 10.1007/s00190-010-0370-x
  • Dergi Adı: JOURNAL OF GEODESY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Sayfa Sayıları: ss.319-325
  • Anahtar Kelimeler: VLBI, Intensive sessions, Universal Time 1, Troposphere gradients, POLAR MOTION, SERVICE, TERRESTRIAL, GEODESY, ERRORS
  • Hacettepe Üniversitesi Adresli: Evet

Özet

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 mu s level with maximum differences of up to 50 mu s, which is clearly above the formal uncertainties of the UT1 estimates (between 5 and 20 mu s). 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.

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.