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Open Access

Wet path delay and delay gradients inferred from microwave radiometer, GPS and VLBI observations

  • Lubomir P. Gradinarsky1Email author,
  • Rüdiger Haas1,
  • Gunnar Elgered1 and
  • Jan M. Johansson1
Earth, Planets and Space201452:BF03352266

Received: 25 December 1999

Accepted: 21 June 2000

Published: 24 June 2014


Very Long Baseline Interferometry (VLBI) is collocated with a permanent Global Positioning System (GPS) receiver and a Water Vapor Radiometer (WVR) at the Onsala Space Observatory in Sweden. Both space geodetic techniques are affected by the propagation delay of radio waves in the atmosphere, while the remote sensing technique is sensitive to the atmospheric emission close to the center of the 22 GHz water vapor emission line. We present a comparison of estimated equivalent zenith wet delay and linear horizontal delay gradients from an independent analysis of simultaneous VLBI, GPS, and WVR observations. Using different constraints for the variability of the delay and the horizontal gradient in the analysis of the VLBI and the GPS data did not have a large influence on the agreement with the WVR estimates. We found that the weighted rms differences between wet delay estimates from the geodetic techniques and the WVR estimates generally increased for an increased variability in the atmosphere.


Global Position SystemVery Long Baseline InterferometryGlobal Position System DataTotal Zenith DelayInternational VLBI Service