Earth Planets Space, Vol. 52 (No. 10), pp. 695-698, 2000LETTER
Lubomir P. Gradinarsky, Rüdiger Haas, Gunnar Elgered, and Jan M. Johansson
Onsala Space Observatory, Chalmers University of Technology, Onsala, Sweden
(Received December 25, 1999; Revised June 9, 2000; Accepted June 21, 2000)
Abstract: 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.