Comparison of tropospheric delays from Raman lidar, radiosondes, GPS and DORIS during the MANITOUL experiment

Abstract

International audienceWater vapor measurements from a Raman lidar developed conjointly by IGN and LATMOS/CNRS are used for documenting water vapor heterogeneities in the lower troposphere and correcting geodetic radio-signal propagation delays in clear sky conditions. This instrument has both capabilities for realizing zenith pointing and slant pointing measurements. During fall 2009, the system was deployed in Toulouse (France) in collaboration with Météo-France, IPGP, CNRS and CNES for an experiment devoted to investigate the impact of water vapor heterogeneities on the propagation of DORIS and GPS signals and subsequent position estimates. During this experiment the lidar was operated for the first time in a slant pointing mode realizing sky maps of slant wet delays which will be used for correcting GPS observations. A second pointing mode was used to track DORIS satellites (Envisat, SPOT4 and SPOT5) for assessing slant wet delays retrieved from DORIS geodetic solutions. The first results from this campaign show a good agreement between both geodetic techniques for zenith wet delay retrieval. The agreement between geodetic techniques, lidar, and radiosoundings are rather good as well, despite a bias remains. Lidar slant pointing measurements are intended to be compared to GPS and DORIS slant retrievals and then used for correcting the GPS data. They are expected to improve the positioning accuracy, especially the vertical component