The impact of microwave absorber and radome geometries on geodetic measurements with ground-based GNSS antennas

We present results from a investigation on the impact of microwave absorber, i.e. ECCOSORB®, and radome geometries on geodetic measurements with ground-based Global Navigation Satellite System (GNSS) antennas. A 12 m baseline of two GNSS stations was used. One is an experimental station which can perform observations with systematic implementation of the Eccosorb and the radome. The other is the permanent ONSA station of the IGS network. Nine months of data from the baseline were analyzed with five different elevation cutoff angles from 5° to 25°). The 5.0 version of the GIPSY software, which provides antenna calibration and enables usage of the new GPS orbit and clock products from JPL, was used for the data processing. We found that the elevation-angle dependent variations of the estimate of the vertical component of the relative site coordinates are significantly reduced by using the Eccosorb. The horizontal components are less affected. Two different configurations of the Eccosorb on the antenna give similar results. Small offsets were seen (~1-2 mm ) in the estimates of the vertical component of the baseline for 5°, 10°, and 15° solutions when the antenna is covered by a radome with a hemispheric top and a conical body. Using the Eccosorb also yields significant changes in the estimate of the atmospheric content of Integrated Water Vapour (IWV). The impact of using the radome affects the IWV less than 0.5 kg/m^2.

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