Tropospheric path-length correction using a dual-frequency transportable radiometer.

PULIAFITO, ENRIQUE; ; BÜRKI, B.

Helsinki, Finlandia

Simposio; International Geoscience and Atmospheric Remote Sensing Symposium; 1991

IGARSS

Radio-astronomical measurements and applications in satellite-geodesy such as Very Long Baseline Interferometry (VLBI) and Global Positioning System (GPS) require accurate determination of the path delay along the propagation path. While the path delay due to dry air is quite stable and can be well calibrated by surface meteorological measurements, the effect due to water vapor and liquid water within the troposphere is highly varying. Therefore no surface modelling has been satisfactory up to now. This tropospheric path delay can be obtained fairly accurate by means of a dual frequency ground based water vapor radiometer (WVR) operating at 23.8 and 31.5 GHz. Simulation studies as well as calibration and test measurements indicate that the residual error of the tropospheric path delay is better than 0.8 cm in zenith and better than 4 cm for elevations above 15 degrees. The entire equipment is transportable and can be operated on a normal tripod. The WVR construction in connection with a Laptop PC enables to track the actually measured GPS Satellites.