Citation
Abstract
Brightness temperatures measured at frequencies of 19.8 and 26.3 GHz are utilized to obtain the line-of-sight water-vapor path delays that are compared with nearby Global Positioning System (GPS) and dedicated water-vapor radiometer measurements. The presented method of radiometric determination of water-vaporinduced path delays allows direct calibration of range measurements at the full range of elevation angles. The application of an a priori linear water-vapor retrieval coe–cient to these exploratory measurements indicates an agreement with stochastically estimated GPS values at a level range of 0.2 to 0.8 cm at zenith. The calculated mean zenith-delay difierence between these techniques is up to 0.4 cm. The known sources of these discrepancies are (1) the presence of radio sources in the measurements, (2) an inadequate brightness-temperature calibration, (3) water-vapor retrieval algorithm uncertainties, and (4) an inadequate method of GPS estimation of delays. From the current data, the lowest achievable zenith path-delay error is estimated to be 0.03 cm; that is an order of magnitude lower than the above discrepancies.
Keywords
Details
- Volume
- 42-141
- Published
- May 15, 2000
- Pages
- 1–15
- File Size
- 340.4 KB