A compact Sun tracking radiometer with two different beamwidth antennas for detection of atmospheric water vapor

A compact radiometer system having two small antennas of different beamwidths was developed to detect water vapor concentration by measuring atmospheric attenuations of the solar radiation at the K -band. To obtain continuous monitoring of the total water-vapor fluctuation, a simplified measuring method was used, which was a cancellation of the thermal radiation of the atmosphere by measuring the temperature difference of the two antennas fluctuation by taking the ratio of measured data at two frequency points in the water-vapor absorption spectrum. Errors in the estimation of total water vapor arising from the simplified method were evaluated. Experimental results have shown general agreement in the trend of theoretically calculated results against absolute humidity at ground level, and hence, total water-vapor content or integrated water vapor, when the standard atmospheric altitude distribution of water vapor is assumed