LONG-RANGE RADIOMETER MEASUREMENTS WITH A CLOSE-RANGE REFERENCE

A correction procedure is described for the use of a radiometer for tr ansmission measurements. In this application a blackbody is presented to the radiometer at close range as a field calibration. The radiomete r is then used to measure atmospheric attenuation by looking at a blac kbody source at a much longer range. Three factors that limit the accu racy of this approach to transmission measurements are identified, and a correction factor is derived. The theoretical correction factor is verified by measurements. Excellent agreement between the measurements and the theory suggests that the major factors limiting this techniqu e have been identified and properly accounted for.