Long-range radiometer measurements with a close-range reference

A correction procedure is described for the use of a radiometer for transmission measurements. In this application a blackbody is presented to the radiometer at close range as a field calibration. The radiometer is then used to measure atmospheric attenuation by looking at a blackbody source at a much longer range. Three factors that limit the accuracy 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 technique have been identified and properly accounted for.