General problems involved in sensing atmospheric water vapor in the tropopause and stratosphere are discussed. The specific problem of performing these measurements with a dew-point instrument on a large balloon and the results of a program which included the development of the alpha radiation hygrometer are presented. These results are considered in the light of laboratory investigations and theoretical considerations to determine the validity of the obtained profiles. (Author).

General problems involved in sensing atmospheric water vapor in the tropopause and stratosphere are discussed. The specific problem of performing these measurements with a dew-point instrument on a large balloon and the results of a program which included the development of the alpha radiation hygrometer are presented. These results are considered in the light of laboratory investigations and theoretical considerations to determine the validity of the obtained profiles. (Author)

Abstract : "A frost-point hygrometer for use on W-47 aircraft has been designed utilizing alpha radiation techniques to measure the condensate thickness on cooled surfaces. A study of the problems associated with making frost-point measurements from high-speed aircraft was made as part of the design program." (Author).

Abstract: "This report describes a new type of automatic frostpoint hygrometer for measurement of the atmospheric distribution of water vapor. The mass of the frost deposit on a cooled surface is detected directly by energy attenuation of alpha radiation. An automatic control maintains a constant amount of this frost by controlling the direction of current flow through a thermoelectric cooler. The instrumentation of this hygrometer is described in some detail, and balloon-flight tests of prototype units are presented."