Acoustic Experiment to Determine the Composition of an Unknown Planetary Atmosphere

Abstract

Measurement of the speed of sound and the acoustic impedance, combined with a knowledge of ambient pressure and temperature, provide sufficient data for determining the relative abundance of constituents in a mixture of nitrogen, argon, and carbon dioxide. Sound absorption and dispersion yield additional information for checking the consistency of the results. An instrument has been developed to measure the acoustic properties of an unknown gas mixture. Laboratory results demonstrate the feasibility of determining the gas composition within a few percent. The technique of velocity measurement by use of phase comparison over several wavelengths is quite sensitive and may be useful in other applications.