Atmospheric Sodium measured by a Tuned Laser Radar

THE layer of sodium atoms present in the atmosphere at a height of about 90 km has been extensively studied by observations of the resonance scattering of sunlight in daytime and twilight¹. Rocket measurements of the daytime height distribution of the resonance radiation^2,3 have shown that the simple photochemical model based on the equilibrium between Na and NaO must be modified. In recent discussion of models involving a dust layer as a source of sodium⁴, attention has been drawn to the need for data on the night time abundance and distribution of atomic sodium. We report preliminary measurements at night by a new optical radar.