Horizontal Atmospheric Transmittance Measurements with a Thallous Sulfide Cell Transmissometer*

Abstract

Measurements of horizontal atmospheric transmittance were made over 1.24- and 4.07-sea-mile paths with an automatically recording near-infrared transmissometer. The transmissometer comprised a tungsten source, modulated at 60 cps, and a thallous sulfide cell receiver. The visual transmittance was simultaneously recorded with a photomultiplier-tube receiver using the same source. New results of total transmissivity per sea mile in the 0.7- to 1.1-micron region of the spectrum are presented and compared with results of the Naval Research Laboratory and the Admiralty Research Laboratory in the visual and infrared regions of the spectrum. A graph of transmissivity versus wavelength from 0.3 to 12 microns was made. This graph is useful in finding the transmissivity in the “windows” of the infrared spectrum when the transmissivity has been determined at a particular wavelength or for a small band of wavelengths.