Observations of a Searchlight Beam to an Altitude of 28 Kilometers

Abstract

The beam of a high intensity searchlight directed over an observing station 18.4 km distant at angles of 30° and 45° to the horizontal was visible to a vertical altitude of about 20 km and was photographed to 28 km on clear nights. The intensity of the beam measured from the photographs was of the same order of magnitude as that calculated from the Rayleigh theory of molecular scattering using standard tables of stratospheric densities. At 5 km the observed intensity was greater than the theoretical intensity by a factor of about 7, the factor decreasing to about unity above 10 km, as would be accounted for by a small number of haze particles at 5 km which decreased to an imperceptible amount above 10 km.