The biological effectiveness of solar electromagnetic radiation in space

An attempt has been made to determine the solar ultraviolet action spectrum for dried coliphage T-1 exposed to space under various filters at sounding rocket altitudes between 80 to 150 km. The survival of these microorganisms was compared with the preliminary results of laboratory ultraviolet irradiation experiments using monochromatic light sources of wavelengths of 1633 angstroms, 2062 angstroms, 2537 angstroms and of 3064 angstroms to 3200 angstroms. The results indicate that ultraviolet light of wave-lengths between 2000 angstroms to 3000 angstroms was mainly responsible for the killing of the filter protected microorganisms. More studies of the biological action spectrum of the vacuum ultraviolet light including the Lyman alpha emission are needed to determine the cause of the more than 100 fold higher death rate of the microorganisms which were not protected during the space exposure by filters.