Solar electromagnetic radiation of wavelengths ranging from 260–1300 A was measured by a grazing-incidence grating spectrometer on OSO-III, which operated as a monochromator with a wavelength bandwidth of about 2 A and an acceptance angle covering the whole disk without any instrumental discrimination of source locations. The monochromator was commanded either to scan the whole spectrum or to operate at variously chosen fixed wavelengths. The latter mode of operation afforded a high-time resolution in the observation of temporal variations such as those associated with solar flares, and also allowed accurate determinations of the absorption characteristic of the earth's upper atmosphere (near sunset and sunrise).