Intensity of Lyman-Alpha Line in the Solar Spectrum

The Lyman-alpha line appeared on a rocket spectrogram recently obtained by a group at the Physics Department of the University of Colorado. The grazing-incident spectrograph had been pointed directly at the sun during the 28-second exposure by a biaxial sun-follower in an Aerobee rocket. The average altitude during exposure was 81 km. Lyman-alpha was the only line observed in the far ultraviolet. It is about 5 angstroms broad and exhibits, for the altitude range of the rocket during the exposure, a narrow emission center with broad emission wings. The total intensity outside the earth's atmosphere is estimated to be 0.05 microwatt/${\mathrm{cm}}^2$. Instrumental scattering could have masked the light of any faint far-ultraviolet continuum which may have penetrated to the atmospheric levels reached by the rocket during the exposure.