Ultraviolet stellar occultation measurement of the H 2 and O 2 densities near 100 km in the Earth's atmosphere

The density of molecular hydrogen in the earth's atmosphere has been measured between 95 km and 108 km. The technique involved use of the high resolution ultraviolet spectrometer of the Orbiting Astronomical Observatory Copernicus to observe radiation from the γ² Velorum near the R(0) line of the (0,0) Lyman absorption band at 1108Å as the star was occulted by the earth's atmosphere. The result shows H 2 densities varying from 1.05 −0.14 +0.15 × 10 8 cm −3 at 95 km to 1.1 −0.08 +0.05 × 10 7 cm −3 at 108 km. These densities agree quite well with recent theoretical predictions. The measured O 2 density profile generally agrees with the models except for a wave‐like structure between 104 km and 114 km.