Terrestrial atmospheric composition from stellar occultations.

Stellar ultraviolet light transmitted through the earth's upper atmosphere is strongly absorbed by ozone and molecular oxygen. The stellar ultraviolet photometers aboard the Orbiting Astronomical Observatory (OAO-2) satellite have measured the intensity changes of several stars during occultation of the star by the earth's atmosphere. From the occultation data the nighttime vertical number density profiles of molecular oxygen at altitudes from 120 to 200 kilometers and of ozone at altitudes from 60 to 100 kilometers have been obtained.