UV stellar occultation measurements of nighttime equatorial ozone

The Princeton University Ultraviolet Spectrometer-Telescope on the NASA Orbiting Astronomical Observatory Copernicus was used for stellar occultation measurements of atmospheric ozone. Two sets of observations of the target star β-Cen were carried out on 26 July 1975 and 13-14 June 1976 at wavelengths from 2550A to 3100A. After unfolding of the data, ozone density profiles near the equator within 3 hours of local midnight were obtained at altitudes from 47 to 114 km. A secondary maximum at 97 km has been observed in both sets of data. The ozone density between 47 and 75 km is a factor of 2 to 3 times as large as current models predict. At the lower boundary, about half the ozone destruction should be caused by NOx and ClOx. Above 55 km, virtually all loss is due to HOx. These results suggest an overestimate of HOx and ClOx loss processes or a serious underestimate of the Ox production rate. A minimum in O3 density near 87 km and a maximum at about 97 km are probably caused by reactions of O3 with atomic hydrogen and maximum nocturnal O3 production near 97 km.