UV stellar occultation measurements of nighttime equatorial ozone

The ultraviolet spectrometer-telescope on Copernicus was used for stellar occultation measurements of atmospheric ozone. Two sets of observations of the target star Beta-Cen were carried out on 26 July 1975 and 13-14 June 1976 at wavelengths from 2550 A to 3100 A. 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.