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 8-Cen were carried out on 26 July 1975 and 13-14 June 1976 at wavelengths from 2550• to 3100•. 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 predic t . At the lower boundary, about half the ozone destruction should be caused by NO x and ClO x. Above 55 km, virtually all loss is due to HO x. These results suggest an overestimate of HO x and ClO x loss processes or a serious underestimate of the Ox production rate. A minimum in 03 density near 87 km and a maximum at about 97 km are probably caused by reactions of 03 with atomic hydrogen and maximum nocturnal 03 production near 97 km. Observation Technique The stellar occultation technique for measurements of atomic species from satellites has been used and described by a number of researchers [Hays and Roble, 1973: Rie•ler et al., 1976; Atreya et al., 1976]. In the usualSapplications of the occultation method, the'line-of-sight to the star crosses the limb of the earth during a time interval of approximately 10 to 25 seconds depending on the satellite orbit and the atmospheric species observed. In the observations to be discussed her•, an observing geometry in which the line-of-Sight grazes the earth's limb *Guest Investigator with the Princeton Telescope on the Copernicus satellite which is sponsored by the National Aeronautics and Space Admini-