ATMOS-ATLAS-1 MEASUREMENTS OF THERMOSPHERIC AND MESOSPHERIC NITRIC-OXIDE

The atmospheric trace molecule spectroscopy (ATMOS) instrument obtaine d solar occultation spectra of the terrestrial atmosphere during the A tmospheric Laboratory for Applications and Science (ATLAS 1) mission o f March 26-April 4, 1992. During this time, A(p) varied between 11 and 18 while the F-10.7 index was near 192. The analyses of the 5.3-mu m spectral data to derive nitric oxide densities in the lower thermosphe re and mesosphere are described here. The results show that a peak NO density of 1.0 x 10(8) cm(-3) occurs at 105 +/- 2.5 km for the latitud e range 38 degrees N-58 degrees S. The density values are higher than previously reported using UV measurements. These measurements worsen t he discrepancy with photochemical models at low latitudes where models already underpredict nitric oxide.