THERMOSPHERIC NITRIC-OXIDE FROM THE ATLAS-1 AND SPACELAB-1 MISSIONS

Spectral and spatial images obtained with the Imaging Spectrometric Ob servatory on the ATLAS 1 and Spacelab 1 missions are used to study the ultraviolet emissions of nitric oxide in the thermosphere. By synthet ically fitting the measured NO gamma bands, intensities are derived as a function of altitude and latitude. We find that the NO concentratio ns inferred from the ATLAS 1 measurements are higher than predicted by our thermospheric airglow model and tend to lie to the high side of a number of earlier measurements. By comparison with synthetic spectral fits, the shape of the NO gamma bands is used to derive temperature a s a function of altitude. Using the simultaneous spectral and spatial imaging capability of the instrument, we present the first simultaneou sly acquired altitude images of NP gamma band temperature and intensit y in the thermosphere. The lower thermospheric temperature images show structure as a function of altitude. The spatial imaging technique ap pears to be a viable means of obtaining temperatures in the middle and lower thermosphere, provided that good information is also obtained a t the higher altitudes, as the contribution of the overlying, hotter N O is nonnegligible. By fitting both self-absorbed and nonabsorbed band s of the NO gamma system, we show that the self absorption effects are observable up to 200 km, although small above 150 km. The spectral re solution of the instrument (1.6 Angstrom) allows separation of the N+( S-5) doublet, and we show the contribution of this feature to the comb ination of the NO gamma (1,0) band and the N+(S-5) doublet as a functi on of altitude (less than 10% below 200 km). Spectral images including the NO delta bands support previous findings that the fluorescence ef ficiency is much higher than that determined from laboratory measureme nts, The Spacelab 1 data indicate the presence of a significant popula tion of hot NO in the vehicle environment of that early shuttle missio n.