Infrared emission from NO2(asterisk) and NO(asterisk) desorbed from spacecraft surfaces

Infrared photons from the radiative cascade accompany both the gas phase NO2 continuum chemiluminescence (which originates from its 282 and 281 states) and the NO beta bands. When these upper electronic states are excited by recombination/desorption at surfaces of low earth orbiting spacecraft, similar IR emission spectrums will be observed. The principal NO2 features (other than the long wavelength tail of its electronic transitions) are the nu sub 3 fundamental sequence near 6.2 microns and nu sub 1 + nu sub 3 intercombination bands near 3.6 microns; NO would emit the delta v = 1 and delta v = 2 systems above 5.3 and 2.7 microns. Because of the long radiative lifetimes of the upper vibrational states, the infrared radiances in projections parallel to the vehicle surface (which are estimated) are substantially less than those of the visible and ultraviolet glows. (Author)