Nitrogen dioxide emitted from space shuttle surfaces and shuttle glow

Abstract

Photographs taken on early space shuttle flights have indicated the presence of a surface glow in the ram direction1. Examination of airglow data from the AE and DE satellites has shown, the presence of a similar glow2, suggesting that the phenomenon is general to spacecraft in low Earth orbit, with the emission being concentrated in the ram direction. Several explanations have been offered for the glow: (1) OH formed by surface reactions of fast 0 atoms3; (2) plasma discharge mechanism4; (3) surface-induced decomposition of N2 followed by recombination into an excited state5; (4) surface emission by impact of O2 and O (ref. 6); and (5) near-continuum emission (at a resolution of ∼3.4 nm) in the region 400–800 nm from electronically excited NO2 (ref. 7). With reference to the last hypothesis we discuss here data on the number density of NO2 measured inside the payload bay of the shuttle orbiter. We also derive fluxes of NO2 near shuttle surfaces. Our data are shown to be consistent with the hypothesis of the glow being caused by NO2 emission.