Excitation of N₂ Lyman‐Birge‐Hopfield Bands emission by low Earth orbiting spacecraft

Abstract

The spectral distributions in the artefactual Lyman‐Birge‐Hopfield bands observed from the S3‐4 satellite and Spacelab 1 are shown to be consistent with excitative recombination of ground‐state N atoms catalyzed by spacecraft and instrument surfaces exposed to the atmosphere. This heterogeneous (and most probably Langmuir‐Hinshelwood) reaction is analogous to the homogeneous reactions that produce the well‐known VUV afterglow of active nitrogen. Promoting/interfering surface processes (perhaps involving conditioning) and undocumented systematic changes in vehicle orientation are among the possible causes of the strong dependence of the measured nadir system intensities on the ambient density of N(4S).

Upper limits on spacecraft‐induced ultraviolet emissions from the space shuttle (STS‐61C)

“…Similar emission, also at a level of several R/•, has also been observed in spectra from the space shuttle Spacelab 1 experiment [Torr et al, 1985] from an altitude of 250 km. Various mechanisms have been proposed to explain the induced N 2 LBH glow [Kofsky, 1988;Swenson and Meyerott, 1988;Cuthbertson and Langer, 1989] that are consistent with a [N2] 3 or [N21210] altitude dependence.…”

Optical Aeronomy

“…LBH bands are conspicuous features in vehicle glow, [e.g., Conway et al 1987]. There has been considerable interest in understanding this particular emission, with surface chemistry models advanced by Kofsky [1988], Swenson and Myerott [1988], Myerott and Swenson [1990], and Cuthbertson and Langer [1989]. For other work of interest on modeling of spacecraft‐atmosphere interactions see Gordon and Seebaugh [1989], Elgin et al [1990 a,b ].…”

A surface chemistry model for the altitude dependence of the N2 Lyman‐Birge‐Hopfield glow on spacecraft

“…Thus the N 2 formed through this mechanism can leave the surface highly excited. Not enough is known experimentally to exclude definitely the possibility of a contribution to the glow from the LH process, and in fact Kofsky [1988] argues that the vibrational spectrum inferred from the S3-4 data is evidence for an LH process. However, our energy considerations do suggest a Rideal process, and we assume a Rideal source for our model.…”