A preliminary spectroscopic assessment of the Spacelab 1/shuttle optical environment

The Spacelab 1/Shuttle mission which orbited for 10 days following launch on November 28, 1983, carried amongst the complement of instruments, an array of imaging spectrometers known as the Imaging Spectrometric Observatory. Because the instrument covers a broad wavelength range extending from the vaccum ultraviolet to the near infrared and has a relatively high spectral resolution (3–6 Å), it has provided some of the first spectral information on the Shuttle optical environment. Shuttle flights to date have shown that surfaces directed into the velocity vector develop a bright orange‐red glow. As there are extensive plans for optical studies from the Shuttle, as well as other orbiting structures such as the Space Telescope and Space Station, there has been considerable concern as to whether such glows and other sources of optical contamination might prevent or limit observations. In this paper we present spectral data from 1150 to 8000 Å measured with the instrument looking tangentially away from the earth and into the velocity vector. (Detailed quantitative studies are underway, but because of the numerous instrument design activities in process at this time which could benefit from this information, we present a preliminary assessment here.) We find that the spectrum in general contains the expected atmospheric features in addition to bright molecular bands between 6400 and 8000 Å. These bands appear to be part of the N 2 First Positive system. Several other features of lesser significance have yet to be identified. If the bulk of the emission is due to the N 2 first positive system, there appear to be two possible excitation mechanisms: direct collisional excitation of the local Shuttle atmosphere by the terrestrial atmosphere, or a surface interaction which generates metastable N 2 (A), which subsequently radiates via inverse first positive N 2 transitions followed by first positive transitions.