Observations of optical emissions on STS-4

Following the discovery of intense vehicle glow of the space shuttle on the STS-3 mission, a new experiment to probe this phenomenon was developed and flown on the shuttle STS-4 mission. A conventional camera was equipped with an objective transmission grating and several photographic exposures were taken of the shuttle tail from the aft flight deck window. Vehicle glow surrounding shuttle surfaces exposed to the ram direction was observed on a long (400 second) exposure. From analysis of the resulting spectral data it appears that the shuttle glow has a diffuse spectral component in the region 6300 to 8000A. In addition, it has been possible to assess the spectral character of light emitted by the firing of a reaction control system thruster. Our data show that the light emitted from the thruster gases is confined to wavelengths shorter than 7200A.