Measurement and Interpretation of Contaminant Radiations in the Spacecraft Environment

Video photographs and spectra of the optical radiations excited by reactions of the energetic exhaust gases from space shuttle's aspect-controlling bipropellant rocket engines with the orbital atmosphere are analyzed. The data were taken with the Air Force Maui Optical Station's cameras and a new imaging spectrograph as these 400 kgf Primary Reaction Control System thrusters operated in ram-wake-perpendicular to the trajectory sequences planned by Geophysics Directorate. Emission originated from a few km parallel and transverse to the symmetry axis of the exhaust; the surface brightness distributions from the firings to windward are well fit by Gaussians; and the total sterances determined by calibration against known stars were in the approximate ration 10 (ram) : 5 (perpendicular) : 1 (wake), showing that the kinetic energy of the combustion products plays a major part in exciting chemiluminescence. Three orders of magnitude less radiation arose from the spacecraft region than from the much larger volume in which the exhaust interacts, from which the hard body appeared physically separated.