SPECTROGRAPHIC OBSERVATION AT WAVELENGTHS NEAR 630 NM OF THE INTERACTION BETWEEN THE ATMOSPHERE AND THE SPACE-SHUTTLE EXHAUST

The collision between the exhaust from the Primary Reaction Control System (PRCS) engines (870 pounds thrust) of the space shuttle and the ambient atmosphere has been observed from the Air Force Maui Optical Station (AMOS). Spectra have been obtained in the wavelength region near 630 nm, The temporal, spatial, and spectral distribution of the emission in this region has been recorded. The results reported here indicate that when the exhaust of the space shuttle interacts with the atmosphere in the ram direction, an intense, long-lasting emission at 630 nm due to O(1D --> 3P) is generated. A substantial amount of O(1D) is swept back onto the orbiter. Two processes are proposed for the formation of O(1D): (1) excitation of atmospheric O(3P) by collisions with the exhaust of the space shuttle engines; and (2) charge exchange between ambient O+ and exhaust H2O. Calculations using the SOCRATES code show excellent agreement with the data.