A variety of emissions from molecular products of plumes from the space shuttle have been identified and characterized. For example, a near ultraviolet (UV) emission band at approximately 336 nm from a plume of the space shuttle primary reaction control system (PRCS) and vernier reaction control system (VRCS) has been assigned to an electronic transition NH(A→X) of nitrogen monohydride (which also may be referred as imidogen), resulting from interaction between atmospheric atomic oxygen and an atomic or molecular species in the plume. For further details, see Viereck et al., “The interaction of the atmosphere with the space shuttle thruster plume: The NH(A-X) 336-nm emission,” Journal of Geophysical Research 101(A3): 5371-5380 (1996). In addition to the NH(A→X) emission at approximately 336 nm, a near UV emission band at approximately 310 nm resulting from interaction between atmospheric gas and an atomic or molecular species in the plume has been assigned to an electronic transition OH(A→X) of the hydroxyl radical. For further details, see Bernstein et al., “Far-field spectral analysis of a Space Shuttle vernier reaction control system firing,” Journal of Spacecraft and Rockets 43(6): 1370-1376 (2006), the entire contents of which are incorporated by reference herein. Additionally, emission from the Cameron bands from CO(a 3Πr) radiating to the ground state has been observed resulting from interaction between atmospheric gas and a space shuttle plume. For further details, see Dimpfl et al., “Molecular dynamics from remote observation of CO(a) from space shuttle plumes,” Journal of Spacecraft and Rockets 42(2): 352-362 (2005), the entire contents of which are incorporated by reference herein.
A computational tool referred to as SOCRATES (Spacecraft/Orbiter Contamination Representation Accounting for Transiently Emitted Species) has been developed for use in simulating spacecraft plumes and interactions of molecular species therein with atmospheric gases, and is based upon direct simulation Monte Carlo (DSMC) modeling. Presently, the use of SOCRATES is only available upon registration with the Defense Logistic Information Service (DLIS), certification to receive export-controlled Department of Defense (DoD) technical data, and a request to the Air Force Research Laboratory (AFRL). For a discussion of the theory behind the SOCRATES code, see Elgin et al., “The Theory Behind the SOCRATES Code,” Tech. Rep. PL-TR-92-2207, Geophysics Directorate, Phillips Laboratory, Hanscom Air Force Base, Mass. (1992), the entire contents of which are incorporated by reference herein. For a discussion of the exemplary use of SOCRATES to simulate an emission at 630 nm attributed to a transition between the O(1D) excited state and the O(3P) ground state resulting from collision of atmospheric oxygen with the exhaust of a space shuttle, see Setayesh et al., “SOCRATES simulation of the emission at wavelength 6300 Å generated by the interaction between the atmosphere and the space shuttle exhaust,” Tech. Rep. PL-TR-93-2186, Geophysics Directorate, Phillips Laboratory, Hanscom Air Force Base, Mass. (1993), the entire contents of which are incorporated by reference herein. Certain other references mentioned herein may describe the use of SOCRATES to simulate spacecraft plumes and interactions thereof with the atmosphere.