The Chemical Physics Of Ultraviolet Rocket Plume Signatures

Abstract

Space and aircraft based sensors working in the ultraviolet spectral region may offer many advantages over longer wavelength systems designed to monitor, identify and track rockets. However, the ultraviolet signatures of various rockets are known to display great sensitivity to operational parameters such as propellant type, oxidizer/fuel ratio, and combustor and nozzle design, as well as trajectory parameters including altitude and degree of solar illumination. This paper will review the basic chemical physics which govern both the emitted and scattered ultraviolet rocket plume signatures for selected rocket types in both low and high altitude regimes. Key chemiluminescent and thermal emission processes will be discussed along with important solar fluorescence and Mie scattering processes. Important emitting and scattering species in the near ultraviolet (400-300 nm), mid ultraviolet (300-200 nm) and far ultraviolet (200-100 nm) spectral regions will be identified and their impact on both spectral signatures and spatial images will be discussed. The ultraviolet absorption properties of the atmosphere and their effects on the utility of the various ultraviolet spectral regions for aircraft and satellite borne sensors will also be presented. Major areas which require further laboratory or theoretical research will be identified.