Optical Emissions from the High Speed Rocket Exhaust Interaction with the Ionosphere

An increasing number of space shuttle and rocket launches have inspired an investigation into the effects of vehicle exhaust on the earth's upper atmosphere. A controlled Charged Aerosol Release Experiment (CARE) will be carried out in September 2009 from Wallops Island, Virginia. The high speed exhaust from the Nihka motor on the rocket contains primarily Al2O3, H2O, CO, HCl, N2, CO2 and H2, would have an exit velocity of 2.8 km/s, and the exhaust would last for 18 seconds. The heavy particles are expected to form a charged dust layer in the lower thermosphere and the ionospheric E region. Sunlight scattered from the particulates will produce a bright optical display that can be observed with a ground spectrograph. In addition, the interactions of these molecular ions with the background ionospheric electrons are expected to also produce optical emissions in the range of 400-1000 nm. Observations from the CARE campaign were obtained using a ground based Visible/NIR spectrograph and the Millstone Hill ionospheric incoherent scatter radar located in Massachusetts. The chemical processes behind the expected emissions are compared with the observed optical emissions for both temporal and spatial scales. The spectral emissions observed with the spectrograph from the Wallops site are also compared to those observed at other ground based optical diagnostics sites. The temporal evolution of the emissions is correlated with that of the formation of the ionospheric layers as observed with the Millstone Hill radar. Finally, the significance of these results and future plans for more and enhanced observation techniques will be discussed.