Ultraviolet spectra between 2000 and 2800 ¿ of an IBC II+ aurora were obtained by a rocket-borne Ebert-Fastie monochromator at 15-¿ resolution over Fort Churchill, Manitoba. The v'=0--8 progressions of the N2 Vegard-Kaplan system, the Δv=8 sequence of the Lyman-Birge-Hopfield system, and a progression attributed to the Herman-Kaplan system were identified by a synthetic spectrum analysis. Relative populations of the first eight vibrational levels of the A3&Sgr;u+ state at high altitude were obtained from the theoretically generated spectra, and quenching rate coefficients were derived for these eight levels by using an atomic oxygen concentration derived from the data from another experiment on board. For v=0 the quenching rate coefficient was found to be 2.0--10-10 cm3 s-1 and was not found to increase for higher vibrational levels. The intensity of the (0,2) band of the Herman-Kaplan (E3&Sgr;u+→A3&Sgr;u+) systme was found to be ~5 times the theoretically predicted value, but even so, the cascade from E3&Sgr;g+ provides less than 2% of the A3&Sgr;u+ state population.