Direct measurements at high spectral resolution of the O(1S) emission line profile at 5577 ¿ made using the Fabry-Perot interferometer on Dynamics Explorer are reported. The line profile is found to have marked nonthermal characteristics in the nightglow. The nighttime emission line profiles measured in the equatorial region, have been analyzed using a simple collisional relaxation model. The branching ratio for the dissociative recombination of O2+ leading to O(1S) is inferred. The result showns that the O(1S) +O(1D) channel is favored over the O(1S)+O(3P) channel by a factor of 4, in disagreement with the ratio previously reported by Hernandez. This result is, however, consistent with the active channel for O(1S) production being via the 1&Sgr;u+ repulsive state of O2 as suggested by the theoretical calculations of Guberman. A value for the excitation exchange cross section for O(1S) for 2.45¿0.8¿10-16 cm2 is obtained.