Optical spectra of the terrestrial nightglow in the 520-to 900-nanometer region, as measured by the W. M. Keck telescope on Mauna Kea in Hawaii and the associated high-resolution echelle spectrograph, showed many bands belonging to the important O-2(b-X) Atmospheric Band emission system. Previous ground-based measurements have shown only a single band, from the lowest vibrational level of the emitting state. Of particular interest is the fact that at the 762-nanometer position of the b-X 0-0 band, where earlier studies have shown only absorption features, these results showed both absorption at the (OO)-O-16-O-16 line positions and well-resolved emission at the positions of many of the (OO)-O-18-O-16 and (OO)-O-17-O-16 lines. These findings show that substantial advances can be made in understanding atmospheric emission phenomena by the use of astronomical tools.