Spectroscopic observations have been made of the terrestrial ultraviolet dayglow (850-1850 ¿) using newly developed instrumentation in a sounding rocket payload. The atmospheric conditions and viewing geometry were such as to suppress nitrogen emissions relative to those from atomic oxygen. This permitted the identification and measurement of the weak O I 1173-¿ (3s' 3D0-2p4 1D) intercombination multiplet and the 1641-¿ (3s 3S0-2p4 1D) lines as well as the strong 989-¿ and 1304-¿ emissions. The 1173-¿ emission rate increased at lower altitudes, while the 989-¿ emission, from the same upper level, decreased at lower altitudes. This behavior is consistent with the radiative entrapment model of Meier (1982) and the laboratory value of the 1173-¿/989-¿ branching ratio of 1.5¿10-4 (Morrison, 1985). The 1641-¿/1304-¿ emission ratio is also consistent with a radiative entrapment model and a branching ratio near 5.0¿10-6. Lack of detection of the 1484-¿ branching ratio, confirming that emission in this line is less significant in depleting the 3s' 3D0 term than is 1173-¿ emission.