The altitude dependent emission rate in the Δ-bands of nitric oxide has been measured in the earth's atmosphere at night by a scanning ultraviolet spectrometer. The reaction responsible is the two-body association of nitrogen and oxygen atoms. The measurements reveal a vertical intensity beneath the layer for the Δ-band system of 19 R. The horizontal emission rate increases from 70 R at 117 km to 140 R at 150 km. The data have been analyzed with a one-dimensional, time-dependent, vertical-transport model of odd nitrogen photochemistry. The calculated and measured intensities agree if the quenching of N(2D) by atomic oxygen is near 5¿10-13 cm3 s-1. The diurnal variation of Δ-band emission, N(4S), and NO densities resulting from model calculations are presented and discussed.