We use data from two NASA satellites and a general circulation model of the upper atmosphere to elucidate the key factors governing the abundance and diurnal variation of nitric oxide (NO) at near-solar minimum conditions and low latitudes. This has been difficult to do previously, because NO data are typically taken from satellites in sun-synchronous orbits, meaning that they only acquire data in fixed local times. We overcome this limitation through model simulations of the NO diurnal cycle.