A nitric oxide(NO) detector, making use of a newly developed fast cam-driven absorption cell system is developed for launch on board a Brazilian SONDA III rocket, to measure the height profile of the NO gamma band dayglow emission intensity and thereby to estimate the height profile of the number density of atmospheric NO in the equatorial region. Two absorption cells, one of them containing the gas NO and the other nitrogen are brought in front of the photocathode of a photomultiplier (PM) tube alternately using a cam system. Each cell remains in front of the PM tube for an interval of time fixed by the cam shape. The cam is designed to optimize the time needed for positioning the cells one after the other and also to simplify the operation of the step motor responsible for the movement of the absorption cells. The advantages of this new system over the conventional wheel mounting are also presented.Material digitalizado en SEDICI gracias a la colaboración de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP).Asociación Argentina de Geofísicos y Geodestas