Abstract: A radiation sensor improved to increase the signal-to-noise ratio in the presence of a luminous background of high light intensity and to reduce the danger of direct detection of solar radiation. The sensor comprises optoelectric shutter means associated with the transparent slits of the optical mask in order to pass substantially only the radiation emitted by the source to be located and received by the associated detector. The shutter can be provided from a plate of ferroelectric ceramic material so arranged as to form juxtaposed elements controlled selectively by a circuit as a function of the positioning of the source in the form of data processed by an ancillary computer.