[en] The flash tube hodoscope was an essential element of the HEAO-3 Copenhagen-Saclay instrument: track information is needed to know the direction of incidence of each particle in a geographic coordinate system, from which the precise geomagnetic cut off can be computed for each observed particle. In addition trajectory reconstruction of the particles is needed to correct the signals from the counters for pathlength and non uniformity variations and help select good events from background. In this paper, we present the main characteristics of the hodoscope and its flight behaviour, and we try to compare its performances with those attained in space by other determining devices