Distribution of basic rotational properties of the inner Solar System asteroid populations. Top panel: Rotational frequency versus absolute magnitude. The dashed horizontal line marks the breakup limit of main belt asteroids, corresponding to a rotational period of 2.2 h (Pravec & Harris 2000). Bottom panel: Light curve amplitude versus rotational frequency. Dashed curves correspond to constant critical densities, as calculated by Pravec & Harris (2000). In both panels, the symbols with different colours correspond to the data sources, as indicated in the legend. The three targets discussed in this paper are marked with large blue symbols.