particle crosses a laser curtain, and is detected by photoelectric sensors (GDS, grain detection system) registering a signal (proportional to the particle cross section times the albedo) and the time at which the laser curtain is crossed. Then the particle hits the impact sensor (IS, with the same GDS cross section, A=10−2m2), which registers the individual particle impact momentum and its travel time from GDS to IS. The combination of GDS and IS measurements (GDS+IS particles) provides the particle mass and velocity, and constrains the particle bulk density by means of calibration curves (Della Corte et al. 2016) derived on the ground using cometary analogues (Ferrari et al. 2014). If the particle is too small to be detected by the GDS system, it may be detected by the IS sensor only (IS particles): in this case the particle momentum is converted to the mass assuming the mean value of the velocities of the GDS+IS particles in the same momentum bin, or assuming the velocities predicted by tail models (Fulle et al. 2010) if Ngds+is =0 in that mass bin. The spacecraft velocities listed in Table 1 are always much lower than the dust velocities measured by GIADA.
