  Space missions often carry antenna instruments that are sensitive to dust
impacts, however, the understanding of signal generation mechanisms remained
incomplete. A signal generation model in an analytical form is presented that
provides a good agreement with laboratory measurements. The model is based on
the direct and induced charging of the spacecraft from the collected and
escaping fraction of free charges from the impact-generated plasma cloud. A set
of laboratory experiments is performed using a 20:1 scaled-down model of the
Cassini spacecraft in a dust accelerator facility. The results show that impact
plasmas can be modeled as a plume of ions streaming away from the impact
location and a cloud of isotropically expanding electrons. The fitting of the
model to the collected antenna waveforms provides some of the key parameters of
the impact plasma. The model also shows that the amplitudes of the impact
signals can be significantly reduced in typical space environments due to the
discharging effects in the ambient plasma.
