Abstract
Antenna instrument carried by spacecraft is complementary to dedicated
dust detectors by registering transient voltage perturbations caused by
impact-generated plasma. The signal waveform contains information about
the interaction between the impact-generated plasma cloud and the
elements of spacecraft – antenna system. Variability of antenna signals
from dust impacts has not yet been systematically characterized. A set
of laboratory measurements are performed to characterize signal
variations in response to spacecraft parameters (bias voltage and
antenna configuration) and impactor parameters (impact speed and
composition). These measurements demonstrate that dipole antenna
configurations are sensitive to impact location because of how the
asymmetric expansion of impact plasma cloud produces different signals
among antennas. This result revises previous conclusions that dipole
antenna configurations should be insensitive to impacts. When dust
impacts occur at low speeds, antenna instruments typically register
smaller amplitudes and less characteristic impact signal shapes. In this
case, impact event identification becomes challenged by low
signal-to-noise ratios and complex waveforms, indicating the compound
nature of non-fully developed impact-generated plasmas. Laboratory
studies of aluminum dust particle hypervelocity impacts were used to
explore the dependence of impact waveform variability on dust
composition. No significant variations were determined compared to
common iron dust measurements, consistent with prior studies.
Additionally, electrostatic model fitting is used to obtain impact
plasma parameters from antenna-detected waveform signals. The recovered
parameters are comparable to those from Fe dust. This suggests a
similarity of fully developed impact plasma cloud behaviors upon
hypervelocity impact.