Top panel: power amplitude of the mutual impedance spectrogram, normalized to that obtained in vacuum, expressed in dB (right color bar) in the [0–600] kHz frequency range. The black dots indicate the identified plasma frequency for each spectrum. Middle panel: electric potential measured by the Langmuir probe RPC-LAP1, operated in floating mode, with respect to spacecraft potential. Bottom panel: plasma densities extracted from the RPC-MIP mutual impedance spectra (black dots) together with the estimated maximum measurement errors (shaded gray region) and RPC-MIP/LAP plasma densities obtained from the cross-calibration of the RPC-LAP floating potential measurement with the RPC-MIP absolute density measurements (blue line).