The acoustic sounding and receiving system of CASSE has two principal operation modes:
Listen passively, like a seismometer, into the comet nucleus and locate noise sources, caused by thermal stress, seismic effects, particle impacts or Lander instruments.
Perform actively, like a sonar, a sounding of the surface layers. One can calculate the elastic constants of the cometary surface from the measured sound velocities cP and cS of compressional and shear waves. It is intended to conduct a deep sounding in order to detect layering and other inhomogeneities, like holes. This requires a complex analysis of the acoustic signals.