The sounds and spectrograms in this video represent data collected by Cassini’s Radio and Plasma Wave Science (RPWS) instrument as the spacecraft made the first dive through the gap between Saturn and its rings as part of the mission’s Grand Finale, on April 26, 2017.
As tiny, dust-sized particles strike Cassini and three RPWS antennas, the particles are vaporized into tiny clouds of plasma. These tiny explosions make a small electrical signal that RPWS can detect.
Researchers on the RPWS team convert the data into visible and audio formats for analysis. Ring particle hits sound like pops and cracks in the audio.
The colors on the spectrogram indicate the emitted power of the radio waves, with red as the most powerful. Time is on the x-axis, and frequency of the radio waves is on the y-axis.
Very few pops and cracks are audible in the April 26 data at all.
The audible whistle in the April 26 data, just before ring plane crossing, is due to a type of plasma wave that will be the subject of further study.
In addition, there is an abrupt change beginning at the 09:00:00 mark on the spectrogram that represents a change in the RPWS antenna’s operational configuration (from monopole mode to dipole mode).
In comparing the two data sets, it is apparent that while Cassini detected many ring-particles striking it when passing through the Janus-Epimetheus ring, the first Grand Finale crossing -- in stark contrast -- was nearly particle free.
Credit: NASA / JPL-Caltech / University of Iowa.