Detection of Icy Particles in the Experimental Research on Enceladus' Plumes

Abstract

The Cassini mission discovered the existence of plumes on the surface of Enceladus. These plumes have been recreated in a laboratory to experimentally investigate the properties of the plumes. This research project focuses on the detection of solid ice particles ejected from an experimental model of the Plumes of Enceladus. The research begins by establishing a baseline experiment in which the detection technique is to be applied. The results from the preliminary investigation, including both the experimental and simulation models, indicate several possibilities of nucleation occurring within the channel. The concept generation phase yielded two general detection principles to be assessed for trade-off analysis: optical methods and impulse-based methods. As a result of the trade-off, an impulse-based method using piezoelectric sensor – a method based on the measurement of impulse caused by the impact of solid particles onto the sensor surface – was selected to be the most appropriate technique for this application. To test the selected detection method, the test campaign was conducted in two phases: drop test and plume model test. The drop test was conducted to investigate the response of the sensor using grains of known masses and variable drop height. A linear relationship between the grain impulse and the voltage response was identified, and this result allowed the impulse of an incident particle to be extrapolated given a voltage response. The second phase of the test campaign integrated the detection system into the plume mode in the vacuum chamber. Several waveforms were detected throughout the experiment: damped wave, attributed to solid particles ejected from the model, turbulent wave, attributed to an unsteady flow of vapor during the initial boiling phase, and low-amplitude periodic waves, attributed to a flock of small particles ejected from the plume model. These results indicate the presence of solid particles in the plume model, and given a particle velocity, the particle size may be determined. A noise analysis of the sensor in the plume model was performed, yielding a plot of the minimum detectable particle size to the particle velocity.