Unsupervised detection of Saturn magnetic field boundary crossings from plasma spectrometer data

We investigate unsupervised time-series analysis techniques for real-time identification of magnetic field boundaries in data collected by the Cassini Plasma Spectrometer (CAPS) on the Cassini mission to Saturn. Previous research has sought to identify these boundaries either in a supervised setting, where a subset of labeled boundary crossing events are available to the algorithms, or using magnetometer data in which these boundaries are significantly clearer. We find that Saturn bow shock transitions can be reliably detected by the methods we consider, while magnetopause transitions are harder to identify across different years, indicating that generalization of algorithm parameters remains a challenge. We identify the Plasma Instrument for Magnetic Sounding (PIMS) on the upcoming Europa Clipper Mission as a promising beneficiary of the use of similar processing methods. By performing onboard detection of events such as Jovian plasma sheet crossings, Europa ionosphere boundaries, and water vapor plumes, Europa Clipper could benefit from in-situ adaptation to increase science return and data quality, such as by changing the instrument's observing mode depending on the spacecraft's current environment.