Dust Mass Spectrometer for Compositional Mapping of the Galilean Moons
Résumé
We present the SUDA (Surface Dust Analyzer) instrument that will provide detailed answers to the main goals of ESA's JUICE mission about habitability, surface composition and exchange processes with the interior. The surfaces of the icy moons of Jupiter can be analyzed to unprecedented mass resolution and sensitivity down to the ppm level using modern dust analyzer instruments. The measurement method is based on analyzing the chemical composition of dust particles released from the surfaces of the moons. These dust particles populate the exosphere with densities sufficient for obtaining a valuable compositional picture even from a few flybys. The SUDA instrument is well suited for the detection of water ice particles with traces of the expected hydrated minerals such as sodium carbonates and magnesium sulphates, hydrated sodium chloride, and of organic materials. The value of a dust analyzer is well demonstrated by Cassini's Cosmic Dust Analyzer that has analyzed Enceladus's plume particles and E ring grains. SUDA is a time-of-flight, reflectron-type impact mass spectrometer, optimized for high mass resolution. The small size (268×250×171 mm3), low mass (< 4 kg) and large sensitive area (220 cm2) makes the instrument well suited for the challenging demands of the JUICE mission. A full-size prototype was used to demonstrate the performance through calibration experiments with a variety of cosmochemically relevant dust analogues. The effective mass resolution of m/Δm of 150- 200 is achieved for mass range of interest m = 1-150.