OpenTOF, a compact and novel mass spectrometer for fast spacecraft flybys: molecular measurements free of fragmentation at hypervelocity encounters

Abstract

Abstract. The exploration of the Solar System is important to understand the origin and evolution of celestial bodies in a planetary system and to gather information about the possible appearance and development of life on other bodies than the Earth. In this endeavour, the study of the upper layers of the Earth's atmosphere, the characterisation of the plumes on Enceladus and Europa, or the investigation of Io all contribute to discovering a more global and complete picture. In this context, with the aim to gather needed data since in situ measurements are needed, the Unit for Space Research and Planetary Sciences in Bern developed a compact mass spectrometer for space applications, featuring a novel gas inlet labelled Direct Open Source (DOeS). This new instrument is designed to measure ions and neutral molecules at high relative speeds up to 20 km/s, thus enabling fast spacecraft ybys of the targeted atmospheres, without high relative velocity impact fragmentation to preserve parent molecules. Building up on previous contributions to the project, this work prepared a compact setup with an ion and neutral beam, called LEIS, to test mass spectrometers. Furthermore, OpenTOF was tested and optimised voltage sets of the instrument were found for several speeds, especially 10 km/s and 20 km/s. For fast ions, masses up to m/z 293 were measured above 11 km/s, while masses m/z below 69 were detected at speeds above 23 km/s. Finally, rst tests with fast molecules were already successful. Masses up to m/z 136 were detected at 17 km/s. This work delivered a proof of concept, showing that the instrument and its novel gas inlet ful l their purposes at high relative velocities. Therefore, OpenTOF was proven to be a promising instrument for the near-future investigation of atmospheres in the Solar System.