MIDAS – The Micro-Imaging Dust Analysis System for the Rosetta Mission

The International Rosetta Mission is set for a rendezvous with Comet 67 P/Churyumov-Gerasimenko in 2014. On its 10 year journey to the comet, the spacecraft will also perform a fly-by of the two asteroids Stein and Lutetia in 2008 and 2010, respectively. The mission goal is to study the origin of comets, the relationship between cometary and interstellar material and its implications with regard to the origin of the Solar System. Measurements will be performed that shed light into the development of cometary activity and the processes in the surface layer of the nucleus and the inner coma. The Micro-Imaging Dust Analysis System (MIDAS) instrument is an essential element of Rosetta’s scientific payload. It will provide 3D images and statistical parameters of pristine cometary particles in the nm-μm range from Comet 67P/Churyumov-Gerasimenko. According to cometary dust models and experience gained from the Giotto and Vega missions to 1P/Halley, there appears to be an abundance of particles in this size range, which also covers the building blocks of pristine interplanetary dust particles. The dust collector of MIDAS will point at the comet and collect particles drifting outwards from the nucleus surface. MIDAS is based on an Atomic Force Microscope (AFM), a type of scanning microprobe able to image small structures in 3D. AFM images provide morphological and statistical information on the dust population, including texture, shape, size and flux. Although the AFM uses proven laboratory technology, MIDAS is its first such application in space. This paper describes the scientific objectives and background, the technical implementation and the capabilities of MIDAS as they stand after the commissioning of the flight instrument, and the implications for cometary measurements.