Abstract
MicroMED is an optical particle counter that will be part of the ExoMars 2020 mission. Its goal is to provide the first ever in situ measurements of both size distribution and concentration of airborne Martian dust. The instrument samples Martian air, and it is based on an optical system that illuminates the sucked fluid by means of a collimated laser beam and detects embedded dust particles through their scattered light. By analyzing the scattered light profile, it is possible to obtain information about the dust grain size and speed. To do that, MicroMED’s fluid dynamic design should allow dust grains to cross the laser-illuminated sensing volume. The instrument’s Elegant Breadboard was previously developed and tested, and Computational Fluid Dynamic (CFD) analysis enabled determining its criticalities. The present work describes how the design criticalities were solved by means of a CFD simulation campaign. At the same time, it was possible to experimentally validate the results of the analysis. The updated design was then implemented to MicroMED’s Flight Model.
Highlights
The optical particle counter MicroMED (Figure 1) [1,2,3,4,5] is conceived to provide the first ever in situ measurements of airborne dust in Martian atmosphere
ExoMars 2020 mission, and it is a miniaturized version of the sensor MEDUSA [6,7], previously developed at the INAF (Istituto Nazionale di AstroFisica) Astronomical Observatory of Capodimonte (OAC) in Naples, Italy, where the characterization of dust in Earth and planetary atmospheres has been the main focus of the research activities for years [8,9,10,11,12,13,14]
The Knudsen number (Kn) for MicroMED was calculated (Kn is the ratio of the gas mean free path to the instrument characteristic length), and it was verified that Kn < 0.1
Summary
The optical particle counter MicroMED (Figure 1) [1,2,3,4,5] is conceived to provide the first ever in situ measurements of airborne dust in Martian atmosphere. Theespecially sensing volume, dust grains detect large dust grains (15–20 μm in diameter) withWhile high crossing efficiency, in the presence of scatter light differently depending on their size and speed, so the amplitude and duration of the signals wind [1,2] These results highlighted the need for a detailed fluid dynamic analysis of the instrument are directly related to those characteristics of the dust grains. MicroMED’s design was updated to what is the Flight Model design in order to correct those issues The results for both CFD runs and laboratory tests show that a relevant improvement of the instrument’s efficiency has been obtained
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