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Airborne dust monitoring is crucial to characterize Martian atmosphere’ thermal structure, balance and dynamics. In order to achieve this objective, the MicroMED instrument has been selected to join the Dust Suite payload within the ExoMars 2020 mission. The particle analyzer is mainly developed to characterize the dust on Mars but, the instrument is suitable to be mounted on different landers or rovers thanks to the limited mass and size. In this study, the design of the instrument has been reported as long as preliminary testing in representative environment of a mockup of the pumping system. [ABSTRACT FROM AUTHOR]

Suspended dust plays a critical role in regulating the Martian climate by influencing the atmospheric thermal gradient, altering the amount of infrared and visible energy absorbed and scattered by the atmosphere, and acting as condensation nuclei for CO 2 ice-clouds particles. There are many well demonstrated, dust-related effects on martian climate which depend on dustsize, concentration, chemical and bulk composition. Currently, an accurate estimation of these parameters is lacking as they are derived from indirect measurement of the optical depth acquired from the surface and orbital data. These indirect measurements require a priori assumptions on the grain distribution curve and are hence subject to possible biases. To overcome these limitations, an optical particles counter called MicroMED has been developed under the National Institute of Astrophysics (INAF) leadership. MicroMED can measure the sizes of individual dust grains in a specific volume of air thus providing the grain size distribution and concentration. MicroMED has been selected to join the Dust Complex payload on board the ExoMars 2022. The Flight Model of the instrument has been developed and optimized starting from two prototype BreadBoard versions. Here we present the sub-systems that constitute MicroMED and their testing and characterization process, performed using the Breadboard models. We discuss the optimizations and improvements introduced on the basis of the prototype results and the overall performances of the final design. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• MicroMED is the first OPC developed to monitor airborne dust on Mars. • MicroMED is characterized by low mass, size, and power consumption. • The optical design is simplified by using an optical fibre coupled to a laser source. • The optical system is designed to detect dust particles with diameters ≥ 0.4 µm. Airborne dust monitoring is crucial to characterize the thermal structure and evolution of the Martian atmosphere and climate. For this purpose, the MicroMED instrument has been selected within the ExoMars program to be deployed on Mars. It is an optical particle counter that measures the dust amount and size distribution of airborne dust close to the Martian surface. MicroMED is characterized by low mass, size and power consumption and is suitable to be accommodated on both rovers and landers. In this paper, the MicroMED optical design is described along with the analysis performed to prove compliance with all requirements needed for its nominal performance. [ABSTRACT FROM AUTHOR]

• Developed of an optical particle counter able to work in atmospheric Martian condition. • Developed a particular solutions in order to verify the properties of aspiration flow. • Measurement of the maximum displacement of flow outgoing from inlet as function of aspired particles. • Verify of the fluid dynamic properties after to change external Inlet of sensor. Suspended dust has a prominent role in Martian climatology. Several significant dust related phenomena can be observed at various scales, starting from global dust storms to local dust devils, which have important effects such as the increase of troposphere temperature, the modification of the wind regime and the localized motion of sand at the surface. These phenomena depend on dust grain characteristics such as the size distribution or the chemical and bulk composition. Currently, we do not have direct measurement of the dust properties; the only available information in this regard are derived from spectrometric measurements, optical depth, and albedo coming from instruments aboard satellites and in-situ. Herein, we describe the tests performed on the optical particle counter named MicroMED, designed and built to perform the first ever direct in-situ measurement of suspended dust grains in the Martian atmosphere close to the surface. MicroMED is a dust particle size analyzer which was selected to join the Dust Complex payload aboard the ESA/Roscosmos ExoMars 2022 mission. It has the capability to suck in dust that is suspended in atmosphere and to measure the sizes of single grain. The sensor sucks in the dust grains using a sampling system, guides the grains through ducts and concentrates them in an area illuminated by laser. Detecting the intensity of the light scattered by the grains during the crossing through the illuminated area, it is possible to determinate the size of grain. Here we present the innovative techniques in order to verify the performances in terms of dust suction efficiency of the MicroMED Flight Model, using a prototype called MM1. [ABSTRACT FROM AUTHOR]

• The instrument is able to detect particles with high efficiency for most cases. • Effect of environmental parameters on MicroMED's efficiency were analyzed. • The optimum operating conditions of the pump were found. • CFD analysis showed criticalities in MicroMED's Breadboard allowing a design update. Characterization of dust is a key aspect in recent space missions to Mars. Dust has a huge influence on the planet's global climate and it is always present in its atmosphere. MicroMED is an optical particle counter that will be part of the "Dust Complex" suite led by IKI in the ExoMars 2020 mission and it will determine size distribution and concentration of mineral grains suspended in martian atmosphere. A Computational Fluid Dynamic (CFD) analysis was performed aimed at the optimization of the instrument's sampling efficiency in the 0.4–20 µm diameter range of the dust particles. The analysis allowed to understand which conditions are optimum for operations on Mars and to consequently optimize the instrument's fluid dynamic design. [ABSTRACT FROM AUTHOR]