MicroMED (Micro Martian Environmental Dust Systematic Analyzer (MEDUSA)) instrument was selected for the ExoMars 2020 mission to study the airborne dust on the red planet through in situ measurements of the size distribution and concentration. This characterization has never been done before and would have a strong impact on the understanding of Martian climate and Aeolian processes on Mars. The MicroMED is an optical particle counter that exploits the measured intensity of light scattered by dust particles when crossing a collimated laser beam. The measurement technique is well established for laboratory and ground applications but in order to be mounted on the Dust Suite payload within the framework of ExoMars 2020 mission, the instrument must be compatible with harsh mechanical and thermal environments and the tight mass budget of the mission payload. This work summarizes the thermo-mechanical design of the instrument, the manufacturing of the flight model and its successful qualification in expected thermal and mechanical environments.

Outgassing or thruster’s generated contaminants are critical for optical surfaces and optical payloads because scientific measurements and, in general, the performances can be degraded or jeopardized by uncontrolled contamination. This is a well-known issue in space technology that is demonstrated by the growing usage of quartz crystal microbalances as a solution for measuring material outgassing properties data and characterizing the on-orbit contamination environment. Operation in space requires compatibility with critical requirements, especially the mechanical and thermal environments to be faced throughout the mission. This work provides the design of a holding structure based on 3D printing technology conceived to meet the environmental characteristics of space application, and in particular, to face harsh mechanical and thermal environments. A kinematic mounting has been conceived to grant compatibility with a large temperature range, and it has been designed by finite element methods to overcome loading during the launch phases and cope with a temperature working range down to cryogenic temperatures. Qualification in such environments has been performed on a mockup by testing a prototype of the holding assembly between −110 ${}^{\circ }$C and 110 ${}^{\circ }$C and allowing verification of the mechanical resistance and stability of the electrical contacts for the embedded heater and sensor in that temperature range. Moreover, mechanical testing in a random environment characterized by an RMS acceleration level of 500 m/s² and excitation frequency from 20 to 2000 Hz was successfully performed. The testing activity allowed for validation of the proposed design and opened the road to the possible implementation of the proposed design for future flight opportunities, also onboard micro or nanosatellites. Moreover, exploiting the manufacturing technology, the proposed design can implement an easy assembling and mounting of the holding system. At the same time, 3D printing provides a cost-effective solution even for small series production for ground applications, like monitoring the contaminants in thermo-vacuum chambers or clean rooms, or depositions chambers.

MicroMED is an optical particle counter that has been selected to join the ExoMars 2020 mission as part of the Dust Suite payload. The instrument will allow monitoring airborne dust of the Red Planet, focusing on the characterization of the atmosphere thermal structure, balance and dynamics. The MicroMED has been developed by consortium of Italian research Institutes and Spanish space agency. This study summarizes detailed thermo-mechanical design of the instrument and its validation in expected mechanical and thermal environments.

This work describes the qualification of MEMS differential pressure sensors to be used in a particle analyzer for Mars 2020. Two different types of sensors have been initially considered MEMS-33A-001D and NPH-8-002.5-GH, in order to select the most suitable in terms of S/N ratio and sensitivity. Sensors have been calibrated at ambient pressure using as reference a water column differential manometers, selected for the unmatchable stability, key property for tests expected to span across many days. The pressure signal has been generated using the water column manometer itself, allowing to reach the full scale of the instruments and by means of a vane pump in low pressure environment where a capacitive manometer has been used as reference. No variation in the sensor sensitivity has been evidenced after exposure to the expected temperature range for the instruments mounted on the platform of the ExoMars Lander. The final selection of the sensor to be flight-qualified has been made on the SNR because both candidates proved to be compatible with the mechanical loads expected during launch and Martian landing and the expected space environment through all mission phases.