# Structural Optimization of MicroMED Dust Analyzer
## 1 Introduction  
Aerospace components demand lightness as an essential design characteristic, a particularly relevant requirement in the space industry as well. Indeed, mass reduction is considered one of the most valuable drivers during the thermomechanical design of space hardware and aerospace components [1; 2; 3; 4]. This objective can be effectively tackled by coupling the choice of high strength-to-density ratio materials with structural optimization, resulting in performant and lightweight components. However, due to their excessively high costs in procurement and manufacturing, qualification, and certification, [5] innovative materials have had low mileage concerning the design of spacecrafts components. Conversely, structural optimization tools played a significant role in the aerospace industry. Optimal design proposals can be obtained by exploiting a streamlined design-to-manufacturing track. Among the non-conventional thermomechanical design approaches, the Topology Optimization (TO) perfectly fits this framework. The TO couples mathematical optimization algorithms to Finite Elements Analysis (FEA) to suggest structural design outcomes ensuring an optimal material distribution within a given reference domain. Specified optimization objectives, design constraints, loads, and boundary conditions are applied to the study case [6]. Stresses, displacements, natural frequencies, and geometrical featuresare typically encompassed as design constraints towards the achievement of an optimal solution, although they can also be included as the TO objectives to be pursued within the optimization iterations [7]. Since the optimal material distribution may lead to complex geometry, the TO outcomes can become ready-made Additive Manufacturing (AM) designs. Alternatively, a further post-processing stage can be introduced to adapt the design for traditional--material subtractive--manufacturing techniques. Nevertheless, this strategy allows to bypass the time-consuming engineering and iterative design mechanisms, as the optimal solution coincides with the outcome of the process itself. The TO is rapidly widespread in aerospace components design and improvement, and a multitude of examples can be retrieved in the literature [8; 9]. Worth mentioning are the VEGA launcher connector support [10], a structural component obtained via a frequency-driven TO, or the Airbus A320 nacelle hinge bracket [11], an aircraft part manufactured exploiting Additive Layer Manufacturing (ALM) after its optimization. Another significant example is the antenna support for the ESA Sentinel 1 satellite [12; 13], a component redesigned exploiting TO towards the achievement of mass minimization and finally manufactured via Selective Laser Sintering (SLS). This research work extensively describes the MicroMED Dust Analyzer Optical Bench (OB) TO-driven redesign workflow and results assessment activities. The instrument is an amplitude-dependent single Optical Particle Counter (OPC) designed and qualified for the ESA ExoMars 2022 mission towards Mars [14; 15; 16]. The instrument includes several subassembibles and hardware components arranged in a compact and lightweight design, whose locations are depicted in Figure 1 and was intended to infer the airborne dust size and size distribution in situ at the lowest troposphere of the Red Planet [17; 18; 19]. This would be a groundbreaking achievement because, at present, data about dust on Mars were exclusively acquired using remote sensing (e.g., thermal IR instruments, near-IR spectrometers, and Terrestrial ground-based telescopes). A proper fluidic system was designed to suction the Martian aerosol--a multiphase mixture of gases and solid dust particles--and transfer it to the MicroMED Optical Head (OH). There, the fines are invested by a collimated low-power NIR laser beam (having a  
Figure 1: MicroMED Dust Analyzer model overview (**a**) and exploded view (**b**). The main subassemblies are highlighted: A.