After defining the mission requirements and exploring several design concepts in our previous article, the next challenge was to transform those ideas into a functional prototype. A scientific instrument is only valuable if it can be operated efficiently in the field, especially during a Mars analog mission where time, mobility, and robustness are essential. This phase of the Caillou project focused on turning our concept into a compact synthetic Raman spectrometer ready for analog mission operations.

Developing an instrument for an analog mission means balancing many competing requirements. The system had to remain lightweight enough for easy handling, compact enough to fit on a rover, robust enough to withstand transportation, and simple enough to be operated with minimal training. Every design iteration involved trade-offs between functionality, manufacturability, and ease of use.

For the team, transitioning from abstract CAD models on a screen to working with the physical 3D-printed parts was a significant milestone in this project. Experiencing first-hand the practical challenges of hardware integration—such as adjusting mechanical tolerances to ensure the Raspberry Pi fits securely within the custom enclosure—provided valuable insights into the design process. Seeing the prototype take shape physically confirmed that our structural choices were moving in the right direction.

To guide our design decisions, we created a user story representing a typical scientific operation during AMADEE-27. Imagine a rover or an astronaut arriving at a location identified as scientifically interesting. The instrument is removed from its support and positioned above a rock using the visible laser as an aiming guide. Once correctly aligned, the onboard camera captures an image of the sample to provide visual context. The instrument is then lowered into its measurement position, where the Raman acquisition is simulated and a synthetic spectrum is generated. Finally, both the image and the synthetic spectrum are transmitted to the science team, allowing them to evaluate the sample and decide on the next exploration steps.

This operational scenario became the foundation of our design process. Every component and mechanical feature was selected to support this workflow while keeping the instrument as simple and reliable as possible. Rather than maximizing scientific performance, our priority was to reproduce the operational experience of using a compact Raman instrument. The prototype combines commercially available components within a custom-designed enclosure. We chose to use a Raspberry Pi, for its versatility and ease of use. It controls the laser, captures images with the camera, and manages data transmission, all while being powered by a lightweight power bank.

One of our practical design challenges was ensuring adaptability for different mission scenarios. To achieve this simply and robustly, we designed a modular enclosure where the top cover can be unscrewed and replaced depending on the user. This allows us to switch between a cover fitted with a rover mount and options with handles for manual operation, ensuring the prototype remains versatile without adding mechanical complexity.

Author: Léa Hourriez