MiLi project has successfully completed the Requirement Definition Phase, which was led by the scientific requirements study. During the production of this study, a complete research on the possible scientific returns of the use of a LiDAR in Mars were conducted. More precisely, the following topics were addressed:
a) determination of the aerosol optical (extinction and backscatter coefficients, depolarization ratio) and macro-physical (altitude range, geometrical layer thickness) properties, by using generalized lidar-based methods.
b) estimation of the aerosol micro-physical (effective radius, mass loads) properties by applying advanced inversion methods and models.
c) study of the interactions between dust and clouds (e.g. nucleation, dust scavenging) and the seasonal and year-to-year variability.
The scientific requirement document was then used as the main input to specify the MiLi LiDAR technical requirement document, which has setup a solid base for the ongoing Design Definition Phase.
The design phase started with a concurrent engineering study, carried out by the whole team with the knowledgeable support of the DLR (German Aerospace Center) engineers, at the Institute of Space Systems in Bremen. This study, allowed the consortium to achieve, with a multi-disciplinary approach, the following objectives in a very short period of time:
a) Agreement on requirements and identification of potential non-compliances.
b) Down-selection of identified LiDAR system options into an instrument preliminary design.
c) Define and analyse the initial system budgets (e.g. power, thermal and mass).
d) Identify the required technology test to be carried out, as well the validation and prototyping planning.
In parallel with the definition and design of the LiDAR instrument, the consortium has made strong progress on the maturing of the basic technologies, that will be used as building blocks in the final instrument assembly.
• One of the challenges targeted by MiLi is to fabricate lightweight athermal opto-mechanical components based on novel ceramic nanocomposites that can withstand the severe working conditions under which MiLi’s LiDAR must work. During this period the CINN (Spanish Research Centre of Nanomaterial and Nanotechnology) has worked on the conditioning of innovative ceramic powders (aluminosilicates and metallic carbides) selected for ensuring the thermal stability of the LiDAR telescope. The efforts carried out have allowed to define the best conditions for preparing stable suspensions from the raw materials, and evolved the techniques for sintering by Spark Plasma technique. Both innovations will be used to obtain materials with zero CTE (Coefficient of Thermal Expansion), as well as ready-to-press granules.
• Another innovation of the MiLi project, is the use of new evolving optoelectronics technologies for this kind of instrument, that has never been used before. This is the case of the SiPM (Silicon PhotoMultiplier) sensors, that require less conditioning that typica APD (Avalanche Photodetector) and have a wider dynamic range. During this period INTA (Spanish National Institute of Aerospace Technique) has been characterizing the most advanced sensors of this kind and testing them to assure their suitability for LiDAR instruments.
