The SCALE instrument (Short Comb Atmospheric LIDAR Experiment) is an innovative micro-comb frequency LIDAR concept designed to perform column measurements of atmospheric greenhouse gases. At the end of 2020, CNES initiated an Exploratory Project (“PEX”) to develop and validate an experimental airborne version of the SCALE instrument, targeting CO₂ as the key molecule to accurately assess and understand its performance.

An initial airborne campaign conducted in 2023 as part of MAGIC demonstrated the relevance of the SCALE concept for CO₂ measurements and identified some limitations of the instrument.
The second campaign, conducted in October 2024 with an improved SCALE instrument, gathered extensive measurements alongside ground-based references (three EM27 instruments from LMD, CNES, and LERMA) and balloon-based references (two AirCores from LMD/CNES). This collaboration is expected to enable the detailed performance analyses anticipated.

For SCALE, the next steps will involve extrapolating these performance metrics to a satellite configuration of a SCALE-type instrument and evaluating the contribution that these active measurements could make to CO₂ assimilation models.