SCARBO: A constellation of small satellites for the monitoring of anthropogenic greenhouse gases

The Space CARBon Observatory project (SCARBO), is a project funded by the European Union's H2020 research and innovation programme, supporting one of the key challenges of anthropogenic greenhouse gases (GHG) monitoring from space: a significant increase of the temporal revisit over the various sites of interest while meeting the accuracy and spatial resolution requirements. This is achieved by implementing a novel miniaturised static spectrometer on a constellation of small satellites. The project is coordinated by Airbus Defence and Space, and features a consortium of 8 European organisations, including scientific institutes and SMEs. The challenges identified at the start of the project such as the uncertainties due to aerosols, the provision of both high accuracy measurements and the high temporal frequency of GHG measurements have been investigated during the four year project. The SCARBO project has also addressed the technical feasibility of the miniaturised CO₂ and CH₄ instrument- NanoCarb - and performed simulations of the science data retrieval chain. The overall measurement concept was validated during an airborne campaign held in October 2020. The project has been successfully completed in December 2021, and has comforted the ambition to overcome the current technological and economical obstacles of other existing and planned GHG missions. It is demonstrated that an intraday revisit can be offered by a 24 small satellite constellation valuably complementing the reference Copernicus CO₂M mission. High accuracy measurements are achieved by collocating on NanoCarb satellites an ultra-compact aerosol sensor, SPEXone, and by cross-calibrating measurements with other CO₂ reference instruments such as CO₂M. The spectrometer technology has been raised from TRL2 to close to TRL5 with the development of a prototype for the airborne campaign. A market analysis assessed the commercial perspectives of the SCARBO mission services at global, regional and local scales, demonstrating SCARBO mission's added-value through the analysis of real-life use cases representative of CO₂ and CH₄ related issues. The paper presents the project outcomes in more details, together with the roadmap for future endeavours. With an unprecedented measurement frequency over the entire globe, the SCARBO constellation, costing no more than two mid-sized satellites, is a key step in European CO₂ and CH₄ emission tracing. Other complementary developments, such as HOLDON and LEMON projects, were also funded by the European Union's Horizon 2020 research and innovation program. Abstracts on these projects are submitted to the IAC B1.2 Earth Observation Symposium and B1.3 Earth Observation Sensors and Technology sessions.