End to end simulation chain for flux restitution of the spectral imaging concept Nanocarb

CH₄ is the second anthropogenic contributor to global warming after CO₂. Monitoring methane emissions is therefore essential in order to mitigate climate change. Satellite missions have the potential to offer more spatial coverage than ground stations, however their coverage is currently insufficient. This leads to the development of satellite missions that can be envisaged as constellations. For this purpose a concept currently studied is Nanocarb, relying  on the patent  WO2018002558A1 (ImSPOC). This instrument is a compact and robust spectral imaging concept relying on a static array of Fabry-Perrot interferometers to retrieve partial interferograms of the incident radiance. This study is focused on developing and using the appropriate tools and models to simulate the flux restitution performances of a methane focused Nanocarb instrument with two intertwined inverse approaches.

We have developed an end-to-end simulation chain of the flux restitution by the instrument Nanocarb. First an atmospheric situation is simulated from an inventory such as TNO's by the chemistry transport model Chimere. Then this atmospheric situation is used to simulate Nanocarb measurements, with a direct and backward ImSPOC conception and processing software called MEDOC which relies on the radiative transfer code 4A-OP. Those simulated measurements have realistic noise added and are used to recover atmospheric methane columns. Eventually this new atmospheric situation allows for the retrieval of atmospheric methane fluxes, thanks to the Community Inversion Framework (CIF), coupled with Chimere. Those fluxes can be compared to the initial situation to quantify the introduced biases.

We present this simulation chain, and specifically developments made on Medoc and columns obtained for an atmospheric simulation in the north of France. This simulation chain aims to model the flux retrieval ability of the instrument Nanocarb for point sources and area sources of methane.