Regional flux estimation of greenhouse gases using GOSAT and airborne spectrometers

GOSAT and GOSAT-2 have been providing long term radiance spectra data with Fourier transform spectrometer technology since 2009 and 2018, respectively. With FTS multiplex advantages, they can measure carbon dioxide (CO$ _{2}$) and methane (CH$ _{4}$) absorption bands of solar reflected light with two linear polarizations and thermal emission, simultaneously. By combing all these spectra data, partial column densities of upper (4-12 km) and lower (0-4 km) troposphere can be retrieved even under thick aerosol conditions. With two-axis pointing systems, they can target large point sources and mega cities and have shown enhancement of CO$ _{2}$ and CH$ _{4}$. However, local flux estimations using GOSAT include large uncertainties due to too large footprint, lack of proper upwind reference observation, and lack of wind information. To contribute to the global stocktake of the Paris Agreement, we need an observation system to estimate local flux from individual source sectors. We have developed imaging spectrometer suites with optimized spectral resolution and coverage for air borne observations. We flew over industrial zoned and we acquired imaging data oxygen (O$ _{2}$), CO$ _{2}$, CH$ _{4}$ and nitrogen dioxide (NO$ _{2}$) under different wind conditions. The NO$ _{2}$ image with plume direction and spreading have detected CO$ _{2}$ sources and provided wind information.