Quantifying CO2 Emissions From Smaller Anthropogenic Point Sources Using OCO-2 Target and OCO-3 Snapshot Area Mapping Mode Observations

We quantify CO₂ emissions from smaller anthropogenic point sources compared with earlier satellite studies, which have mostly focused on mid-sized (∼10 MtCO₂/year) and larger fossil fuel burning power plants. Two types of Orbiting Carbon Observatory (OCO) observation modes are used: OCO-2 Target mode and OCO-3 Snapshot Area Mapping (SAM) mode. Methods previously used with OCO-3 SAMs are adapted to quantify CO₂ emissions with OCO-2 Targets for the first time, demonstrating a similar capability to track emission changes at the Bełchatów Power Station. SAMs and Targets are then applied to quantify emissions from smaller sources in Canada: the Boundary Dam and Poplar River Power Stations in Saskatchewan, and the Suncor and Syncrude Mildred Lake mined oil sands processing facilities in northern Alberta. We verify our method on the nearby Colstrip Power Station in Montana by comparison with hourly reported values. For Canadian sources, only annual emissions are reported, to which our emission estimates cannot be directly compared. Emissions derived from a single satellite overpass correspond to daily or finer temporal scales and thus do not account for source intermittency or variability, which requires multiple revisits to reliably estimate annual emissions. Finally, we average OCO-3 SAMs on repeated revisits to improve weak enhancement signals above background noise. Averaging SAMs yields mixed results, with improvements achieved only under certain conditions. These studies help to clarify the capabilities and limitations of CO₂ point source emission quantification with current satellites in advance of plans for operational monitoring with future CO₂ satellite missions.