Monitoring anthropogenic CO2 emissions from space: Insights from NASA's Orbiting Carbon Observatory-3 (OCO-3) mission

As global efforts intensify to verify emission reduction goals, the precise monitoring of CO₂ emissions from human activities becomes increasingly crucial. While missions like GOSAT and OCO-2 have enhanced our understanding of the carbon cycle, their ability to monitor emissions from "hot spots" such as urban areas and  industrial facilities is limited by their spatio-temporal coverage constraints.

In contrast, the OCO-3 instrument, operated aboard the International Space Station, adopts a targeted observation approach specifically designed for monitoring urban emissions. Through its Snapshot Area Mapping (SAM) mode, OCO-3 captures multiple adjacent swaths of XCO₂ observations in a two-dimensional sweeping pattern over an area approximately 80x80 km². This unique feature of the SAM mode, along with frequent revisit times, generates a robust dataset ideal for studying the carbon cycle at urban and local scales.

In this presentation, we will highlight scientific findings from studies utilizing the rich information provided by these fine-scale CO₂ maps. We will illustrate how OCO-3 SAM data can be utilized to constrain CO₂ emissions across entire city domains down to individual point sources using various approaches such as Gaussian plume, cross-sectional flux, and integrated mass enhancement methods.

We will also focus on innovative studies demonstrating how OCO-3 SAM data, when combined with measurements from other space- and ground-based sensors, can yield information about emission ratios of co-emitted gases, providing insights into factors like combustion efficiencies on sub-city scales. Additionally, we will discuss the potential of using SAM observations to disaggregate sector-specific emissions over megacities like Los Angeles – a crucial aspect in assessing the effectiveness of local emission reduction policies.

We will conclude this presentation by discussing the implications of this dataset for future GHG sensors and the role these can play towards developing an independent, atmospheric data-based GHG Measurement, Reporting, and Verifying (MRV) system in the future.