Limiting Factors of the Orbiting Carbon Observatory Missions for Monitoring Urban Emissions

A growing number of space-based platforms, like the Orbiting Carbon Observatory (OCO-2 and OCO-3) missions, observe Earth’s atmospheric carbon dioxide (CO2) concentrations with high accuracy and precision. With the original goal of constraining natural CO2 fluxes at regional to global scales, these instruments have now become popular tools for studying anthropogenic emissions from cities around the world. As signatories of the Paris Climate Agreement are expected to produce nationally determined contributions (NDC) to global carbon emissions, continued monitoring, reporting, and verification (MRV) of these estimates will be essential. While the use of OCO-2 and OCO-3 missions for MRV purposes is increasing, several physical and environmental factors limit data collection. Using the continental United States as a test case, the influences of orbital mechanics and environmental factors on local- and nationallevel emissions estimates are explored. Results suggest that, due to environmental factors, western regions of the U.S. are more likely to be constrained at a sub-annual scale than eastern regions. Additionally, the physical characteristics of the instruments’ setups vary the effectiveness of observations in both space and time. Implications for observation-derived emission estimates at local and national scales and remedies for such shortcomings in future missions are discussed.