The OCO-3 Mission: Performance of the Snapshot Area Map and Target Mode Observations and Coincident Measurements with the OMPS and TROPOMI Air Quality Sensors

The Orbiting Carbon Observatory 3 (OCO-3) was launched to the International Space Station (ISS) on 4 May 2019 and was successfully installed on 10 May 2019. First Light occurred in late June 2019, and the in-orbit check out of the instrument extended through July 2019. OCO-3 records reflected sunlight in the near-Infra Red spectral region to estimate the column average CO₂ dry air mole fraction (XCO₂) and solar-induced chlorophyll fluorescence (SIF). It complements the OCO-2 mission by employing a dedicated Snapshot Area Mode (SAM) to map spatial areas of up to 80x80 km² on the Earth’s surface, including cities, volcanoes, and photosynthetically active surface types. The inclination of the ISS orbit limits OCO-3 to observations within +/- 52º latitude, but allows measurements at all times of day between sunrise and sunset to resolve diurnal variations in XCO₂ and SIF.

CO₂ emissions and air quality are closely linked, particularly over large urban agglomerates. OCO-3’s Snapshot Area Mode allows, for the first time, to conduct detailed studies of the relationship between CO₂ emissions and air quality tracers over megacities. Compared to CO₂, NO₂ is short-lived and can serve as indicator not only for temporally and locally enhanced fossil fuel emissions, but also for longer-term trends of urban development and growth. This presentation focuses on the comparison and correlation of OCO-3 SAM and Target Mode measurements of XCO₂ with NO₂ observations from NASA’s Ozone Monitoring and Profiler Suite on Suomi/NPP and JPSS-1 and ESA’s Sentinel-5 Precursor/TROPOMI. We present details on the performance of selected OCO-3 SAM and Target Mode observations, identify temporally and spatially near-coincident OMPS and TROPOMI measurements, and derive correlation statistics between CO₂ and the air quality tracers, with the aim to establish coincidence data record over the OCO-3 life time. For SIF, we report direct comparisons of OCO-3 and TROPOMI measurements.