OCO-2 + OCO-3 (Orbiting Carbon Observatory)

NASA’s column-averaged atmospheric CO₂ mission family. OCO-2 (2014–) flies a dedicated sun-synchronous orbit; OCO-3 (2019–) mounted on the ISS, sees mid-latitudes (±52°). Together they generate the canonical NASA atmospheric CO₂ record, plus the unanticipated bonus of solar-induced fluorescence (SIF) as a proxy for photosynthesis.

What it sees

• Column-averaged CO₂ (XCO₂) — total dry-air-mole-fraction column from satellite to surface, derived from O₂ A-band and CO₂ near-infrared absorption
• Solar-Induced Fluorescence (SIF) — chlorophyll fluorescence emitted by plants during photosynthesis; a remote-sensing proxy for gross primary productivity (GPP)
• ~3 km nadir pixel footprint; OCO-3 SAM mode does targeted ~80×80 km dense raster over specific points

Why it matters

• OCO-2 + OCO-3 is the longest continuous space-based CO₂ record (2014–present, plus the predecessor GOSAT from JAXA going back to 2009).
• XCO₂ data feeds flux-inversion models (the OCO MIP suite) that estimate continental + regional CO₂ source/sink budgets — informs IPCC reporting and national greenhouse-gas accounting.
• SIF is the single most important new variable for carbon-cycle science since the 1990s — direct observation of photosynthesis from space.
• OCO-3 SAM mode can target specific point sources: power plants, megacities, volcanic outgassing.

Where to get the data

• earthaccess Python: short_name="OCO2_L2_Lite_FP", OCO3_L2_Lite_FP, OCO2_L2_Lite_SIF, OCO3_L2_Lite_SIF
• GES DISC: disc.gsfc.nasa.gov (OCO products)
• OCO-2/3 MIP: gml.noaa.gov/ccgg/OCO2_v10mip/ — flux-inversion intercomparison outputs

What it enables

• Atmospheric CO₂ trend mapping (global + regional)
• Anthropogenic CO₂ source attribution (cities, power plants — via SAM mode)
• Biospheric uptake estimation via SIF (forests, croplands, grasslands as carbon sinks)
• Volcanic + wildfire carbon emission quantification
• Cross-validation of flux-tower + atmospheric-inversion estimates
• Climate-model evaluation (CMIP comparisons)

Gotchas

• OCO-3 has ±52° latitude coverage only. ISS orbit; no polar CO₂ from OCO-3. Use OCO-2 for high latitudes.
• Cloud-screening removes most observations. A scene-level success rate of 10-25% is typical; budget for sparse coverage in cloudy regions.
• The XCO₂ signal is ~2 ppm seasonal cycle on top of ~420 ppm background — sensitivity to systematic errors is high. Bias corrections + quality filtering are essential.
• SIF is NOT a calibrated photosynthesis measurement. It correlates with GPP but the relationship varies by ecosystem, species, water stress, etc. Use as a proxy, not a direct measurement.
• OCO-3 SAM acquisitions are scheduler-driven — not every facility gets observed every overpass. Check the SAM target list.

Related missions

• GOSAT / GOSAT-2 (JAXA): predecessor + complementary CO₂ + CH₄ mission family.
• TROPOMI (S-5P): NO₂ + CH₄ + CO + HCHO at coarser resolution; complementary atmospheric chemistry.
• MERRA-2 (GMAO): assimilated atmospheric reanalysis — combine OCO with MERRA-2 for advection + flux inversion.
• OCO-2 v11 + OCO-3 v11: latest releases as of 2026; recompute if you have older v10 cached.

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