The GeoCarb greenhouse gas retrieval algorithm: simulations and sensitivity to sources of uncertainty

The Geostationary Carbon Cycle Observatory (GeoCarb) was selected as NASA's second Earth Venture Mission (EVM-2). The scientific objectives of GeoCarb were to advance our knowledge of the carbon cycle, in particular, land-atmosphere fluxes of the greenhouse gases carbon dioxide (CO.sub.2) and methane (CH.sub.4) and the effects of these fluxes on the Earth's radiation budget. GeoCarb would retrieve column-integrated dry-air mole fractions of CO.sub.2 (XCO2), CH.sub.4 (XCH4) and CO (X.sub.CO ), important for understanding tropospheric chemistry), in addition to solar-induced fluorescence (SIF), from hyperspectral resolution measurements in the O.sub.2 A-band at 0.76 µm, the weak CO.sub.2 band at 1.6 µm, the strong CO.sub.2 band at 2.06 µm, and a CH.sub.4 /CO band at 2.32 µm. Unlike its predecessors (OCO-2/3, GOSAT-1/2, TROPOMI), GeoCarb would be in a geostationary orbit with a sub-satellite point centered over the Americas. This orbital configuration combined with its high-spatial-resolution imaging capabilities would provide an unprecedented view of these quantities on spatial and temporal scales accurate enough to resolve sources and sinks to improve land-atmosphere CO.sub.2 and CH.sub.4 flux calculations and reduce the uncertainty of these fluxes.