The GeoCARB Mission

This paper presents a space mission (geoCARB) that would provide measurements of atmospheric carbon dioxide (CO₂), methane (CH₄), and carbon monoxide (CO) from geostationary orbit. The geoCARB mission would deliver multiple daily maps of column integrated mixing ratios of CO₂, CH₄, and CO over the observed landmasses at a spatial resolution of roughly 5 x 8 km., which will establish the scientific basis for CO₂ and CH₄ flux determination at the unprecedented time and space scale. This determination would produce a fundamental change in our scientific understanding of the terrestrial source/sink dynamics of carbon cycle as well as produce the kind of flux information that would be needed to support international agreements on greenhouse gas emission reductions.

The instrument would exploit four spectral regions: The Oxygen A-band for pressure and aerosols, the weak and strong bands of CO₂ near 1.61 and 2.06 microns, and a region near 2.32 microns for CO and CH₄. The O₂ and CO₂ band selection are very similar to the instrument aboard OCO-2, and so we envision OCO-2 in geostationary orbit with the addition of a fourth channel to measure CO and CH₄, but without an oceanic capability. The O₂ A-band also provides for retrieval of Solar Induced Fluoresce (SIF).

The geoCARB Mission’s persistent fine-scale mapping-like measurements, multiple times a day under changing conditions, enable significant advances on an important range of CO₂ issues: CO₂ fertilization, change in primary production because of nitrogen deposition, and the influence of climatic patterns on terrestrial sources and sinks. Similarly, the mission’s high space- and time-measurements of CH₄ enable important analyses of human impacts via agriculture and industry vs. natural phenomena on methane sources.

The geoCARB measurements of CO concentrations and SIF provide essential information for CO₂ and CH₄ source attribution. For example, CO helps distinguish between biotic fluxes of CO₂ and CH₄ from fluxes associated with combustion. SIF measurements are directly related to gross primary production (GPP; photosynthesis), and when coupled with inversions of concentrations, SIF can support partitioning of Net Ecosystem Exchange (NEE) into GPP and ecosystem respiration.

We will provide results for 3 orbital slots: 70°E, 110°E, and 90°W.