The NASA Orbiting Carbon Observatory -2

The Orbiting Carbon Observatory-2 (OCO-2) is the first NASA satellite designed to measure atmospheric carbon dioxide (CO2) with the precision, resolution, and sampling needed to quantify surface fluxes on regional scales over the globe. OCO-2 is currently scheduled to launch in late 2014. It will fly in formation with the Afternoon Constellation (A-Train). This 705 km altitude, sun synchronous orbit has a 1:30 PM nodal crossing time and a 16-day ground track repeat period. The observatory carries and points a single instrument that incorporates 3, high-resolution, imaging, grating spectrometers. These spectrometers are designed to collect co-bore-sighted spectra of reflected sunlight in the CO2 bands centered near 1610 and 2060 nm, and in the molecular oxygen (O2) A-band centered near 764 nm. These co-bore-sighted soundings will be analyzed with a remote sensing retrieval algorithm to yield surface-weighted estimates of the column-averaged CO2 dry air mole fraction, XCO2. The instrument will collect 12 to 24 soundings per second along a narrow (0.8°) ground track, yielding > 200 soundings per degree of latitude or > 500,000 soundings over the sunlit hemisphere each day. Between 5 and 30% of these soundings are expected to be sufficiently cloud and aerosol free to yield full-column XCO2 estimates with accuracies of ~0.3% on regional scales. Once validated against surface in situ and remote sensing measurements, these XCO2 estimates can be combined with the ground based CO2 measurements and assimilated by chemical tracer transport models to quantify CO2 surface fluxes. Each cloud-free sounding also provides an estimate of the surface pressure, with accuracies around 1-2 hPa. While the planned, single data downlink each day will not support an operational weather forecasting schedule, these pressure estimates could be assimilated into numerical weather reanalysis models to assess their value for improving the coverage over the ocean, tropical continents, and other data sparse regions.