NASA's Orbiting Carbon Observatory-2 (OCO-2) was a replacement mission for the original OCO platform, which failed during launch. Launched on July 2, 2014, OCO-2 acquires space-based global measurements of atmospheric carbon dioxide (CO₂) with the precision, resolution, and coverage needed to characterize its sources and sinks (fluxes) on regional scales (≥1000km). Data from OCO-2 help quantify CO₂ variability over seasonal cycles and are also being used to help validate space-based measurement approaches and analysis concepts that could be used for future systematic CO₂ monitoring missions.

OCO-2 flies in a Sun-synchronous, near-polar orbit with a group of Earth-orbiting platforms with synergistic science objectives that cross the equator around 13:30 hours Mean Local Time (MLT). Near-global coverage of the sunlit portion of Earth is provided over a 16-day (233-revolution) repeat cycle. OCO-2’s single instrument incorporates three high-resolution grating spectrometers that measure the near-infrared absorption of reflected sunlight by carbon dioxide and molecular oxygen.

The OCO-2 instrument acquires data in three different measurement modes. In Nadir Mode, the instrument views the ground directly below the spacecraft. In Glint Mode, the instrument tracks near the location where sunlight is directly reflected on Earth's surface, which enhances the instrument's ability to acquire highly accurate measurements, particularly over the ocean. In Target Mode, the instrument views a specified surface target continuously as the satellite passes overhead. Target Mode provides the capability to collect a large number of measurements over sites where alternative ground-based and airborne-instruments also measure atmospheric CO₂.