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.
ABSCO Tables Information
The ACOS/OCO-2/OCO-3 absorption coefficient (ABSCO) tables are “lookup tables” that supply cross section values for absorbing gases in the Level 2 algorithm retrieval process. They record molecular absorption cross-sections over the range of relevant wavelengths, temperatures, and pressures in units of cm2 /mol for the gases O2, H2O, and CO2.
Updated ABSCO tables are released together with each major build of the OCO-2 Level 2 algorithm and using the most recent tables is recommended.
Read the ABSCO User Guide for more information.