The NASA Orbiting Carbon Observatory Mission

The orbiting carbon observatory (OCO) is a NASA Earth system science pathfinder (ESSP) mission that is currently under development at the Jet Propulsion Laboratory (JPL). OCO will make global, space-based measurements of atmospheric carbon dioxide (CO
₂
) with the precision, resolution, and coverage needed to characterize regional-scale sources and sinks of this important greenhouse gas. The observatory consists of a dedicated spacecraft bus that carries a single instrument. The bus employs single-string version of orbital sciences corporation (OSC) LEOStar-2 architecture. This 3-axis stabilized bus includes a propulsion system for orbit insertion and maintenance, provides power, points the instrument, receives and processes commands from the ground, and records, stores, and downlinks science and engineering data. The OCO instrument incorporates 3 co-boresighted, high resolution grating spectrometers that will make coincident measurements of reflected sunlight in near- infrared CO
₂
and molecular oxygen (O
₂
) bands. The instrument was designed and manufactured by Hamilton Sundstrand (Pomona, CA), and then integrated, flight qualified, and calibrated by JPL. It is scheduled for delivery to OSC (Dulles, VA) for integration with the spacecraft bus in the spring of 2008. OCO will be launched from the Vandenberg Air Force Base on a dedicated OSC Taurus XL launch vehicle in December 2008. It will fly in formation with the earth observing system afternoon constellation, a group of satellites that files in a 98.8 minute, 705 km altitude, sun-synchronous orbit. This orbit provides coverage of the sunlit hemisphere with a 16-day ground track repeat cycle. OCO will fly ~4 minutes ahead of the EOS Aqua platform, with an ascending nodal crossing time of ~1:26 PM. The OCO science data will be transmitted to the NASA ground network stations in Alaska and Virginia, and then transferred to the OCO ground data system at JPL. There, the CO
₂
and O
₂
spectra will be analyzed by the OCO Science Team to provide spatially resolved estimates of the column-averaged CO
₂
dry air mole fraction, X
<sub>CO

2</sub>
. These measurements are expected to improve our understanding of the nature and processes that regulate atmospheric CO
₂
enabling more reliable forecasts of CO
₂
buildup and its impact on climate change.