Observatory

The Orbiting Carbon Observatory (OCO) was a dedicated spacecraft that carried a single instrument comprised of three high resolution grating spectrometers. The instrument, developed by Hamilton Sundstrand Sensor Systems, would have acquired the most precise measurements of atmospheric CO₂ ever made from space. The spacecraft, developed by Orbital Sciences Corporation, was based upon the LeoStar-2 architecture. The same LeoStar-2 design was used on the successful Earth orbiting SORCE and GALEX missions. The Observatory was launched from the Vandenberg Air Force Base in California on a dedicated Taurus XL rocket on February 24, 2009. Although OCO failed to reach orbit, the Observatory would have flown in a near polar orbit that enabled the instrument to observe most of the Earth's surface at least once every sixteen days.

The abundance of CO₂ in the atmosphere varies both with time of day and with season. OCO measurements would record changes in CO₂ abundance over annual seasonal cycles. To remove the effect of changes in CO₂ abundance over each day, and discriminate between seasonal variations and long term changes, OCO would have always acquired measurements at the same time of day. Thus, the spacecraft would fly in Sun synchronous orbit so that all observations took place at about 1:18 PM.

The Observatory would fly in loose formation with a series of other Earth orbiting satellites known as the Earth Observing System Afternoon Constellation, or the A-train. This coordinated flight formation would enable researchers to correlate OCO data with data acquired by other instruments on Earth observing spacecraft. In particular, Earth scientists would have compared OCO data with nearly simultaneous measurements acquired by the Atmospheric Infrared Sounder (AIRS) instrument. The AIRS instrument files on the Earth Observing System Aqua platform.

To provide the mission with additional flexibility, the Observatory would have acquired 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 the Earth's surface. Glint Mode 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. The OCO Science Team would have compared Target Mode measurements with those acquired by ground based and airborne instruments to calibrate the OCO instrument and validate mission data.

The Observatory had a planned operational life of 2 years.