An Overview of the First Year of the OCO-3 Mission

The Orbiting Carbon Observatory 3 (OCO-3) was installed on the International Space Station (ISS) in May 2019 and will continue the observation of global CO₂ and solar-induced chlorophyll fluorescence (SIF) observations using the flight spare instrument from OCO-2. This talk will focus on the science data products, early operations, abd a few highlights from early mission data.

The low-inclination ISS orbit lets OCO-3 sample the tropics and sub-tropics across the full range of daylight hours with dense observations at northern and southern mid-latitudes (+/- 52º). The combination of these dense CO₂ and SIF measurements provides continuity of data for global flux estimates as well as a unique opportunity to address key deficiencies in our understanding of the global carbon cycle. The instrument utilizes an agile, 2-axis pointing mechanism (PMA), providing the capability to look towards the bright reflection from the ocean and validation targets. The PMA also allows for the collection of dense datasets over 80km by 80km areas called snapshot area maps (SAMs).

The in-orbit check out of the instrument was conducted through July 2019. In this phase the engineering team verified the performance of all systems, the calibration team began collecting the needed calibration data, and the mission operations team verified the performance of all measurement modes and the mission operations planning tools. Since August 2019, OCO-3 has been collecting routine nadir, glint, target, and SAM data.

Target mode observations over surface-based Total Carbon Column Observing Network (TCCON) sites help to identify and minimize potential instrument biases in the OCO-3 data. Other validation activities include direct comparisons to XCO₂ estimates from OCO-2 and comparisons to predictions from near-real-time models. These comparisons will be discussed and early results will be presented. In addition, several hundred SAMs have been collected over (mega-)cities, powerplants, volcanos, and other terrestrial carbon focus areas.  The steadily growing number of SAM observations provides a unique dataset for scientific studies on local scales. We discuss the potential of these observations, alone and in conjunction with simultaneous observations from other space-based sensors, to yield greater insights into carbon cycle science.