* 24 February 2009 - Orbiting Carbon Observatory was launched on a Taurus XL rocket but failed to achieve orbit when the fairing failed to separate from the satellite.
* 1 February 2010 - The 2010 President's budget included funding for development and re-flight of an OCO replacement.
* October 2010 - The Orbiting Carbon Observatory-2 project went into implementation phase.
* 2 July 2014 - OCO-2 was successfully launched from Vandenberg Air Force Base with a Delta II rocket.
* 2015 - Funding for the OCO-3 project cancelled.
* 22 December 2015 - OCO-3 project authorized to proceed. Funding was included in the 2016 spending bill.
* 16 March 2017 - OCO-3 was not included in the proposed FY2018 presidential budget.
* 23 March 2018 - Funding for the OCO-3 project was restored.
* May 2018 - Instrument underwent TVAC testing.
* 4 May 2019 - Launched using a Falcon 9 rocket from Cape Canaveral Air Force Station. The delivery was part of SpaceX CRS-17, which also included delivery of STP-H6 and a cargo resupply.
* After arrival - Robotic installation onto Exposed Facility Unit 3 (EFU 3) on the JEM-EF.