The operations ramp-up phase refers to the period starting at the completion of the first spacecraft launch and commissioning, and continues until the Full Operational Capacity (FOC) is reached with the constellation. Major milestones are listed below:
| Date | Major milestones |
| 16 February 2016 | Successful Launch of S3A from Plesetsk, Russia. |
| 18 February 2016 | LEOP phase concluded successfully
|
| 26 February 2016 | Platform In-Orbit Verification completed |
| 04 March 2016 | Payload In-Orbit Verification completed
|
| 07 March 2016 | Cal/Val Phase of S3A commences |
| April/May 2016 | Mid-Term-Reviews for OLCI, SLSTR and SRAL |
| mid- May 2016 | Release of Level 1 and Level 2 sample data products to expert users for all instruments |
| 28-30 June 2016 | Expert users meeting – first feedback from S3 validation teams |
| 11/12 July 2016 | In-Orbit Commissioning Review (IOCR)– successful completion of commissioning phase, start of ramp-up phase (initial operational) |
| 13 July 2016 | ESA internal handover from development to operations team; Handover of flight operations from ESA to EUMETSAT |
| 10 October 2016 | Handover of Marine PDGS from ESA to EUMETSAT |
| 20 October 2016 | Release of OLCI Level 1 core data to all users |
| w/c 14 November 2016 (TBC) | Release of SLSTR Level 1 core data to all users |
| Early December 2016 (TBC) | Release of SRAL L1A, L1B and L2 NRT and STC core data to all users |
| January 2017 | Release of SRAL L1B core data to all users |
| Early 2017 | Release of OLCI Level 2 and SLSTR Level 2 |
| IOCR + 9 months | RORR: Routine Operation Readiness Review. End of S3A ramp-up phase. |
| Q3 2017 | Release of Aerosol Optical Depth (AOD) and Fire Radiative Power (FRP) products |
| 27 April 2018 | Successful Launch of Sentinel-3B from Plesetsk, Russia. |