On 16 February 2016 at 18:57 CET (17:57 GMT), Sentinel-3A will be launched on top of a Rockot from the Russian Plesetsk Cosmodrome.

This satellite will be the third Sentinel for the Copernicus Programme. 

Copernicus is the most ambitious Earth Observation programme to date. It will provide accurate, timely and easily accessible information to improve the management of the environment, understand and mitigate the effects of climate change and ensure civil security. This initiative is headed by the European Commission (EC) in partnership with the European Space Agency.

ESA coordinates the delivery of data and is developing a new family of satellites, the Sentinels, specifically for the operational needs of Copernicus. The EC, acting on behalf of the European Union, is responsible for the overall initiative, setting requirements and managing the services. 

These services fall into six main categories: land management, the marine environment, atmosphere, emergency response, security and climate change.

This video explains what the Sentinels represent within Copernicus.