The biggest civil Earth-observation programme ever conceived begins its roll-out on Thursday with the launch of a radar satellite from French Guiana.

The EU's Sentinel-1a spacecraft will be followed into orbit by a fleet of other satellites in the coming years.

Together, they will return an unprecedented volume of data on the state of the planet.

European nations have so far committed 7.5bn euros (£6.2bn; $10.3bn) to the Copernicus project, through to the decade's end.

Jonathan Amos reports.