The launch marked the Ariane 5's first flight this year and only the fourth for the 780-tonne heavy-lift version.More details at BBC.
The ECA has the power to push 10,000kg of payload towards geostationary orbit, 36,000km above the Earth.
The mission had originally been scheduled for 21 February but was put off three times because of technical problems with ground support equipment, the payload and the upper stage of the launcher.
Ariane 5-ECA launches two satellites

The Ariane 5-ECA - Europe's most powerful rocket - has brought two satellites into orbit today. The rocket launched from French Guiana and carried satellites for the Spanish defence ministry and a French telecoms company.