The Ariane rocket carrying Skynet 5A, part of a £3.6 billion British armed forces programme, had been set to take off from the European spaceport at Kourou in French Guiana last night.
But because of concerns about the launchpad's "water deluge" system, the blast-off was abandoned after a 33-minute launch window expired.
Lift off: The Ariane rocket launches
Engineers carried out checks today and the rocket successfully left the ground at 9.55pm last night.
A live internet link relayed the events at Kourou around the world on the website.
The countdown clock was stopped yesterday with just seven minutes to go before the start of the launch window after experts detected the problem.
The deluge system is designed to pump out million of gallons of water at the moment of take-off to cool the launchpad and deaden vibrations to protect the cargo on board.
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