A Soyuz rocket lifted off on its maiden flight from Europe's space base here, carrying the first two satellites in the Galileo geo-positioning system.
The launch marked an unprecedented step in space cooperation, being the first by the veteran rocket beyond Russia's historic bases at Plesetsk and Baikonur.
As mission controllers counted off the final seconds, Soyuz's main engines ignited, a cluster of umbilical masts flipped back and at 1030 GMT the rocket clawed its way skywards through a pounding tropical rain.
After a nine-minute flight through Earth's atmosphere, its final stage, the Fregat, fired up to drive the satellites toward their orbital slots, a last leg that should take more than three hours.
“The first part of this mission has gone well,” said Jean-Yves Le Gall, chief executive of Arianespace, which markets launches at Kourou.
Friday's launch came after a 24-hour postponement caused by a faulty valve in a ground system designed to disconnect fuel lines to the rocket's third stage just before flight.
Soyuz is a space legend, for it traces its lineage to 1957 with Sputnik, the first satellite, and to the first manned flight, by Yuri Gagarin, in 1961. Friday's launch was the 1,777th in the Soyuz saga. It has a success rate of 94.4 per cent. A symbol of national pride in Russia, the rocket was deployed at a specially-built pad at Kourou under a 2003 deal intended to complete Arianespace's marketing range.
Arianespace says it has orders for 14 Soyuz launches from Kourou, including the third and fourth satellites in the Galileo constellation next year. Galileo is intended to give Europe independence in satellite navigation, a vital component of the 21st-century economy, from the U.S. Global Positioning System (GPS). When completed in 2020, it will comprise 27 satellites and provide accuracy to within a metre, compared to three to eight metres for the GPS.