Europe's heavy-lift Ariane 5 rocket is set to blast off on Saturday with its largest payload yet.
The ECA can lift more for less
It carries two telecommunications satellites with a combined weight of more than nine tonnes.
The 2344 GMT launch from the Kourou spaceport in French Guiana will be the fourth flight this year of an Ariane 5.
But the beefed-up heavy-lift version of the vehicle - known as the Ariane 5-ECA - has flown successfully only once before, in February 2005.
Its maiden flight in 2002 ended in disaster, when the rocket had to be destroyed as it veered off course over the Atlantic Ocean.
The second mission, described as a qualification flight, successfully placed two satellites in orbit: the Spanish XTAR-EUR military communications payload and an experimental spacecraft, called SloshSat.
Saturday's flight carries two telecommunications satellites: the US-owned Spaceway 2 and Indonesia's Telkom 2. The launch window extends for 45 minutes from 2344 GMT.
GUIDE TO SATELLITES
What satellites are for, where they go, and how they are launched
Launch company Arianespace believes the ECA will be crucial in helping it maintain a strong market position.
"We are going to put a record payload into orbit," said a spokesperson from the France-based company. "We will show that we can launch the heaviest payloads from Kourou."
The Ariane 5-ECA is designed to haul payloads of up to 10 tonnes into orbit.
Its predecessor - the Ariane 5-Generic - can deliver about six tonnes to a geostationary transfer orbit.
The two solid boosters of the beefed-up version have been engineered to carry more propellant and there is more thrust from a new cryogenic upper stage.
There is a new version, too, of the Vulcain engine on the main cryogenic stage.
This was the part of the launcher that failed on the maiden flight. An inquiry board that looked into the accident identified the probable cause as a leak in the Vulcain nozzle's cooling circuit.