A European-made rocket will blast off Tuesday from French Guiana for the 100th time, in a symbolic landmark for its manufacturer as it comes under increasing pressure from Elon Musk's SpaceX programme.
The Ariane 5 spacecraft will take off from the Caribbean launch site at 18:53 (21:53 GMT), propelling two telecoms satellites into orbit.
In service for more than two decades and capable of blasting heavy payloads into the sky, the Ariane 5 has become the workhorse of European space launches under the guidance of the European Space Agency (ESA).
But it will soon be replaced by an updated model, the Ariane 6, which will be an estimated 40 percent cheaper to make.
This is partly in response to SpaceX's arrival on the commercial space flight scene, with its reusable Falcon 9 rocket holding the potential to undercut rival programmes.
SpaceX has outpaced European manufacturer Arianespace in terms of number of launches for two straight years.
"We are having to face unprecedented competition," Arianespace head Stephane Israel told AFP.
Since it was first launched in 1996, the Ariane 5 has put 205 satellites into orbit including for Europe's Galileo GPS system.