With 74 successful launches in a row, Ariane 5 now matches the reliability of Ariane 4 - while an experiment is helping the development of Ariane 6.

Arianespace announced liftoff at 20:30 GMT (17:30 local time, 22:30 CEST) from Europe's Spaceport in Kourou, French Guiana for a dual payload mission lasting about 32 minutes.

Sky Muster II, with a mass of 6405 kg at liftoff, was the first satellite to be released about 28 minutes into the mission. The 3404 kg GSAT-18 was released into it own orbit four minutes later.

Sky Muster II will provide high-speed Internet across Australia, including the Norfolk, Christmas, Macquarie and Cocos islands. India's GSAT-18 will provide telecommunication services nationally.

The payload mass for this launch was 10 663 kg. The satellites totalled about 9809 kg, with payload adapters and carrying structures making up the rest.

After satellite separation, in an experiment run by ESA and Airbus Safran Launchers, the upper stage coasted for another 30 minutes to mimic the longer missions of Ariane 6. During this time, 65 sensors and a camera inside the liquid hydrogen tank observed the propellant's behaviour under microgravity as the stage manoeuvred. The collected data, returned through the New Norcia ground station in Australia, will help in designing the Ariane 6 upper stage.

Flight VA231 was the fifth Ariane 5 launched this year.