The Indian space agency on Saturday at 12.07 a.m. began the 24-hour countdown for the launch of its heavy-lift rocket GSLV Mk III - renamed for this mission as LVM3 M2 - carrying 36 'OneWeb' satellites.

The 43.5 metre tall and weighing 644 ton LVM3 M2 rocket is scheduled to blast off from the first second pad at India's rocket port in Sriharikota in Andhra Pradesh at 12.07 a.m. on Sunday.

"The countdown is in progress smoothly. The gas charging and propellant filling operations of L110 stage are progressing," an Indian Space Research Organisation (ISRO) official told.

During the countdown, the rocket and satellite systems will be checked. The fuel for the rocket will also be filled.

Normally the GSLV rocket is used for launching India's geostationary communication satellites. And hence it was named as GeoSynchronous Satellite Launch Vehicle (GSLV). The GSLV MkIII refers to the third generation rocket.

As the rocket that will fly on Sunday morning will be orbiting the OneWeb satellites in Low Earth Orbit (LEO), the ISRO has renamed GSLV MkIII as LVM3 (Launch Vehicle MkIII).

The rocket, just over 19 minutes into its flight, will sling the 36 small broadband communication satellites of Network Access Associated Ltd (OneWeb) in LEO.

OneWeb, is a joint venture between India Bharti Global and the UK government.

The satellite company plans to have a constellation of about 650 satellites in low earth orbit (LEO) to offer communication services.

The LVM3 M2 is a three stage rocket with the first stage fired with liquid fuel, the two strap on motors powered by solid fuel, the second by liquid fuel and the third is the cryogenic engine.

The ISRO's heavy lift rocket has a carrying capacity of 10 ton to the LEO and four ton to the Geo Transfer Orbit (GTO).

"The total launch mass of OneWeb satellites will be 5,796 kg," said ISRO.

The 36 satellites will be on a dispenser system made by the Swiss based Beyond Gravity, formerly RUAG Space.

The Beyond Gravity had earlier provided the satellite dispensers for launching 428 OneWeb satellites to Arianespace.

"The dispenser with 36 satellites was supplied by the vendor. It was used in all their earlier launches," the official told .