Ferrying the country's latest communication satellite GSAT-12A, a fully fuelled up Indian rocket is all set to blast off from the space port here on Friday evening.

"All the four stages/engines have been fuelled up. The countdown for the evening launch is progressing well. Over the next few hours all the mandatory checks on all the rocket systems will be carried out," Indian space agency director S. Satish said in Sriharikota, about 80 km from Chennai.

The director in charge of publications and public relations said fuelling of the rocket's second stage that began Thursday night was completed Friday morning.

Indian Space Research Organisation (ISRO) officials told IANS that the propellant and helium gas chambers are in the process of being adequately pressurised.

The sky is clear and the weather good for the launch of Rs.90 crore rocket, Polar Satellite Launch Vehicle-C17 (PSLV-C17), scheduled at 4.48 p.m., officials said.

Around 20 minutes into the flight the rocket is expected to place GSAT-12 in the intended sub-geosynchronous transfer orbit (sub GTO).

The Rs.80 crore GSAT-12 satellite has 12 extended C-band transponders - automatic receivers and transmitters for communication and broadcast of signals.

The satellite is expected to serve the Very Small Aperture Terminal (V-SAT) sector. VSATs are used to transmit data like point of sale transactions or to provide satellite internet access.

It will also be useful for various communication services like tele-education, tele-medicine and for village resource centres.

The satellite will augment transponder capacity of Indian National Satellite (Insat) system that presently comprises eight satellites - Insat-2E, Insat-3A, Insat-3C, Insat-3E, Insat-4A, Insat-4B, Insat-4CR and GSAT-8 providing 175 transponders in the S, C, extend C and Ku bands.

On Thursday, the rocket's fourth stage/engine was fuelled with liquid propellants. The gas and propellant chambers were pressurised.

The PSLV-C17 rocket standing 44 metres tall and weighing around 320 tonnes is a four-stage rocket powered by solid and liquid propellants alternatively.

The first and third stage engines are fired by a solid propellant and the second and fourth stages by a liquid propellant.

The solid fuel stages are cast ready while the liquid propellant are filled only hours before the blast-off.

ISRO will be using its third PSLV rocket variant - PSLV-XL - with longer strap-on motors with higher fuel capacity.

The other two rocket variants are the PSLV standard version with 11.3 metres six strap-on motors and the PSLV Core Alone (CA) rocket without the six strap-on motors.

The rocket to be launched Friday evening will have 13.5 metres long strap-on motors to carry 12 tonnes of solid fuel than the normal strap-on motors measuring 11.3 metres with nine-tonne fuel capacity.

This will be the second time ISRO will be launching a rocket with this specification. The earlier one was for the Chandrayaan moon mission.

This will also be only the second time that ISRO will be using a PSLV rocket for launching a satellite to be finally placed in geostationary orbit. The first was Kalpana-1 satellite (originally named as Metsat), a meteorological satellite launched in 2002.

The GSAT-12 satellite will be co-located with Inst-2E and Insat-4A satellites and will have a life of eight years.