Sriharikota (Andhra Pradesh) Jul 15 (IANS): India notched another milestone in its space programme Friday evening when it successfully launched a heavy-duty rocket that placed a major communications satellite in space.

A beaming Indian Space Research Organisation (ISRO) chief K. Radhakrishnan told reporters after the 4.48 p.m. launch Friday that the mission was a success.

"It is a tricky mission. I am extremely happy to state that the PSLV (Polar Satellite Launch Vehicle)-C17 GSAT-12 mission is successful. The satellite was launched in the intended orbit," he said at the launch site here, 80 km north of Tamil Nadu's capital Chennai.

V. Narayanasamy, Minister of State in the Prime Minister's Office, said: "I am extremely happy (at the successful launch). I am coming here for the second time, and it is a second successful launch. On behalf of the prime minister, UPA chairperson Sonia Gandhi, I congratulate the ISRO scientists for the wonderful performance."

The PSLV blasted off successfully at 4.48 p.m., carrying the 1,410 kg GSAT-12 satellite from the spaceport here. The satellite has a life span of about seven years.

With this, India added 12 more communication transponders to its space-based network.

The launch took place under a cloudy sky, with the Rs.95 crore rocket PSLV-C17 - measuring 44 metres in height and weighing 320 tonnes - soaring off into space with a roar.

It ferried the Rs.105 crore GSAT-12 having 12 extended C-band transponders - automatic receivers and transmitters for communication and broadcast of signals.

With a rich orange flame at its rear, the one-way ticket rocket left behind a huge tail of white plume as it rose into the sky to the cheers of ISRO scientists and media team assembled at the launch centre.

People perched atop of the nearby buildings too happily applauded as PSLV-C17 went up.

Around 20 minutes after the blast off, the rocket achieved its mission by placing the latest Indian communication satellite in the intended sub geosynchronous transfer orbit (sub GTO).

The GTO is an intermediate orbit from where normally communication satellites will be moved to its final geosynchronous orbit by firing the on-board motors.

Radhakrishnan said the rocket's navigation systems were powered by Indian-made advanced Vikram processors.

"We needed to make modifications in the rocket's navigational software for this mission," Radhakrishnan said.

The GSAT-12 carries around 851 kg of fuel on-board to fire the motors. (A geosynchronous orbit is one directly above the earths' equator. For an observer from the earth a satellite in geosynchronous orbit will seem motionless, stationary at one point in the sky).

The rocket placed the satellite in sub GTO with a 284 km perigee (nearest point to earth) and 22,020 km apogee (farthest point from the earth). The satellite will be raised to 36,000 km apogee from 22,020 km over the next two days.

The satellite will be useful for various communication services like tele-education, tele-medicine and for village resource centres, Radhakrishnan said.

The GSAT-12 satellite is also 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.

T.K. Alex, director of ISRO Satellite Centre, said the initial operations after putting the satellite in orbit went of smoothly.

"The solar panels were deployed and are generating power. The satellite orbit will be raised from 22,020 km apogee to 36,000 km apogee tomorrow and day after. All the 12 transponders in the satellite will be tested by the end of this month," Alex said.

He said there will be sufficient fuel left in GSAT-12 after carrying raising its orbit to 36,000 km apogee so that it can be in operation for seven years.

Immediately after satellite ejection, ISRO with its network of ground stations monitored its health.

The satellite will augment transponder capacity of Indian National Satellite (Insat) system which at present comprises of eight satellites -- Insat-2E, Insat-3A, Insat-3C, Insat-3E, Insat-4A, Insat-4B (working at 50 percent capacity) Insat-4CR and GSAT-8 providing 175 transponders in the S, C, extend C and Ku bands.

The Indian space agency has leased 86 more transponders from various foreign satellites. It is estimated there is an unmet demand for 170 transponders.

ISRO used its third PSLV rocket variant - PSLV-XL - with longer strap-on motors with higher fuel capacity - to put the latest communication satellite in the space.

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

The PSLV-C17 that went up Friday had 13.5 metres long strap-on motors carrying 12 tonnes of solid fuel than the normal strap-on motors measuring 11.3 metres with nine-tonne fuel capacity.

This is the second time ISRO has launched a rocket with this specification. The earlier one was for the Chandrayaan moon mission.

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

The PSLV has an excellent success record since 1994, launching many Indian and foreign satellites.

ISRO officials told IANS that a remote sensing satellite - Megha-Tropiques - is being planned for launch later this year.