Overcoming technical snags, India on Sunday successfully placed into orbit its latest communication satellite from the spaceport at Sriharikota, giving a major boost for Direct-To-Home television services.

In a textbook launch, the rocket GSLV-F04 carrying INSAT-4CR satellite blasted off at 6:21 pm from the Satish Dhawan Space Centre, two hours behind schedule after computers put off the launch following unsatisfactory performance of vent valve of the rocket.

The scientists took about one hour 40 minutes to set right the problem and the rocket was cleared for launch at around 6:00 pm.

The Geosynchronous Satellite Launch Vehicle-F04 placed the 2,130 kg satellite into a Geosynchronous Transfer Orbit at an altitude of 248 km about 17 minutes after the liftoff.

The 49-metre tall launch vehicle, the fifth in the GSLV series, soared into the space carrying the 2130 kg (415 tonne) satellite which was put into the orbit using its own propulsion system.

"It has been an excellent performance of the launch vehicle. There have been a number of critical moments on this happy occasion," Indian Space Research Organisation chief G Madhavan [Images] Nair told reporters.

INSAT-4CR is a replacement of its earlier version INSAT-4C that was destroyed on July 10 last year when the launch vehicle GSLV-F02 crashed 56 seconds after lift-off due to malfunctioning of a strap-on motor.

"It has been almost a year since we had a debacle. At that time, we had declared that in a year's time we will turn back and demonstrate the performance capability of GSLV. Today, ISRO has really achieved it," he said.

GSLV-FO2, carrying INSAT-4C, was discarded due to a snag resulting out of sudden loss of thrust in one of the four liquid propellant strap-on motors (S4), resulting in the vehicle veering away from its designated path.

The INSAT 4C satellite is expected to boost DTH television services, Digital News Gatheriing Service (DNGS), VSAT and other high bit rate data transmission in the country, and has a mission life of ten years. It is powered by solar array providing 2870W, two 70 Ampere-hour Nickel-Hydrogen batteries.

After the launch, the aluminium alloy payload fairing, measuring 7.8 metres in length and 3.4 metres in diameter, was discarded after the vehicle reached an altitude of 115 km.

For many scientists, the successful launch of GSLV-FO4, was an occasion to rejoice as they were witness to the abortive launch of the previous GSLV-F02 in July 2006.

INSAT-4CR is the third in the INSAT-4 series and follows the previous two successful launches in December 2005 and March 2007.

The launch of the rocket today was first scheduled to take place at 4.21 pm but was postponed three seconds before the blast off due to "technical snag in parameters related to launch," ISRO said.

As mediapersonnel waited with bated breath to watch the lift-off came the news that it had been deferred by 50 minutes.

It was then announced that the blast-off would be scheduled for 5.20 pm and then later it was deferred to 6.10 pm and then to 6.20 pm.

Soon after its injection into the orbit, the solar panels of the satellite will be deployed and in the following days, manoeuvred into its 36,000 km high Geosynchronous Orbit (GSO) by firing Liquid Apogee Motor (LAM) on board the satellite.

In GSO, INSAT-4CR will be co-located with the INSAT-4C, KALPANA- 1 and EDUSAT at 74 degree East Longitude.

The INSAT-4CR, built within a year of the loss of INSAT-4C, is expected to augment the domestic communication satellite system INSAT, which functions in meteorological imaging and data relaying.

The communication payloads include 12 ku-band 36 MHz bandwidth transponders employing 140 W TWTAs to provide an Effective Isotropic Radiated Power of 51.5 dBW at Edge of Coverage with footprint covering Indian mainland.

It also has Ku-band Beacon as an aid to tracking the satellite.

The INSAT (Indian National Satellite) is the largest Indian domestic communication satellite system and was established in 1983. It ushered in a revolution in the nation's television and radio broadcasting, telecommunications and meteorological sectors.

Today, INSAT is the largest domestic communication system in the Asia-Pacific region, according to the Indian Space Research Organisation, with ten satellites in service.

GSLV-FO4 is the fifth in India's GSLV series, after the GSLV-D1, GSLV-D2, GSLV-F01 and the ill-fated GSLV-F02.

In its first operational flight, the GSLV successfully launched the 1950 kg EDUSAT into a predetermined GTO.

The significance of GSLV lies in the fact that its third stage is cryogenic.

With increased efficiency, it provides more thrust for every kilogram of propellant it burns compared to solid and earth-storable liquid propellants, used in its two earlier stages.

In fact, in the present configuration, the GSLV is capable of placing 2,200 kg class satellites into the GTO.

However, once its Russian-supplied upper stage is replaced by ISRO-developed cryogenic stage, it will be able to place 2,400 kg class satellites into the GTO.

The GSLV MK III, now under development, will be capable of placing four tonne satellites into the same orbit.