India’s PSLV C-17 Rocket Successfully Launches GSAT-12 Telecommunications Satellite

By SpaceRef Editor
July 15, 2011
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PSLV C17 Launch
MUMBAI: It was a giant leap for India’s nearly 50-year-old space programme on Friday evening with the successful launch of the advanced version of the four-stage Polar Satellite Launch Vehicle (PSLV) carrying a 1410 kg communication satellite, GSAT-12.

Once operational in about 10 days, the satellite with 12 transponders will increase the total number of transponders in the country from 175 to 187. GSAT-12 will have societal applications mainly in areas relating to tele-medicine, tele-education, disaster management and in village resource centres.

Dubbed as a “fast track” mission, the primary role of this flight is to enhance the communication needs of the country. The Indian Space Research Organisation (ISRO) chairman, K. Radhakrishnan, was quoted as saying recently that in the beginning of the 11th five year plan (2007-2012) Isro had 211 transponders and the target then set was raise it to almost 500 by the end of the plan period. But, except for 24 transponders added by GSAT-8, ISRO had not been able to enhance these numbers since September 2007.

During the period most of the communication satellites had completed their normal life span or there were premature terminations. Consequently, the original target of having 211 transponders could not be adhered to. The number as a result dropped to 175. “There is a lot of unfulfilled demand to be met,” the ISRO chief said.

Normally a communication satellite would have been launched by the larger three-stage Geosynchronous Satellite Launch Vehicle (GSLV), since the PSLV is mainly meant for carrying remote sensing satellites. However, since the GSLV is facing technical problems, ISRO decided to carry GSAT-12 with a PSLV, a versatile work horse of the space agency.

The thunderous lift off from the Satish Dhawan Space Centre, Sriharikota was at 4.48 p.m. (IST) on Friday triggered a loud round of applause from the scientists and engineers in the hitech mission control room.

Space scientists explained to SpaceRef that it was a giant leap for a number of reasons. First, for the first time an indigenous advanced mission computer named Vikram for navigating, guiding and controlling the rocket was being used.

Second, again for the first time the satellite has been initially placed in a sub-geosynchronous transfer orbit with an apogee at 21,000 kms as against the normal 30,000 kms. Its perigee is 284 kms. “The reduced orbit was driven primarily because of the powerful capability of the rocket. In the next few days, the liquid apogee motor of the satellite will be used to raise both the apogee and perigee of the satellite to place it in a circular geosynchronous orbit at an altitude of 36,000 kms,” said an official.
This is the second time in the last nine years that a PSLV is being used for carrying a communication satellite, the first one was on September 12, 2002, when it flew India’s first dedicated meteorological satellite, Metsat, renamed as Kalpana-1 in honour of Kalpana Chawla.

It was the 19th flight of the PSLV and it was the “XL” version. In this type the six extended solid strap ons engines carried 12 tonnes of solid propellants as against nine. Again, this is the second time such a configuration is being flown, the earlier one being the PSLV-C11 during India’s mission to the moon, Chandrayaan-1 in October 2008.

Scientists said that the “XL” version has been used because to place a satellite into the geostationary transfer orbit, the rocket needs to impart almost 40 per cent additional velocity than while placing it in the polar orbit.

The first and third stage of the rocket have solid propellants while the second and fourth use liquid propellants.

Moments prior to the launch the mood in the mission control room was one of nervous apprehension combined with a sense of excitement. Adding to their worry was the weather which became a bit cloudy. But, after studying the conditions, weather was a ‘go,’ giving a tremendous sense of relief to the Isro team.

At T-15 minutes the internal battery of GSAT-12 was activated and a minute later it was declared ready for launch. At T-10 minutes the range was a ‘go’ and the vehicle director gave the formal authorization for the launch. This was followed by an announcement by mission director, P. Kunhikrishnan, saying: “This is the mission director, Based on the satisfactory conditions, PSLV C-17/GSAT-12 has been authorized for launch.” A display board showed that tracking, telemetry, instruments and range were all ready for launch and the status was green.

The automatic launch sequence system was initiated and the on board computers in the rocket were in flight mode. Five minutes away from the launch, the scientists were glued to their computers studying the telemetry, the different flight parameters and various critical events. Some of them clasped their hands in a silent prayer.

There were dark clouds over the launch pad, but still at sharp 4.58 p.m. the PSLV’s strap on boosters ignited, and the rocket steadily rose gaining velocity every second.

Its ear deafening awesome roar reverberated throughout the vast spaceport, and the mighty 44.4 metre rocket could be seen zooming higher and higher travelling in a yellowish plume. The sight of the rocket soaring upwards set off an applause among the large number of spectators assembled in the terraces and balconies in the buildings at the spaceport. Some of them in fact choked with emotion. A short while later the vehicle disappeared into the clouds and its sound too gradually faded away.

Ninety two seconds into the flights at an altitude of 40 kms while the rocket was flying at a speed of 2030 kms per second, the strap-ons separated. Following this was the detachment of the first stage at 115 seconds and the heat shield detached at 186 seconds. The third stage separated at 517 seconds and the fourth stage at 1187 seconds.

There were an exchange of congratulatory hand shakes and warm embraces among the ISRO team in the mission control room when it was announced that the GSAT-12 had separated at 1190 seconds. The atmosphere in the control room which was so far somewhat tense instantly turned one of joy and there was an immense sense of relief among the scientists and engineers.

From the mission control room Radhakrishnan declared: “PSLV C-17/ GSAT-12 mission is successful. The satellite was injected precisely into its orbit.” The total cost of the mission is approximately $42 million USD (Rs 190 crores).

SpaceRef staff editor.