Things are getting set for the lift-off of the GSLV-D3 (Geo-synchronous Satellite Launch Vehicle – Development flight 3) from Sriharikota on April 15 around 4.30 p.m. The three stages of the gigantic vehicle have already been stacked up in the sophisticated Vehicle Assembly Building in the second launch pad on the seashore. It will put in orbit an advanced communication satellite called GSAT-4.
The significance of the mission is that the GSLV will be powered for the first time by India's own cryogenic upper stage. This stage with its engine, electronics and fuel tanks was built at the Liquid Propulsion Systems Centre (LPSC) of the Indian Space Research Organisation (ISRO) at Mahendragiri in Tamil Nadu. The previous five GSLV missions from Sriharikota were propelled by the Russian cryogenic engines. Cryogenic engines that use liquid oxygen and liquid hydrogen at very low temperatures are needed to put heavier, communication satellites in a geosynchronous transfer orbit with an apogee of 36,000 km. and a perigee of 200 km.
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P.S. Veeraraghavan, Director, Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, said: “We have done our best. Detailed reviews have been completed. We have taken all steps to ensure that the launch goes all right.”
The VSSC has built GSLV-D3 which is 49 metres tall and weighs 419 tonnes. The 2,200-kg GSAT-4 has been built by the ISRO Satellite Centre, Bangalore.
Mr. Veeraraghavan said three highlights of the GSAT-4 were its communication system in Ka-band; its GAGAN payload which would help in the landing accuracy of commercial aircraft at airports in India; and the satellite's electric propulsion system which would help in correcting the spacecraft's attitude and ensuring a longer life in orbit. (GAGAN stands for GPS-aided Geo-augmented Navigation System. GPS is short for Global Positioning System. The Ka-band will help in relaying more information).
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Big breakthrough
The ISRO achieved a big breakthrough in the “exotic” cryogenic technology when it fully qualified its own cryogenic stage with a 720-second full duration test at Mahendragiri on November 15, 2007. ISRO officials said it was not easy to handle liquid oxygen at minus 183 degrees Celsius and liquid hydrogen at minus 260 degrees Celsius; putting them on fire from such low temperatures; and burning the hydrogen in a controlled manner.