The first developmental test flight of India's Geosynchronous Satellite Launch Vehicle, GSLV, was successfully carried out this evening (April 18, 2001) from SHAR Centre, Sriharikota, about 100 km north of Chennai, marking a major milestone in the Indian space programme. With this launch, India has demonstrated its capability to launch communication satellites, into geostationary transfer orbit with perigee (nearest to the earth) of 180 km and an apogee (farthest to the earth) of 36,000 km. This paves the way for end-to-end capability of application - spacecraft launching in the communication area also.
The 401 tonne, 49 m tall GSLV, carrying an experimental, 1540 kg, satellite, GSAT-1, lifted off from Sriharikota at 3-43 pm IST. Seventeen minutes after lift off, GSAT-1 was successfully placed in an orbit of 181 km perigee and an apogee 32, 051 km with the orbit inclination of 19.2 degree with respect to the equator. The injection of the satellite into orbit occurred about 5000 km from the launch centre.
It may be recalled that the first launch attempt of GSLV was aborted one second before the lift-off on March 28, 2001 by the Automatic Launch Processing System (ALS) after it detected that one of the strap-on boosters did not develop the required thrust. After detailed analysis, the exact reason was identified, recovery operations were completed in 18 days and the vehicle was made ready for re-launch.
The count-down commenced 57 h 49 m prior to lift-off, i.e., 5:56 am on April 16, 2001. The count-down activities like filling of fuel for second stage and the four strap-on motors, arming of pyros, movement of Mobile Service Tower, filling of cryostage and electrical checks were done smoothly. After station checks, on all mission elements, the authorization for the mission was given at 16 minutes before lift-off. The Automatic Launch Processing System took over at 12 minutes before lift-off.
As the count down for the launch proceeded, at 4.6 seconds before the count zero, the four liquid propulsion strap on stages, each carrying 40 tonne of propellant, were ignited. After confirming the normal performance of the liquid propulsion strap-on motors, the whole system was released one second before lift-off and at count zero, the mammoth 125 tonne solid propellant first stage motor was ignited and GSLV blazed into the evening sky. The first stage burned for 100 seconds while the liquid propulsion strap on stages continued thrusting up to 162 seconds from lift-off taking the vehicle to an altitude of 75 km. At the end of the first stage burn out the GSLV had reached a velocity of 2.63 km per second.
The second stage, which carried 37.5 tonne of liquid propellant, ignited 1.6 seconds before the burn out of the first stage strap-on motors. This stage burned for 147 seconds taking the vehicle to an altitude of 126 km and increasing its velocity to 5.18 km per second. During the second stage operation, when the vehicle was at an altitude of 116 km and thus cleared the dense atmosphere, the heat shield that protects the spacecraft from the aerodynamic heating, was discarded.
After the separation of the second stage at 314 seconds from lift off, the cryogenic stage was ignited. The cryogenic stage, which carried 12.5 tonne of liquid hydrogen and liquid oxygen burned for 693 seconds taking the satellite and vehicle equipment bay to an altitude of 195 km and increasing the velocity to 10.17 km per second as required for placing the satellite in the geostationary transfer orbit. The stage which was procured from Russia and interfaced with ISRO developed electronics, was separated from the spacecraft at about 1036 seconds from lift off at an altitude of 202 km about 5000 km from the launch pad at Sriharikota. After the spacecraft separation, the cryogenic stage was reoriented to avoid any collision with the satellite and passivated.
All through the flight, the vehicle was guided by the inertial navigation and guidance systems. The performance data of the GSLV was tele-metered to the ground stations in Sriharikota, Port Blair and stations at Brunie and Biak in Indonesia which were networked with SHAR Centre.
The first signals acquired from the GSAT-1 indicate normal performance of the satellite. Further operations like orbital manoeuvres to take the satellite from the geosynchronous transfer orbit to its final geostationary orbit at 36,000 km using the on board apogee motor and deployment of its appendages like solar array, solar sail and the antenna, GSAT-1 will be carried out in the coming days. GSAT-1 carrying three C-band transponders and one S-band transponder, will be used for conducting communication experiments like digital audio broadcast, internet services, compressed digital TV transmission. Several new spacecraft elements like improved reaction control thrusters, fast recovery star sensors and heat pipe radiator panels are also being tested on this satellite.
The successful accomplishment of GSLV-D1/GSAT-1 Mission is the culmination of a decade of efforts of ISRO Centres' in design and development and supported by several educational and academic as well as R&D institutions in the country. Many of the GSLV hardware including motor cases, inter-stages, heat shield, engine components, electronic modules are manufactured by the Indian industry. About 150 industries, both public and private sectors are involved.
GSLV is the most technologically challenging mission undertaken so far under the Indian space programme. It is the culmination of efforts of a large number of scientists, engineers and technicians, over the last ten years. The mission heralds a significant milestone towards the establishment of indigenous capability for launching communication satellites like INSAT. Having already established indigenous capability for launching IRS class of remote sensing satellites through PSLV, the launch of GSLV makes the Indian space programme even more self-reliant while tuning the programme towards national development.
This article was published in the Indian Space Research Organisation website www.isro.org on the day GSLV was launched successfully.