Seventeen minutes at ISRO

By Our Staff Reporter

SRIHARIKOTA, APRIL 18. ``This was the longest seventeen minutes in our lives. It was also the most challenging and exciting. Words cannot describe our feelings,'' Dr. K. Kasturirangan, chairman, ISRO, said moments after the launch, telecast for the ISRO community at SHAR (Sriharikota Range).

There was tension in the air at SHAR, and in the faces of engineers, scientists, technicians and former space managers who came to watch the launch. The aborted March 28 launch was in the back of their minds. ISRO staff climbed onto rooftops while local people watched from all vantage points, including palm-tree tops, as second-zero approached.

At 4.6 seconds to count zero, as ISRO personnel waited with bated breath, eyes glued to the computers in front of them, each of the four liquid strap-on stages carrying 40 tonnes of propellants, were ignited. This time there was no thrust problem. The personnel in the Mission Control heaved a collective sigh of relief after confirming the normal performance of the liquid stages. The Automatic Launch Sequence had given the go- ahead.

The hold system was released one second before lift- off and at zero count, the mammoth 125-tonne solid stage was ignited. Cheers and claps drowned the voices at Mission Control and throughout the centre as the GSLV blazed into the afternoon sky. More tension; the ASLV experience is still fresh in the minds of many old-timers (The flight of ASLV-D2 launched on July 13, 1988 was normal only up to 46 seconds after lift-off).

This time the machine held on; the first stage burned a full 100 seconds while the liquid propulsion strap-on stages continued their thrust up to 162 seconds.

Altitude 75 km. Velocity 2.63 km per second. The first stage separated, bringing in more cheers. The second stage ignited as planned, 1.6 seconds before the first stage burn-out. More anxious faces and after 147 very long seconds, the vehicle kept course and reached 126 km, at 5.18 km per second.

Then came the most crucial phase - ignition of the untested cryogenic stage. But telemetry data from Port Blair and Indonesia indicated that all was well - after separation of the second stage at 314 seconds from lift-off, the Russian cryogenic stage was ignited.

Carrying 12.5 tonnes of liquid hydrogen and liquid oxygen, the stage burned for 693 seconds taking the satellite and vehicle equipment bay to an altitude of 181 km. It was separated some 5,000 km from the launchpad, Sriharikota, and re-oriented to avoid any collision with the satellite. Seventeen minutes after lift-off, GSAT-1 was successfully placed in an orbit of 181 km perigee and an apogee of 32,051 km. with an orbit inclination of 19.2 degrees with respect to the equator.

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