Countdown for GSLV launch begins

By R.K. Radhakrishnan

CHENNAI, MARCH. 26. The countdown for the most-awaited moment of the Indian space programme - the launch of the Geosynchronous Satellite Launch Vehicle (GSLV) - began at the Sriharikota range this morning. The GSLV is slated to lift off at 3.47 p.m. on Wednesday, March 28. The window period of the launch extends till 7.41 p.m. that day.

``The countdown began at T minus 58 hours (58 hours before take- off time, at 5.47 a.m.),'' said Mr. S. Krishnamurthy, a spokesperson of the Indian Space Research Organisation (ISRO), Bangalore. ``We are also organising a live telecast of the launch programme on the national channel.''

Top scientists and managers of the space programme from all over the country are now overseeing the countdown at the mission control centre at the Sriharikota range (Shar).

The GSLV is the most technologically-challenging mission undertaken so far by the Indian space programme.

It is not just the space programme staff and the planners in New Delhi who look forward to the lift-off. Personnel and managers of nearly 150 industries, both in the public and private sector, who manufactured various components, inter-stages and electronic modules also wait with bated breath.

In the first developmental test flight, the three- stage GSLV, will place a 1,540-kg experimental satellite, GSAT-1, in a Geosynchronous Transfer Orbit (GTO).

The GSLV project was initiated in 1990 with the objective of acquiring launch capability for geosynchronous satellites.

The first test flight, GSLV D-1, is intended to validate the various systems of the vehicle in an actual flight. Several performance parameters of propulsion stages, avionics, control and guidance system, the stage and spacecraft separation system will be monitored in flight. The design margins too will be more realistically estimated from the in-flight test.

The vehicle will be launched at an azimuth of 104 degrees. It takes about 1020 seconds for the flight from lift-off to the injection of the satellite into the GTO. About 150 critical events have to be gone through during the flight, before the satellite is placed in orbit.

On the launch pad, the four liquid propellant strap-on stages will be ignited first. The solid propellant stage will be ignited 4.6 seconds later, after the strap-ons are declared `normal'.

This stage will burn for 100 seconds while the strap- ons last up to 160 seconds. By the end of this, the vehicle would have attained an altitude of about 73 km.

The second stage ignites 1.6 seconds before separation of the first and burns for about 150 seconds. This stage `falls off' about 314 seconds from lift-off, at about 127 km above the earth.

The cryogenic stage, third and most important, burns for about 710 seconds. The cryogenic engine burns liquid oxygen and liquid hydrogen. It is currently the most efficient rocket engine available and produces the highest thrust per kg of propellant of any engine.

The spacecraft and the equipment bay are separated at an altitude of 195 km. Before separation, it gives the spacecraft the required injection velocity of 10.2 km per second to place it in the GTO.

The GSLV will be declared operational after two successful developmental flights. The ISRO says efforts are on to improve the payload in the GTO up to 2000 kg and beyond in ``about two to three years.'' Other than the GTO missions, the GSLV is also capable of performing polar and LEO missions.

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