The countdown began on Saturday afternoon at the Satish Dhawan Space Centre at Sriharikota for the launch of India’s latest communication satellite INSAT-4CR at 4:20 pm on Sunday by the geosynchronous launch vehicle, GSLV-FO4.

The GSLV-F04, the fifth in the GSLV series, will put INSAT-4CR into a geosynchronous transfer orbit about 16 minutes and 40 seconds after lift-off. The satellite will subsequently be manoeuvred into geostationary orbit by using its own propulsion system.

The satellite will carry 12 high-power Ku-band transponders for direct-to-home television services, video picture transmission and digital satellite news gathering.

The failure precedent
It has been built within a period of one year to replace an identical satellite, INSAT-4C that was lost due to failure of the previous GSLV flight in July 2006.

The previous flight, GSLV-FO2, strayed from its path due to lack of thrust in one of its four thruster engines.
The fault was detected two seconds after lift-off and the rocket was destroyed 56 seconds later.

The 2,130-kg INSAT-4CR satellite (R denoting remake of the destroyed satellite) has already been integrated with the launch vehicle and the vehicle has been moved to the second launch pad from where it will blast off.
The 49-metre-tall, 414-tonne GSLV is a three-stage vehicle.

The first stage comprises a core motor with 138 tonnes of solid propellant and four strap-on motors each with 42 tonnes of hypergolic liquid propellants. The second stage has 39 tonnes of the same liquid propellant.
The third is the cryogenic stage with 12.6 tonnes of liquid oxygen and liquid hydrogen.

The three-axis attitude stabilisation of the vehicle is achieved by autonomous control systems provided in each stage.

The closed loop guidance scheme in the on-board computer ensures the required accuracy in the injection conditions.

GSLV uses S-band telemetry and C-band transponders for the vehicle performance monitoring, tracking, range and flight safety and preliminary orbit determination.

Complex stage
The most complex is the cryogenic third stage.

The cryogenic stage is much more efficient and provides more thrust for every kg of propellant it burns compared to solid and earth-storable liquid propellants. However, it is technically a very complex system due to the use of propellants at extremely low temperatures and the associated thermal and structural problems.

With the present configuration, GSLV is capable of placing 2,200 kg class satellite into geostationary transfer orbit (GTO). Once its Russian supplied upper stage is replaced by the ISRO supplied cryogenic stage, it will be able to place 2,400 kg class satellites into GTO.

Indigenous development of the cryogenic stage has reached an advanced level. It was ground tested for a long duration of eight minutes on August 4 at the liquid propulsion test facility at Mahendragiri in Tamil Nadu.
The test validated the design, robustness and performance adequacy of the engine.