INSAT-3C satellite built by ISRO, was successfully launched early this morning (January 24, 2002) by the Ariane-4 launch vehicle of Arianespace. The 147th flight of Ariane, carrying ISRO's 2,750 kg INSAT-3C, lifted off at 05:17 am IST from Kourou, French Guyana in South America. INSAT-3C was injected into a Geo-synchronous Transfer Orbit (GTO), 21 minutes after the lift-off, in a 3-axis stabilised mode, with a perigee of 570 km and an apogee of 35,920 km and an inclination of 4 deg. with respect to the equator. The satellite is at present going round the earth with an orbital period of about 10.5 hours.

The INSAT Master Control Facility (MCF) at Hassan in Karnataka acquired the telemetry signal from INSAT-3C at 5:47 am IST. The initial health checks on the satellite indicate that the performance of the satellite is normal. First operations on this satellite were carried out by issuing commands from the Master Control Facility (MCF) at Hasssan. The outermost panel of the stowed solar array on the south side of the satellite was oriented towards the sun to start generating the electrical power required by the satellite during its transfer orbit phase. Subsequently, the earth viewing face was oriented towards earth and calibration of the gyros on board the satellite has been carried out.

INSAT-3C is being tracked, monitored and controlled from MCF, Hassan. During the initial phase of the operation, MCF also utilises INMARSAT Organisation's ground stations at Beijing (China), Fucino (Italy) and Lake Cowichan (Canada). The satellite's orbit is being precisely determined by continuous ranging from the participating Telemetry Tracking and Command (TTC) stations.

In the coming days, orbit raising operations on INSAT-3C will be carried out by firing the 440 Newton liquid apogee motor on board in stages till the satellite attains its final geo-stationary orbit, about 36,000 km above the equator. The satellite has about 1.5 tonne of propellant (Mono-Methyl Hydrazine - MMH and Mixed Oxides of Nitrogen - MON-3) for orbit raising operations as well as for station keeping and in-orbit attitude control. The on orbit fuel availability will enable maintaining the satellite for operational services for a period of 12 years.

When the satellite reaches near geo-stationary orbit, deployment of the two solar panels and the two antennas will be carried out and the satellite put in its final 3-axis stabilised mode. The payloads will be subsequently checked out before the commissioning of the satellite.

INSAT-3C will be co-located with INSAT-1D at 74 deg East longitude. Other INSAT satellite locations are: INSAT-2C and INSAT-2B at 93.5 deg East longitude, INSAT-2E and INSAT-3B at 83 deg East longitude, INSAT-2A at 48 deg East longitude and INSAT-2DT at 55 deg East longitude.

INSAT-3C carries 24 C-band transponders, six extended C-band transponders, two S-band transponders and a Mobile Satellite Service transponder operating in S-band up-link and C-band down link.

INSAT-3C has the main body in the shape of a cuboid of 2 X 1.7 X 2.8 m. When the two solar panels are fully deployed in orbit, it will measure 15.5 m in length. The sun tracking solar panels generate 2.75 kW of power. Two 60 Ah Nickel-Hydrogen batteries support full payload operations even during eclipses. INSAT-3C, like all its predecessors in the INSAT series, is a 3-axis body-stabilised spacecraft using momentum/reaction wheels, earth sensors, sun sensors, inertial reference unit and magnetic torquers. It is equipped with unified bi-propellant thrusters. The satellite has two deployable antennas and three fixed antennas that carry out various transmit and receive functions.

INSAT-3C is the second satellite to be launched in the INSAT-3 series. The first satellite, INSAT-3B, was launched on March 22, 2000. INSAT-3C is expected to augment the present INSAT capacity for communication and broadcasting, besides providing continuity of the services of INSAT-2C when it reaches the end of mission life late this year.

With ISRO Satellite Centre (ISAC), Bangalore, as lead centre, INSAT-3C was realised with major contributions from Space Applications Centre (SAC), Ahmedabad, Liquid Propulsion Systems Centre (LPSC) at Valiamala and Bangalore, Vikram Sarabhai Space Centre (VSSC) and ISRO Inertial Systems Unit (IISU), Thiruvananthapuram. Besides, several industries in both public and private sectors have contributed to the realisation of INSAT-3C. MCF is responsible for initial and in-orbit operation of all geo-stationary satellites of ISRO.