MUMBAI: Indian space agency ISRO has chosen Arianespace again to launch its INSAT 4A and INSAT 4B communications satellites.
After today's successful Ariane 5 mission that placed INSAT 3A into orbit from Kourou, ISRO chairman Dr. Kasturirangan and Arianespace CEO Jean-Yves Le Gall announced the signing of launch contracts for two more payloads - the INSAT 4A and 4B spacecraft.
These are the 12th and 13th Isro satellites to be booked on the European launcher. Since the launch of the Apple experimental satellite in 1981 on Flight L03, Arianespace has orbited ten Indian satellites. Arianespace is slated to launch another ISRO payload, the INSAT 3E satellite, later this year.
Designed, built and integrated by Isro, the INSAT 4A and INSAT 4B satellites each weigh about 3,200 kg at liftoff. INSAT 4A and INSAT 4B are dedicated to telecommunications, with 12 Ku band and 12 C-band transponders each. Their coverage zone is the Indian sub-continent.
Meanwhile, the 160th flight of Ariane, carrying Isro's 2,950 kg INSAT-3A and GALAXI-XII of US, lifted off at 4.22 am IST from Kourou, French Guyana. INSAT-3A was injected into a Geosynchronous Transfer Orbit (GTO), 30 minutes after the lift-off in 3-axis stabilized mode, with a perigee (nearest point to earth) of 859 km and an apogee (farthest point to earth) of 36,055 km and an inclination of 1.99 deg. with respect to the equator. The satellite is at present going round the earth with an orbital period of about 10 hours 47 minutes, according to the agency.
The Master Control Facility (MCF) at Hassan in Karnataka acquired the telemetry signal from INSAT-3A at 04.52 am IST. The initial health checks on the satellite indicate that the performance of the satellite is normal. First operations on the satellite were carried out by issuing commands from the MCF. The outermost panel of the stowed solar array of INSAT-3A was oriented towards the Sun to start generating the electrical power required by the satellite. Subsequently, the earth viewing face was oriented towards the earth and calibration of the gyros on board the satellite was carried out.
INSAT-3A is being tracked, monitored and controlled from MCF. During the initial phase of INSAT-3A operations, 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) ground stations.
In the coming days, orbit raising operations of INSAT-3A will be carried out by firing its 440 Newton Liquid Apogee Motor (LAM) in stages till the satellite attains its final geostationary orbit, which is about 36,000 km above the equator. The satellite has about 1.6 tonne of propellant (Mono-Methyl Hydrazine - MMH fuel and Mixed Oxides of Nitrogen - MON-3 oxidiser) for orbit raising operations as well as for station keeping and in-orbit attitude control. The on-orbit propellant availability will enable maintaining the satellite for operational services for a period of 12 years.
When the satellite reaches near-geostationary orbit, deployment of its solar panels and the two antennas as well as the solar sail will be carried out and the satellite put in its final 3-axis stabilised mode. This will be followed by trim manoeuvres to take the satellite to its designated orbital slot. The payloads will be subsequently checked out before the commissioning of the satellite.
INSAT-3A will be positioned at 93.5 deg East longitude in the geostationary orbit.
