The multipurpose satellite, INSAT-3A, built by ISRO, was successfully launched early in the morning (April 10, 2003) by the Ariane-5 launch vehicle of Arianespace. INSAT-3A is the third satellite in the INSAT-3 series; INSAT-3B and INSAT-3C were launched by Ariane-5 and Ariane-4 launch vehicles on March 22, 2000 and January 24, 2002 respectively. 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.
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. Other INSAT satellite locations are: INSAT-2DT at 55 deg East longitude, INSAT-2E and INSAT-3B at 83 deg East longitude, INSAT-3C and KALPANA-1 at 74 deg East longitude.
INSAT-3A has the main body in the shape of a cuboid of 2.0 x 1.77 x 2.8 m. When its solar panel and solar sail are fully deployed in orbit, the satellite will measure 24.4 m in length. INSAT-3A’s Sun tracking solar panels generate 3.1 kW of power. Two 70 Ah Nickel-Hydrogen batteries support full payload operations even during eclipses. INSAT-3A, like all its predecessors in the INSAT series, is a 3-axis body-stabilised spacecraft using earth sensors, sun sensors, inertial reference unit, momentum/reaction wheels and magnetic torquers. It is equipped with bi-propellant thrusters. The satellite has two deployable antennas and one fixed antenna that carry out various transmit and receive functions.
INSAT-3A Communication Payloads comprise:
12 C-band transponders, nine of which have expanded coverage providing an Edge-of-Coverage (EoC) Effective Isotropic Radiated Power (EIRP) of 38 dBW and other three having India coverage beam providing an EoC-EIRP of 37 dBW. Six upper extended C-band transponders having India beam coverage providing an EoC-EIRP of 37 dBW.
Six Ku-band transponders having India coverage beam providing an EoC-EIRP of 47.5 dBW and A Satellite Aided Search & Rescue (SAS&R) transponder. The Meteorological Payloads include:
Very High Resolution Radiometer (VHRR) with 2 km resolution in the visible spectral band and 8 km resolution in infrared and water vapour bands.
Charge Coupled Device (CCD) camera operating in visible, near infrared and shortwave infrared bands with 1 km resolution.
Data Relay Transponder (DRT)
INSAT-3A is expected to augment the present INSAT capacity for communication and broadcasting, besides providing meteorological services along with INSAT-2E and KALPANA-1.
With ISRO Satellite Centre (ISAC), Bangalore, as the lead Centre, INSAT-3A 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-3A. MCF is responsible for initial and in-orbit operation of all geo-stationary satellites of ISRO.