December 22, 2005 

ISRO's latest satellite, INSAT-4A, was successfully launched early this morning (December 22, 2005) by the European Ariane-5G launch vehicle of Arianespace. With 12 high power Ku-band transponders INSAT-4A is the first satellite to meet the requirement of Direct-To-Home (DTH) television services apart from carrying 12 C-band transponders to augment the INSAT capacity for communication and TV services. Weighing 3080 kg at lift-off, INSAT-4A is the heaviest satellite of ISRO so far.

The 169th flight of Ariane (Ariane-5G), with ISRO's 3080 kg INSAT-4A and its co-passenger, a meteorological satellite, MSG-2 of the European EUMETSAT, lifted off at 4:03 am Indian Standard Time (IST) from Kourou, French Guyana. About 30) minutes after lift-off, INSAT-4A was placed in the Geosynchronous Transfer Orbit (GTO) in 3-axis stabilised mode. INSAT-4A is now orbiting the earth with a perigee (nearest point to earth) of 622 km and an apogee (farthest point to earth) of 36152 km and an inclination of 4.02 deg with respect to the equator. The orbital period is about 10 hours 46 minutes.

The Master Control Facility (MCF) at Hassan in Karnataka acquired the first signals from INSAT-4A at 4:32 am IST. The initial checks on the satellite indicated normal health of the satellite. MCF subsequently issued commands to the satellite to make the earth viewing face to orient towards earth. The calibration of the gyros on board the satellite was also carried out.

INSAT-4A is being tracked, monitored and controlled from MCF. During the initial phase of INSAT-4A operations, MCF also utilises INMARSAT Organisation's Telemetry, Tracking and Command (TTC) ground stations at Beijing (China), Fucino (Italy) and Lake Cowichan (Canada). The ISRO Telemetry, Tracking and Command Network (ISTRAC) ground station at Biak in Indonesia is also monitoring the satellite. The satellite's orbit is being precisely determined by continuous ranging from the participating ground stations.

In the coming days, INSAT-4A will be manoeuvred to its final geostationary orbit, which is about 36,000 km above the equator, by firing its 440 Newton Liquid Apogee Motor (LAM). When the satellite reaches near geosynchronous orbit, deployment of its solar panels and the two antennas 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-4A will be positioned at 83 degree East longitude along with INSAT-2E and INSAT-3B.

INSAT-4A carries the following payloads:

• 12 Ku- band 36 MHz bandwidth Transponders employing 140 W TWTAs to provide an EIRP of 52 dBW over the footprint covering Indian main land.
• 12 C-band 36 MHz bandwidth transponders employing 63 W TWTA to provide an EIRP 39 dBW with expanded radiation patterns encompassing Indian geographical boundary, area beyond India in southeast region and in northwest regions and some parts of Asia Pacific and Gulf countries.

INSAT-4A measure 15.16 metre with its solar arrays are fully deployed in orbit. The spacecraft propulsion system employs a 440 N Liquid Apogee Motor with 1500 kg of MON-3 (Mixed Oxides of Nitrogen) and MMH (Mono Methyl Hydrazine) to take the satellite from GTO to its final geosynchronous orbit. The satellite will be 3-axis body stabilised in orbit using sensors, momentum and reaction wheels, magnetic torquers and eight 10 Newton and eight 22 Newton Reaction Control Thrusters. The satellite has two solar arrays together generating 5,500 Watt of electrical power backed up by three 70 Ah Nickel Hydrogen Batteries.

The satellite has two deployable antennas and one fixed antenna for various transmit and receive functions.

With ISRO Satellite Centre (ISAC), Bangalore, as the lead Centre, INSAT-4A 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-4A. MCF is responsible for initial phase and in-orbit operation of all geostationary satellites of ISRO.