Untitled Document

ISRO’s latest communication satellite, INSAT-4B, was successfully launched on March 12, 2007 by the European Ariane-5 ECA launch vehicle of Arianespace. The 3,025 kg INSAT-4B is the second satellite in INSAT-4 series. Its identical predecessor, INSAT-4A, was also launched by Ariane-5 on December 22, 2005. With 12 high power Ku-band transponders and 12 C-band transponders, INSAT-4B will further augment INSAT capacity for Direct-To-Home (DTH) television services and other communication and TV services.

INSAT-4B was the thirteenth Indian satellite to be launched by Arianespace. The 31st flight in Ariane-5 series, carrying ISRO’s INSAT-4B and its co-passenger, Skynet-5A of EADS Astrium, lifted off at 03:33 am Indian Standard Time (IST) from Kourou, French Guyana on March 12, 2007. About 30 minutes after lift-off, INSAT-4B was placed in Geosynchronous Transfer Orbit (GTO) with a perigee (nearest point to earth) of 250 km and an apogee (farthest point to earth) of 35,886 km and an inclination of 4.5 deg with respect to the equator. Its orbital period was about 10 hours 34 minutes. The Master Control Facility (MCF) at Hassan in Karnataka acquired the first signals from INSAT-4B at 4:02 am IST.

The first critical orbit-raising manoeuvre on INSAT-4B was successfully conducted at 5:35 am on March 13, 2007 with the firing of its 440 Newton Liquid Apogee Motor (LAM) for 93 minutes by commanding the satellite from MCF at Hassan in Karnataka. With this LAM operation, INSAT-4B perigee was raised to 14,244 km. The apogee was at 35,752 km and the inclination of the orbit with respect to the equatorial plane was reduced to 1.15 deg. The orbital period had increased to 15 hours 21 minutes.

In the second orbit raising manoeuvre conducted at 12:47 (IST) on March 14, 2007, LAM was fired for 41 minutes. With this, INSAT-4B perigee was raised to 32,878 km while the apogee was at 35,736 km. The inclination of orbit was reduced to 0.19 deg. The orbital period had increased to 22 hours 41 minutes and the satellite remained in continuous radio visibility of MCF, Hassan.

In the third and final orbit-raising operation by firing LAM for a duration of 3 min 50 sec at 10:36 am on March 16, 2007, INSAT-4B was successfully placed in near-geosynchronous orbit with an orbital period of 23 hours and 52 minutes.

After placing INSAT-4B in near-geosynchronous orbit, the deployment of its two solar panels and two antennas was successfully completed.

The satellite was put to its three-axis stabilised mode subsequently.

INSAT-4B undergoing electromagnetic compatibility tests at the newly established ISRO Satellite Integration and Test Establishment

INSAT-4B was located at 74.88 deg E longitude on March 26, 2007 and drifting towards its final orbital position of 93.5 deg E. The satellite drift will be arrested at 80.5 deg E longitude to carry out in-orbit testing of the payloads after which, it will be moved to 93.5 deg E longitude where it will be colocated with INSAT-3A.

INSAT-4B measures 15.4 metre with its solar arrays fully deployed in orbit. The satellite is 3-axis body stabilised in orbit using earth 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 5,860 W of electrical power backed up by three 100 Ah Lithium-Ion Batteries. INSAT-4B has two deployable antennas for various transmit and receive functions.

INSAT-4B Communication Payloads

• 12 Ku-band transponders – Nine with 36 MHz and three with 27 MHz usable bandwidth — providing an EIRP of 52 dBW over the footprint covering Indian main land.

• 12 C-band 36 MHz bandwidth transponders providing an EIRP of 39 dBW with expanded coverage encompassing Indian geographical boundary, area beyond India in Southeast and Northwest regions.

Indian National Satellite (INSAT), which was established in 1983, is the largest domestic communication satellite system in the Asia
Pacific Region. It provides services in telecommunication, television broadcasting, meteorology including disaster warning,
tele-education and telemedicine. The system has 175 transponders at present for communication services besides meteorological instruments —Very High Resolution Radiometer and Charged Coupled Device cameras — for providing meteorological data. With the commissioning of INSAT-4B, the communication capacity will be increased to 199 transponders.

INSAT System satellites launched so far