INSAT 2

The INSAT 2 program was underway in 1983 to develop an indigenous multi-purpose GEO spacecraft that relied heavily on the previous Ford Aerospace design. In 1985 the basic spacecraft configuration was adopted, calling for an on-station dry mass of 860 kg which later rose to 910 kg (1,160 kg at beginning of life). The communications payload was increased with six additional 7/5 GHz transponders for a total of 18, plus two S-band transponders. The spacecraft bus is rectangular with side dimensions of 1.6 m by 1.7 m by 1.9 m. The asymmetric, accordion type solar panel produces 1.4 kW at beginning of life and is offset on the other side of the bus by an extendible solar sail (References 91-93).

INSAT 2A was finally launched on 9 July 1992 by an Ariane booster, about three years behind schedule. The spacecraft was positioned at the primary INSAT location of 74 degrees E, which was vacated by INSAT 1B in April, 1992. INSAT 2B was launched 22 July 1993 by an Ariane rocket and positioned at 93.5 degrees E. (References 94-95).

In March, 1994, India selected Arianespace to launch INSATs 2C and 2D in 1995 and 1996, respectively. The design lifetime is nine years.The spacecraft are similar to the earlier INSATs but are 200 kg heavier at launch (2,100 kg) and will carry larger solar arrays for 1.6 kW of electrical power. The communications payload consists of 12 C-band, 6 extended C-band, 3 Ku-band, and 2 S-band transponders plus a new low-power C-band transponder for a mobile communicatins feeder. INSAT-2C and INSAT-2D, in addition to carrying communication transponders in INSAT-2A and 2B, incorporate Ku-band transponders for business communication, extended coverage C-band transponders to enable TV programme outreach beyond Indian boundaries catering to the population from South East Asia to the Middle East and transponders for mobile service. They do not have the meteorological payload. INSAT-2C and INSAT-2B are co-located in the geostationary orbit thus enabling efficient use of allocated orbital slots.

While INSAT-2A and INSAT-2B are almost identical twins INSAT-2C and INSAT-2D are different; they do not carry the meteorological payload. But INSAT-2E, which was successfully launched on 03 April 1999 by the European Ariane Rocket at Kourou in French Guyana, carries an improved version of the VHRR as the meteorological payload. INSAT 2E also features a special INTELSAT compatibility. DOS will lease to INTELSAT organization eleven 36 MHz equivalent units of C-band capacity on board INSAT-2E. The capacity for use by INTELSAT is being built into INSAT-2E. (References 96-99).

Each INSAT satellite is the product of the well-orchestrated effort of the four major centres of ISRO. The main frame of the satellite which carries the controls, telemetry and tele-command, deployment and power systems is manufactured by the ISRO Satellite Center at Bangalore, which also does the mission planning and analysis and manages the whole project. The gyro units, reaction wheels and momentum wheels, to keep the satellite stable in orbit, are fabricated at the Vikram Sarabhai Space Center, Thiruvanthapuram, which is also responsible for the antenna reflectors and scanning mechanism for the Very High Resolution Radiometer(VHRR), that forms the main meteorological payload of INSAT. The VHRR itself is a contribution of the Space Applications Center, Ahmedabad, which also provides for communications transponders. Another vital component, the apogee boost motor (that takes the satellite from its transfer orbit to the geostationary orbit) and the thrusters (required for maintaining the satellite in its assigned slot in orbit) are manufactured at the Liquid Propulsion Systems Center at Thiruvanthapuram.

INSAT has enabled a vast expansion in the television service with over 800 TV transmitters linked through INSAT. The television network provides access to over 80 per cent of India's population. INSAT-2C and INSAT-2D enable Indian television outreach beyond Indian boundaries catering to the population from South East Asia to Middle East. Educational television service through INSAT has been introduced both at university level in the national network and at primary school level in several states including Andhra Pradesh, Orissa, Maharashtra, Gujarat and Uttar Pradesh. A channel on the INSAT has been dedicated for development of education and training. A two-year pilot project for demonstration of satellite-based developmental communication and training has been taken up in Jhabua district of Madhya Pradesh.