Satellite Systems

SATELLITE SYSTEMS

Indian satellite systems fall into two categories; Remote-Sensing & Communications. The main programs being;

INSAT - Indian National Satellite System - The INSAT 2 Series

The construction of the two Indian-built, INSAT-2 test spacecraft was approved in April 1985, with Ariane launches in 1992-93, followed by three more operational satellites beginning 1994-95 aboard procured vehicles. The total number of satellites launched of the INSAT-2 series range include 4 (INSAT-2A, -2B, -2C and -2D), the most recent launch being that of INSAT-2D on 4 June 1997. Unlike the INSAT-1 class satellites, these are indigenously produced and later members (INSAT-2E and later) will be carried by India's own GSLV launcher.

After the last in the INSAT-2 series is launched in the latter half of 1998, a new generation of INSAT-3 series are to be launched. Five satellites of the INSAT-3 series are planned, starting in 1999. The last three satellites of the INSAT-3 series should be launched by the GSLV. INSAT has applied for 29 new GEO slots in 1997; from 51.5°E to 113.5°E and 13°W and 108°W.

INSAT-2A: Launched on 9 July 1992 from Kourou for location at 74°E. It entered service on 6 August 1992. It has a design life of seven years.

The INSAT 2A's Transponders;

• 124.5 SSPA 5930-6410/ 3705-4185 MHz and six (three backup; 2-for-1) 6735-6975/ 4510-4750 MHz up/down C-band and external C-band, all-India beam, 36MHz bandwidth, 32dBW EOL EIRP for 16 transponders, 34dBW for two.

• Two (plus one backup) 50W TWTA 5858-5930 /2550-2630MHz up/down S-band all-India BSS beam, 36MHz bandwidth, 42 dBW EOL EIRP.

• Single 402.75MHz Data Collection System transponder.

• Single 406MHz Cospas/Sarsat search & rescue package.

INSAT-2B: Specifications same as INSAT-2A. Launched on 22 July 1993 from Kourou and was declared operational at 93.5°E on 10 August 1993.

INSAT-2C: Launched on 6 December 1995 from Kourou. The INSAT-2C replaced the imaging payload with improved telecom services. Declared operational at 93.5°E.

The INSAT-2C's Transponders;

• 12 C-band (2x50W TWTA, tx10WSSPA & 3x4W SSPA) all-India beam.

• Six extended C-band (2x10W & 4x4W SSPAs), all-India beam.

• Three 20W TWTA Ku-band all-India, 41dBW EIRP

• Two (plus one backup) 50W TWTA 5858-5930 /2550-2630MHz up/down S-band all-India BSS beam, 36MHz bandwidth, 42 dBW EOL EIRP.

• One 50W TWTA 2670-2690/2500Mhz up/down S-band all-India mobile communications beam.

• 1 (plus one backup) 4W SSPA C-band all-India mobile communications feeder link.

INSAT-2D: Launched on 4 June 1997 from Kourou. This satellite gave a big boost to television and telephone services. Specifications same as the -2C. However in October 1997, a major power failure occurred in the satellite and all attempts to bring it back were unsuccessful. It was finally abandoned.

INSAT-2E: Launched on 03 April 1999, the 2550 kg satellite has a design life of 12 years and carries 17 C-band transponders of which 11 transponders have been leased to the International Telecommunication Satellite Organisation (Intelsat). For the first time, the satellite, carries an improved version of a very high resolution radiometer (VHRR) and a high-resolution charge coupled device (CCD) camera. The VHRR payload will be used for imaging the cloud coverage including cyclone formation. Data from the CCD camera will assist in cyclone analysis, local storm monitoring, heavy rain forecast, snow detection and long term climatic studies.

The INSAT-2E satellite

The satellite is configured with a single sided solar array consisting of four panels which will deploy in an accordion fashion by a single command operation. The satellite's power system provides regulated dual power bus wherein certain subsystems could be connected to any of the bus by ground command. Apart from regular and selected power buses, an uninterrupted power bus is available for the domestic power control electronics and tele-command functions. The solar panels are populated with gallium-arsenic/germanium cells to generate a net power of about 2240 Watts to meet spacecraft power demands with adequate margin. The payload power requirement alone is 1755 Watts.