|Mission type||Earth observation|
|Mission duration||3 years (planned)|
12 years and 4 months
|Launch mass||975 kg|
|Start of mission|
|Launch date||29 August 1991,|
|Rocket||Vostok-2M s/n I15000-079|
|Launch site||Baikonur, Site 31/6|
|End of mission|
|Last contact||20 December 2003|
|Reference system||Geocentric |
|Perigee altitude||859 km|
|Apogee altitude||915 km|
|Epoch||29 August 1991|
IRS-1B, the second of the series of indigenous state-of-art remote sensing satellites, was successfully launched into a polar sun-synchronous orbit on 29 August 1991 from the Soviet Cosmodrome at Baikonur. IRS-1B carries three cameras, LISS-1, LISS-2A and LISS-2B with resolutions of 72.5 metres (238 ft) and 36.25 metres (118.9 ft) respectively with a swath width of about 140 kilometres (87 mi) during each pass over the country. It was a part-operational, part-experimental mission to develop Indian expertise in satellite imagery. It was a successor to the remote sensing mission IRS-1A, both undertaken by the Indian Space Research Organisation (ISRO).
Improved features compared to its predecessor (IRS-1A): gyro referencing for better orientation sensing, time tagged commanding facility for more flexibility in camera operation and line count information for better data product generation.
The spacecraft was a box-shaped 1.6 x 1.56 x 1.1-metre bus with two Sun-tracking solar arrays of 8.5 square metres each. Two nickel-cadmium batteries provided power during eclipses. The three-axis stabilised sun-synchronous satellite had a 0.4° pitch/roll and 0.5° yaw pointing accuracy provided by a zero-momentum reaction wheel system utilising Earth/Sun/star sensors and gyros.
IRS-1B carried three solid state push broom scanner Linear Imaging Self-Scanner (LISS) cameras:
The satellite carried three LISS push broom CCD sensors operating in four spectral bands compatible with Landsat Thematic Mapper and Spot HRV data. The bands were 0.45-0.52, 0.52-0.59, 0.62-0.68, and 0.77-0.86 microns. The LISS 1 sensor had four 2048-element CCD imagers with a focal length of 162.2 centimetres (63.9 in) generating a resolution of 72.5 metres (238 ft) and a 148 kilometres (92 mi) swath width. The LISS 2A/B sensors had eight 2048-element CCD imagers with a focal length of 324.4 millimetres (12.77 in) generating a ground resolution of 36.25 metres (118.9 ft) and a 74 kilometres (46 mi) swath width. The two LISS 2 imagers bracketed the LISS 1 imager providing a 3 kilometres (1.9 mi) overlap. Data from the LISS 1 were downlinked on S-band at 5.2 Mbps and from the LISS 2 A/B at 10.4 Mbps to the ground station at Shadnagar, India. The satellite was controlled from Bangalore, India.
IRS-1B was operated in a Sun-synchronous orbit. On 29 August 1991, it had a perigee of 859 kilometres (534 mi), an apogee of 915 kilometres (569 mi), an inclination of 99.2°, and an orbital period of 102.7 minutes.
IRS-1B successfully completed its mission on 20 December 2003, after operating for 12 years and 4 months.