The second IRS satellite, launched from Baikonur in August 1991, which served for more than twelve years.
No longer operational, according to the public satellite catalogue.
IRS-1B carried the same three push-broom cameras as IRS-1A: LISS-1 at 72.5 m resolution and LISS-2A and LISS-2B at 36.25 m.
It added improvements: gyroscopes for better sensing of its orientation, time-tagged commands for more flexible camera use, and line-count information for better image products.
IRS-1B weighed 975 kg and had 600 watts of power. It was three-axis stabilised with four reaction wheels and magnetic torquers, and had sixteen 1 N hydrazine thrusters.
A Vostok rocket launched IRS-1B from Baikonur on 29 August 1991. Like IRS-1A it flew a polar sun-synchronous orbit at about 904 km with a 22-day repeat cycle.
The mission ended on 20 December 2003, after 12 years and 4 months. An engineering model of the IRS-1A/1B design was later turned into the IRS-1E satellite, which was lost in the unsuccessful PSLV-D1 launch in September 1993.