IRS 1B

IRS 1B is an active satellite operated by India, launched on 1991-08-29 from Baikonur, Kazakhstan. With over 35 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 883 km and 919 km with an inclination of 99.4°. It travels at approximately 26,653 km/h (7.40 km/s), completing one full orbit every 103 minutes — that’s roughly 13.98 orbits per day. Its near-polar, sun-synchronous orbit means it passes over any given point on Earth at approximately the same local solar time, ideal for consistent Earth observation lighting conditions. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~100–500 years. Orbital Radar tracks IRS 1B in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

IRS 1B orbits at an average altitude of 901 km in a sun-synchronous orbit (SSO), a specialised subset of LEO where the orbital plane precesses to maintain a constant angle relative to the Sun. This provides consistent lighting conditions on every pass — essential for Earth observation, weather monitoring and environmental science. Within ±50 km of IRS 1B’s average altitude, there are currently 217 active payloads and 1,353 tracked debris or rocket body fragments. With an inclination of 99.4°, IRS 1B passes over latitudes between 99.4°N and 99.4°S, providing near-global coverage including the polar regions. Polar and near-polar orbits are used for reconnaissance, weather monitoring and Earth-observation missions that need to image every part of the planet. India operates approximately 108 active satellites in total, of which 4 share a similar altitude band with IRS 1B.