IRS 1D

IRS 1D is an active satellite operated by India, launched on 1997-09-29 from SRI. With over 29 years in orbit, it has far exceeded many satellites’ design lifetimes. It orbits in Low Earth Orbit (LEO) at altitudes between 737 km and 810 km with an inclination of 98.8°. It travels at approximately 26,890 km/h (7.47 km/s), completing one full orbit every 100 minutes — that’s roughly 14.36 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 ~25–100 years. Orbital Radar tracks IRS 1D in real time using the latest two-line element set (TLE) data, providing live position, altitude, speed and orbital path updated continuously.

IRS 1D orbits at an average altitude of 774 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 1D’s average altitude, there are currently 386 active payloads and 2,117 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0179, ONEWEB-0455. With an inclination of 98.8°, IRS 1D passes over latitudes between 98.8°N and 98.8°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 12 share a similar altitude band with IRS 1D.