EOS-05: India’s New Space Eye
Why in News?
Recently, ISRO successfully launched its advanced Earth observation satellite EOS-05 aboard GSLV-F17. It will allow continuous observation of the subcontinent from an altitude ranging between 34,903 km and 35,884 km.
The EOS-05 is the first Earth observation satellite launched into a geosynchronous orbit by ISRO. It has been placed in a slightly elliptical geosynchronous orbit instead of a circular geostationary orbit.
What is the EOS-05 mission?
About Satellite: Dubbed "Eye in the Sky," EOS-05 is a state-of-the-art Earth observation spacecraft with advanced optical and infrared payloads to provide continuous, real-time imagery. Weighing 2,367 kg, it is the heaviest payload successfully injected into orbit by a standard GSLV configuration.
Launch Vehicle: The mission was executed by GSLV-F17, marking the 19th operational flight of India's Geosynchronous Satellite Launch Vehicle.
GSLV is a three-stage vehicle: the first stage uses a solid core with four liquid strap-on boosters, followed by a liquid second stage and an indigenous cryogenic upper stage (CUS) for launching heavier payloads into deep transfer trajectories.
The Orbit: Unlike conventional Earth observation satellites in Low Earth Orbit (LEO) with limited revisit windows, EOS-05 is India's first dedicated imaging satellite designed to operate from Geosynchronous Orbit (GEO), about 36,000 km above Earth.
Mission Profile & Orbit Raising: GSLV-F17 precisely injected the spacecraft into a sub-geosynchronous transfer orbit (Sub-GTO). Satellite will progressively fire its onboard Liquid Apogee Motor (LAM) over multiple maneuvers to reach its designated geostationary slot over the Indian subcontinent.
Significance of Imaging Satellites in GEO: LEO platforms pass over an area in minutes, leaving blind spots of hours or days before the next pass. GEO provides continuous persistence and unblinking, wide-area view. GEO imaging enables persistent, high-frequency tracking of rapidly evolving hazards like cloudbursts, cyclones, flash floods, and forest fires, where hourly updates are vital for disaster relief.
What are Different Types of Satellite Orbits?
Orbit: As per ESA, an orbit is the curved path an object follows around another body under gravity. Earth orbits are broadly classified into three altitude classes:
Low Earth Orbit (LEO):
| Altitude & Speed: | 160 km to 2,000 km above Earth. Satellites complete orbit in 90-120 minutes, traveling at high velocity to counteract gravity. |
| Applications: | Proximity minimizes signal latency, ideal for high-resolution imaging, broadband mega-constellations, and crewed platforms like the ISS. |
| Subsets: | Includes Sun-Synchronous Orbit (SSO) for consistent solar illumination and Very Low Earth Orbit (VLEO) for ultra-high resolution but high atmospheric drag and fuel use. |
| Density: | As of late 2026, over 15,500 active satellites operate in LEO; India maintains 22 operational satellites in this band. |
Medium Earth Orbit (MEO):
| Altitude: | 2,000 km to 35,786 km, positioned directly beneath the geosynchronous belt. |
| Characteristics: | Balances low signal latency and expansive ground coverage. |
| Applications: | Primarily hosts Global Navigation Satellite Systems (GNSS) like the EU's Galileo (30 satellites) and the US GPS network. |
Geosynchronous Orbit (GSO) & Geostationary Orbit (GEO):
| Altitude & Motion: | Positioned at ∼35,786 km geosynchronous. Satellites orbit eastward, matching Earth's rotational period of 23 hours 56 minutes 4 seconds. |
| GEO Distinction: | When an orbit has zero-degree inclination over the equator, it is a geostationary orbit (GEO). To observers on the ground, a satellite appears permanently fixed at one point in the sky. |
| Footprint: | A single GEO satellite observes nearly one-third of the globe; three evenly spaced satellites can give near-global coverage. |
Conclusion
EOS-05 marks a strategic shift for ISRO, from LEO-based periodic imaging to GEO-based persistent observation. By placing a heavy 2,367 kg imaging payload in geosynchronous orbit via GSLV-F17, India now has an unblinking "Eye in the Sky" for real-time tracking of cyclones, cloudbursts, floods, and fires, strengthening disaster management, weather forecasting, and national security.
