ISRO launches EOS-05: What are the different types of satellite orbits, and why do they matter?

Science & Technology - Space Technology · 6 September 2026 · Based on Indian Express (original report)

2-minute summary

The Indian Space Research Organisation (ISRO) successfully launched India's first dedicated imaging satellite, EOS-05, into a geosynchronous orbit using the GSLV-F17 rocket from Sriharikota. Weighing 2,367 kg, EOS-05 is positioned approximately 36,000 km above the Earth. Unlike traditional Earth observation satellites operating in Low Earth Orbit (LEO) that offer high-resolution imagery but suffer from intermittent coverage windows due to high speeds, geosynchronous and geostationary satellites match the Earth's rotation. This allows them to remain stationary relative to the surface and provide persistent, continuous observation of specific regions. Because launching heavy payloads directly into geosynchronous orbit is energy-prohibitive, ISRO deposited the satellite into a sub-Geosynchronous Transfer Orbit (sub-GTO), from where the satellite uses its own onboard propulsion to reach its final operational orbit. This capability significantly enhances India's strategic situational awareness, disaster management, weather monitoring, and natural resource tracking by eliminating coverage gaps.

Why it's in the news

ISRO launched India's first dedicated imaging satellite, EOS-05, into a geosynchronous orbit using the GSLV-F17 rocket, highlighting the critical operational differences, advantages, and engineering mechanics of satellite orbits ranging from Low Earth Orbit (LEO) to Geosynchronous Orbit (GSO).

Background and context

India's space programme, spearheaded by ISRO since its inception in 1969, has progressively evolved from experimental sounding rockets to robust launch vehicles like the Polar Satellite Launch Vehicle (PSLV), Geosynchronous Satellite Launch Vehicle (GSLV), and Launch Vehicle Mark-3 (LVM3). Historically, Indian Earth observation and imaging satellites have predominantly operated in Low Earth Orbits (LEO) and Sun-Synchronous Orbits (SSO) to maximize image resolution for cartography, agriculture, and resource mapping. However, LEO observation satellites suffer from limited dwell times over any given geographic area due to their high orbital speeds. To overcome these coverage gaps for continuous tracking—essential for rapid weather event monitoring, maritime domain awareness, and border surveillance—ISRO has increasingly leveraged geosynchronous and geostationary orbits. The launch of EOS-05 via GSLV demonstrates India's maturing orbital insertion techniques, utilizing transfer orbits like sub-GTO and spacecraft propulsion to optimize heavy payload delivery.

International organisations

• European Space Agency (ESA) — Provides foundational scientific definitions and classifications for satellite orbits (LEO, MEO, GEO) referenced globally in space research.

Previous UPSC questions on this theme

• Prelims GS-1 2023 — Consider the following statements : 1. Ballistic missiles are jet-propelled at subsonic speeds throughout their flights, while cruise missiles are rocket-powered only in the initial phase of flight. 2. Agni-V is a medium-range supersonic cruise missile, while BrahMos is a solid-fuelled intercontinental ballistic missile. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2
• Prelims GS-1 2018 — With reference to India's satellite launch vehicles, consider the following statements : 1. PSLVs launch the satellites useful for Earth resources monitoring whereas GSLVs are designed mainly to launch communication satellites. 2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth. 3. GSLV Mk III is a four-staged launch vehicle with the first and third stages using solid rocket motors; and the second and fourth stages using liquid rocket engines. Which of the statements given above is/are correct ? (a) 1 only (b) 2 and 3 (c) 1 and 2 (d) 3 only

Mains practice: Discuss the strategic and operational significance of placing Earth observation satellites in geosynchronous orbits compared to Low Earth Orbits (LEO).

Introduction:

Earth observation satellites are foundational to modern resource management, weather forecasting, and national security. While Low Earth Orbit (LEO) has traditionally dominated imaging missions, the recent deployment of satellites like ISRO's EOS-05 into geosynchronous orbit marks a strategic shift toward continuous, persistent monitoring.

Body:

• Operational Differences: LEO satellites operate between 160 km and 2,000 km, offering high-resolution imagery due to proximity but suffering from rapid transit times and significant coverage gaps. Conversely, geosynchronous satellites operate at ~36,000 km, matching Earth's rotation to remain stationary relative to the surface.

• Persistence and Continuous Coverage: Unlike LEO constellations that rely on periodic revisits, geosynchronous imaging provides uninterrupted observation of large regions without temporal gaps.

• Disaster Management and Weather Tracking: Persistent viewing is critical for tracking rapidly evolving meteorological phenomena such as cyclones, cloud bursts, forest fires, and floods in real time.

• Strategic Domain Awareness: Geosynchronous imaging enhances situational awareness across India's land and maritime borders, enabling constant surveillance rather than snapshot-based intelligence.

• Engineering Trade-offs: While GSO offers persistence, it faces challenges regarding lower image resolution due to distance and severe gravitational perturbations from the Sun and Moon, requiring active station-keeping and fuel consumption.

Conclusion:

Placing dedicated imaging payloads like EOS-05 in geosynchronous orbit bridges critical gaps in India's space-based surveillance architecture. By combining LEO's high-resolution snapshots with GSO's persistent watchfulness, India significantly fortifies its disaster response, resource management, and strategic security frameworks.

Prelims practice questions

Q1. Consider the following statements regarding satellite orbits: 1. Low Earth Orbit (LEO) satellites typically complete an orbit around the Earth in 90 to 120 minutes. 2. Geostationary Earth Orbit (GEO) satellites are positioned in a circular orbit directly over the Earth's equator with a zero-degree inclination. 3. Medium Earth Orbit (MEO) is exclusively used for meteorological imaging and cannot house navigation satellite systems. Which of the statements given above is/are correct?

1. 1 only
2. 1 and 2 only
3. 2 and 3 only
4. 1, 2 and 3

Answer: B. Statement 1 is correct: LEO satellites typically circle the planet every 90–120 minutes. Statement 2 is correct: Geostationary orbits (GEO) are a subset of geosynchronous orbits placed in a circular orbit directly over the equator with zero inclination, making them appear stationary. Statement 3 is incorrect: MEO houses global navigation satellite systems like Galileo and GPS, not just meteorological imaging.

Q2. With reference to the recent launch of EOS-05 by ISRO, why do launch vehicles typically deposit heavy payloads destined for geostationary orbits into a Geosynchronous Transfer Orbit (GTO) first?

1. To directly capture high-resolution imagery during the initial launch phase
2. To conserve rocket fuel by utilizing the satellite's own onboard propulsion to circularize and raise the orbit subsequently
3. To prevent atmospheric drag from completely destroying the satellite in the upper thermosphere
4. To bypass international space treaties regulating low Earth orbits

Answer: B. Directly launching a heavy satellite like the 2,367 kg EOS-05 into a 36,000 km geosynchronous orbit requires immense rocket fuel. Instead, rockets deposit payloads into a GTO or sub-GTO, and the satellite uses its own onboard propulsion system to circularize and reach its operational orbit.

Q3. Which of the following advantages do Low Earth Orbit (LEO) observation satellites possess compared to Geosynchronous (GSO) observation satellites?

1. Continuous, un-interrupted persistence over the exact same patch of Earth
2. Higher image resolution due to closer proximity to the Earth's surface
3. Absence of signal latency during data transmission
4. Zero susceptibility to atmospheric drag and solar-radiation pressure

Answer: B. LEO satellites are much closer to Earth (160–2,000 km) compared to GSO satellites (~36,000 km), which allows them to capture much higher resolution imagery. However, they lack persistent coverage because they move rapidly across the sky.

Revision flashcards

• What is the altitude range defining Low Earth Orbit (LEO)? 160 km to 2,000 km above the Earth's surface.
• What is the key operational difference between a Geosynchronous Orbit (GSO) and a Geostationary Orbit (GEO)? While all geostationary satellites are geosynchronous, GEO specifically requires a circular orbit directly over the equator with a zero-degree inclination so it appears completely fixed relative to Earth.
• Why are satellites in Low Earth Orbit (LEO) unable to observe a specific patch of Earth continuously? Because of their proximity to Earth, they must travel at extremely high speeds to counteract gravity, causing them to hurtle past target areas quickly.
• What launch vehicle was used by ISRO to launch the EOS-05 satellite? The GSLV-F17 rocket.
• What is the primary advantage of placing an imaging satellite like EOS-05 in a geosynchronous orbit? It enables continuous, persistent, and high-frequency observation of large regions without gaps caused by periodic satellite revisits.