On 4 September 2026 the Prime Minister congratulated ISRO on the successful launch of GSLV-F17 carrying EOS-05, described as India's first-ever imaging satellite from geosynchronous orbit, and pointed to the growing partnership between ISRO and Indian industry as the source of new scale in the programme.
Two ideas are packed into that sentence — the orbit and the launcher — and each carries a set of facts that NDA papers return to year after year.
Why "from geosynchronous orbit" is the whole point
Almost every Earth-observation satellite India has flown sits in low Earth orbit, typically a sun-synchronous polar orbit at 500 to 800 km. Such a satellite circles the planet in about 90 minutes and passes over a given spot every few days, at the same local time, taking sharp pictures because it is close.
A geosynchronous satellite sits at roughly 35,786 km above the equator, where its orbital period equals the Earth's rotation. From the ground it appears to hang still. Communications and weather satellites — the INSAT and GSAT series — live there for that reason.
Putting an imaging camera at that altitude trades one thing for another:
| Low Earth orbit imaging | Geosynchronous imaging | |
|---|---|---|
| Altitude | ~500–800 km | ~35,786 km |
| Resolution | Very high — metres or better | Coarser — the camera is 50 times further away |
| Revisit | Days between passes over one spot | Continuous — the same hemisphere is always in view |
| Best for | Mapping, detailed surveillance, cartography | Real-time monitoring — cyclones, floods, forest fires, cloud motion, fast-changing events |
The gain is persistence. A LEO satellite photographs a developing cyclone once and then leaves; a GEO imager can watch the whole subcontinent every few minutes, all day. For disaster management and for keeping a standing eye on borders and coasts, that persistence is worth the loss of fine detail.
This is a concept ISRO had attempted before. In August 2021, GSLV-F10 carried EOS-03, the first geo-imaging satellite, and the mission was lost when the cryogenic upper stage failed to ignite. EOS-05's success completes that unfinished business, five years on.
The launcher
GSLV stands for Geosynchronous Satellite Launch Vehicle, and its Mk II version is a three-stage rocket:
- First stage — a solid motor with four liquid strap-on boosters.
- Second stage — liquid, powered by the Vikas engine.
- Third stage — the cryogenic upper stage, burning liquid hydrogen and liquid oxygen at very low temperatures.
The third stage is the one to remember. Cryogenic propulsion gives the highest efficiency of any chemical rocket stage, which is what makes it possible to push a payload of roughly two tonnes out to geosynchronous transfer orbit. India's own cryogenic engine first flew successfully on GSLV-D5 in January 2014, after a decade of development following the denial of the technology in the 1990s. Every GSLV since then has used it, and the 2021 failure was a reminder of how unforgiving it is.
Three launchers, three jobs — a standard NDA question:
| Vehicle | Role | Typical capacity |
|---|---|---|
| PSLV | Workhorse for polar / sun-synchronous orbits; most Earth-observation satellites | ~1.75 t to SSO |
| GSLV Mk II | Geosynchronous transfer orbit — communication, navigation and now geo-imaging satellites | ~2–2.5 t to GTO |
| LVM3 (formerly GSLV Mk III) | Heavy lift — Chandrayaan-3, Gaganyaan, large communication satellites | ~4 t to GTO |
All launch from the Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh. The recent GSLV record shows the vehicle's growing routine: F12 (NVS-01, 2023), F14 (INSAT-3DS, 2024), F15 (NVS-02, January 2025 — the 100th launch from Sriharikota), F16 (NISAR, July 2025), and now F17.
The industry line
The Prime Minister's emphasis on the ISRO-industry partnership points to a structural change. Since 2020, IN-SPACe has served as the single-window authoriser for private space activity, and NewSpace India Limited (2019) is ISRO's commercial arm. Consortia of Indian firms now build PSLV stages and, increasingly, whole launchers under ISRO's oversight. The direction is that ISRO designs and qualifies, industry manufactures and eventually operates — the same arc the DPSU model has followed in defence.
The same day, the Space Minister and France's Minister for Higher Education, Research and Space, Philippe Baptiste, met virtually to prepare an International Space Summit in Paris, at which the ISRO Chairman is to speak on India's future human spaceflight in low Earth orbit, and to confirm French participation in the Bengaluru Space Expo. France has been India's longest-standing space partner — the Vikas engine itself descends from the French Viking — and the current agenda runs from Gaganyaan support to joint climate satellites.
🔑 Revision block
- 4 September 2026: GSLV-F17 launched EOS-05 — India's first imaging satellite from geosynchronous orbit.
- GEO ≈ 35,786 km, period = one day, satellite appears fixed. LEO/SSO ≈ 500–800 km, ~90-minute orbit, passes every few days.
- GEO imaging = continuous view, coarser resolution — real-time monitoring of cyclones, floods, fires. LEO imaging = high resolution, periodic revisit.
- Earlier attempt: EOS-03 on GSLV-F10, August 2021, lost to a cryogenic stage ignition failure.
- GSLV Mk II: solid first stage + 4 liquid strap-ons → liquid second stage (Vikas) → cryogenic third stage (LH₂/LOX). Indigenous cryogenic engine first flew on GSLV-D5, January 2014.
- PSLV → polar/SSO, ~1.75 t. GSLV Mk II → GTO, ~2–2.5 t. LVM3 → GTO ~4 t; Chandrayaan-3, Gaganyaan.
- Launch site: Satish Dhawan Space Centre, Sriharikota. GSLV-F15 (NVS-02, Jan 2025) was the 100th Sriharikota launch.
- IN-SPACe (2020) authorises private space activity; NSIL (2019) is ISRO's commercial arm.
- India-France: International Space Summit, Paris; Bengaluru Space Expo; Vikas engine derives from the French Viking.
🎯 Practice MCQs
Q1. A geosynchronous satellite orbits at an altitude of approximately: (a) 800 km (b) 2,000 km (c) 36,000 km (d) 100,000 km → (c).
Q2. The chief advantage of imaging from geosynchronous orbit is: (a) higher resolution (b) continuous coverage of the same region (c) lower launch cost (d) polar coverage → (b).
Q3. The third stage of the GSLV Mk II is: (a) solid (b) liquid, Vikas-powered (c) cryogenic (d) electric → (c).
Q4. Cryogenic engines burn: (a) kerosene and LOX (b) liquid hydrogen and liquid oxygen (c) UDMH and N₂O₄ (d) solid HTPB → (b).
Q5. India's first successful indigenous cryogenic stage flew on: (a) GSLV-D3 (b) GSLV-D5 (c) GSLV-F10 (d) LVM3-M1 → (b), in January 2014.
Q6. The GSLV-F10 mission of August 2021 failed because of: (a) a strap-on booster failure (b) cryogenic upper stage ignition failure (c) fairing separation failure (d) a guidance error → (b).
Q7. ISRO's heavy-lift launcher used for Chandrayaan-3 is: (a) PSLV (b) GSLV Mk II (c) LVM3 (d) SSLV → (c).
Q8. Most Indian Earth-observation satellites are placed in: (a) geostationary orbit (b) sun-synchronous polar orbit (c) Molniya orbit (d) lunar orbit → (b).
Q9. The 100th launch from Sriharikota was: (a) GSLV-F14 (b) GSLV-F15 carrying NVS-02 (c) LVM3-M4 (d) PSLV-C60 → (b), January 2025.
Q10. IN-SPACe was set up to: (a) build cryogenic engines (b) authorise and promote private space activity (c) launch foreign satellites (d) train astronauts → (b).
Q11. The Vikas engine is derived from the French: (a) Vulcain (b) Viking (c) Vinci (d) Ariane → (b).
Q12. Consider the following: 1. PSLV is primarily used for geosynchronous transfer orbit missions. 2. LVM3 has a higher payload capacity to GTO than GSLV Mk II. (a) 1 only (b) 2 only (c) Both (d) Neither → (b) — PSLV is the polar-orbit workhorse.
📋 How this gets asked (PYQ pattern)
Space questions run in four shapes. The orbit item — GEO altitude and period, or the difference between geostationary and sun-synchronous, asked as a definition. The launcher item — PSLV, GSLV and LVM3 matched to orbit and payload, with the stages of the GSLV as a follow-up. The engine item — cryogenic propellants, and the year the indigenous stage first flew. The mission item — a named launch matched to its payload and year.
The fresh 2026 hook is GSLV-F17 / EOS-05 and the phrase "first imaging satellite from geosynchronous orbit", likeliest as a straight identification paired with the GSLV's cryogenic stage. A statement pair on GEO period and the cryogenic third stage is the most probable two-statement item. As always, we describe the recurring pattern, not any exact past question.
Preparing for the NDA? Space questions reward one table of launchers and one clear picture of orbits — get those and each new launch becomes a one-line addition. Build the base with our NDA science hub and notes on work, energy and power, follow the daily NDA current affairs, and train with our ex-officer faculty in the upcoming Cavalier courses in Delhi.
✍️ Written by Col D.N. Sharma — Defence studies & technology faculty at The Cavalier. Reviewed by the Cavalier Faculty Desk. The Cavalier, founded by ex-Army officers, has trained NDA/CDS/SSB aspirants since 2001 (Facebook · YouTube).
Source: PIB / Prime Minister's Office and Department of Space, 4 September 2026. Orbital mechanics and launcher details cross-verified with independent sources.