Space & Defence Technology for UPSC Prelims — ISRO, DRDO, Missions & Missiles Made Simple
Learn the core space and defence facts UPSC tests: ISRO vs DRDO, PSLV/GSLV rockets, key missions like Chandrayaan-3 and Mangalyaan, and India's missiles.
By the PadhoDost Team · 📖 8 min read · Updated 4 August 2026
Part of UPSC Civil Services prepThink of India's science and technology story like a family with two ambitious siblings. One sibling (ISRO) looks up at the sky and dreams of reaching the Moon, Mars, and the Sun. The other sibling (DRDO) looks at the borders and builds the shields and swords that keep the country safe. For UPSC Prelims, you do not need to be an engineer. You need to know WHO built WHAT, and the simple idea behind each machine. This explainer teaches exactly that.
Part 1: The Two Big Organisations
Almost every fact in this chapter connects to one of two agencies. ISRO (Indian Space Research Organisation) handles space. It was set up in 1969 and its headquarters is in Bengaluru. Its founding father was Dr. Vikram Sarabhai. DRDO (Defence Research and Development Organisation) handles weapons and defence technology. It was set up in 1958 and its headquarters is in New Delhi.
Part 2: How Rockets Reach Space
🧠 A rocket is a stack of throwaway water bottles
Imagine climbing a hill carrying heavy water bottles. As each bottle empties, you throw it away so you become lighter and climb faster. A rocket works the same way. It is built in 'stages'. When one stage burns all its fuel, it drops off, making the rocket lighter for the next push. This is why rockets are called multi-stage launch vehicles.
India has two main workhorse rockets. Their names tell you their job. PSLV (Polar Satellite Launch Vehicle) places satellites into low, polar orbits close to Earth. It is called ISRO's 'workhorse' because it is very reliable and has launched hundreds of satellites, including foreign ones. GSLV (Geosynchronous Satellite Launch Vehicle) is more powerful and places heavier satellites far away, about 36,000 km up, where they stay fixed over one spot. The most powerful Indian rocket is the LVM3 (earlier called GSLV Mark III).
| Orbit type | Height (roughly) | Used for |
|---|---|---|
| Low Earth Orbit (LEO) | A few hundred km | Spy/imaging satellites, space stations |
| Sun-synchronous (polar) | ~600–800 km | Remote sensing, weather, mapping |
| Geostationary (GEO) | ~36,000 km | TV, communication, weather (stays over one spot) |
Part 3: India's Famous Space Missions
Must-remember missions (durable facts)
- ✓Chandrayaan-1 (2008): India's first Moon mission. It helped confirm the presence of water molecules on the Moon.
- ✓Chandrayaan-3 (2023): India made a soft landing near the Moon's SOUTH POLE. India became the FIRST country to land near the south pole, and the 4th country ever to soft-land on the Moon (after USSR, USA, China). Its lander was 'Vikram' and rover was 'Pragyan'.
- ✓Mars Orbiter Mission / Mangalyaan (launched 2013, reached Mars orbit 2014): India became the first country to reach Mars orbit on its very first attempt.
- ✓Aditya-L1: India's first mission to study the Sun, placed at the Lagrange point L1.
- ✓Gaganyaan: India's planned first human spaceflight mission (to send Indians to space).
Also know India's satellite families by their job. Communication satellites are the INSAT and GSAT series. Earth-watching (remote sensing) satellites are the IRS series. For navigation, India built its own GPS-like system called NavIC (based on the IRNSS satellites), which gives position information over India and the nearby region.
Part 4: Defence and Missiles
India's missile story began with the IGMDP (Integrated Guided Missile Development Programme), started in 1983. Dr. A.P.J. Abdul Kalam led it, which is why he is called the 'Missile Man of India'. The easiest way to remember the missiles is by what they hit.
| Missile | Type / Role |
|---|---|
| Prithvi | Surface-to-surface, short range |
| Agni | Ballistic missile family, long range (Agni-V is over 5,000 km) |
| Akash | Surface-to-air (shoots down enemy aircraft) |
| Nag | Anti-tank guided missile |
| BrahMos | Supersonic cruise missile (India–Russia joint venture) |
🧠 Ballistic vs Cruise missile
A ballistic missile is like throwing a stone: you give it a big powered push at the start, then it flies in a high curved (parabolic) path and falls on the target using gravity. A cruise missile is like a self-driven aeroplane: it keeps its engine running the whole flight, cruises low to avoid radar, and steers itself to the target. BrahMos is a cruise missile; Agni is ballistic.
Quick revision anchors
- ✓ISRO = space, 1969, Bengaluru, Vikram Sarabhai.
- ✓DRDO = defence, 1958, New Delhi.
- ✓PSLV = polar/low orbits (workhorse); GSLV/LVM3 = heavy, far orbits, cryogenic engine.
- ✓Chandrayaan-3 = near Moon's south pole; Mangalyaan = Mars in first attempt.
- ✓Missile Man = Dr. A.P.J. Abdul Kalam (IGMDP, 1983).
- ✓Agni = ballistic (thrown stone); BrahMos = cruise (self-driven plane).
⚡ Quick check
Which statement is correct about India's space and defence technology?
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