Defence, Space and Science-Technology

India's armed forces answer to the civilian government. The President is the Supreme Commander, the Defence Minister runs the Ministry of Defence, and the three services (Army, Navy, Air Force) are led by their own Chiefs. Since 2019 there is also a Chief of Defence Staff (CDS), a four-star officer who heads the Department of Military Affairs and coordinates the services. Start with the big picture, then learn the small tables: commands, ranks, academies and the paramilitary forces. These tables are where most questions come from.

Three things to hold together. First, the Chief of Defence Staff (CDS) is not the commander of all three chiefs; he coordinates them and is the Principal Military Adviser to the Defence Minister. Second, the Indian Coast Guard is under the Defence Ministry, while CRPF, BSF, ITBP, SSB, CISF, Assam Rifles and NSG are under the Home Ministry. Third, service chiefs retire after three years or at age 62, whichever is earlier, so the names keep changing; learn the rule, and check the latest names just before your exam.

Every year Indian forces train with friendly armies, navies and air forces. Exam writers love these exercises because each one has a name that must be linked to a partner country and a service. The names are not random: many are built from a word in the partner's language or from a symbol of the two countries. Learn the pair 'exercise - partner' together, and the question becomes a one-second recall.

Exercises are peacetime practice. Operations are real missions, and they too are asked with year and purpose. Notice that the code name often hides a story: 'Sindoor' recalls the vermilion mark of a married woman, and the name was chosen after the terror attack in Pahalgam in which many women lost their husbands.

Operation Sindoor (7 May 2025) is the most important recent operation. After the terror attack at Pahalgam in Jammu and Kashmir on 22 April 2025, Indian forces struck terror-related sites in Pakistan and Pakistan-occupied Kashmir in the early hours of 7 May. Cross-border drone and missile attempts followed and were met by India's air defence, and a ceasefire understanding came on 10 May 2025. The press briefings were given by Foreign Secretary Vikram Misri with two women officers, Colonel Sofiya Qureshi of the Army and Wing Commander Vyomika Singh of the Air Force.

Defence diplomacy also means access to facilities abroad and legal agreements that let militaries work together.

India's missiles did not come by import; they came from a plan. In 1983 the Integrated Guided Missile Development Programme (IGMDP) was launched under the guidance of Dr A. P. J. Abdul Kalam, the 'Missile Man of India'. It built five families of missiles, which you can remember as PATAN: Prithvi, Agni, Trishul, Akash, Nag. The programme was closed in 2008 after it met its aims, and the work now continues under the DRDO (Defence Research and Development Organisation).

Read a missile name by asking two questions. First, from where to where? 'Surface-to-surface' hits land targets from land, 'surface-to-air' defends against aircraft or missiles, 'air-to-air' is fired by a fighter at another aircraft, and 'anti-tank' is a short-range weapon against armour. Second, how does it fly? A ballistic missile is pushed up by a rocket and then falls along a curve, so it is fast and long-range. A cruise missile flies like a small aeroplane with its own engine all the way, so it can fly low and turn towards the target.

Nuclear deterrence rests on a simple idea: India follows a No First Use policy but promises a massive retaliation. India's first nuclear test, Smiling Buddha, was on 18 May 1974 at Pokhran; the Pokhran-II tests, Operation Shakti, were on 11 and 13 May 1998, and 11 May is celebrated as National Technology Day. The Nuclear Command Authority was created in 2003, and the Strategic Forces Command looks after the weapons. A full triad (land, air, sea) became real when INS Arihant, the first indigenous nuclear-powered ballistic missile submarine (SSBN), was commissioned in 2016; the second, INS Arighaat, followed in August 2024.

Behind every weapon is a producer. DRDO designs, and the Defence Public Sector Undertakings (DPSUs) build. The old Ordnance Factory Board of Kolkata was corporatised on 1 October 2021 into seven DPSUs: Munitions India Limited, Armoured Vehicles Nigam Limited (AVANI), Advanced Weapons and Equipment India Limited, Troop Comforts Limited, Yantra India Limited, India Optel Limited and Gliders India Limited.

The story of Indian space begins with one man's dream. Dr Vikram Sarabhai, the 'Father of the Indian Space Programme', argued that a poor country should go to space not for prestige but to solve ordinary problems: weather, communication, education and mapping of resources. Dr Satish Dhawan later shaped ISRO's engineering culture, and the Sriharikota launch centre now carries his name. Keep the line in mind: first rockets, then satellites, then our own launchers, and finally the Moon, Mars and the Sun.

A good habit for dates: ask who launched and from where. Aryabhata (1975) went up on a Soviet rocket, so it is not India's own launch. India's first self-launched satellite is Rohini (1980) on SLV-3 from Sriharikota. That one distinction answers 'first satellite' and 'first indigenous launch' questions without confusion.

Chandrayaan-1 (2008) was launched by PSLV-C11 and it orbited the Moon. Its Moon Impact Probe hit the lunar surface near the Shackleton crater on 14 November 2008 and carried the tricolour, and the mission is credited with helping confirm water molecules on the Moon, together with NASA's M3 instrument. Chandrayaan-2 (22 July 2019) had an orbiter, the lander Vikram (named after Vikram Sarabhai) and the rover Pragyan; the lander lost control in the last minutes of descent on 7 September 2019, but the orbiter still works.

Chandrayaan-3 (14 July 2023, LVM3-M4) corrected that failure. The lander Vikram touched down on 23 August 2023 near the lunar south pole, and the rover Pragyan rolled out. India became the fourth country to soft-land on the Moon (after the USA, the Soviet Union and China) and the first to land near the south polar region. The landing site was named Shiv Shakti Point, and 23 August is celebrated as National Space Day.

Mangalyaan, the Mars Orbiter Mission (MOM), was launched on 5 November 2013 by PSLV-C25 and entered the Martian orbit on 24 September 2014. India became the first Asian country to reach Mars orbit, and the first country in the world to do so on its first attempt, at a cost of roughly 450 crore rupees, less than the budget of some films. Aditya-L1, launched on 2 September 2023 by PSLV-C57, is India's first solar mission. It sits in a halo orbit around the Sun-Earth Lagrange Point 1 (L1), about 1.5 million km from Earth, where gravity from the Sun and the Earth balances, so the spacecraft can watch the Sun without any eclipse. It reached that orbit on 6 January 2024 and studies mainly the corona, the outer atmosphere of the Sun.

Two more space observatories are worth knowing. AstroSat (28 September 2015, PSLV-C30) is India's first dedicated multi-wavelength space observatory, and it studies the sky simultaneously in visible, ultraviolet and X-ray light, for example black holes and neutron stars. XPoSat (1 January 2024, PSLV-C58) is India's first mission to study the polarisation of X-rays from cosmic sources, such as black holes; only one other space mission, NASA's, had been built for this purpose.

Finally, the people and the places. ISRO is headquartered at Bengaluru and works under the Department of Space, which reports directly to the Prime Minister.

A satellite is useful only when it sits in the right orbit, and a rocket is useful only when it can carry the satellite there. So this topic has two parts: the orbits (where) and the launch vehicles (how). First, the orbits, from the lowest to the highest.

A rocket cannot drop a satellite straight into a distant orbit. It first places it in a Geosynchronous Transfer Orbit (GTO), an oval path whose far point touches the height of the geostationary ring. The satellite's own engine then fires at the far point to make the path a circle. That is why the launch masses of heavy communication satellites are quoted for GTO.

Now the rockets. A launch vehicle has stages; each stage burns its fuel and falls away, so the remaining rocket is lighter and goes faster. Fuels come in three kinds: solid (simple and strong, cannot be switched off), liquid (controllable), and cryogenic (liquid hydrogen and liquid oxygen kept at extremely low temperatures, giving the greatest thrust per kilogram of fuel). A cryogenic engine is very hard to build, which is why mastering it was a big step. India developed its own cryogenic engine CE-7.5 for GSLV (first successful flight: GSLV-D5, January 2014) and the stronger CE-20 for LVM3.

India's satellites are grouped into families by job. Each family has an easily remembered purpose.

NavIC (Navigation with Indian Constellation, earlier called IRNSS) is India's own regional navigation system. The original constellation has seven satellites: three in geostationary orbit and four in inclined geosynchronous orbit. It covers India and a region extending up to about 1,500 km around it, and gives an open Standard Positioning Service and a restricted service for the military. Global systems are the US GPS, Russian GLONASS, European Galileo and Chinese BeiDou. A second generation of NavIC satellites began with NVS-01 (May 2023, GSLV-F12) and NVS-02 (January 2025, GSLV-F15).

India's next great step in space is to send its own people to orbit. Gaganyaan is India's first human spaceflight programme. The plan is to carry three astronauts to a low Earth orbit of about 400 km for a mission of up to three days, and then bring them safely back for a splash-down in the sea. Safety is the whole point of the design, so ISRO has built a Crew Escape System (CES): if the rocket fails at lift-off, small rockets on the crew capsule pull it away from the main vehicle and the capsule parachutes down.

A real taste of space came in 2025. Group Captain Shubhanshu Shukla flew as pilot of the private Axiom-4 mission on a SpaceX Falcon 9, launched on 25 June 2025. He reached the International Space Station (ISS) on 26 June and came back to Earth on 15 July 2025. He is the second Indian in space after Rakesh Sharma (1984) and the first Indian to visit the ISS.

SpaDeX (Space Docking Experiment) was launched by PSLV-C60 on 30 December 2024 with two small satellites, SDX01 (Chaser) and SDX02 (Target). On 16 January 2025 they joined in space, which made India the fourth country in the world, after the USA, Russia and China, to master space docking. Docking is the key skill needed for a space station, for refuelling in orbit and for bringing back samples from the Moon.

NISAR (NASA-ISRO Synthetic Aperture Radar) is the first Earth-observation mission built jointly by NASA and ISRO. It was launched on 30 July 2025 by GSLV-F16 into a sun-synchronous orbit. It carries two radars, an L-band one from NASA and an S-band one from ISRO, fixed to a large 12-metre mesh antenna reflector supplied by NASA, on ISRO's I-3K satellite bus. Because radar works through clouds, day and night, NISAR can map the whole globe every 12 days, tracking land movement, glaciers, forests, crops and the threat of earthquakes and landslides.

Space was opened to private companies by the Indian Space Policy 2023. IN-SPACe (2020, Ahmedabad) is the single-window agency that authorises private activity, and NSIL (NewSpace India Limited, 2019) is ISRO's commercial arm. Several start-ups have already made history.

Why does a nation need to join two satellites in orbit, an 'exercise' as simple as docking? Because a space station cannot be launched in one piece. Modules go up separately and must find, approach and lock to each other without any human hand. SpaDeX is therefore a rehearsal for the Bharatiya Antariksh Station and for sample return from the Moon, in which a capsule from the Moon must meet a vehicle in lunar orbit.

India's science is done in institutes, and exams love to ask which institute sits in which city. Think of them in families: the CSIR laboratories (civil science), the atomic energy centres, the DRDO laboratories (defence), the space centres and the astronomy observatories. Learn one anchor city for each family and the rest fall into place.

Atomic energy is run by the Department of Atomic Energy (DAE). Its main centres are BARC at Trombay (Mumbai), IGCAR at Kalpakkam (Tamil Nadu), RRCAT at Indore, VECC at Kolkata and TIFR in Mumbai. The Institute for Plasma Research (IPR) is at Gandhinagar. Homi Bhabha's plan for the country's nuclear power has three stages, built around India's large thorium reserves.

Astronomy and space-science observatories are placed where the sky is dark and the air is thin. Hanle (Ladakh), at about 4,500 m, hosts the Indian Astronomical Observatory of the Indian Institute of Astrophysics, with the 2-metre Himalayan Chandra Telescope, and also the MACE gamma-ray telescope. The Hanle Dark Sky Reserve was declared in 2022. The GMRT (Giant Metrewave Radio Telescope) is at Khodad near Pune.

A 'Cherenkov' telescope like MACE does not look at the star directly. A very high-energy gamma ray hits the upper atmosphere and creates a shower of particles; the shower gives a faint blue flash of Cherenkov light, and the mirror catches that flash. So MACE detects gamma rays by their effect in the atmosphere, not by space-based sensors.

The Deep Ocean Mission is led by the Ministry of Earth Sciences. Its manned submersible Matsya-6000 is being built by the National Institute of Ocean Technology (NIOT), Chennai to carry three people to a depth of 6,000 m under the Samudrayaan project. One aim is to study and, in time, mine polymetallic nodules from the Central Indian Ocean Basin.

Science-and-technology news from 2025 that papers have used: SSI Mantra, an Indian surgical robot, did two cardiac telesurgeries over 286 km in January 2025; IIT Madras opened India's first hyperloop test track in March 2025; the India Meteorological Department adopted the Bharat Forecast System (developed by IITM Pune) in May 2025; and ISRO developed the Vikram 3201 and Kalpana 3201 microprocessors.