Missions That Made History: Chandrayaan to Gaganyaan

Space missions are India's calling card to the world: each major flight has demonstrated a new capability, from finding water on the Moon to reaching Mars on a famously frugal budget. This article walks through the missions UPSC asks about most: the Chandrayaan lunar series, the Mars Orbiter Mission, the Aditya-L1 solar observatory, the NISAR radar mission, and the coming human spaceflight era of Gaganyaan and the Bharatiya Antariksh Station.

Chandrayaan-1: the mission that found water on the Moon

Launched in October 2008 aboard a PSLV, Chandrayaan-1 was India's first lunar mission. It carried Indian and foreign instruments, including a Moon Impact Probe that was deliberately crashed into the lunar surface. Its most famous result was the discovery of water molecules on the Moon, a finding that reshaped global lunar science and set the stage for the hunt for water ice at the poles.

The mission proved India could navigate and operate a spacecraft nearly 400,000 km away, and it announced India's arrival as a serious planetary exploration player. It also demonstrated the value of international payloads flying on Indian spacecraft, a template for later collaborations.

Chandrayaan-2: partial failure, enduring science

Launched in July 2019 aboard the LVM3, Chandrayaan-2 aimed for a soft landing near the south pole with the Vikram lander and Pragyan rover. The lander was lost during its final descent. But the mission's orbiter survived and continues to function, mapping the Moon in high resolution with the sharpest cameras of any lunar orbiter currently flying, and supplying data to scientists worldwide.

UPSC's lesson from Chandrayaan-2 is about partial success: the orbiter's instruments still deliver world-class science years later, and the failure analysis taught ISRO the precise lessons, in navigation, throttling and landing sensors, that made Chandrayaan-3 possible.

Chandrayaan-3: touchdown at the south pole

Launched on 14 July 2023 aboard LVM3-M4 from Sriharikota, Chandrayaan-3 carried a propulsion module, the Vikram lander and the Pragyan rover. On 23 August 2023 it achieved a soft landing near the lunar south pole, making India the first country to land there and only the fourth to soft-land on the Moon. The date is now celebrated every year as National Space Day.

The science was rich. The lander's ChaSTE probe measured sharp temperature swings in the lunar soil, ILSA recorded moonquake-like seismic activity, and the rover's LIBS and APXS instruments detected sulphur, aluminium, calcium, iron, titanium, oxygen and silicon on the surface. The sulphur detection matters because it hints at an ancient magma ocean phase in the Moon's history and marks the region as promising for in-situ resource utilisation (ISRU), the future practice of living off local lunar materials instead of carrying everything from Earth.

Technologically, the mission validated autonomous navigation and hazard detection and avoidance systems that will be reused for Gaganyaan, the planned Chandrayaan-4 sample-return mission and future planetary flights. Strategically, it placed India at the centre of global lunar diplomacy, from the Artemis Accords to the planned Indo-Japanese LUPEX mission, designated Chandrayaan-5, an ISRO-JAXA collaboration with an Indian lander and a Japanese rover targeting 2028.

The propulsion module carried its own passenger: SHAPE (Spectro-polarimetry of Habitable Planet Earth), which turned its gaze back home to study Earth's spectral and polarimetric signatures from lunar orbit. Its job is to help astronomers recognise Earth-like exoplanets around other stars. And the lander itself was named Vikram after Vikram Sarabhai, the father of India's space programme.

Chandrayaan-4: bringing a piece of the Moon home

Approved as part of the expanded lunar programme, Chandrayaan-4 is targeted for 2027 and aims to do what only a handful of nations have managed: collect lunar samples and return them to Earth. A sample-return mission must land precisely, scoop material, launch off the Moon's surface, dock in lunar orbit and fly home, which is why the SpaDeX docking demonstration was a necessary prerequisite. Success would put India in an elite club and feed directly into the national goal of a crewed lunar landing by 2040.

The mission, approved by the Union Cabinet in September 2024 and targeted for 2027, will deploy a 350-kg rover, more than thirteen times heavier than Chandrayaan-3's 26-kg Pragyan, and set down in the Moon's rim region, an unexplored terrain likely rich in volatiles and geological diversity. The hardest part is the return leg: after collecting surface and possibly sub-surface samples, an ascender must lift off the Moon and dock with an orbiter in lunar orbit, a manoeuvre on the lines of China's Chang'e-5, which brought lunar samples home in 2020. Only the United States, the Soviet Union and China have achieved sample return so far.

Mangalyaan: Mars on a frugal budget

The Mars Orbiter Mission (MOM), popularly Mangalyaan, launched in November 2013 and entered Martian orbit in September 2014, making India the first country to reach Mars on its first attempt and the first Asian nation to do so. Built for about Rs 450 crore, it became the global symbol of frugal engineering, doing interplanetary science at a fraction of typical mission costs.

MOM carried instruments studying the Martian surface, atmosphere and methane, and it operated far beyond its designed life of six months, lasting nearly eight years. Beyond the science, the mission proved India could plan interplanetary trajectories with extraordinary precision, and it opened the door to the Venus Orbiter Mission planned for 2028.

Aditya-L1: staring at the Sun

Aditya-L1 is India's first space-based solar observatory. Launched on 2 September 2023 aboard PSLV-C57, it travelled to a halo orbit around the Sun-Earth Lagrange point L1, about 1.5 million km from Earth. A Lagrange point is a spot where the gravity of the Sun and Earth balance so a spacecraft can hover with minimal fuel, and from L1 the Sun is never eclipsed by Earth, giving uninterrupted observations.

The spacecraft carries seven indigenous payloads studying the photosphere, chromosphere and corona, the Sun's visible surface, middle and outer atmosphere. Its targets include the mystery of coronal heating (why the corona is far hotter than the surface below it), the birth of coronal mass ejections (CMEs), huge eruptions of solar plasma, and the solar wind that streams past Earth.

The name Aditya means the Sun, and May 2024 underlined why watching it matters: that month Earth was hit by a G5-class geomagnetic storm, the most intense in over two decades, producing auroras at unusually low latitudes and disrupting GPS and radio communications. Space-weather forecasting is Aditya-L1's real-world payoff.

The payoff is practical: CMEs and solar storms can damage satellites, disrupt power grids and scramble communications, so Aditya-L1's real-time data sharpens space weather forecasting and protects both civilian and strategic assets. It works alongside NASA's Parker Solar Probe and ESA's Solar Orbiter in a global effort to understand our star, and its SUIT telescope has already captured novel images of solar flare activity.

NISAR: when NASA and ISRO build together

NISAR (NASA-ISRO Synthetic Aperture Radar) is the first major joint Earth-observation mission of the two agencies. Launched on 30 July 2025 from Sriharikota aboard GSLV-F16, it carries a dual-frequency synthetic aperture radar: an L-band radar built by NASA and an S-band radar built by ISRO, now in its science phase after deployment and commissioning.

Synthetic aperture radar (SAR) creates high-resolution images from microwave pulses instead of sunlight, so it sees through clouds and darkness, day and night. By combining two radar frequencies, NISAR can detect centimetre-scale changes on Earth's surface: shifting tectonic plates, sinking groundwater basins, melting glaciers, changing forests and crops, and damage after disasters. It is among the most ambitious Earth-science missions ever flown, and a landmark of India-US space cooperation.

Gaganyaan: Indians in space, on Indian rockets

Gaganyaan is India's first indigenous human spaceflight mission. The plan is to carry three astronauts to low Earth orbit, about 400 km up, keep them there for three days, and bring them safely home to a splashdown in Indian waters. Four astronaut-designates, all Indian Air Force test pilots including Group Captain Shubhanshu Shukla, have completed training, and Shukla has already flown to the International Space Station on the Axiom-4 mission.

The mission demands technologies India has never flown: a crew escape system that can pull astronauts clear of a failing rocket, life support systems that recycle air and water in a sealed cabin, and re-entry systems that survive the fiery plunge through the atmosphere. The project cost is estimated at about Rs 10,000 crore. Uncrewed test flights, the Vyommitra humanoid robot mission and abort demonstrations are the stepping stones to the crewed flight.

Success would make India only the fourth nation capable of independent human spaceflight, after the USA, Russia and China. The spin-offs in medicine, materials and engineering, and the inspiration for a generation of students, are part of the mission's rationale.

In April 2026 ISRO added a human-factors chapter: Mission MITRA (Mapping of Interoperable Traits and Response Assessment), a first-of-its-kind analogue mission run from 2 to 9 April 2026 in Leh, Ladakh, at about 3,500 metres altitude. An analogue mission is a simulated space mission on Earth that recreates spaceflight stresses, from isolation to thin air, without leaving the ground. Led by ISRO's Human Space Flight Centre with the IAF's Institute of Aerospace Medicine, MITRA used Ladakh's hypoxia, sub-zero cold and isolation as a natural stand-in for spaceflight, studying how gaganyatris and ground-control teams communicate and decide under stress.

The medical challenges are real. Astronauts face elevated radiation exposure with long-term health risks, the disorienting transition between gravity fields that affects hand-eye and head-eye coordination, and the physiological toll of microgravity on muscles and bones. Mission MITRA and the Vyommitra robotic flights are designed to probe all of this before any Indian flies.

SpaDeX: the docking that unlocks the future

In January 2025, ISRO's SpaDeX (Space Docking Experiment) autonomously docked two small satellites, SDX01 (the chaser) and SDX02 (the target), in low Earth orbit, making India the fourth country to master space docking. Docking is the controlled joining of two spacecraft in orbit, and it is the key that unlocks everything ambitious: space stations are assembled by docking modules, sample-return missions must dock in lunar orbit, and future servicing missions will refuel and repair satellites in place, extending their lives and cutting costs.

Bharatiya Antariksh Station: India's home in orbit

The Bharatiya Antariksh Station (BAS) is India's planned national space station, approved by the Union Cabinet in September 2024 as part of the expanded Gaganyaan programme. The plan calls for eight missions under the revised Gaganyaan programme, including the first BAS unit, to be completed by December 2028, and a five-module station by 2035, orbiting 400 to 450 km above Earth.

A station gives India what satellites cannot: a permanent laboratory for microgravity research in medicine, materials science and agriculture, a platform for Earth observation and disaster monitoring, and the operational experience needed for the 2040 crewed Moon landing. The revised programme cost, covering Gaganyaan and the station together, is about Rs 20,193 crore.

The road ahead: Venus, reusable rockets and a Moon landing

The mission queue is full. The Venus Orbiter Mission, targeted for 2028, will study the Venusian surface, its runaway greenhouse atmosphere and the Sun's influence on it. The Next-Generation Launch Vehicle (NGLV), aimed for 2032, is designed to be reusable and low-cost. And the national goal, set under Space Vision 2047, is an Indian astronaut on the Moon by 2040.

On the private side, startups are adding their own firsts: GalaxEye's Mission Drishti, launched in May 2026, was billed as the world's first satellite fusing optical and radar imaging on one platform, and two world-class Ladakh observatories sanctioned in the 2026-27 Budget, the National Large Solar Telescope (NLST) at Merak and the National Large Optical-IR Telescope (NLOT) at Hanle, will exploit the region's high altitude and clear skies for deep-space observation.

Missions at a glance

Key Terms

• Space missions: Here 'space missions' is used as a section theme for the major missions of the Indian space programme, from launch vehicles and satellites to planetary exploration and human spaceflight. In the article context it covers missions such as Chandrayaan, Mangalyaan, Aditya-L1, Gaganyaan, SpaDeX and the upcoming Venus Orbiter Mission, illustrating how ISRO balances scientific exploration, applications and strategic goals. Example: Chandrayaan-3's successful soft landing near the Moon's south pole in August 2023, making India the first country to land there.
• Chandrayaan: Chandrayaan (Sanskrit for 'moon craft') is ISRO's lunar exploration programme. Chandrayaan-1 (2008) orbited the Moon, and its Moon Impact Probe confirmed the presence of water molecules on the lunar surface. Chandrayaan-3 (2023) achieved India's historic soft landing near the south pole, making India the fourth country to land on the Moon and the first to land near the south pole. Example: Chandrayaan-1's discovery of water on the Moon was confirmed by NASA and reshaped global lunar exploration plans.
• Mars Orbiter Mission: India's first interplanetary mission, launched by ISRO on 5 November 2013 aboard PSLV-C25 from Sriharikota, which entered Mars orbit on 24 September 2014. Built at a cost of about Rs 450 crore, it made India the first nation to reach Mars on its maiden attempt and only the fourth space agency to orbit the red planet. It studied the Martian surface, atmosphere and methane. Example: The mission's success on a shoestring budget became a global showcase of frugal engineering in space exploration.
• Aditya-L1: Aditya L1 is ISRO's first dedicated solar observatory, launched on 2 September 2023 aboard PSLV C57 and inserted into a halo orbit around the Sun Earth Lagrange point L1 on 6 January 2024. Positioned about 1.5 million km from Earth, it carries seven payloads to study the solar photosphere, chromosphere and corona, including flares and coronal mass ejections. For UPSC it is a flagship science and technology current affairs topic. Example: Its primary payload, the Visible Emission Line Coronagraph (VELC), images the solar corona to study coronal mass ejections.
• NISAR: NISAR (NASA-ISRO Synthetic Aperture Radar) is the first joint Earth-observation satellite of NASA and ISRO, launched on 30 July 2025 aboard GSLV-F16 from Sriharikota. It is the first satellite to carry two radar frequencies, NASA's L-band and ISRO's S-band synthetic aperture radars, on a single platform with a 12-metre reflector antenna. It scans nearly all land and ice surfaces every 12 days, detecting centimetre-scale surface changes for disaster response, glacier monitoring, and agriculture. Example: NISAR will track ground deformation before earthquakes and ice-sheet movement in near real time with its dual-band radar.
• Gaganyaan: Gaganyaan is ISRO's human spaceflight programme, India's first crewed orbital mission. It will use the human-rated LVM3 launcher from Sriharikota to carry up to three astronauts in a crew module to low Earth orbit for about three days. The programme includes uncrewed test flights, the Vyommitra humanoid robot, crew escape system trials and astronaut training. Success would make India the fourth nation with independent human spaceflight. For UPSC it is the flagship of India's space ambitions. Example: The October 2023 TV-D1 test flight that validated the crew escape system.
• Bharatiya Antariksh Station: The Bharatiya Antariksh Station (BAS) is India's planned indigenous modular space station, announced by ISRO as a long-term goal following the Gaganyaan human spaceflight programme. The station is targeted for completion by 2035, with the first module planned for launch by 2028, and it will serve as an independent platform for long-duration human spaceflight, microgravity research and space technology development. It represents the next phase of India's human spaceflight ambitions and a step toward a sustained Indian crewed presence in low Earth orbit. Example: ISRO plans to assemble the Bharatiya Antariksh Station in multiple modules, starting with the first module by 2028.
• PSLV: The Polar Satellite Launch Vehicle is ISRO's workhorse expendable launch vehicle, a four-stage rocket using solid and liquid stages that is best known for placing satellites into sun-synchronous polar orbits. Operational since the 1990s, it has an exceptional reliability record and has launched landmark missions including Chandrayaan-1 and the Mars Orbiter Mission. It also serves the commercial market through dedicated commercial launches. Example: The PSLV-C37 mission in 2017 set a world record by deploying 104 satellites in a single flight.
• Chandrayaan-1: Chandrayaan-1 is India's first lunar mission, launched by ISRO on 22 October 2008. The orbiter carried eleven scientific payloads, including NASA's Moon Mineralogy Mapper, and its data provided decisive evidence of water molecules on the lunar surface, reshaping lunar science. It also released an impact probe that struck near Shackleton crater. For UPSC, the mission established India as a deep-space actor and anchors questions on space science and technology missions. Example: The Moon Mineralogy Mapper's 2009 detection of hydroxyl and water molecules across the lunar surface remains the mission's landmark finding.
• Moon Impact Probe: The Moon Impact Probe (MIP) was a 29-kilogram impactor carried by India's Chandrayaan-1 lunar orbiter in 2008. On 14 November 2008 it was released and deliberately crash-landed near the Moon's south pole, and during its descent its instruments analysed the thin lunar atmosphere and detected signatures of water, making India the first to find water on the Moon in this manner (later confirmed by NASA's LCROSS mission). The probe also carried the Indian tricolour painted on its sides. Example: Its spectrometers detected water molecules in the lunar exosphere before impact near the south pole's Shackleton crater region.
• water molecules: A water molecule (H2O) consists of two hydrogen atoms bonded to one oxygen atom, and its polar structure gives water its solvent power, high specific heat, and ability to form ice. Water molecules are of special interest in space exploration because lunar or asteroid water could supply drinking water, oxygen, and rocket propellant for future missions, removing the need to lift them from Earth. Chandrayaan-1's Moon Mineralogy Mapper detected absorption signatures of water molecules in sunlit lunar soil in 2009. Example: Chandrayaan-1 (2008) discovered water molecules on the Moon, and Chandrayaan-3's (2023) south-pole landing targeted the region where such water is thought to be trapped as ice.
• LVM3: LVM3, the Launch Vehicle Mark-3 (earlier called GSLV Mk III), is ISRO's heavy-lift rocket and the workhorse for India's most ambitious missions. A three-stage vehicle with two solid strap-on boosters, a liquid core stage and an indigenous cryogenic upper stage, it can place about 8 tonnes in low Earth orbit and 4 tonnes in geosynchronous transfer orbit. It has launched Chandrayaan-2, Chandrayaan-3 and the Gaganyaan uncrewed test flights, and is the designated launcher for the Gaganyaan human spaceflight mission. Example: Chandrayaan-3 rode to space on the LVM3-M4 flight in July 2023, the mission that achieved India's historic soft landing near the lunar south pole the following month.
• Chandrayaan-2: Chandrayaan-2, launched in July 2019, was India's second lunar mission, carrying an orbiter, the Vikram lander and the Pragyan rover. The lander lost communication during its final descent and crashed, but the orbiter continues to operate and has mapped the Moon in high resolution, including with its dual-frequency synthetic aperture radar. Its scientific payloads study lunar mineralogy, the exosphere and water ice. Example: The Chandrayaan-2 orbiter's Terrain Mapping Camera-2 has produced some of the most detailed three-dimensional maps of the lunar surface.
• Vikram: Vikram is the lunar lander of India's Chandrayaan missions, named after Vikram Sarabhai, the father of the Indian space programme. The Chandrayaan-2 Vikram lander was lost during its final descent in 2019, but the Chandrayaan-3 Vikram achieved a historic soft landing near the Moon's south pole on 23 August 2023, making India the first country to land there. It carried the Pragyan rover and instruments to study lunar soil, seismic activity and the thin lunar exosphere. Example: The Chandrayaan-3 landing day, 23 August, is now observed in India as National Space Day.
• Pragyan: Pragyan is the six-wheeled solar-powered rover that rode to the Moon aboard Chandrayaan-3's Vikram lander in August 2023, the successor to Chandrayaan-2's rover which never got to operate. It traversed the lunar south pole for about one lunar day, using its APXS and LIBS instruments to analyse soil composition, and confirmed the presence of sulphur along with aluminium, calcium, iron and other elements. Example: Pragyan's in-situ measurements gave India the first direct chemical assay of soil at the Moon's south pole.
• LVM3-M4: LVM3-M4 was the fourth operational flight of ISRO's heavy-lift Launch Vehicle Mark-3, and the one that carried Chandrayaan-3 into space. Launched from Sriharikota on 14 July 2023, it injected the Chandrayaan-3 stack, comprising the propulsion module, lander Vikram and rover Pragyan, into the intended Earth parking orbit with high precision. The success of this flight was the first step in the mission that ended with India's soft landing near the lunar south pole on 23 August 2023. Example: The precise orbital injection by LVM3-M4 meant Chandrayaan-3 needed fewer correction manoeuvres, saving fuel for the critical lunar orbit and landing phases.
• Chandrayaan-3: Chandrayaan-3 is ISRO's second lunar landing attempt and the mission that made India the first country to soft-land near the Moon's south pole, on 23 August 2023, and only the fourth country to soft-land on the Moon. Its Vikram lander and Pragyan rover confirmed the presence of sulphur and other elements in the lunar soil during their brief surface mission. For UPSC, it is the flagship example of frugal, indigenous space engineering for science and technology answers. Example: The Vikram lander touched down near 69 degrees south latitude, a region chosen for its permanently shadowed craters and water-ice potential.
• south pole: In the Indian space context, the south pole means the lunar south pole, the region around the Moon's south pole that is scientifically prized because its permanently shadowed craters may hold water ice. Chandrayaan-3's Vikram lander touched down near it in August 2023, making India the first country to soft-land in this region. Confirming water ice there would be decisive for future lunar bases. Example: Chandrayaan-3's Vikram lander touched down at Shiv Shakti Point near the lunar south pole on 23 August 2023.
• National Space Day: National Space Day is observed in India on 23 August to commemorate the successful soft landing of Chandrayaan-3's Vikram lander on the Moon's south pole on 23 August 2023, which made India the first country to land near the lunar south pole. It was first celebrated in 2024 to inspire youth towards space science and honour India's space achievements. Events include outreach programmes by ISRO and educational institutions on space exploration. Example: The first National Space Day in 2024 featured nationwide activities highlighting the Chandrayaan-3 and Aditya-L1 missions.
• ChaSTE: ChaSTE (Chandra's Surface Thermophysical Experiment) is a payload aboard the Vikram lander of ISRO's Chandrayaan-3 mission, which landed near the Moon's south pole on 23 August 2023. Its motor-driven probe, fitted with ten temperature sensors, penetrated 10 centimetres into the lunar soil and recorded a surface temperature of about 70 degrees Celsius, surprisingly higher than expected. It produced the first in-situ temperature profile of the lunar south pole, vital for understanding water ice stability and future lunar habitats. Example: ChaSTE's readings showed temperature dropping sharply with depth, with a variation of nearly 50 degrees Celsius within the top few centimetres of soil.
• ILSA: ILSA, the Instrument for Lunar Seismic Activity, is a MEMS (micro-electro-mechanical systems) based seismometer carried on Chandrayaan-3's Vikram lander. It is the first seismometer deployed at the Moon's south pole, recording moonquake-like seismic activity to probe the lunar interior, and it detected a natural seismic event on 26 August 2023. Example: ILSA recorded the first seismic data from the Moon's south pole, the first such measurements from the lunar surface since the Apollo era.
• LIBS: LIBS stands for Laser-Induced Breakdown Spectroscopy, an analytical technique that fires a laser pulse at a material to create a tiny plasma and reads the light it emits to identify the elements present. Because it needs no sample preparation and works at a distance, it is ideal for planetary rovers analysing rocks and soil on other worlds. India's Chandrayaan-3 mission carried a LIBS instrument on its Pragyan rover, which made the first in-situ elemental analysis of the lunar south pole region. Example: In August 2023 the Pragyan rover's LIBS instrument confirmed the presence of sulphur on the lunar surface near the south pole, the first such direct detection, along with aluminium, calcium, iron and other elements.
• APXS: The Alpha Particle X-ray Spectrometer carried by the Pragyan rover of Chandrayaan-3, developed by the Physical Research Laboratory, Ahmedabad. It bombards the lunar surface with alpha particles and X-rays to determine the elemental composition of the soil and rocks near the landing site. Example: APXS measurements near the Moon's south pole detected elements such as aluminium, calcium, iron and sulphur in the lunar regolith. Example: On Chandrayaan-3's Pragyan rover, it identified elements such as aluminium, calcium, iron and sulphur near the lunar south pole.
• magma ocean: A magma ocean is a phase in a planet's early history when its surface was entirely molten, covered by a global ocean of liquid rock. The Moon is thought to have passed through this stage after a giant impact formed it, and as the ocean cooled, light minerals like plagioclase floated up to form the bright lunar highlands while heavier minerals sank. Evidence from Moon rocks about this phase helps scientists reconstruct the early evolution of the Earth-Moon system. Example: Chandrayaan missions analysing lunar soil composition have provided clues about the Moon's ancient magma ocean phase, which explains why the lunar crust is rich in the mineral anorthosite.
• hazard detection and avoidance: Hazard detection and avoidance is a technology used by landing spacecraft to scan the landing area during descent and steer away from dangers such as boulders, craters, and steep slopes. Cameras and sensors image the terrain in real time, and onboard software selects a safe touchdown point on its own. It is critical for soft landings on bodies with rough, poorly mapped surfaces. Example: Chandrayaan-3's Vikram lander carried the Lander Hazard Detection and Avoidance Camera (LHDAC), developed at SAC/ISRO, which imaged the lunar surface to pick a safe landing site.
• Chandrayaan-4: Chandrayaan-4 is ISRO's planned lunar sample-return mission, approved by the Union Cabinet in September 2024 with a budget of about Rs 2,104 crore. It aims to collect soil and rock samples from the lunar surface and bring them back to Earth, a feat achieved so far only by the United States, the Soviet Union and China. The mission will demonstrate complex technologies like lunar docking and is a stepping stone toward an Indian crewed lunar landing targeted for 2040. Example: The mission plans to collect samples from the lunar south pole region and return them to Earth for laboratory analysis.
• Artemis Accords: The Artemis Accords are a set of US-led principles for responsible civil exploration of outer space, covering peaceful purposes, transparency, interoperability, registration of objects, debris mitigation, and use of space resources. They guide cooperation among nations participating in NASA's Artemis programme to return humans to the Moon. Signing them signals alignment with a rules-based order for lunar and deep-space activity. Example: India signed the Artemis Accords on 21 June 2023 in Washington, becoming the 27th signatory, during the Prime Minister's state visit to the United States.
• LUPEX: LUPEX, the Lunar Polar Exploration Mission, is a joint India-Japan mission to explore water and water-ice at the Moon's south pole, now also designated Chandrayaan-5. Under the collaboration, ISRO builds the lunar lander and JAXA builds the rover, with launch on Japan's H3 rocket, and scientific instruments contributed by ISRO, JAXA, the European Space Agency and NASA. Approved by the Indian government in March 2025 and with an implementing arrangement signed in August 2025, it targets the permanently shadowed regions near the lunar south pole, where volatiles may hold clues to the Moon's history and resources for future missions. Launch is planned around 2028. Example: LUPEX will drill into the lunar regolith in permanently shadowed craters to measure water content directly, testing whether the Moon's poles could supply water for future human bases.
• sample-return mission: A sample-return mission is a space mission that collects material from another celestial body, or from space itself, and brings it back to Earth for laboratory analysis. Because Earth-based laboratories can use instruments too large and sensitive for any spacecraft, returned samples yield far more precise dating and composition data than remote sensing or in-situ instruments. Such missions are the gold standard for confirming the origin and history of planetary bodies. Example: China's Chang'e-5 (2020) returned lunar samples, and NASA's OSIRIS-REx (2023) returned material from the asteroid Bennu.
• SpaDeX: SpaDeX (Space Docking Experiment) is ISRO's technology-demonstration mission that proved autonomous in-orbit rendezvous, docking and undocking of two small satellites. Launched by PSLV-C60 on 30 December 2024, the two 220-kg spacecraft (SDX01 as Chaser and SDX02 as Target) docked on 16 January 2025, making India the fourth country after the US, Russia and China to demonstrate docking. Docking capability is essential for building the Bharatiya Antariksh Station, crewed lunar missions and satellite servicing. Example: The successful docking of the SDX01 and SDX02 satellites on 16 January 2025, followed by undocking and further manoeuvres later in 2025.
• Mangalyaan: Mangalyaan is ISRO's Mars Orbiter Mission, India's first interplanetary spacecraft. Launched on 5 November 2013 aboard PSLV-C25 from Sriharikota, it carried scientific payloads to study the Martian surface, atmosphere, and methane. For UPSC it matters because India became the first country to reach Mars orbit on its maiden attempt and the first Asian nation to do so, showcasing low-cost frugal engineering in space science. Example: Launch on 5 November 2013
• frugal engineering: An engineering philosophy of achieving high-tech goals at radically low cost through simplicity, indigenous components and lean management, closely associated with ISRO's space programme. Rather than cutting corners on reliability, frugal engineering uses proven technologies, minimal redundancies and efficient mission design to deliver results at a fraction of international costs. It is often cited as a model of Indian innovation and a source of national soft power. Example: ISRO's Mars Orbiter Mission (Mangalyaan, 2013), which reached Mars on its first attempt at a cost of about $74 million, less than the budget of the Hollywood film Gravity.
• Venus Orbiter Mission: The Venus Orbiter Mission, unofficially called Shukrayaan, is ISRO's planned first mission to Venus to study the planet's surface, atmosphere and interaction with the Sun. It was formally approved by the Union Cabinet in September 2024 with a budget of about Rs 1,236 crore and is targeted for launch on 29 March 2028 aboard the LVM-3 rocket, reaching Venus in July 2028. Venus, often called Earth's twin, holds clues to runaway greenhouse warming, since it is nearly Earth's size but has a crushing carbon dioxide atmosphere. Example: The orbiter will carry 19 scientific payloads, including Indian and international instruments, and use aerobraking over six to eight months to settle into a low science orbit.
• PSLV-C57: PSLV-C57 was the 59th mission of ISRO's Polar Satellite Launch Vehicle, launched on 2 September 2023 from the Satish Dhawan Space Centre, Sriharikota, in the PSLV-XL configuration. It carried Aditya-L1, India's first space-based solar observatory, which was placed in a halo orbit around the Sun-Earth Lagrange point L1, about 1.5 million km from Earth, to study the solar corona, chromosphere and space weather with seven indigenous payloads. Example: PSLV-C57 injected Aditya-L1 into a 235 by 19500 km orbit, from where the spacecraft cruised for about 127 days before reaching its L1 halo orbit on 6 January 2024.
• halo orbit: A halo orbit is a three-dimensional, halo-shaped orbit around a Lagrange point, a location in space where the gravitational pulls of two large bodies balance out. A spacecraft in a halo orbit circles the empty point while staying fixed in position relative to the two bodies, making it an ideal stable observation post. These orbits are used by missions that need a continuous, unobstructed view of a target. Example: ISRO's Aditya-L1 mission operates in a halo orbit around the Sun-Earth Lagrange point L1, about 1.5 million km from Earth, giving it a constant view of the Sun.
• Lagrange point L1: Lagrange point L1 is the gravitational balance point on the line between the Earth and the Sun, about 1.5 million km from Earth toward the Sun. A spacecraft in a halo orbit around L1 stays permanently between the Earth and the Sun, giving it an uninterrupted view of our star and early warning of solar storms heading Earth's way. India's Aditya-L1 solar observatory, launched in September 2023, operates from this point, as do missions such as the Solar and Heliospheric Observatory. Example: Aditya-L1's position at Sun-Earth L1 lets its coronagraph watch the solar corona continuously without the Earth ever eclipsing the Sun, something impossible from Earth orbit.
• Lagrange point: A Lagrange point is one of five special positions in the orbital plane of two large bodies, such as the Sun and Earth, where the gravitational pulls of the two bodies and the orbital motion of a small object balance out. A spacecraft placed at such a point stays in a fixed relative position with very little fuel, making these points ideal parking spots for observatories and solar missions. The five points are labelled L1 to L5; Sun-Earth L1 hosts solar observatories like Aditya-L1, while Sun-Earth L2 hosts deep-space telescopes like the James Webb Space Telescope. Example: Because a satellite at Sun-Earth L1 sits permanently between the Earth and the Sun, it gets an uninterrupted view of the Sun, which is why solar missions are sent there.
• photosphere: The photosphere is the visible surface of the Sun, the layer from which most of the sunlight we receive is emitted. It is about 5,500 degrees Celsius at its surface and only about 500 kilometres thick, though the Sun has no solid surface at all. Almost everything we observe of the Sun, including sunspots and granulation, is a feature of this layer. Example: The sunspots tracked by India's Aditya-L1 solar mission are cooler, darker regions of the photosphere where strong magnetic fields suppress heat flow.
• chromosphere: The chromosphere is the middle layer of the Sun's atmosphere, lying between the visible surface (photosphere) and the outer corona. It is the region where solar phenomena such as spicules and prominences originate. Example: Payloads aboard India's Aditya-L1 solar observatory study the chromosphere along with the photosphere and corona.
• corona: The Sun's outermost atmospheric layer: a tenuous halo of ionised gas (plasma) at over a million degrees Celsius, stretching millions of kilometres into space. It is normally invisible because of the Sun's glare, but appears as a pearly-white halo during a total solar eclipse. Studying the corona is key to understanding solar wind, space weather and phenomena like coronal mass ejections. Example: Aditya-L1, India's first dedicated solar observatory parked at the Sun-Earth Lagrange point L1, carries instruments to study the solar corona and solar wind.
• coronal heating: The long-standing unsolved problem of why the Sun's corona is heated to over a million degrees Celsius while the visible surface below it (the photosphere) is only about 5,500 degrees Celsius. The leading explanations invoke energy released by magnetic waves and by magnetic reconnection, the snapping and rejoining of magnetic field lines. Solving it matters because coronal energy release drives solar flares and coronal mass ejections that affect satellites and power grids on Earth. Example: Instruments on ISRO's Aditya-L1 and NASA's Parker Solar Probe are both tasked with collecting data on the coronal heating problem.
• solar wind: The solar wind is the continuous stream of charged particles, mainly protons and electrons, blowing outward from the Sun's corona at hundreds of kilometres per second. It shapes the heliosphere, causes auroras and geomagnetic storms, and can disrupt satellites, communications and power grids. Space-weather forecasting depends on monitoring it in real time. Example: ISRO's Aditya-L1 mission, stationed at the Sun-Earth L1 point, studies the solar wind and solar storms.
• space weather forecasting: Space weather forecasting is the prediction of disturbances in the space environment around Earth caused by solar activity such as coronal mass ejections, solar flares, and the solar wind. These events can damage satellites, disrupt power grids, scramble GPS and communications, and endanger astronauts. Forecasting relies on Sun-watching observatories and models of how solar plasma travels through space, turning solar physics into an operational warning service. Example: Aditya-L1, stationed at the Sun-Earth L1 point, streams real-time data on solar storms that helps protect civilian and strategic space assets.
• Parker Solar Probe: NASA's Parker Solar Probe, launched in August 2018, is the first spacecraft to fly through the Sun's outer atmosphere, the corona, studying the solar wind and space weather at their source. Named after the living physicist Eugene Parker, it became the fastest human-made object ever built at about 690,000 km per hour, and its carbon-foam heat shield let it survive a closest approach of about 6.1 million km from the Sun's surface. Example: On 24 December 2024 Parker Solar Probe passed within 3.8 million miles of the visible Sun, closer than any human-made object before it, and phoned home a beacon tone two days later to confirm it had survived.
• Solar Orbiter: Solar Orbiter is a joint European Space Agency (ESA) and NASA mission launched in February 2020 to study the Sun up close. It carries ten instruments, including the first telescopes to image the Sun's poles, and works in tandem with NASA's Parker Solar Probe to study the solar wind, coronal mass ejections and space weather. Its findings help predict space weather events that can disrupt satellites, power grids and communications on Earth. Example: Solar Orbiter's close flybys that returned the highest-resolution images yet of the Sun's corona and polar regions.
• SUIT: The Solar Ultraviolet Imaging Telescope is one of the seven scientific payloads aboard ISRO's Aditya-L1, India's first solar observatory mission launched in September 2023. Developed by the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, it images the Sun's photosphere and chromosphere in near-ultraviolet light (200-400 nm) using 11 calibrated filters. It studies solar flares, jets and eruptions, and for the first time measures spatially resolved solar spectral irradiance relevant to the sun-climate relationship. Example: SUIT's observation of an X6.3-class solar flare, one of the most intense categories of solar eruptions.
• GSLV-F16: GSLV-F16 is a specific flight of ISRO's Geosynchronous Satellite Launch Vehicle that launched the NASA-ISRO Synthetic Aperture Radar (NISAR) mission on 30 July 2025 from Sriharikota. NISAR is the first major joint Earth-observation mission of NASA and ISRO, carrying a dual-frequency synthetic aperture radar with NASA's L-band and ISRO's S-band instruments. Example: GSLV-F16 placed NISAR, the first major NASA-ISRO joint mission, into orbit for all-weather mapping of Earth's land and ice surfaces.
• dual-frequency synthetic aperture radar: A dual-frequency synthetic aperture radar is an earth-observation radar that images the surface simultaneously in two microwave frequency bands, combining their complementary strengths. Longer wavelengths penetrate vegetation and clouds while shorter wavelengths give finer surface detail, and radar works day and night in all weather. The flagship example is NISAR, the NASA-ISRO mission launched on 30 July 2025 aboard GSLV-F16, which pairs NASA's L-band radar with ISRO's S-band radar to scan the entire globe every 12 days for land deformation, ice dynamics, ecosystems and disasters. Example: NISAR using its L-band radar to see through dense forest canopy and its S-band radar for fine surface detail in a single 12-day global scan.
• low Earth orbit: Low Earth orbit is the region of space close to Earth, generally up to about 2,000 kilometres above the surface, where the International Space Station and most Earth-observation satellites operate. Being near Earth makes launches cheaper and communication delays tiny, but satellites here must travel at around 7.8 km/s to stay in orbit and face atmospheric drag. It is the most crowded and commercially contested zone of space, raising concerns about debris and collisions. Example: Most of ISRO's remote sensing satellites, such as the Cartosat series, operate in low Earth orbit a few hundred kilometres up, giving high-resolution imagery with short revisit times.
• Group Captain Shubhanshu Shukla: Group Captain Shubhanshu Shukla is an Indian Air Force officer and one of the four astronaut-designates of ISRO's Gaganyaan human spaceflight programme. He served as mission pilot on Axiom Mission 4, launched on 25 June 2025 aboard a SpaceX Falcon 9 and Crew Dragon, becoming the first Indian to visit the International Space Station. His flight marked India's return to human spaceflight after Rakesh Sharma's 1984 mission, and he returned to Earth on 15 July 2025. Example: During his stay on the ISS he conducted microgravity experiments designed by ISRO, covering life sciences and materials research.
• International Space Station: The largest multinational space project, a habitable modular space station in low Earth orbit whose assembly began in 1998, built and operated by the space agencies of the United States, Russia, Europe, Japan and Canada. It serves as a microgravity research laboratory and a platform for international cooperation in human spaceflight. Example: Astronauts from the partner agencies conduct long-duration science experiments aboard the International Space Station, from materials science to human physiology.
• crew escape system: A safety mechanism on a crewed spacecraft that rapidly pulls the crew module away from the launch vehicle in an emergency, such as a rocket failure on the launch pad or during ascent. It is the last line of defence for astronaut safety and is tested uncrewed before any human flight. A successful escape-system test is a mandatory milestone for any human spaceflight programme. Example: On 21 October 2023, ISRO's TV-D1 mission successfully demonstrated the Gaganyaan Crew Escape System, pulling the crew module away from the booster mid-flight.
• life support systems: Life support systems are the integrated technologies in a spacecraft or space station that keep humans alive in the vacuum of space: they supply oxygen, remove carbon dioxide, maintain temperature and pressure, recycle water and manage waste. Because resupply from Earth is limited, modern systems increasingly regenerate resources in a closed loop, for example by recovering drinking water from urine and sweat. Their reliability is a precondition for long human missions to the Moon and Mars. Example: The International Space Station's Environmental Control and Life Support System recycles most of its water and generates oxygen, and ISRO is developing similar regenerative life support for the Gaganyaan crewed mission.
• Vyommitra: Vyommitra is ISRO's half humanoid female robot developed to fly aboard the uncrewed test missions of the Gaganyaan human spaceflight programme before astronauts go up. It can monitor module parameters, operate switches, respond to mission control queries and simulate human functions such as speech, helping validate the crew module's life support and safety systems. Flying a humanoid first reduces risk to human life and demonstrates India's robotics capability in space. Example: Vyommitra is scheduled to fly on Gaganyaan's uncrewed orbital test flights as a precursor to India's first crewed mission.
• SDX01: SDX01 is the Chaser satellite of ISRO's SpaDeX (Space Docking Experiment) mission, launched on 30 December 2024 aboard PSLV-C60 together with SDX02, the Target. It demonstrated autonomous rendezvous, docking and undocking in low Earth orbit, with the first successful docking on 16 January 2025. The mission made India the fourth country to master space docking, a capability essential for the Bharatiya Antariksh Station and future human spaceflight. Example: SDX01's first docking with SDX02 on 16 January 2025.
• SDX02: SDX02 is the Target satellite of ISRO's SpaDeX (Space Docking Experiment) mission, launched with SDX01 on 30 December 2024 to demonstrate rendezvous, docking and undocking in orbit. While SDX01 actively chased, SDX02 was the passive spacecraft captured during the January 2025 docking. The pair also demonstrated electrical power transfer between docked spacecraft, a technology useful for satellite servicing and future stations. Example: SDX02 being captured by SDX01 during the January 2025 SpaDeX docking.
• space docking: Space docking is the manoeuvre in which two spacecraft rendezvous and join in orbit, a capability needed for space stations, satellite servicing, refuelling and crewed lunar missions. It requires precise autonomous guidance to match speeds and align docking ports within centimetres. On 16 January 2025, ISRO's SpaDeX mission docked two 220-kg satellites, making India the fourth country to demonstrate the technology after the US, Russia and China. Example: ISRO's SpaDeX mission achieved India's first space docking in January 2025, a stepping stone to the planned Bharatiya Antariksh Station.
• Docking: Docking is the manoeuvre in which two spacecraft meet in orbit and physically join to function as one vehicle, following a precise sequence of rendezvous, approach, capture and rigidisation. It is essential for crew transfer, assembling space stations, in-orbit refuelling and satellite servicing. On 16 January 2025 ISRO's SpaDeX mission docked its two satellites, SDX01 (Chaser) and SDX02 (Target), making India the fourth country, after the US, Russia and China, to demonstrate space docking. Example: ISRO plans to use docking technology to assemble the modular Bharatiya Antariksh Station in orbit.
• microgravity: Microgravity is the condition of near-weightlessness experienced by objects in continuous free fall, such as aboard the International Space Station, where Earth's gravity is still about 90 percent as strong but everything falls together. In this state, fluids, flames, crystals and living cells behave very differently than on Earth, which is why scientists use it to study protein crystallisation, combustion and human physiology. India plans microgravity research as part of its human spaceflight and space station ambitions. Example: Experiments on the International Space Station grow protein crystals in microgravity that are larger and more perfect than Earth-grown ones, helping design better drugs; ISRO aims to host similar science on the planned Bharatiya Antariksh Station.
• Space Vision 2047: Space Vision 2047 is the long-term roadmap for India's space programme, unveiled after a review chaired by the Prime Minister in October 2023, targeting India's emergence as a leading space power by the centenary of independence. Its headline milestones are the Bharatiya Antariksh Station (first module BAS-01 targeted for 2028, full station by 2035), an Indian crewed landing on the Moon by 2040, and missions like Chandrayaan-4, the Venus Orbiter and the Next Generation Launch Vehicle. It also envisions ISRO focusing on advanced R&D while private industry provides scale. Example: The Cabinet-approved plan to launch the first module of the Bharatiya Antariksh Station by 2028 as the first concrete step of the vision.
• GalaxEye's Mission Drishti: Mission Drishti is GalaxEye's first satellite, launched in May 2026 and billed as the world's first satellite fusing optical and radar imaging on one platform. By carrying both an optical camera and a synthetic aperture radar, it can image the Earth in all weather and lighting conditions. Example: Mission Drishti demonstrated that an Indian startup-built satellite could combine optical and synthetic aperture radar imaging, enabling surveillance even through cloud cover.
• Key takeaways: Key takeaways is a quick-revision summary box placed at the end of each article, listing the most exam-relevant points in a short numbered list. It distils definitions, dates, figures, provisions and examples into a form suited for last-minute revision before Prelims and Mains. Together with the article's practice questions, it turns every topic into a self-contained study unit.
• in-situ resource utilisation (ISRU): In-situ resource utilisation is the practice of using materials found at the destination of a space mission, such as the Moon or Mars, instead of carrying everything up from Earth. It includes making rocket fuel from lunar water ice, extracting oxygen from regolith, and 3D-printing habitats from local soil. ISRU is considered essential for any long-term human presence beyond Earth, because launching supplies from Earth is enormously expensive. Example: NASA's Artemis programme plans to harvest water ice from the Moon's south pole to produce drinking water, air, and rocket propellant.
• Chandrayaan-5: Chandrayaan-5, also called LUPEX (Lunar Polar Exploration Mission), is a planned joint lunar mission by ISRO and JAXA to explore water and water-ice in the permanently shadowed regions of the Moon's south pole. Approved by the Union Cabinet in March 2025 and targeted for launch around 2028 on Japan's H3 rocket, ISRO will build the lander while JAXA provides the 350 kg rover, with contributions from NASA and ESA, and the mission is planned to last about 100 days. Example: The mission builds on Chandrayaan-3's south-pole landing by drilling into lunar regolith to measure the quantity and quality of water that could support future human exploration.
• coronal mass ejections (CMEs): Gigantic eruptions of magnetised plasma hurled from the Sun's corona into space, often travelling at millions of kilometres per hour. When a CME aimed at Earth strikes our magnetosphere, it can trigger geomagnetic storms that disrupt satellites, GPS navigation, aviation communications and even power grids. CMEs are among the most violent space-weather events and a key reason nations monitor the Sun continuously. Example: The severe geomagnetic storm of May 2024, one of the strongest in two decades, was caused by a series of CMEs and produced auroras visible far from the polar regions.
• Synthetic aperture radar (SAR): Synthetic aperture radar is a radar imaging technique in which the motion of the antenna is used to synthesise the effect of a very large antenna, producing high-resolution images. Because it uses microwaves, SAR can image the Earth's surface day and night and through clouds, making it invaluable for flood monitoring, crop assessment and defence surveillance. ISRO's RISAT satellites carry SAR payloads. Example: RISAT satellites use SAR to monitor monsoon floods even when clouds block optical cameras.
• Next-Generation Launch Vehicle (NGLV): ISRO's planned partially reusable heavy-lift launch vehicle, developed under the project name Soorya, intended to succeed the current fleet for the coming decades. The three-stage vehicle is designed to place about 30 tonnes in low-Earth orbit, with LOX-methane lower stages, a cryogenic upper stage and a first stage recovered through vertical landing, at a project outlay of roughly Rs 8,240 crore. Example: NGLV is the designated launcher for the Bharatiya Antariksh Station targeted by 2035 and India's planned crewed lunar landing by 2040.
• National Large Solar Telescope: The National Large Solar Telescope (NLST) is a proposed 2 metre aperture telescope to be installed at Merak near Pangong Tso in Ladakh, also funded in the Union Budget 2026-27. It will study solar dynamics, magnetism and space weather and serve as India's third ground based solar observatory, complementing ISRO's Aditya-L1 mission. Example: The Kodaikanal (1899) and Udaipur (1975) observatories are India's two existing ground based solar observatories.
• National Large Optical-IR Telescope: The National Large Optical-Infrared Telescope (NLOT) is a proposed 13.7 metre segmented mirror telescope to be built by the Indian Institute of Astrophysics at Hanle, Ladakh, funded in the Union Budget 2026-27. With 15 times the light collecting power of India's current telescopes, it will study exoplanets and the early universe, with first light targeted for 2038. Example: A smaller 3.7 metre pathfinder telescope will first test India's segmented mirror technology, developed through participation in the Thirty Meter Telescope consortium.

• SHAPE (Spectro-polarimetry of Habitable Planet Earth) is the payload on Chandrayaan-3's propulsion module that studied Earth's spectral and polarimetric signatures from lunar orbit to help recognise Earth-like exoplanets.

• Mission MITRA (Mapping of Interoperable Traits and Response Assessment) was ISRO's first-of-its-kind analogue mission, run 2 to 9 April 2026 in Leh, Ladakh, studying crew-ground communication under spaceflight-like stress.

• An analogue mission is a simulated space mission on Earth that recreates spaceflight stresses, from isolation to thin air, without leaving the ground.

• The orbital module is the combined crew module and service module of Gaganyaan that will carry Indian astronauts to low Earth orbit and back.

• Chang'e-5 was China's 2020 lunar sample-return mission, the manoeuvre template for Chandrayaan-4's planned ascender-orbiter docking in lunar orbit.

Prelims practice