Chandrayaan programme

• 1. Introduction

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  The Chandrayaan programme is India's ongoing series of Moon missions, run by the Indian Space Research Organisation, or ISRO. Long before any spacecraft existed, the case for it rested on a single line. A national task force studied whether India should even attempt the Moon. Its report closed with this: it is not whether we can afford it, it is whether we can afford to ignore it. That line was written years before India had a rocket built for anything beyond Earth orbit.

  Three missions later, the programme has put an orbiter into lunar orbit and watched a lander crash into the surface. It has also landed a second craft safely near a pole no country had ever reached before. Along the way, it found something almost no one expected to be there.

  What made a country with no history of planetary missions take that first gamble? What went wrong the first time a Chandrayaan spacecraft tried to land? And what did it actually find, waiting in the Moon's darkest craters?

• 2. Making The Case

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  In 1999, a meeting of the Indian Academy of Sciences raised the idea of a lunar mission. The Astronautical Society of India carried it forward in 2000. A National Lunar Mission Task Force then formed, combining ISRO with leading Indian scientists and technologists, to study whether the idea was even feasible. On the 15th of August 2003, then prime minister Atal Bihari Vajpayee announced the project publicly. The government approved it that November, backing a mission built around a single orbiter. Its job was mineralogical and chemical mapping of the lunar surface.

  While the orbiter was still being assembled, then president A. P. J. Abdul Kalam visited ISRO's office. He argued that an orbiter alone would not be enough. He suggested adding an instrument that could be dropped onto the surface itself. Engineers responded by designing the Moon Impact Probe, or MIP, a 35 kilogram craft built to operate for about 25 minutes. It carried a radar altimeter, a video imaging system and a mass spectrometer. It was designed to be released from an altitude of 100 kilometres. Building the mission also forced India to construct its own deep space network for the first time. Both the network and the probe riding on it were about to be tested for real.

• 3. First Contact

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  On the 22nd of October 2008, Chandrayaan-1 lifted off aboard a PSLV rocket, carrying the Moon Impact Probe with it. After a series of manoeuvres and a trans-lunar injection burn, the spacecraft entered lunar orbit on the 10th of November. That made India the fifth nation ever to orbit the Moon. Days later, the probe separated and struck the surface near the Shackleton crater, in the lunar south pole region. That made India the fifth country ever to reach the lunar surface at all.

  On the 25th of November 2008, just weeks into the mission, the orbiter's temperature climbed to 50 degrees Celsius. It was absorbing heat from both the Sun and the Moon at once. Ground controllers rotated the craft by 20 degrees, shut down its mission computers and raised its orbit to 200 kilometres. A year later, that same overheating turned out to have damaged the star sensors that kept the craft oriented. Only its gyroscopes were left to hold it steady. Contact was lost on the 28th of August 2009, ending the mission a year earlier than its planned two years. ISRO later judged it 95 percent successful anyway. Onboard the descending probe, one small instrument had already logged something far stranger than a temperature spike. That finding would not be announced for close to a year.

• 4. When Everything Fell Apart

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  In 2007, ISRO signed an agreement with Russia's Roscosmos for a second lunar mission. Under the deal, ISRO would launch, orbit and deploy a rover named Pragyan, while Russia supplied the lander. ISRO finished its spacecraft design in 2009, and a 2013 launch was targeted. Everything changed when Russia's Fobos-Grunt mission failed, exposing technical problems in parts meant for the Chandrayaan-2 lander. Russia then asked ISRO to shrink its rover, to compensate for a heavier lander, without offering a firm new timeline. India chose to build the entire mission alone instead. With a Mars transfer window opening in 2013, ISRO repurposed the orbiter hardware built for Chandrayaan-2 into the Mars Orbiter Mission.

  Left without Russia's help, ISRO began building a mock lunar landing site at Challakere. Its craters were shaped to match the real thing, for testing the lander and rover's electronics. A launch in the first quarter of 2018 was targeted, on the GSLV Mk-II rocket. Design changes that same year added a fifth engine, larger landing legs and two extra propellant tanks. They also introduced a new descent profile, where the lander would circle the Moon before landing rather than descending directly. The added mass pushed the mission onto the more powerful, already-flown LVM3 rocket instead. A landing test in February 2019 damaged two of the lander's legs, after a faulty test orientation. That pushed the launch into the second quarter of the year.

  Chandrayaan-2 finally launched on LVM3 on the 22nd of July 2019, reaching lunar orbit on the 20th of August. On the 6th of September 2019, contact with the lander Vikram was lost during its final descent. ISRO's chairman at the time, K. Sivan, said the lander performed as expected until it reached 2.1 kilometres above the ground. There, it began drifting off course. Four years on, his successor, S. Somanath, named three causes. The lander's five engines produced more thrust than planned, letting small errors build up over time. It also could not turn quickly enough to correct itself. And its landing zone, just 500 by 500 metres, left almost no room for error. None of those three failures, ISRO decided, could be allowed to happen again.

• 5. Sticking The Landing

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  Two months after Chandrayaan-2 crashed, ISRO proposed a third mission built around the lander and rover alone. This time, there was no scientifically ambitious orbiter. The goal was to finally prove India could land safely, clearing the way for a planned rover partnership with Japan's JAXA. On the 19th of December 2019, P. Veeramuthuvel was named director of the project. By January 2020, then chairman K. Sivan said the launch might come as early as 2021. That March, the government confirmed a first-half 2021 target. ISRO also rebuilt its Challakere test site, which had deteriorated since Chandrayaan-2, at further cost.

  The COVID-19 pandemic then pushed the launch to 2022, and later to the third quarter of that year. Work on the propulsion module, lander and rover had all fallen behind. Further changes, stronger landing legs, refined instruments and a new failure-based design approach, moved the target again. The new date was the second quarter of 2023. By May 2023, the spacecraft was in final assembly at the U R Rao Satellite Centre. Launch was expected in July.

  Chandrayaan-3 lifted off on LVM3 on the 14th of July 2023. It entered the Moon's gravitational influence on the 5th of August. On the 23rd of August 2023, the lander Vikram touched down in the lunar south pole region. That made India the first country ever to land there. It also became only the fourth country to soft land on the Moon at all, after the Soviet Union, the United States and China. Hours later, the rover Pragyan rolled down its ramp and drove 8 metres across the surface. That made India only the third country to operate a rover on the Moon, after the Soviet Union and China.

  Vikram's redesign had replaced Chandrayaan-2's five engines with four, each still producing 800 newtons of thrust. But now each engine could adjust its direction on the fly. The lander's attitude correction rate also rose, from 10 degrees per second to 25. On landing day, the lander descended from a low point of 30 kilometres. It held an altitude of 7.5 kilometres for 10 seconds, then dropped to 150 metres. There, it hovered twice for about thirty seconds before setting down. On the 3rd of September 2023, before putting Vikram to sleep, ISRO fired its engines in a hop test. The lander lifted 40 centimetres off the ground and set down again. It was the first vertical take-off and landing ever performed on another world.

  Chandrayaan-3's orbiter was really a propulsion module, carrying a single Earth observation payload called SHAPE. It separated from the lander a day after reaching orbit, and kept working long afterward. Precise fuel use during the journey left it with more than 100 kilograms of propellant to spare. ISRO used that fuel to send it back toward Earth in October 2023, instead of letting it drift. It kept operating until the 22nd of August 2024, two years after Vikram had already gone quiet.

• 6. Chasing Water

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  A 1961 study had already argued that the Moon's polar regions, cold enough to trap ice, were a better bet for water than the equator. Samples the Apollo missions brought back from equatorial sites found no proof either way. That left the poles as the only untested option. It is why the Moon Impact Probe was aimed at the lunar south pole instead of anywhere else.

  On the 12th of November 2008, the probe separated from Chandrayaan-1 and began its fall toward the surface. During that descent, its onboard mass spectrometer, called ChACE, detected molecules with an atomic mass of 18, the signature of water. It also detected ionised fragments of water. Three months later, an American instrument on the Chandrayaan-1 orbiter, the Moon Mineralogy Mapper, found the same thing from a different angle. It spotted the light-absorption pattern of water ice in the 1.0-2.5 micrometre range, inside shadowed craters near the pole.

  The two instruments did not agree perfectly. ChACE's readings rose steadily from 20 degrees south, peaked around 60-70 degrees south, and then fell. The Mapper's data, starting at 43.1 degrees south, kept climbing all the way to the pole instead. Some scientists worried ChACE might simply be picking up water contamination carried from Earth. The Indian mathematician Ramaiyengar Sridharan offered another explanation. If the ice was slowly sublimating in the Moon's near-vacuum, ChACE would be measuring rising vapour. The Mapper, meanwhile, would be separately imaging the solid ice those vapours came from.

  Chandrayaan-1's mission had ended a year early, but its data kept working long after. In 2018, Dr. Shuai Li at the University of Hawaii reused the Mapper's old readings. He was hunting for water ice inside permanently dark craters, using faint sunlight bounced off crater walls. He traced that light for the same telltale wavelengths the Mapper had already flagged. After ruling out instrument error through careful statistical analysis, Li summarized his own conclusion in one line: "The most convincing evidence that you actually do have true water ice at the uppermost surface, what we call the optical surface, of the Moon." That verdict didn't come from a fresh mission. It came from data ten years old, gathered by a probe no one had expected to find anything at all.

• 7. Mapping A Hidden World

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  Chandrayaan-1's Terrain Mapping Camera switched on for the first time on the 29th of October 2008. At that point, the spacecraft was still within Earth's own orbit. Over roughly 3,000 orbits of the Moon, it captured more than 70,000 images. Its resolution was 5 metres, sharper than the 100 metre resolution typical of other lunar missions at the time. Each image also covered a swath 40 kilometres wide.

  Studying those maps for rilles and lava tubes, ISRO's scientists found a large lava tube near the equator. It sat in the Oceanus Procellarum region, north of a rille called Rima Galilaei. The tube measured about 2 kilometres long and 360 metres wide. Such tubes shield their interior from cosmic radiation, solar radiation, meteorite impacts and extreme temperature swings. For that reason, they are now considered candidate sites for any future lunar outpost. No mission has visited one yet.

• 8. What Comes Next

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  Chandrayaan-4 is already planned as ISRO's next step, a full sample return mission. It is built from four separate modules: a Transfer Module, a Lander Module, an Ascender Module and a Reentry Module. It is designed to land near Statio Shiv Shakti, the same site where Chandrayaan-3's Vikram touched down. The mission is expected to last a single lunar day.

  ISRO is also working with Japan's JAXA on the Lunar Polar Exploration Mission, known as Chandrayaan-5. It is aiming for a launch in the 2028-29 window. The Indian government approved the mission on the 14th of March 2025. Unlike earlier Chandrayaan landers, it is meant to analyse collected lunar material on site. It will also test technology for surviving the two week lunar night.

  Missions from Chandrayaan-6 onward are meant to build the infrastructure a crewed lunar landing would need. Former ISRO chairman S. Somanath has said as much directly. He has said India intends to keep sending robotic explorers even after its astronauts reach the Moon. He added that the robotic programme will continue after that too. Several of those planned missions, including two later crewed flights, still carry no confirmed date at all.