On the Moon

ON THE EVENING of August 23, as the Chandrayaan-3 land­er module touched down in the south­ern polar region of the moon at lunar dawn after a 39-day voyage, the brightest object in our night sky seemed to shine even brighter with our collective pride and joy. “We have achieved soft-landing on the moon,” the Indian Space Research Organisation (ISRO) Chairman S Somanath announced, at a little past 6PM, at the Mission Operations Complex (MOX), ISRO Telemetry, Tracking and Command Network (ISTRAC), in north Bengaluru as it erupted in celebra­tions. “India is on the moon.” The online telecast of the event became the most viewed livestream ever, with over eight million watching. In an interview last month, Somanath had compared space missions to cricket matches. With Chandrayaan-3, ISRO not only played to win but it also played to the gallery, beam­ing high-quality live video as the lander module de­scended over several minutes to the cratered surface before alighting upright, like some exotic insect. (We did not get to witness the precise moment, however, as ISRO switched to an animation towards the end.)

Since Chandrayaan-3 blasted off on board Launch Vehicle Mark-3 (LVM3) on July 14 at 2.35PM, the moon has loomed larger than ever over India. Schools, shop and small-town maidans put up cutouts and thermocol models of the launch vehicle with its large payload fairing. A new genera­tion of space enthusiasts now revels in creating orbit manoeuvre animations and 3D printed models of the lander Vikram. Never before have Indians geeked out on a space mission, refreshed a space agency’s social media pages every few hours, or waxed tech­nical on YouTube about thrusters, gyros and sensors. In many ways, Chandrayaan-3 has kindled the wild, wide-open magic of space in Indians.

WHILE WE BASK in the reflected sparkle of a little cosmic dust, let us also foreground the importance of the landing. First and foremost, it is a technical demonstration of India’s landing and roving capabilities, which are crucial to future planetary missions. A soft-landing on a cold and desolate side of the moon is the perfect opening setpiece for a new chapter in India’s space journey, declaring its readiness to take greater leaps—to Venus, for instance. Second, it is a stra­tegic advantage to land in the southern lunar region, much of which remains uncharted. The moon is the Rosetta Stone with which man hopes to unlock the mysteries of the solar system, and the south pole is where much of the evidence lies. In 2009, a NASA instrument aboard India’s maiden moon probe detected the presence of hydration—hydroxyl or water molecules—on the moon. The previous year, Chandrayaan-1 had landed a probe in the Shackleton crater located at the south pole, a region that scientists already suspected harboured the largest deposits of ice on the moon. Studies indicate that in the permanently shadowed regions at the lunar poles, water does not sublimate and may be available at the surface. This water could one day be used to make rocket fuel and to provide oxygen and drinking water for future lunar settlements. As space becomes a coveted refuge of rich countries—and entrepreneurs—the moon assumes new sig­nificance as the most accessible resource hub for future colonies as well as a gateway to travelling to far-off planets. The US, China and Japan are all in the race to explore the moon’s deep craters at the south pole where no one has yet soft-landed. India’s landing in the south polar region, at a targeted latitude of 69.367621°S and a longitude of 32.348126°E, is the closest.

As the first to soft-land in the south polar region, India made history just days after Russia’s Luna-25 had spun out of control and crashed into the same region of the moon. Two other attempts to land on the moon earlier this year, by Japanese and Israeli private companies, also ended in failure. “It is not in ISRO’s culture to be intimidated by low odds or by previous failures. They were confi­dent of executing a soft-landing because they had worked hard on perfecting every aspect of the mission,” says Mylswamy Annadurai, the retired ISRO executive who saw through the successful launch of Chandrayaan-1 as project director and served as project director of Chandrayaan-2 till 2013. “From the autonomous landing to the instruments on board, Chandrayaan-3 is a culmination of ISRO’s painstaking efforts over the years to develop, test and perfect highly complex systems indigenously,” he adds.

At a ridiculously low budget—assumed to be about ₹615 crore as per a 2020 statement by then ISRO Chairman K Sivan—India has become only the fourth country to land on the moon, ahead of Japan, which is set to launch its lunar lander mission SLIM on August 26. Two American companies are aiming to land on the moon later this year, one of them at the south pole. NASA even­tually intends to land astronauts at the lunar south pole as part of its Artemis mission and also to use the moon as a gateway to manned missions to Mars. Currently, China’s moon mission, the Chang’e Project, is the most advanced. The first soft-landing on the far side of the moon was that of Chang’e-4, which landed in 2018 inside a 110-mile-wide depression in the South Pole-Aitken Basin, the moon’s largest impact feature, and it continues to explore this unknown region. In 2020, China undertook another successful mission to the moon to retrieve 2kg of regolith—lunar soil. It has planned several subsequent missions with a view to developing an autonomous lunar research station near the moon’s south pole.

HOURS AFTER THE Indian landing, at around 1.30AM, the rover Pragyan started trundling over the lunar sur­face on its six wheels, leaving symbolic imprints of the Ashoka Chakra and the ISRO logo. Over the next fortnight, its two science payloads are expected to collect important data from an unexplored region. The Alpha Particle X-ray Spectrometer to study the chemical and mineralogical composi­tion of the lunar surface was developed by the Physical Research Laboratory (PRL), Ahmedabad, and the Laser Induced Breakdown Spectroscope to determine the elemental composition was built at the Laboratory for Electro Optics Systems (LEOS) in Bengaluru. The 1,752kg lander Vikram will meanwhile deploy four payloads of its own: the Radio Anatomy of Moon Bound Hypersensi­tive ionosphere and Atmosphere and Langmuir Probe (RAMBHA-LP), developed by the Space Physics Laboratory at the Vikram Sarabhai Space Centre (SPL-VSSC) in Thiruvananthapuram to measure plasma density near the lunar surface; Chandra’s Surface Thermo-physical Experiment (ChaSTE), also by SPL-VSSC, to measure the ther­mal properties of the surface down to a depth of 10cm; the Instrument for Lunar Seismic Activ­ity (ILSA) by LEOS to study the seismicity of the landing site; and the Laser Retroreflector Array by NASA, which will serve as a lunar surface navi­gation aid for future lunar orbiters. In addition, a payload on the propulsion module—which sepa­rated from the lander on August 17—will study the Earth as an exoplanet using an Acousto-Optic Tunable Filter-based spectro-polarimeter with a view to benchmarking the observations of tem­perate and Earth-like exoplanets.

Although Chandrayaan-2 crashed into the lunar surface after a glitch in its final descent in 2019, the high-quality instruments on its orbiter—which also serves as a contingency communications re­lay for Chandrayaan-3’s lander module—includ­ing a high-resolution camera, a terrain-mapping camera, a dual-band synthetic aperture radar to look for subsurface water-ice, and an advanced IR spectrometer, continue to function as expected. They have in fact filled in many gaps in our under­standing of the moon, including confirming the presence of water in sunlit zones, and finding chro­mium and an abundance of sodium on the moon’s surface. Invariably, though, scientific epiphanies are drowned out by the more adventurous aspects of space missions. “We were in shock after Chandrayaan-2 failed to land,” says Sam Dayala Dev, former director of the ISRO Inertial Sys­tems Unit (IISU) in Thiruvananthapuram. His unit was responsible for the laser gyro-based Inertial Reference unit and Accelerometer Package, the sensor that provides vital data on the lander’s orienta­tion and acceleration. IISU also built the Laser Altimeter (LASA) and the Ka Band Altimeter (KaRA) that measure the distance of the craft from the moon’s surface. “We were confident in our sensors but the lander’s five engines produced more thrust than expected that led to a lot of errors. The craft sped up to correct its course and ended up crashing,” he says. Ahead of the Chandrayaan-3 landing, Somanath and the ISRO team had exuded a rare confidence in sticking the landing this time round. “If everything fails, if all the sensors fail, nothing works, still it (Vikram) will make a landing. That’s how it has been designed—provided that the propulsion system works well. Even if two of the engines do not work, this time the lander will be able to land. It has been designed in such a way that it should be able to handle multiple failures,” he had said. “I wanted to add the caveat that if the gyros fail, the entire mission is doomed, because it’s the gyros alone that give the attitude,” says Dayala Dev. “The problems last time were actually fairly simple ones once we had figured them out. We had not considered acceleration last time, for instance. Also, the overperformance of the thrusters in the ini­tial phase could not be corrected by the guidance system. This time round, nothing was left to chance. Sensors were added, the software algorithm was improved in consultation with experts, and meticulous testing was done, closely simulating conditions on the moon.”

Dayala Dev was part of the failure analysis committee ISRO put together in the wake of the crash in 2019. Three minutes before the terminal descent phase, the lander spun over 410 degrees and deviated from its calibrated spin of 55 degrees to land hard on the moon. In his first official state­ment in 2020 on what caused the hard landing, then ISRO Chairman K Sivan had said that it was the result of a less than optimal reduction in the velocity of the lander during a sec­ond “camera coasting phase’’. The camera coasting phase was dispensed with in Chandrayaan-3, as ISRO already had access to images of the moon’s surface from the Chandrayaan-2 or­biter camera. “[T]he velocity was beyond the designed limit of the navigation guidance and control system… it finally ended up in a hard landing,’’ Sivan had said.

Scientists at ISRO were quick to realise and recover from their mistakes. The 1,752kg Chandrayaan-3 lander is 280kg heavier than its predecessor, carrying more fuel and better safeguards to ensure a soft touchdown. Hardware upgrades to the lander include stronger legs to absorb mechanical shocks and a new velocity sensor for better navigational measure­ments. There is also an additional computer on the lander this time, adding much-needed redundancy for processing images from the onboard camera and assessing the safety of the landing site.

As for the navigation guidance system on Chandrayaan-3, it was designed to be capable of instantaneously regulating thrust. “If it is possible to pilot the vehicle from the ground, perhaps no one would want the landing to be autonomous, but it is an absolute necessity for such space missions,” says Radhakant Padhi, a professor at the Department of Aerospace Engineering at the Indian Institute of Science, Bengaluru, who collaborated with ISRO to help improve the guidance system performance. “It is a more cautious descent this time,” says Padhi, who was also Somanath’s classmate at IISc for his Masters. In an earlier publication,  Padhi’s lab had suggested minimum-jerk third-order polynomial guidance with hard-boundary conditions to en­sure initial position, velocity and acceleration continuity at the beginning of the second phase of landing, which assures attitude continuity of a vehicle with strap-down thrusters. Encouraging results from this paper may have been the motivation for ISRO in selecting such a guidance system for the fine-braking phase, Padhi says.

ISRO’S FEVERISH AND purposeful pursuit of the moon after Chandrayaan-2’s unfortunate crash on the lunar surface in 2019 has inspired citizens to become stakeholders in what has become a nation-building project. But not much is known of the three-year-long exercise to re­build for the next mission. After ISRO raked over every aspect of the Chandrayaan-2 mission, sparing no detail, in internal reviews, it decided to enhance the target landing site, from 500mx500m last time to 4kmx2.4km. The lander underwent special tests to assess the performance of all sensors under different test configurations and flight profiles, and of the propulsion system under engine firing conditions. The ISRO test site at Ullarthi in Chitradurga, Karnataka, was prepared with moon-like craters and targets to validate navigational abilities. “The biggest lesson learned was to build—and test— for failure,” says Annadurai. “We have demonstrated, beyond any doubt, the resilience of our space mission, and of course, its future-readiness.”

“This is the seventh mission of LVM3 and the third launch this year. We are now gearing up for the launch, in September, of Aditya-L1, India’s first solar observational mission,” says S Unnikrishnan Nair, director, VSSC. With the reliability of LVM3 improving, there is an urgent need to ramp up produc­tion, he says. “There is limited industry available that can produce 4-5m-class hardware. We are working to foster new partnerships with industry to shore up our capacity.” India launched 389 foreign satellites in the past decade, earning ₹3,300 crore. LVM3, ISRO’s heaviest rocket, which launched Chandrayaan-2 and Chandrayaan-3, was also deployed to launch commercial satellites, including 72 satellites for the Sunil Bharti Mittal-backed OneWeb constellation in two separate launch events. India is also set to launch, sometime next year, the NASA-ISRO Synthetic Aperture Radar (NISAR) to map the Earth over 12 days and monitor changes in its land and ice surfaces.

India’s much-delayed maiden manned mission, Gagan­yaan, has meanwhile started to gain pace, with ISRO testing drogue parachutes, which play a pivotal role in reducing the velocity of the crew module to a safe level during re-entry, earlier this month. The objective of the mission is to send a human crew of three into a 400km orbit for three days and to bring them back safely to Earth by landing in the sea.

While India’s new space policy encourages ISRO to take up “missions on in-situ resource utilisation, celestial prospecting and other aspects of extra-terrestrial habitability”, India’s bud­get for the Department of Space has been stuck at about 0.05 per cent of GDP for over a decade. India is known for its incredible cost efficiency—it spent ₹450 crore on the Mars Orbiter Mis­sion (MOM), a fraction of the cost of NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft—but without heavier rockets, better landing technology and a radioisotope thermoelectric generator (RTG) to supply heat and power to increase the life span of exploratory missions beyond a lunar day, our space programme cannot hope to leapfrog. A sense of possibility, however, reigns—a feeling that we are on the precipice of something great. Paving the way for international collaborations, India recently signed the Artemis Accords, a US-led international partnership on planetary exploration and research that has been signed by 26 countries till date, includ­ing Japan, Australia, the UK, France, and Canada. Somanath told the media earlier this year that ISRO may contribute to the Gateway, an upcoming NASA-led international lunar orbital station for Artemis astronauts, in return for which it may get a chance to send its own astronauts to space—possibly before the Gaganyaan mission comes to fruition. Another mission that is on the cards—pending Indian governmental approval—is the Indo-Japanese Lunar Polar Exploration Mission (LUPEX), targeted for launch between 2026 and 2028, which will study the moon in detail over three months or more to better map and understand its deposits of water.

As ISRO presses on towards some of its most interesting excursions, Chandrayaan-3’s textbook execution will serve as a happy reminder of the vitality of Indian science and technology. Any space mission’s journey is a chiaroscuro of successes and failures. The important thing is to aim for the next big impossible thing.

Team Chandrayaan

The brain trust behind the mission

S Somanath, Chairman, ISRO

The face of the Indian space programme, he has stepped up the pace of work at ISRO—and its outreach efforts—since he took charge in January 2022. Credited with expediting India’s upcoming solar mission Aditya-L1 and the ambitious manned space flight programme, he has also ramped up testing at the agency to ensure success at first attempt. At a time when space-faring is transforming into a spectator sport, Somanath, 60, has been pushing for greater transparency on the part of ISRO. He has addressed students, given a technical interview to a science YouTuber and openly discussed the agency’s intents, strengths and setbacks at public forums. His term so far has also seen the agency’s social media pages go from dull to positively buzzy.

P Veeramuthuvel, Project director, Chandrayaan-3

An engineer by training and spiritual by disposition, the 46-year-old keeps a low profile. ISRO counted on his technical prowess and his experience working on Mangalyaan and Chandrayaan-2 to execute the many critical manoeuvres required to land on the lunar south pole. Succeeding M Vanitha as project director leading India’s efforts to reach the moon, Veeramuthuvel, who hails from Villupuram in Tamil Nadu, worked in the private sector and at Hindustan Aeronautics Limited in Bengaluru before finally joining ISRO to fulfil a childhood dream.

S Unnikrishnan Nair, Director, VSSC

An expert in aerospace systems and mechanisms, Nair is also the director of the Indian Institute of Space Science and Technology in Thiruvananthapuram and the founding director of the Human Space Flight Centre in Bengaluru, which spearheads the Gaganyaan programme. At the
Vikram Sarabhai Space Centre, Nair and his team ensured the Launch Vehicle Mark-3 (LVM3), dubbed Fat Boy, successfully did the heavy lifting for India’s second attempt to land on the moon. The rocket executed a near-perfect lift off from Sriharikota on July 14, launching Chandrayaan-3 into orbit around the Earth.

M Sankaran, Director, UR Rao Satellite Centre

As head of the facility in Bengaluru where all of ISRO’s satellites are designed, developed and assembled, Sankaran has had a hand in nearly all recent missions including the three moon missions, Mangalyaan and Astrosat, and was instrumental in designing power generation and distribution systems for them. He has also helped indigenise electronics and power system components by fostering relationships with industry.

A Rajarajan, Director, Satish Dhawan Space Centre

Launch vehicle integration, operations, telemetry, tracking and mission control—the Satish Dhawan Space Centre in Sriharikota is where all the action is. Overseeing the launch infrastructure at India’s sole spaceport, which is gearing up to see more action this year, including the launch of India’s solar mission Aditya-L1 in September, Rajarajan and his team are working towards ramping up solid motor production and improving launch vehicle integration facilities.

Anil Bhardwaj, Director, UR Rao Satellite Centre

Much of the science that may come out of a successful landing will be thanks to payloads like the Alpha Particle X-ray Spectrometer developed by PRL. The spectrometer will help analyse the elemental composition of the lunar surface around the landing site. Bhardwaj, 56, won the Infosys Prize 2016 for Physical Sciences for his contributions to planetary studies. The principal investigator of the Mars Exospheric Neutral Composition Analyser (MENCA) experiment on the Mars orbiter mission and the Chandra’s Atmospheric Composition Explorer (CHACE-2) experiment on Chandrayaan-2, Bhardwaj has made key contributions to Chandrayaan-3, including the Chandra’s Surface Thermo-physical Experiment (ChaSTE), which is designed to study the thermal properties of the polar region.

The Indian Space Odyssey

Chandrayaan-3Destination MoonIndian scientistsIsroNarendra ModiS Somanathspace exploration