On July 14, shortly after 5 A.M. EDT, India is set launch its latest attempt at a historic moon landing.
Dubbed Chandrayaan-3, the spacecraft includes the lander Vikram (named after the father of the Indian space program Vikram Sarabhai) and the rover Pragyan (“wisdom” in Sanskrit). Chandrayaan-2, India’s first lunar landing mission, ended in heartbreak in 2019, when that mission’s lander crashed during its final descent phase. Chandrayaan-2 wasn’t a complete failure, however, because it did deploy India's second lunar orbiter, which continues to provide valuable data for lunar science, as well as future exploration planning.
If successful, the new mission will make India the fourth country in history to achieve a lunar landing, following the U.S., the former Soviet Union and China.
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Succeeding through Failure
Chandrayaan-3’s Vikram lander weighs in at 1,752 kilograms—about as much as a small car and about 280 kilograms heavier than its predecessor. Most of that additional weight is linked to extra precautions the Indian Space Research Organization (ISRO) built in after the disappointing crash landing in 2019. Not only does Vikram carry more fuel to better stay on its intended trajectory to the lunar surface, it also has far more redundancies and safeguards to gracefully touch down this time around. These include strengthened legs to absorb the mechanical shock of touchdown and a new velocity sensor for enhanced navigation measurements, as well as various software improvements to accommodate potential sensor failures. All this, combined with numerous ground tests, has ISRO officials confident that this time they will stick the landing.
“Instead of a success-based design, ISRO has this time opted for a failure-based design,” said ISRO’s chairman S. Somanath during a July 6 press briefing. That is, for Chandrayaan-3, ISRO has focused on what can fail and how those failures can be prevented. “We looked at sensor failure, engine failure, algorithm failure, calculation failure,” Somanath said.
With a combined mass of 3,900 kilograms, Chandrayaan-3’s orbiter, lander and rover are just within the lift limit of the mission’s ride to space: the GSLV Mk III, India’s most powerful rocket. After being deployed to a highly elliptical Earth orbit, the Chandrayaan-3 orbiter will propel Vikram to and around the moon and then gradually maneuver it into a circular polar orbit 100 kilometers above the lunar surface.
If all goes well with the launch and the initial journey to Earth’s natural satellite, on August 23 Vikram will begin an autonomous descent to a targeted landing site on the moon’s Earth-facing side, near the lunar south pole.
A High-Latitude Frontier for Lunar Exploration
Located at 69.37 degrees south latitude and 32.35 degrees east longitude, Chandrayaan-3’s lunar landing site is a geologically rich region embedded in a larger rocky highland. ISRO scientists and engineers chose it based on high-resolution photographs and data from their Chandrayaan-2 orbiter and NASA’s Lunar Reconnaissance Orbiter.
“This is the first-ever surface exploration of a high-latitude near-polar region, something that’s never [been] measured in situ,” says Anil Bhardwaj, director of the Physical Research Laboratory (PRL) in Ahmadabad, India, and a scientist involved in several of the nation’s planetary missions.
After a successful touchdown, Chandrayaan-3’s exploration of the lunar surface will begin in earnest with the deployment of the 26-kilogram Pragyan rover via a ramp. The six-wheeled, solar-powered rover will rely on the Vikram lander to maintain communications with Earth as it trundles around the landing region for 14 Earth days—or about one period of lunar daylight.
Pragyan carries two spectrometers to help scientists determine the elements and minerals that make up the soil and rocks around the landing region. One of these is the Alpha Particle X-ray Spectrometer (APXS), a miniaturized, 0.7-kilogram instrument. APXS proved particularly challenging to realize, says its principal investigator Santosh Vadawale, an astrophysicist at PRL. “For APXS to work, it has to be within five centimeters of its target,” he explains. “It took multiple design iterations to make such a mass-constrained instrument deployable without a traditional robotic arm.” The x-ray spectrometer protrudes over the rover’s front and rotates by 90 degrees to study the material below it. Added to this was the challenge of procuring radioactive curium-244, an alpha particle source that is central to APXS—and that Vadawale notes is “available only from Russia.” The instrument’s lead engineer, PRL’s M. Shanmugam, adds, “The procurement started in 2010 and took about seven years.”
The Vikram lander itself hosts four science experiments: A seismometer will detect moonquakes to provide clues about the moon’s internal structure, building on work that began with the deployment of similar instruments by NASA’s Apollo missions. Another experiment will, for the first time, probe plasma created at the lunar surface by incessantly streaming charged particles from the sun. There is also a NASA-contributed retroreflector, an upgraded version of the ones left on the moon by Apollo astronauts. Earthbound scientists can bounce laser pulses off these devices to better understand the gravitational interactions of the Earth-Moon system, as well as the lunar interior.
The fourth experiment is a thermal probe that Vikram will attempt to insert to about 10 centimeters beneath the lunar surface to provide pristine soil temperature measurements throughout the lunar day. “This is the first-ever in situ thermal profiling of the moon’s near subsurface. It will tell us exactly how the sun’s heat propagates downward from the surface,” says PRL planetary scientist K. Durga Prasad, one of the experiment leads. A heater just above the probe’s tip will warm up the soil to help determine its thermal conductivity, as well as its density and other physical properties—something critical for future advanced lunar exploration. “Temperatures dictate the presence, stability and mobility of water on the moon,” Durga says. “The experiment will tell us about stability zones of such resources. Future studies and even extraction operations of lunar soil will benefit from this data.”
A New “Moon Rush”
Chandrayaan-3 feeds into the global frenzy of sending hardware to the moon, particularly to its south pole. The upcoming U.S. Artemis crewed missions, China’s Chang’e robotic craft and the majority of other governmental, as well as private, endeavors plan to explore the moon’s south pole, which contains valuable water ice and other resources that could prove crucial for any sustained human lunar presence. Getting to the lunar surface remains risky, however. Three out of the last four landing attempts—including Chandrayaan-2—have failed. India’s hopefully successful second try with Chandrayaan-3 will help keep the momentum for the moon going.
“India giving the hard problem of moon landing a second try soon after its first attempt is an appreciated investment the whole world will benefit from,” says Jessy Kate Schingler, a researcher in outer space policy and a senior adviser at the Open Lunar Foundation.
In fact, India’s investment in the moon continues to grow. For the Chandrayaan program, ISRO developed its own simulated lunar soil facility to perform hardware testing in preparation for even more lunar activity. For its next moon mission—intended to launch before the end of decade—India is partnering with Japan to have the Lunar Polar Exploration (LUPEX) rover directly study deposits of water ice at the lunar south pole. “LUPEX will help us understand the distribution, nature, as well as quantity, of water ice accessible in the first few centimeters of the polar surface it explores,” Bhardwaj says.
Although most of India’s space program is proudly homegrown, its ambitious aspirations—which include plans for a crewed orbital mission as soon as next year—make international collaboration eminently worthwhile. This helps explain the rationale behind the nation’s agreement on June 21 to join the Artemis Accords, a U.S.-led lunar governance framework that aims to peacefully manage lunar activity from the increasing number of global missions. Because Japan is also a signatory of the Artemis Accords, it’s likely the joint LUPEX mission will provide some of the crucial enabling data for future crewed Artemis missions.
“The accords are a nonbinding political understanding of a signee for mutually beneficial space exploration activities based on the desire to implement provisions of the Outer Space Treaty with focus on the Artemis program. As a signatory, India could accelerate its lunar exploration program by better collaborating with the U.S. and other signee nations,” says Ranjana Kaul of the law firm Dua Associates, who specializes in international space law and policy and is on the board of the International Institute of Space Law.
But there’s a catch. ISRO’s aspiring upcoming space science missions have been facing nothing but delays because of budget shortages and overshadowing priorities. While India’s new space policy, released in April, does encourage ISRO to “undertake ... on in-situ resource utilization [and] celestial prospecting,” failure to increase such science and technology outputs would mean that the nation would be unable to sufficiently leverage the accords to help shape our future at the moon.
“The accords could be a sign that India will invest much more in lunar and space exploration,” Schingler adds. “However, it’s the actual outcome that will at least partially determine the weight [India] can pull in space policy matters.”
One thing is clear. The success of ISRO’s Chandrayaan-3 moon lander will be critical for anchoring India’s long-term role in lunar exploration and governance.