Chandrayaan-2

Why Chandrayaan-2 ?

The Chandrayaan-2 mission, India’s second expedition to the Moon, represented a monumental stride in the nation’s space exploration endeavors. Orchestrated by the Indian Space Research Organisation (ISRO), this highly complex undertaking involved three key components: a sophisticated Orbiter, the Vikram Lander, and the six-wheeled Pragyan Rover.¹ Its primary objective was audacious: to explore the largely unknown territory of the Moon’s South Polar Region, marking a significant technological leap for ISRO.²

Building upon the foundational success of its predecessor, Chandrayaan-1, which provided compelling evidence of water molecules on the lunar surface ², the Chandrayaan-2 mission was conceived as a logical and ambitious progression. Chandrayaan-1’s discovery fundamentally reshaped the scientific rationale for subsequent lunar exploration, pivoting focus towards the poles where water ice was suspected to exist in permanently shadowed craters. Chandrayaan-2 was ISRO‘s direct response, aiming to investigate these findings further through in-situ measurements and high-resolution orbital mapping.² This pursuit justified the mission’s inherent complexity and the significant risks associated with attempting a landing in an unexplored and challenging environment.²

Chandrayaan-2 was not merely a scientific quest; it was a testament to India’s growing technological prowess and its aspirations in the global space arena. It aimed to demonstrate critical capabilities like soft landing and rover mobility, essential stepping stones for future, more complex interplanetary missions.² This ISRO Moon mission captured the imagination of the nation and the attention of the world, signifying a pivotal moment in India lunar exploration.

Background and Approval

The genesis of the Chandrayaan-2 mission lies in the success of Chandrayaan-1, which operated from 2008 to 2009.⁴ Following Chandrayaan-1’s impactful discoveries, planning for a follow-up mission commenced swiftly. Initially, Chandrayaan-2 was envisioned as an international collaboration. On November 12, 2007, ISRO signed an agreement with the Russian Federal Space Agency, Roscosmos, to jointly develop the mission.¹

Under this agreement, ISRO held the prime responsibility for designing and developing the Orbiter, the Pragyan Rover, and providing the launch vehicle, initially planned as a Geosynchronous Satellite Launch Vehicle (GSLV).¹ Roscosmos was tasked with providing the lunar lander module.¹ This collaborative framework received official sanction from the Government of India on September 18, 2008, during a Union Cabinet meeting chaired by then Prime Minister Manmohan Singh.¹ The joint design review involving scientists from both nations was completed by August 2009.¹

However, the partnership encountered significant hurdles. Roscosmos faced delays in developing the lander, partly due to the need to review technical aspects following the failure of its Fobos-Grunt Mars mission in 2011, which shared some design elements.¹ The mission, originally targeted for a 2013 launch, was consequently postponed to 2016.¹ Furthermore, design changes proposed by Roscosmos led to an increase in the lander’s mass. This necessitated modifications to ISRO‘s rover design and introduced potential reliability concerns.¹

Ultimately, Russia communicated its inability to provide the lander even by the revised timeframe of 2015, citing ongoing technical and financial challenges.¹ Faced with these indefinite delays, India made the crucial decision to proceed with the Chandrayaan-2 mission independently. This shift, occurring around mid-2013, marked a pivotal moment.¹

This move fundamentally altered the engineering scope and complexity of the mission for ISRO. The organisation now bore the full responsibility for developing the intricate lander technology from scratch – a capability it had not previously demonstrated.⁴ This indigenous development effort significantly impacted the mission’s timeline, cost, and technical architecture. The increased complexity and mass of the indigenously developed lander system necessitated a switch from the initially planned GSLV Mk II to the more powerful GSLV Mk III launch vehicle.¹

The mission’s budget reflected these changes. Initial post-Chandrayaan-1 estimates were around ₹425 crore.⁴ After the shift to an independent mission with indigenous lander development, estimates rose, eventually settling at a final allocated cost, as reported in June 2019, of ₹9.78 billion (approximately US$141 million). This funding covered ₹6 billion for the space segment (Orbiter, Vikram Lander, Pragyan Rover) and ₹3.75 billion for the launch aboard the GSLV Mk III-M1.¹ This demonstrated India’s commitment to pursuing its lunar ambitions despite the withdrawal of its international partner.

Mission Objectives

The Chandrayaan-2 mission was driven by a well-defined set of scientific and technological objectives, aiming to push the frontiers of lunar science and India’s space capabilities.

Scientific Goals

Building directly on the legacy of Chandrayaan-1, the primary scientific aim was to significantly expand lunar scientific knowledge.² Key objectives included:

1. Lunar Topography and Morphology: To conduct detailed mapping of the lunar surface, generating high-resolution topographic maps and 3D digital elevation models. This data is crucial for understanding the Moon’s geological features and evolution.¹
2. Mineralogy and Elemental Abundance: To map the global distribution and abundance of various minerals and major rock-forming elements (like Magnesium, Aluminium, Silicon, Calcium, Titanium, Iron, Sodium) on the lunar surface.¹
3. Water Ice Exploration: A central goal was the search for and characterization of water molecules (H2O) and hydroxyl (OH) signatures. This involved studying their extent and distribution on the surface, in the shallow subsurface (up to several meters deep), and within the tenuous lunar exosphere, particularly focusing on the scientifically promising Moon south pole exploration where permanently shadowed regions (PSRs) might harbor significant water ice deposits.¹ Understanding the origin and distribution of lunar water was a key scientific driver.
4. Exosphere Studies: To perform in-situ analysis of the composition and density of the Moon’s tenuous atmosphere (exosphere) and study its spatial and temporal variations.¹
5. Surface Properties: To investigate the chemical composition and thermo-physical characteristics (like temperature gradient and thermal conductivity) of the lunar topsoil, known as regolith.³
6. Lunar Seismicity: To measure seismic activity (moonquakes) near the landing site to understand the Moon’s internal structure.⁶
7. Lunar Origin and Evolution: To gather data that contributes to a better understanding of the Moon’s origin, evolution, and its history as an archive of the inner Solar System’s environment.²

Technological Goals

Beyond the scientific pursuits, Chandrayaan-2 served as a crucial platform for demonstrating and validating advanced space technologies necessary for future interplanetary missions.² The key technological objectives were:

1. End-to-End Mission Capability: To demonstrate the full lifecycle of a complex lunar mission, encompassing design, launch, intricate orbital maneuvers, deep-space navigation, lander separation, and communication management.⁹
2. Lunar Soft Landing: To achieve the first successful soft landing of an Indian-developed spacecraft on the lunar surface. This involved mastering complex autonomous descent and landing sequences.¹
3. Rover Operations: To demonstrate the capability of deploying and operating a robotic rover (Pragyan Rover) on the lunar surface, including mobility, navigation, and performing in-situ scientific analysis.¹
4. Technology Validation: To test and qualify critical new technologies developed indigenously, such as high-resolution cameras, altimeters, velocimeters, throttleable liquid propulsion engines, hazard detection and avoidance systems, and associated navigation and control software.¹⁵

These dual objectives – advancing fundamental lunar science, particularly concerning water ice, and mastering essential landing and roving technologies – underscored the mission’s ambition. The strategic choice of the South Polar Region amplified this, offering high scientific potential while presenting significant technological hurdles related to extreme temperatures, lighting conditions, and rugged terrain.² This demonstrated ISRO‘s growing confidence and its commitment to pushing the boundaries of India lunar exploration.

Technical Architecture

The Chandrayaan-2 mission was an intricate system comprising three primary spacecraft modules, all developed within India, and launched by the nation’s most powerful rocket. This architecture reflected the mission’s complexity and ISRO‘s capability in handling multifaceted space projects.¹

Mission Components

1. Chandrayaan-2 Orbiter: This was the command center and primary scientific platform in lunar orbit. Designed for a long operational life, it was placed in a 100 km circular polar orbit around the Moon.¹ Its main functions included detailed mapping of the lunar surface, conducting remote sensing scientific investigations using its suite of eight instruments, and acting as a vital communication relay link between the Vikram Lander on the surface and the Indian Deep Space Network (IDSN) on Earth.¹ The Orbiter’s structure was manufactured by Hindustan Aeronautics Limited (HAL).¹
2. Vikram Lander: Named in honor of Dr. Vikram A. Sarabhai, the visionary founder of the Indian space program, the lander was designed to execute India’s first attempt at a soft landing on the Moon.² It carried the Pragyan Rover within it, along with three scientific instruments of its own and a NASA-provided laser retroreflector.⁶ The Vikram Lander was engineered to function for one lunar day, equivalent to approximately 14 Earth days, before the extreme cold of the lunar night would render it inoperable.⁵
3. Pragyan Rover: The name ‘Pragyan’ translates to ‘wisdom’ in Sanskrit. This 6-wheeled robotic vehicle was designed to roll down from the Vikram Lander after touchdown.⁶ Powered by solar panels, it was intended to traverse the lunar surface for up to 500 meters near the landing site, conducting on-the-spot chemical analysis of the soil and rocks using its two scientific instruments.¹ Data gathered by Pragyan would be relayed back to Earth via the Vikram Lander.⁶ Like the lander, its operational life was planned for a single lunar day.¹

Launch Vehicle: GSLV Mk III-M1

The launch vehicle selected for the Chandrayaan-2 mission was the Geosynchronous Satellite Launch Vehicle Mark III-M1 (GSLV Mk III-M1), also referred to as LVM3 M1.¹ This choice was necessitated by the mission’s substantial total mass of 3,850 kg, which increased significantly after ISRO undertook the indigenous development of the lander system, exceeding the capacity of the initially considered GSLV Mk II.¹

The GSLV Mk III represented India’s most powerful and advanced launch vehicle at the time, developed entirely with domestic technology.² Often nicknamed the ‘Baahubali’ rocket for its sheer power ⁸, it is a three-stage heavy-lift vehicle ²⁸:

• First Stage: Two large S200 solid rocket boosters strapped to the core stage, providing the massive initial thrust required for lift-off. Each booster contained approximately 205 tonnes of solid propellant.²⁹
• Second Stage (Core): The L110 liquid stage, powered by two Vikas liquid engines, using 115 tonnes of liquid propellant (Unsymmetrical Dimethylhydrazine – UDMH and Nitrogen Tetroxide – N2O4).²⁹
• Third Stage (Upper): The C25 cryogenic stage, featuring India’s indigenously developed high-thrust CE-20 cryogenic engine, utilizing 28 tonnes of liquid oxygen (LOX) and liquid hydrogen (LH2).²⁹

Key specifications of the GSLV Mk III include a height of approximately 43.5 meters, a core stage diameter of 4.0 meters, and a lift-off mass of around 640 tonnes.²⁸ It is capable of launching payloads of about 4 tonnes into Geostationary Transfer Orbit (GTO) and 8 to 10 tonnes into Low Earth Orbit (LEO).²⁸ The launch of Chandrayaan-2 marked the first operational flight of the GSLV Mk III-M1 configuration ¹, showcasing its readiness for complex interplanetary missions.

Spacecraft Specifications

The technical specifications quantify the scale and capabilities of the mission’s components. The Orbiter’s substantial propellant mass (1,697 kg out of 2,379 kg total wet mass) ¹ was a key factor enabling its unexpectedly long operational life. The Vikram Lander featured a complex propulsion system critical for the soft landing attempt, comprising five 800 N main engines (four throttleable between 40-100% thrust, one fixed central engine) and eight smaller 58 N thrusters for attitude control.¹ The Pragyan Rover, constrained by its small size and 50 W power budget ¹, relied heavily on the lander for power management and communication, limiting its independent operational scope and lifespan.

Table 1: Chandrayaan-2 Component Specifications

Sources: ¹

This integrated technical architecture, combining three distinct spacecraft modules with India’s most powerful launch vehicle, underlined the mission’s complexity and ISRO‘s comprehensive indigenous capabilities developed over decades.

Scientific Payloads

The Chandrayaan-2 mission carried a comprehensive suite of 14 scientific payloads (13 Indian, 1 from NASA) distributed across its three modules. This diverse instrument array was designed to collectively address the mission’s ambitious scientific objectives, ranging from orbital remote sensing to in-situ surface analysis.²⁰ The selection reflected a clear strategy targeting key questions about lunar geology, composition, water ice presence, and the surrounding environment.

Orbiter Payloads

The Orbiter hosted the majority of the mission’s scientific instruments (eight in total), designed for long-term observation from its 100 km polar orbit. This payload distribution proved crucial, ensuring significant scientific return even after the lander’s failure.³³ The Orbiter payloads were ¹⁰:

1. Terrain Mapping Camera-2 (TMC-2): A stereo imaging system providing high-resolution (5m) panchromatic images to generate detailed 3D maps of the lunar surface, essential for morphological and geological studies. It built upon the experience of the TMC on Chandrayaan-1.¹¹
2. Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS): This instrument utilized X-ray Fluorescence (XRF) spectroscopy. By detecting characteristic X-rays emitted from the lunar surface when excited by solar X-rays, CLASS mapped the abundance of major elements like Magnesium (Mg), Aluminium (Al), Silicon (Si), Calcium (Ca), Titanium (Ti), Iron (Fe), and Sodium (Na).¹¹
3. Solar X-ray Monitor (XSM): Working in synergy with CLASS, XSM measured the incident solar X-ray spectrum (1-15 keV) and intensity with high temporal cadence (every second). This data was crucial for calibrating CLASS measurements and also enabled independent studies of solar phenomena like coronal heating and microflares.¹⁰
4. Orbiter High Resolution Camera (OHRC): This camera provided the sharpest images of the lunar surface taken from orbit to date, with a remarkable ground resolution of approximately 0.25-0.32 meters.³ Its primary functions included detailed imaging of the proposed landing site for hazard assessment and post-landing scientific analysis.
5. Imaging IR Spectrometer (IIRS): A hyperspectral instrument designed to map lunar mineralogy and volatiles (specifically water/hydroxyl) across a broad infrared spectrum (0.8-5.0 µm) with high spectral (~20nm) and spatial (~80m) resolution.¹⁰ Its ability to clearly characterize the absorption feature near 3.0 µm was key for unambiguous detection of hydration.
6. Dual Frequency Synthetic Aperture Radar (DFSAR): This advanced radar system operated in both L-band (providing deeper penetration, up to ~5 meters) and S-band, employing full polarimetry.¹⁰ Its objectives were to map surface and subsurface features, estimate regolith thickness, and quantitatively search for water ice deposits, especially within the permanently shadowed regions (PSRs) near the poles.
7. Chandra’s Atmospheric Composition Explorer-2 (CHACE-2): A Quadrupole Mass Spectrometer (QMA) designed for in-situ study of the neutral composition of the tenuous lunar exosphere (mass range 1-300 amu).¹⁰ It continued the investigation started by the CHACE instrument on Chandrayaan-1.
8. Dual Frequency Radio Science (DFRS) experiment: By analyzing the phase changes in coherent S-band and X-band radio signals transmitted from the Orbiter as they passed through the lunar ionosphere before reaching Earth, DFRS studied the electron density and its temporal variations in this plasma environment.¹⁰

Lander Payloads (Vikram Lander)

The Vikram Lander carried four instruments designed for surface and near-surface measurements during its planned 14-day operational period ⁶:

1. Instrument for Lunar Seismic Activity (ILSA): A sensitive MEMS-based seismometer designed to detect subtle ground vibrations caused by moonquakes or impacts, aiming to characterize the seismic environment of the landing site.¹³
2. Chandra’s Surface Thermo-physical Experiment (ChaSTE): This instrument included a probe designed to penetrate the lunar regolith to a depth of about 10 cm. It measured the vertical temperature gradient and the thermal conductivity of the topsoil, providing insights into the thermal properties of the lunar surface.¹³
3. RAMBHA-LP (Langmuir Probe): (Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere – Langmuir Probe). This probe was designed to measure the density and temperature of the plasma (ions and electrons) very close to the lunar surface and study its variations under different solar conditions.¹³
4. Laser Retroreflector Array (LRA): This passive instrument was a contribution from NASA‘s Goddard Space Flight Center.¹³ It consisted of a small array of mirrors designed to reflect laser beams sent from lunar orbiters (like NASA’s Lunar Reconnaissance Orbiter). Precise timing of these reflections allows for extremely accurate measurements of the lander’s position and contributes to studies of lunar dynamics and the Moon’s interior.

Rover Payloads (Pragyan Rover)

The Pragyan Rover carried two instruments specifically designed for in-situ elemental analysis of the lunar soil and rocks encountered during its traverse ⁶:

1. Alpha Particle X-ray Spectrometer (APXS): This instrument used a radioactive Curium-244 source to bombard the lunar surface with alpha particles and X-rays. By detecting the resulting characteristic X-ray emissions (X-ray fluorescence), APXS could determine the abundance of major rock-forming elements (like Na, Mg, Al, Si, Ca, Ti, Fe) and some trace elements (like Sr, Y, Zr).¹³
2. Laser Induced Breakdown Spectroscope (LIBS): LIBS employed a high-power laser to vaporize tiny amounts of lunar surface material, creating a plasma plume. By analyzing the light spectrum emitted from this cooling plasma, LIBS could identify the elements present and estimate their abundance.¹³

Table 2: Chandrayaan-2 Scientific Payloads Summary

Sources: ¹⁰

This comprehensive payload suite, particularly the Orbiter’s instruments, ensured that the Chandrayaan-2 mission could deliver valuable scientific data across a wide range of lunar science disciplines, significantly contributing to our understanding of the Moon even with the unforeseen landing outcome. The inclusion of instruments targeting water ice from multiple perspectives (IIRS, DFSAR) highlighted the mission’s focus on this key resource.

Launch and Journey to the Moon

The journey of the Chandrayaan-2 spacecraft from Earth to the Moon was a meticulously planned sequence of operations spanning several weeks, showcasing ISRO‘s proficiency in launch, trajectory control, and deep-space navigation.

The mission commenced with the successful launch of the GSLV Mk III-M1 rocket on July 22, 2019, at 09:13:12 UTC (14:43:12 IST) from the Second Launch Pad at the Satish Dhawan Space Centre (SDSC) in Sriharikota, Andhra Pradesh.¹ Approximately 16 minutes after lift-off, the powerful launch vehicle precisely injected the 3,850 kg Chandrayaan-2 composite spacecraft (Orbiter + Lander + Rover) into its planned initial Earth Parking Orbit (EPO), an elliptical path around the Earth with a perigee (closest point) of about 170 km and an apogee (farthest point) of roughly 45,475 km.¹

Following orbital insertion, ISRO‘s mission control centre (ISTRAC – ISRO Telemetry, Tracking and Command Network) took command of the spacecraft. The crucial solar panels were deployed, and the spacecraft began a series of Earth-Bound Maneuvers (EBMs).²³ Over the next few weeks (July 24 to August 6, 2019), five EBMs were executed using the spacecraft’s onboard liquid propulsion system.¹ Each maneuver involved firing the engine at the orbit’s perigee to incrementally raise the apogee, pushing the spacecraft further away from Earth with each pass. The fifth and final EBM placed Chandrayaan-2 into a highly elliptical orbit of approximately 276 km x 142,975 km.¹

The next critical step was the Trans-Lunar Injection (TLI). This maneuver, performed precisely on August 13/14, 2019 (20:51 UTC Aug 13 / 02:21 IST Aug 14), involved a longer engine burn (~1203 seconds) that propelled the spacecraft out of Earth’s gravitational influence and onto a carefully calculated path – the Lunar Transfer Trajectory (LTT) – towards the Moon.¹

After traversing the approximately 384,000 km distance during the LTT phase (lasting about 6 days) ²³, Chandrayaan-2 approached the Moon. On August 20, 2019 (03:32 UTC / 09:02 IST), the Lunar Orbit Insertion (LOI) maneuver was successfully executed.¹ This involved firing the engines again, but this time to slow the spacecraft down sufficiently for it to be captured by the Moon’s gravity, entering an initial elliptical lunar orbit (reported as 114 km x 18,072 km).¹

Once captured in lunar orbit, a series of five Lunar Bound Maneuvers (LBMs) were performed between August 21 and September 1, 2019.¹ These maneuvers systematically reduced the orbit’s apoapsis (farthest point from the Moon) and adjusted the inclination, ultimately circularizing the orbit. By September 1, 2019, the Chandrayaan-2 Orbiter, with the lander still attached, was successfully placed into its final operational orbit: a near-circular polar orbit approximately 100 km above the lunar surface.¹

Table 3: Chandrayaan-2 Key Mission Timeline (Selected Events)

Sources: ¹

This complex sequence of maneuvers, executed flawlessly up to the final landing phase, underscored the robustness of ISRO‘s mission planning and operational control. The remarkable fuel efficiency achieved during this journey proved instrumental later, enabling the significant extension of the Orbiter’s mission life from the planned one year to nearly seven years.³

The Landing Attempt: A Bold Endeavor near the South Pole

The culmination of the Chandrayaan-2 mission‘s journey was the ambitious attempt to soft-land the Vikram Lander near the unexplored South Polar Region of the Moon. This phase represented the mission’s most significant technological challenge and a critical step towards achieving its in-situ science objectives.

Following its successful establishment in the 100 km circular polar orbit, the Vikram Lander, carrying the Pragyan Rover inside, separated from the Chandrayaan-2 Orbiter on September 2, 2019.¹ Subsequently, Vikram performed two de-orbit maneuvers on September 3, 2019, using its onboard propulsion system. These burns precisely lowered its orbit, bringing its perilune (closest point to the Moon) down to approximately 35 km above the lunar surface, setting the stage for the final descent.¹ The lander was now in a 35 km x 101 km orbit.

The landing attempt was scheduled for the late hours of September 6, 2019 (UTC), translating to the early morning of September 7, 2019, in India (IST).¹ The chosen landing site was a high plain located between the craters Manzinus C and Simpelius N, at approximately 70.9 degrees South latitude and 22.8 degrees East longitude.¹⁷ This location was unprecedented, aiming for a landing closer to the lunar south pole than any previous mission, a region of intense scientific interest due to potential water ice deposits but also known for its challenging terrain and lighting conditions.⁵

The final landing sequence, famously dubbed the “15 minutes of terror” by ISRO Chairman K. Sivan, was designed to be fully autonomous.¹⁸ It commenced at 20:08 UTC on September 6 (01:38 IST, Sep 7) when Vikram, traveling at approximately 1.6 kilometers per second (nearly 6,000 km/h) at an altitude of about 30 km, initiated its powered descent.¹ The sequence involved several critical phases ⁷:

1. Rough Braking Phase: The four throttleable corner engines fired powerfully against the direction of motion to drastically reduce both horizontal and vertical velocity.
2. Fine Braking Phase: As the lander approached lower altitudes, it was programmed to reorient itself to a vertical position, with continued engine braking to further reduce speed.
3. Hovering Phase: At an altitude of around 100-400 meters, Vikram was intended to hover briefly. During this phase, onboard sensors, including hazard detection cameras and laser altimeters, would scan the terrain below to identify a safe, flat, and boulder-free spot for touchdown within the target ellipse.
4. Vertical Descent: Once a safe site was confirmed, the lander would begin its final vertical descent, potentially igniting its central fifth engine at a very low altitude (around 13 meters) to minimize dust disturbance upon landing. The target touchdown velocity was less than 2 meters per second (about 7 km/h) for a gentle soft landing.

What Went Wrong

The initial stages of the descent proceeded according to plan. Telemetry data received at the ISRO mission control center in Bengaluru indicated normal performance during the rough braking phase, drawing applause from the assembled scientists and dignitaries.⁷ However, anomalies began to appear as the lander transitioned towards the fine braking phase.

At an altitude of approximately 2.1 km above the lunar surface, Vikram started deviating from its intended trajectory.¹ Shortly thereafter, just moments before the expected touchdown time (around 20:23 UTC / 1:53 AM IST), the communication link between the lander and the IDSN ground station was abruptly lost.¹

Analysis of the final telemetry data received before the communication loss indicated that the lander’s descent velocity was significantly higher than planned. The last reported vertical velocity was approximately 58 meters per second (over 200 km/h) at an altitude of around 330 meters ⁷ – far too fast for a survivable landing. This led to the inevitable conclusion: the Vikram lander crash-landed on the Moon.¹ ISRO Chairman K. Sivan later confirmed that it must have been a hard landing.¹

ISRO’s Analysis

Following the event, ISRO convened a Failure Analysis Committee to investigate the cause of the anomaly. The committee concluded that the crash was primarily caused by a software glitch.¹ While the official detailed report was not made public ¹, subsequent analyses and statements suggest the issue likely occurred during the critical transition from rough braking to fine braking. Potential contributing factors pointed towards problems with the engine throttling control logic, possibly leading to higher-than-expected thrust from the engines during a crucial phase.¹ This could have caused instability, preventing the lander from reducing its velocity sufficiently and maintaining stable orientation, ultimately resulting in the loss of control and the deviation from the planned descent path.⁴

Despite the heartbreaking outcome of the landing attempt, the Vikram Lander had successfully demonstrated numerous new technologies, including the operation of its variable thrust engines and autonomous navigation systems, down to the final critical minutes of the descent.¹⁵ The failure, occurring late in the sequence, provided invaluable, albeit harsh, real-world data on the complexities of lunar landings, particularly concerning guidance software and propulsion control under challenging conditions.

Successes of Chandrayaan-2: The Enduring Orbiter

While the loss of the Vikram Lander and Pragyan Rover prevented the mission from achieving its surface exploration goals, the Chandrayaan-2 mission was far from a total failure. The Orbiter component emerged as a resounding success, significantly contributing to lunar science and exceeding expectations in several key areas, thereby salvaging a large portion of the mission’s overall value.

The Chandrayaan-2 Orbiter was successfully placed into its designated 100 km circular polar orbit around the Moon and remained fully operational after the lander separation and subsequent landing attempt.¹ One of the most significant Chandrayaan-2 achievements was the remarkable extension of the Orbiter’s mission life. Owing to the highly precise launch by the GSLV Mk III-M1 and exceptionally efficient mission management during the complex trajectory maneuvers from Earth to the Moon, ISRO conserved a substantial amount of onboard fuel.³⁶ This fuel saving allowed the operational lifespan of the Orbiter to be extended from the initially planned one year to an estimated seven years.¹

This extended duration provided an unprecedented opportunity for long-term observation and mapping of the Moon. The Orbiter’s eight state-of-the-art scientific payloads continued to function flawlessly, collecting a wealth of high-quality data.³ ISRO estimated that the Orbiter alone fulfilled 90 to 95% of the mission’s overall scientific objectives.¹⁵ Key scientific findings and Chandrayaan-2 Orbiter updates include:

• Water Molecule Confirmation and Mapping: The IIRS payload provided the first unambiguous detection of hydroxyl (OH) and water (H2O) molecules across the lunar surface from orbit, capturing clear spectral signatures near 3.0 µm at high spatial and spectral resolution. This confirmed earlier findings and allowed for detailed mapping of hydration features.¹⁰
• Subsurface Ice Signatures: The DFSAR instrument, with its L-band radar capable of penetrating several meters below the surface, detected signatures consistent with the presence of subsurface water ice, particularly in the polar regions.¹⁰
• Unprecedented High-Resolution Imaging: The OHRC payload delivered stunning, high-resolution images of the lunar surface, achieving a resolution of about 25-30 cm – the best ever from a lunar orbiter. These images provided invaluable data for detailed geological studies and future landing site selection.³ Simultaneously, the TMC-2 provided global context with its 5m resolution topographic mapping.¹¹
• Advanced Elemental Mapping: The CLASS instrument successfully mapped the distribution of major lunar elements and made the first orbital detections of trace elements like Chromium (Cr) and Manganese (Mn) on the lunar surface using X-ray fluorescence.¹⁰
• Novel Exosphere Insights: The CHACE-2 mass spectrometer conducted the first in-situ measurements of the neutral composition of the lunar exosphere from a polar orbit. It notably detected Argon-40 and observed its variability across different latitudes, providing insights into ongoing radiogenic processes within the Moon.⁵
• Lunar Ionosphere Discoveries: The DFRS experiment revealed unexpected characteristics of the Moon’s ionosphere, detecting plasma densities in the lunar wake region (the area shielded from direct solar wind) that were significantly higher (by at least an order of magnitude) than previously measured on the dayside.¹⁰
• Solar Activity Monitoring: The XSM payload provided continuous, high-cadence monitoring of the Sun’s X-ray output, capturing valuable data on solar flares and even detecting faint microflares during quiet solar periods, contributing to understanding coronal heating mechanisms.¹⁰

To ensure the wider scientific community could benefit from these findings, ISRO made the processed data from the Chandrayaan-2 Orbiter payloads publicly accessible through the Indian Space Science Data Centre (ISSDC) PRADAN portal, adhering to the international Planetary Data System 4 (PDS4) standard.⁹

The sustained, high-quality scientific output from the Chandrayaan-2 Orbiter fundamentally reshaped the narrative of the mission. It transformed a potential complete loss into a significant partial success, demonstrating the robustness of ISRO‘s orbiter technology and mission operations, and ensuring a rich scientific legacy for the mission.

Global Recognition and Collaboration

The Chandrayaan-2 mission, particularly its ambitious attempt to land near the lunar south pole, garnered significant attention and recognition from the international community. The mission’s progress was closely followed by space agencies, experts, and media worldwide.⁵⁵

Following the unfortunate hard landing of the Vikram Lander, there was an outpouring of support and acknowledgement from global space players. NASA, the US space agency, issued statements acknowledging the immense difficulty of lunar landings (“Space is hard”) and commending ISRO‘s bold attempt. They expressed that India’s journey was inspirational and reiterated their commitment to future collaborations in exploring the solar system.⁵⁵ Practically demonstrating this collaborative spirit, NASA’s Lunar Reconnaissance Orbiter (LRO) adjusted its schedule to fly over the presumed landing site to capture images that later helped pinpoint the Vikram lander crash location.²¹ LRO also collected valuable data on the atmospheric changes caused by Vikram’s descent thrusters.⁵⁴

Beyond official statements, former US astronauts like Jerry Linenger emphasized that the mission was far from a failure, highlighting the Orbiter’s success and the value of the attempt itself.⁵⁶ Representatives from other space agencies, such as France’s CNES, recognized the strategic importance of exploring the lunar south pole, suggesting it as a potential site for future human settlements.⁵⁵ Space commentators and publications like Nasa Spaceflight and Wired magazine emphasized that with the Orbiter functioning perfectly and carrying the bulk of the experiments, “all is not lost” and the mission should not be considered a total failure.⁵⁶

International media coverage, while reporting the landing failure, often lauded India’s “engineering prowess,” the mission’s ambition, and its remarkable cost-effectiveness.⁵⁶ Chandrayaan-2’s budget of approximately US$141 million was frequently contrasted favorably with the much larger budgets of lunar missions undertaken by other nations.⁵⁶

The mission also embodied continued international scientific collaboration, despite the earlier termination of the partnership with Roscosmos for the lander. The inclusion of the NASA-provided Laser Retroreflector Array (LRA) on the Vikram Lander payload was a tangible example of ongoing US-India cooperation in space science.¹³

The global reaction to Chandrayaan-2 underscored the mission’s high visibility and the respect ISRO commands within the international space community. The largely positive and supportive tone, even in the face of the landing setback, acknowledged the inherent risks of space exploration and solidified India’s position as a significant and capable player in the challenging domain of India lunar exploration.

Impact on Future Missions: The Road to Chandrayaan-3

The Chandrayaan-2 mission, particularly the experience gained from the Vikram lander crash, proved to be an invaluable, albeit challenging, learning opportunity for ISRO. The data and insights derived from the landing attempt directly influenced the design, development, and operational strategy of its successor mission, Chandrayaan-3, ultimately contributing to its historic success.⁴

The failure analysis of the Vikram Lander‘s descent provided critical lessons regarding the complexities of terminal phase guidance, navigation, and control (GNC), especially concerning software logic, sensor performance, and the behavior of throttleable engines under lunar conditions.⁴ These lessons were meticulously incorporated into the Chandrayaan-3 lander design, focusing on enhancing robustness and redundancy ⁵⁸:

• Strengthened Lander Legs: The landing gear was redesigned and reinforced to withstand higher touchdown velocities and absorb greater impact energy, providing a larger margin for landing stability.⁵⁸
• Propulsion System Refinements: Based on the analysis suggesting potential issues with excessive thrust and control during Chandrayaan-2’s descent ⁴, the engine configuration and throttling control algorithms were refined for Chandrayaan-3. Notably, Chandrayaan-3 used four throttleable engines, omitting the fifth central engine present on Vikram.⁵⁸
• Enhanced Sensors and GNC Software: Chandrayaan-3 featured upgraded sensors and improved algorithms for hazard detection and avoidance. A key addition was the Laser Doppler Velocimeter (LDV), providing real-time, accurate measurements of the lander’s velocity in multiple directions, crucial for precise control during descent.¹⁹ The GNC software underwent rigorous testing and validation based on Chandrayaan-2 telemetry.
• Expanded Landing Zone: To provide more flexibility for the autonomous landing system to select a safe spot, the targeted landing area for Chandrayaan-3 was significantly larger (4 km x 2.4 km) compared to the smaller target ellipse for Chandrayaan-2 (reportedly 500m x 500m).⁴
• Rigorous Testing: ISRO conducted more extensive simulations and ground tests for Chandrayaan-3, simulating various failure scenarios identified from the Chandrayaan-2 experience to ensure the system’s resilience.⁵⁸

Furthermore, the highly successful and long-lived Chandrayaan-2 Orbiter played a direct role in the Chandrayaan-3 mission. It served as a pre-existing communication relay satellite in lunar orbit, providing a crucial backup communication link for the Chandrayaan-3 lander and rover, thereby enhancing mission reliability.¹⁹

Even beyond the specific lessons applied to Chandrayaan-3, the Chandrayaan-2 mission successfully validated several key technologies essential for ISRO‘s future deep-space exploration ambitions. These included advanced mission management, deep-space navigation techniques, long-duration orbiter operations in the lunar environment, and aspects of autonomous descent and variable thrust propulsion demonstrated during the initial phases of the landing sequence.¹⁵

In essence, Chandrayaan-2, despite its partial failure, functioned as a critical, high-fidelity testbed. The specific engineering and software improvements implemented in Chandrayaan-3 were a direct consequence of the anomalies encountered in 2019, demonstrating a clear iterative design process where lessons learned paved the way for subsequent success.

Legacy and Importance

The Chandrayaan-2 mission, despite not achieving all its objectives, holds a significant and multifaceted legacy within India’s space program and the broader context of global lunar exploration. Its importance extends beyond the immediate scientific and technological outcomes.

Firstly, the mission undeniably boosted India’s space research capabilities. It showcased ISRO‘s ability to conceive, design, build, and manage highly complex interplanetary missions involving multiple spacecraft components.² The indigenous development of critical technologies like the Orbiter’s advanced payloads, the Vikram Lander (including its throttleable engines), the Pragyan Rover, and the powerful GSLV Mk III launch vehicle demonstrated a significant maturation of India’s technological self-reliance in space.² The successful operation and longevity of the Orbiter, in particular, stand as a testament to ISRO‘s engineering excellence.²¹

Secondly, Chandrayaan-2 served as a powerful source of inspiration. The mission captured the collective imagination of the Indian populace and garnered immense national pride.⁵⁶ The ambition to reach the lunar south pole, the technological challenges overcome, and even the poignant moments surrounding the landing attempt resonated deeply, inspiring countless students, young scientists, and engineers across India and globally to pursue careers in science, technology, engineering, and mathematics (STEM) fields.²

Thirdly, the mission carried strategic significance. By successfully operating a sophisticated suite of instruments in lunar orbit and attempting a landing in the strategically important South Polar Region, Chandrayaan-2 reinforced India’s position as a leading space-faring nation, particularly within Asia.⁴ This demonstrated capability holds relevance for potential future international collaborations, lunar resource utilization discussions, and the evolving dynamics of the global space race.⁶²

Fourthly, the mission experience powerfully reinforced the inherent nature of space exploration – that it is a challenging endeavor fraught with risks, where setbacks are often integral to progress.²¹ The way ISRO handled the landing anomaly, focusing on the Orbiter’s success and channeling the lessons learned into Chandrayaan-3, highlighted the importance of resilience and learning from failures in pushing technological boundaries.⁵⁵

Finally, the scientific contribution of the Chandrayaan-2 Orbiter continues to be substantial. Its ongoing data stream provides valuable insights into lunar geology, mineralogy, the presence and distribution of water molecules, the exosphere, and the lunar plasma environment, enriching the global scientific understanding of the Moon.³

In sum, Chandrayaan-2’s legacy is defined by its tangible technological advancements, significant scientific data return, the critical lessons learned that enabled future success, its profound inspirational impact, and its enhancement of India’s strategic standing in the global space community.

Conclusion

The Chandrayaan-2 mission stands as a landmark undertaking in the history of India lunar exploration. Conceived with ambitious goals to explore the uncharted South Polar Region of the Moon through an Orbiter, Lander (Vikram Lander), and Rover (ISRO rover Pragyan), it represented a significant leap in technological complexity for the Indian Space Research Organisation (ISRO).

While the mission faced a critical setback with the hard landing of the Vikram Lander, preventing surface operations, its overall contributions remain substantial. The Chandrayaan-2 Orbiter component emerged as an outstanding success, not only achieving its planned objectives but far exceeding its designed operational life. For nearly seven years, instead of the planned one, the Orbiter has provided a continuous stream of high-quality scientific data, fulfilling a vast majority of the mission’s scientific goals. Chandrayaan-2 Orbiter updates based on data from its advanced payloads have led to significant discoveries regarding lunar water molecules, elemental composition, high-resolution surface features, and the nature of the lunar exosphere and ionosphere, contributing significantly to global lunar science.²⁴ These Chandrayaan-2 achievements underscore the robustness of ISRO‘s orbiter technology and mission operations.

The challenge encountered during the final descent of the Vikram lander served as a crucial, albeit difficult, learning experience. The anomaly provided invaluable data that allowed ISRO to meticulously analyze the intricacies of lunar soft landing, leading directly to targeted improvements in guidance software, control systems, sensor suites, and lander design robustness. This iterative process, learning directly from the Vikram lander crash, was instrumental in paving the way for the triumphant success of the subsequent Chandrayaan-3 mission.

Ultimately, the Chandrayaan-2 mission reaffirmed that complex space exploration endeavors are inherently challenging and serve as vital stepping stones. Even partial successes yield invaluable knowledge, drive technological innovation, and inspire future generations. Chandrayaan-2 significantly advanced ISRO‘s capabilities, enhanced India’s standing in the global space community, delivered world-class science from orbit, and provided the critical foundation upon which future triumphs in India lunar exploration could be built.²¹ Its legacy is one of ambition, resilience, and the relentless pursuit of knowledge beyond Earth.

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