Chandrayaan-3 Mission - Success and Payloads for UPSC

Chandrayaan-3: How India Landed at the Lunar South Pole and What We Learned

Chandrayaan-3 is India’s proof of end-to-end lunar landing capability. Launched on 14 July 2023 and landed on 23 August 2023 at ~69.37°S, it made ISRO the first to soft-land near the Moon’s south polar region. The mission reused Chandrayaan-2 heritage, added redundancy and hazard-avoidance upgrades, and delivered in-situ science on temperature, plasma, and elemental composition—data critical for future resource use and human-class missions.

Mission Goals and Stack

The design was intentionally simple: no lunar orbiter with heavy payloads, only what was needed to land and operate on the surface.

• Goals: (1) Demonstrate soft-landing autonomy; (2) deploy and drive a rover; (3) collect basic science to characterise the landing environment; (4) keep a relay alive through the propulsion module.
• Launch vehicle: LVM3 (3-stage, cryogenic upper stage) put the spacecraft into an initial 170 x 36,500 km Earth orbit.
• Propulsion Module (PM): Performed orbit-raising burns, Trans-Lunar Injection (TLI), Lunar Orbit Insertion (LOI), and circularisation to ~100 km; carried SHAPE to observe Earth as an exoplanet analog. After lander separation, it stayed in lunar orbit as a relay.
• Lander (Vikram): Four throttleable engines, central fixed engine shut off for final descent, strengthened legs, upgraded guidance; payloads: ChaSTE (thermal properties), ILSA (seismometer), LP (Langmuir Probe), LRA (laser retroreflector).
• Rover (Pragyan): 6-wheel, 26 kg, solar powered; payloads: LIBS and APXS for elemental chemistry. Planned traverse ~100 m during one lunar day.

Why the South Polar Region

High-latitude sites near permanently shadowed regions (PSRs) are attractive for future missions because of potential water ice, stable low temperatures in shaded craters, and unique geology. Landing here is harder due to low sun angles, longer shadows, and uneven terrain. Even landing slightly away from PSRs yields crucial ground truth for navigation, regolith mechanics, and thermal environment.

Trajectory and Operations Timeline

• Earth-bound phase: A series of orbit-raising burns used Earth’s gravity to incrementally increase apogee (a fuel-efficient approach compared to direct translunar injection).
• TLI and cruise: Final burn sent the stack to the Moon; mid-course corrections ensured arrival at the correct lunar approach corridor.
• LOI and circularisation: Braking at perilune to capture into a 164 x 18,000 km orbit, then lowered to near-circular 100 km polar orbit. Two deboost burns reduced periapsis to ~30 km for landing.
• Powered descent (“15 minutes”):
  • Rough braking: From ~25 km altitude, killed most horizontal velocity.
  • Altitude hold: Hovered around ~7 km to map terrain using cameras, altimeters, and LDV.
  • Fine braking: Reduced vertical speed, aligned for final approach.
  • Terminal descent: Central engine off to avoid plume effects; touchdown near 69.37°S, 32.35°E.
• Surface phase: Ramp deployment, Pragyan roll-out, traverse and sampling; instruments ran until sunset. Attempts to wake the lander/rover after lunar night were unsuccessful, as expected for non-radioisotope designs.

Upgrades After Chandrayaan-2

• Redundancy: Multiple sensors (LDV added), dual hazard-detection cameras, and reinforced legs to tolerate higher touchdown velocities and slopes.
• Navigation tolerance: Larger landing ellipse (~4 km x 2.4 km) with updated guidance algorithms to cope with dispersions and late-stage corrections.
• Extensive testing: More drop tests, hardware-in-loop simulations, and integrated rehearsals of the entire descent profile.
• Autonomy: Onboard decision logic to prioritise safe landing over strict target coordinates, reducing dependence on ground intervention during the critical descent window.

Science Returns

Chandrayaan-3’s science focus was modest but meaningful: establish environmental baselines at high latitude and gather compositional clues.

• Elemental composition: LIBS detected sulphur along with Al, Ca, Fe, Ti, Cr, Mn, Si, and O. APXS cross-checked abundances, informing local geology and comparison with orbital spectral data.
• Thermal environment: ChaSTE profiled temperatures in the top centimetres of regolith, showing steep gradients between surface and subsurface—vital for future power system and habitat design.
• Plasma environment: Langmuir Probe measured near-surface plasma density/variability, relevant for electrostatic dust behaviour and radio communications.
• Seismology potential: ILSA recorded vibrations; even limited data help understand regolith response and micro-seismic activity at high latitude.
• SHAPE observations: The propulsion module collected polarimetric signatures of Earth, building reference data for exoplanet characterisation methods.

Strategic Impact for India

• Capability leap: Demonstrated autonomous soft-landing and rover ops—core competencies for sample return, polar resource missions (e.g., LUPEX), and eventual human support systems.
• Cost-effective model: Delivered complex outcomes on a modest budget, enhancing India’s reputation for frugal, reliable space engineering.
• International standing: Enabled India to sign the Artemis Accords and join lunar standards-setting conversations from a position of demonstrated capability.
• Industrial depth: Expanded supply chains for precision sensors, propulsion subsystems, structures, coatings, and autonomy software validated in deep-space conditions.
• STEM and outreach: August 23 recognised as National Space Day; strong public and student engagement supports the talent pipeline for Gaganyaan and future planetary work.

Lessons for Future Missions

• Testing realism matters: Hardware-in-loop and drop tests that mimic lunar dust, slope, and lighting were key to landing success.
• Hazard tolerance: Wider landing boxes, plume-aware final descent, and multiple sensor fusion reduce single-point failures.
• Power and thermal limits: Without radioisotope heaters, polar-night survival is unlikely; future missions may need RTGs or advanced batteries/insulation for multi-night ops.
• Relay strategy: Keeping the propulsion module as a long-lived orbiter improved link reliability and offers a platform for secondary science even after surface assets sleep.

UPSC-Focused Quick Notes

• Payload recall: ChaSTE (thermal), ILSA (seismic), LP (plasma), LRA (retroreflector), LIBS/APXS (rover chemistry), SHAPE (exoplanet benchmarking).
• Trajectory concept: Earth orbit-raising → TLI → LOI → deboost → powered descent; why ISRO uses staged orbit raising (fuel efficiency on LVM3).
• South pole relevance: PSRs, volatiles, uneven terrain, low sun angles; implications for navigation and ISRU.
• Contrast with Chandrayaan-2: Added LDV, stronger legs, wider landing box, refined autonomy/testing.
• Policy link: Artemis Accords, LUPEX collaboration with JAXA, and how Chandrayaan-3 builds readiness for sample return/human missions.

Bottom line: Chandrayaan-3 shows India can autonomously land, rove, and return science at one of the Moon’s toughest locations—data that now inform resource planning, international partnerships, and the next wave of lunar exploration.