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Context

SLIM (Smart Lander for Investigating Moon) entered lunar orbit on December 25 and is scheduled for a moon landing attempt on January 19. Success would place Japan as the fifth nation to softly land a spacecraft on the moon.

Details

• SLIM is a spacecraft launched by the Japan Aerospace Exploration Agency (JAXA) on September 7, 2023, with a weight of 590 kg, significantly lighter than Chandrayaan-3, which weighed 3,900 kg at launch.
• It aims to land on the Moon, becoming Japan's second attempt this year after the HAKUTO-R M1 lander, which crashed in April.

Mission Journey and Approach to the Moon

• Journey Duration: SLIM followed a longer route, taking four months to reach the Moon compared to Chandrayaan-3, which took a month due to the different propulsion system and trajectory.
• Route Strategy: SLIM utilized the weak-stability boundary theory for a fuel-efficient trajectory. It swung around the Earth multiple times to build kinetic energy before heading towards the Moon.

Lunar Arrival and Orbit

• December 25 Entry: SLIM entered an elliptical lunar orbit, with an apogee of 4,000 km and perigee of 600 km above the lunar surface.
• Fuel Efficiency: Sacrificed time for a more fuel-efficient approach, preparing for a landing attempt on January 19.

Land and Exploration Goals

• "Moon Sniper" Title: SLIM aims for an extremely precise landing within 100 meters of its chosen landing site, setting a new standard for moon-landing missions.
• Landing Site: SLIM's target is near the Shioli Crater, utilizing data from JAXA's SELENE orbiter to guide its descent.
• Mission Tools: It will deploy two small rovers, LEV-1 and LEV-2, to study the lunar surface, gather temperature and radiation data, and explore the moon's mantle.

Impact on Chandrayaan-4 (LUPEX Mission)

• LUPEX Mission: Chandrayaan-4, an Indian-Japan joint mission (pending India's approval), will explore the moon's South Pole, aiming to extract water from shadowed craters. Chandrayaan-4 is tentatively set for a launch in 2026.
• Technological Influence: JAXA's SLIM mission, especially its navigation systems and feature-matching algorithm, will be crucial for Chandrayaan-4's success in navigating rocky, crater-ridden terrain closer to the moon's South Pole.
• Collaborative Effort: JAXA is expected to provide the launch vehicle and lunar rover, while India will supply the lander module. The specific landing site for Chandrayaan-4 is yet to be determined, unlike the 'Vikram' lander, which landed 600 km from the South Pole during Chandrayaan-3.

About Moon

• The Moon is Earth's only natural satellite, orbiting our planet at an average distance of about 384,400 kilometers.
• Size: The Moon has a diameter of approximately 3,474 kilometers, around 27% of Earth's diameter, and only 1/6th of Earth's mass.

Structure and Composition

• Layers and Composition: The Moon consists of several distinct layers, including the crust, mantle, and possibly a small metallic core. Its crust is primarily made up of igneous rocks, such as basalt and anorthosite.
• Surface Features: The Moon's surface displays various geological formations, including craters, mountains, valleys, maria (dark plains), and highlands. Impact craters are prominent, formed by meteorite collisions over billions of years.

Lunar Phases and Orbits

• Phases of the Moon: The Moon's phases result from the changing positions of the Moon, Earth, and the Sun. From Earth's perspective, these phases range from the New Moon (when the Moon is not visible) to the Full Moon (when the entire lunar face is illuminated).
• Orbit and Synchronous Rotation: The Moon orbits Earth in an elliptical path, taking approximately 27.3 days to complete one orbit. It's tidally locked, meaning it rotates on its axis in the same period it takes to orbit Earth, always showing the same face to our planet.

Formation of the Moon

• Giant Impact Hypothesis: The most accepted theory suggests a collision between Earth and a Mars-sized object called "Theia," ejecting material that later formed the Moon.
• Evidence: Similar isotopic compositions of lunar and terrestrial rocks support this theory, along with computer simulations of the collision.

Lack of Atmosphere and Gravity

• Atmosphere: The Moon has a very thin atmosphere, primarily composed of trace elements. Lack of atmosphere means no protection from solar radiation or meteoroid impacts.
• Gravity: It has approximately 1/6th the gravity of Earth, affecting astronaut movement during missions.

Significance and Impact

• Scientific Research: The Moon holds critical information about the early solar system and Earth's formation. Studying lunar samples helps scientists understand planetary evolution and the history of impacts in the inner solar system.
• Space Exploration Platform: The Moon serves as a potential launchpad for deeper space exploration missions, acting as a testing ground for technologies and systems needed for future missions to Mars and beyond.

Potential Lunar Resources and Utilization

• Helium-3 and Water Ice: The Moon may contain valuable resources like helium-3 and water ice in permanently shadowed regions. Helium-3 is of interest for potential fusion energy, while water ice could support future human settlements.
• Space Economy and Industry: There is growing interest in lunar mining and utilization of resources to support space missions, including building infrastructure or generating propellants for further space exploration.

Weak-Stability Boundary Theory (WSBT)

• The Weak-Stability Boundary Theory (WSBT) is a concept in celestial mechanics used in spacecraft mission planning.
• It defines regions around celestial bodies, like planets or moons, where the gravitational influences from multiple celestial bodies are delicately balanced.
• This equilibrium enables spacecraft to navigate through space with minimal energy expenditure.
• WSBT exploits areas where the gravitational forces from two celestial bodies, such as Earth and the Moon, counterbalance each other.
• This enables spacecraft to use small changes in velocity or energy to effectively maneuver between these bodies.
• By capitalizing on these regions, spacecraft can travel vast distances within the solar system while conserving fuel.

Hohmann Transfer Orbit

• The Hohmann Transfer Orbit is a specific orbital maneuver used by spacecraft for efficient interplanetary travel between two circular orbits, typically around the same central body, such as Earth and the Moon or Earth and Mars.
• This transfer orbit involves two primary engine burns.
• The first burn occurs in the initial circular orbit around the primary body, increasing the spacecraft's velocity and moving it into a highly elliptical transfer orbit.
• The second burn happens when the spacecraft reaches the apoapsis (the highest point) of the transfer orbit, adjusting its velocity to transition into a new circular orbit around the secondary body, like the Moon or Mars.

Shioli Crater

• The Shioli Crater is a prominent lunar feature located at coordinates approximately 13.3º S and 25.2º E on the Moon's surface.
• This crater is of particular interest to lunar explorers due to its unique geological characteristics.
• Craters like Shioli are intriguing for scientific exploration as they offer insights into the moon's history and geology.
• Additionally, some of these craters contain permanently shadowed regions (PSRs) within them, where sunlight never reaches due to the crater's topography.
• These PSRs might preserve volatile elements like water ice due to the extremely low temperatures, making them potential locations for future lunar missions exploring resources or establishing bases.

Moon's North and South Poles

• The lunar poles, both North and South, are regions of immense interest for scientific exploration.
• These areas exhibit unique environmental conditions due to their proximity to the moon's rotational axis.
• The polar regions experience extreme variations in sunlight and darkness due to the moon's axial tilt, resulting in regions of perpetual shadow.
• These permanently shadowed regions are believed to retain water ice and other volatiles, possibly deposited over millions of years by comet and asteroid impacts.
• Therefore, they are prime targets for future lunar missions aimed at studying potential resources and supporting human exploration and settlement.
• Water ice found in these shadowed regions can serve multiple purposes for future lunar missions. It could be used for drinking water, as a source of oxygen for life support systems, and could be separated into hydrogen and oxygen for rocket fuel. Utilizing these resources on-site could significantly reduce the cost and logistical challenges of lunar missions.
• The lunar south pole is a prime target for establishing future lunar bases or outposts.
• Key Missions Targeting the Lunar South Pole:
  • Chandrayaan-2 (India): This mission, launched by the Indian Space Research Organisation (ISRO), included an orbiter, lander (Vikram), and rover (Pragyan). Although the Vikram lander crash-landed near the south pole, the orbiter continues to provide valuable data.
  • NASA's Artemis Program: NASA's Artemis missions aim to return astronauts to the lunar surface. The Artemis program focuses on the south pole region for landing sites due to its potential resources and scientific significance.

• • Chang'e Missions (China): China's Chang'e missions have shown interest in the lunar south pole. The Chang'e 4 mission successfully landed the Yutu-2 rover on the far side, near the Von Kármán crater, and continues to explore this uncharted terrain.

Lunar Missions

1959-1976:

• Luna 1: Soviet Union (Jan 2, 1959) - Flyby
• Pioneer 4: United States (Mar 3, 1959) - Flyby
• Luna 2: Soviet Union (Sep 12, 1959) - Impact
• Luna 3: Soviet Union (Oct 4, 1959) - Probe
• Ranger series (1-9): United States (1961-1965) - Lunar photography and impact analysis
• Surveyor series (1-7): United States (1966-1968) - Soft landers for surface analysis
• Zond 5: Soviet Union (Sep 15, 1968) - Return Probe
• Luna series (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17): Soviet Union (1963-1970) - Various lunar missions including orbiters, landers, rovers, and sample return

1970-1999:

• Luna series (18, 19, 20, 21, 22, 23, 24): Soviet Union (1971-1976) - Continuation of Luna missions with orbiters, landers, and sample return
• Hiten: Japan (Jan 24, 1990) - Flyby and Orbiter
• Clementine: United States (Jan 25, 1994) - Orbiter
• Lunar Prospector: United States (Jan 7, 1998) - Orbiter

2000-2013:

• SMART 1: European Space Agency (Sep 27, 2003) - Lunar Orbiter
• Chang'e 1: China (Oct 24, 2007) - Lunar Orbiter
• Chandrayaan-1: India (Oct 22, 2008) - Lunar Orbiter
• Lunar Reconnaissance Orbiter: United States (June 17, 2009) - Lunar Orbiter
• LCROSS: United States (June 17, 2009) - Lunar Orbiter and Impactor
• Chang'e 2: China (Oct 1, 2010) - Lunar Orbiter
• GRAIL (Gravity Recovery And Interior Laboratory): United States (Sep 10, 2011) - Lunar Orbiter
• LADEE (Lunar Atmosphere and Dust Environment Explorer): United States (Sep 6, 2013) - Lunar Orbiter
• Chang'e 3: China (Dec 01, 2013) - Lunar Lander and Rover

2014-2019:

• Chang'e 5 Test Vehicle: China (Oct 23, 2014) - Lunar Flyby and Return
• Chandrayaan-2: India (April 2019) - Moon Orbiter, Lander, and Rover
• Beresheet: Israel (Feb 22, 2019) - Lunar Lander

2020 onwards:

• Chang'e 5: China (Nov 23, 2020) - Lunar Sample Return Mission
• CAPSTONE: United States (June 28, 2022) - Lunar Navigation Test Orbiter
• Korea Pathfinder Lunar Orbiter (Danuri): South Korea (Aug 4, 2022) - Lunar Orbiter
• LunaH-Map: United States (Nov 16, 2022) - Lunar Orbiting CubeSat
• Lunar Ice Cube: United States (Nov 16, 2022) - Lunar Orbiting CubeSat
• Lunar InfraRed imaging (LunIR): United States (Nov 16, 2022) - Lunar Flyby and Technology Test CubeSat
• OMOTENASHI: Japan (Nov 16, 2022) - Lunar Lander CubeSat
• EQUULEUS: Japan (Nov 16, 2022) - L2 Orbit Lunar CubeSat
• Artemis 1: United States (Nov 16, 2022) - Lunar Test Flight
• Hakuto-R M1: Japan (Dec 11, 2022) - Japanese Lunar Lander
• Lunar Flashlight: United States (Dec 11, 2022) - Lunar Orbiter CubeSat
• Luna 25: Russia (Aug 10, 2023) - Russian Lunar Lander
• SLIM: Japan (Sep 6, 2023) - Lunar Lander
• Chandrayaan 3: India (July 14, 2023) - Lunar Orbiter, Lander, and Rover
• Lunar Trailblazer: United States (2024) - Lunar Orbiting Small Satellite
• Peregrine Mission 1 (TO 2-AB): United States (Jan 8, 2024) - Lunar Lander
• Intuitive Machines 1 (TO 2-IM): United States (Feb 2024) - Lunar Lander
• VIPER (TO 20A): United States (Nov 2024) - Lunar South Pole Rover
• Prime 1 (IM-2): United States (2024) - Lunar Lander
• Blue Ghost 1 (TO 19D, Firefly): United States (2024) - Lunar Lander
• Chang'e 6: China (2024) - Lunar Sample Return Mission
• Intuitive Machines 3 (TO CP-11): United States (TBD) - Lunar Lander and Rovers
• Draper (TO CP-12): United States (2025) - Lunar Lander
• Chang'e 7: China (2026) - Lunar Survey Mission
• Chang'e 8: China (TBD) - Lunar Technology Test

Conclusion

SLIM's ambitious mission targets an incredibly precise lunar landing and holds immense importance in guiding and influencing Chandrayaan-4's strategies and technological implementations, especially in exploring the challenging terrains near the moon's South Pole.

PRACTICE QUESTION Q. Discuss the significance of recent advancements and missions in lunar exploration and their potential implications for future space exploration and human habitation beyond Earth. (250 Words)