Date : 29/12/2023
Relevance: GS Paper 3- Science & Technology - Space
Keywords: Japan Aerospace Exploration Agency (JAXA), Chandrayaan-4 mission, Hohmann Transfer Orbit, SLIM, Lunar Polar Exploration (LUPEX) mission
Context-
Japan's Smart Lander for Investigating Moon (SLIM) spacecraft has recently entered lunar orbit, with a scheduled moon landing attempt on January 19. This mission holds significant implications for lunar exploration and could revolutionize the approach to lunar landings. SLIM, developed by the Japan Aerospace Exploration Agency (JAXA), distinguishes itself through its lightweight design, innovative fuel-efficient trajectory, and unprecedented precision landing capabilities.
Here we will look into the factors contributing to SLIM's lower weight compared to other lunar exploration missions, its unique trajectory, the mission objectives on the moon, and its potential impact on the upcoming Chandrayaan-4 mission, a joint venture between India and Japan.
SLIM's Lightweight Design: Fuel Efficiency and Payload
At its launch on September 7, 2023, SLIM weighed a mere 590 kg, in stark contrast to India's Chandrayaan-3, which tipped the scales at 3,900 kg. This notable difference in weight is attributed to SLIM's strategic decision to carry significantly less fuel. In comparison, Chandrayaan-3's propulsion module alone weighed 2.1 tonnes, contributing to its substantial overall weight. SLIM's lightweight design is a result of a meticulous balance between fuel efficiency and payload capacity, allowing it to achieve its mission objectives with a reduced mass.
SLIM's Trajectory: Fuel-Thrifty Route vs. Hohmann Transfer Orbit
The journey to the moon is a critical aspect of any lunar exploration mission, and SLIM took an unconventional but fuel-thrifty route based on weak-stability boundary theory. Unlike Chandrayaan-3, which followed a Hohmann transfer orbit and reached the moon in less than a month, SLIM's trajectory spanned four months. This elongated path involved swinging around the Earth multiple times, building up kinetic energy before propelling itself towards the moon's orbit.
Chandrayaan-3's faster journey was a result of a more direct route, propelled by the energy-intensive Hohmann transfer orbit. In contrast, SLIM's trajectory, while time-consuming, showcased fuel efficiency, aligning with its mission goals.
Hohmann Transfer Orbit
The Hohmann transfer orbit, conceived by German scientist Hohmann in 1925 and named in his honor, is a fuel-efficient maneuver. This orbital transfer technique facilitates the movement of a spacecraft from one circular orbit to another by following an elliptical trajectory. The elliptical orbit arises from a mid-course acceleration essential for transitioning from a lower orbit to a higher one.
Weak-stability boundary theory
Introduced by Edward Belbruno in 1987, the concept of the Weak Stability Boundary (WSB), inclusive of low-energy transfer, outlines how a spacecraft can alter its orbit with minimal fuel consumption.
The Weak Stability Boundary is specifically defined within the context of the three-body problem, which involves the motion of a negligibly massed particle, denoted as P, in relation to two larger bodies, P1 and P2, modeled as point masses. P1 and P2 move in circular or elliptical orbits relative to each other, with P2 being smaller than P1. In this restricted three-body problem, the gravitational force between the bodies follows classical Newtonian principles. For instance, P1 can represent Earth, P2 the Moon, and P the spacecraft, or P1 can be the Sun, P2 Jupiter, and P a comet. The Weak Stability Boundary identifies a region around P2 where P can experience temporary capture. This region is defined in position-velocity space, and capture implies that the Kepler energy between P and P2 becomes negative, also known as weak capture.
SLIM's Lunar Objectives:
SLIM's standout feature is its designation as the "moon sniper," a testament to its precision landing capabilities. On January 19, SLIM aimed to touch down within an unprecedented 100 metres of its chosen landing site near the Shioli Crater. This precision far surpasses previous moon-landing missions, such as the Chandrayaan-3's Vikram lander, which targeted an elliptical area measuring kilometres in both downrange and cross-range directions.
This precision landing will be facilitated by SLIM's lower mass, approximately 120 kg excluding fuel, enhancing its manoeuvrability. The chosen landing site and its proximity to the Shioli Crater emphasise SLIM's role in exploring scientifically valuable lunar regions.
Before landing, SLIM will deploy two small rovers, named Lunar Excursion Vehicle (LEV) 1 and 2. These rovers, in conjunction with SLIM, will conduct comprehensive studies of the lunar surface near the landing point, collecting temperature and radiation readings. Additionally, the mission aims to investigate the moon's mantle, contributing to a deeper understanding of lunar geology.
SLIM's Influence on Chandrayaan-4:
The success or failure of SLIM holds implications for the collaborative Lunar Polar Exploration (LUPEX) mission planned by India and Japan. LUPEX, also known as Chandrayaan-4, is set to be a joint venture, with an earliest launch date in 2026. JAXA is expected to provide the launch vehicle and lunar rover, while India will contribute the lander module.
LUPEX aims to explore areas closer to the moon's south pole, an endeavour that demands precise landing technologies. The rocky terrain, craters, and steep slopes in the moon's polar regions necessitate a landing as close to the designated site as possible. SLIM's pioneering efforts in precision landing, facilitated by features like a sophisticated algorithm and advanced navigation systems, will be instrumental in shaping the technologies employed during LUPEX.
Conclusion
In conclusion, Japan's SLIM mission represents a significant advancement in lunar exploration, showcasing innovative approaches to spacecraft design, trajectory planning, and precision landing. Its lightweight design, fueled by strategic decisions on payload and fuel efficiency, sets a new standard in space exploration. The extended trajectory, guided by weak-stability boundary theory, emphasizes the importance of optimizing fuel consumption for future missions.
SLIM's lunar objectives, especially the "moon sniper" precision landing, mark a milestone in the history of moon exploration. The deployment of small rovers adds an extra layer of scientific exploration, enhancing our understanding of the lunar surface and its geological features.
Looking forward, SLIM's success or failure will reverberate into the collaborative efforts between India and Japan on the LUPEX mission. The technologies tested by JAXA, including feature-matching algorithms and navigation systems, will play a crucial role in LUPEX's success, emphasizing the collaborative nature of international lunar exploration.
As SLIM prepares for its historic landing attempt on January 19, the global space community eagerly anticipates the outcomes that could potentially reshape the future of lunar exploration.
Probable Questions for UPSC mains Exam-
- Discuss the key features that make Japan's Smart Lander for Investigating Moon (SLIM) mission unique in the field of lunar exploration, focusing on its lightweight design, trajectory, and precision landing capabilities. How does SLIM's approach differ from traditional methods, such as the Hohmann Transfer Orbit, and what are the potential implications for future lunar missions? (10 Marks, 150 Words)
- Examine the significance of SLIM's success or failure on the collaborative Lunar Polar Exploration (LUPEX) mission between India and Japan, also known as Chandrayaan-4. How does SLIM's pioneering precision landing technology impact the planning and execution of future lunar missions, particularly in challenging terrains like the moon's polar regions? Discuss the collaborative aspects of international lunar exploration highlighted by SLIM's mission. (15 Marks, 250 Words)
Source- THE HINDU
