Here's a detailed report expanding on the ISRO announcement regarding the Chandrayaan-4 landing site selection. I've crafted it as a long-form piece in British English, broken into short paragraphs for readability, drawing on the provided details alongside relevant context from ISRO's lunar exploration program.

ISRO has pinpointed a prime landing site for its ambitious Chandrayaan-4 mission, marking another stride in India's lunar endeavours. Officials from the space agency have zeroed in on the Mons Mouton region, a geologically intriguing area on the Moon's surface. After meticulous analysis, they have selected site MM-4 as the optimal spot for the mission's soft landing.

Mons Mouton, often abbreviated as MM, lies within the lunar near side, near the prominent Rima Ariadaeus fault line. This region captivates scientists due to its mix of volcanic plains and elevated mounds, potentially preserving clues about the Moon's ancient magmatic activity. ISRO's choice underscores the agency's growing prowess in high-precision site selection for lunar missions.

The selection process involved evaluating four candidate sites: MM-1, MM-3, MM-4, and MM-5. High-resolution data from the Orbiter High Resolution Camera (OHRC) aboard Chandrayaan-2 proved instrumental. Multi-view image datasets enabled a comprehensive characterisation of terrain features across these locations.

Among the sites, MM-4 emerged as the frontrunner. A one-kilometre by one-kilometre zone around it boasts the lowest hazard percentage, ensuring safer descent and operations. The mean slope measures a gentle five degrees, minimising risks of tipping or instability for the lander.

Elevational data further bolsters MM-4's suitability, with a mean height of 5,334 metres above the lunar datum. This positioning aids communication links with Earth-based stations and other orbiters. Crucially, the site features the highest number of hazard-free grids, each measuring 24 metres by 24 metres.

Such granular analysis aligns with lessons from prior missions like Chandrayaan-3, which successfully landed near the lunar south pole in 2023. There, ISRO refined hazard avoidance techniques, now scaled up for Chandrayaan-4's more complex architecture. The emphasis on slope, elevation, and grid safety directly addresses challenges like uneven regolith and craters.

Chandrayaan-4 represents a technological leap, comprising five key modules: the Propulsion Module (PM), Descender Module (DM), Ascender Module (AM), Transfer Module (TM), and Re-entry Module (RM). This configuration aims to achieve sample return, a first for India.

The mission's core innovation lies in the DM-AM combined stack, which will execute a soft landing at MM-4. The propulsion system will handle the initial descent, while advanced navigation, guidance, and control algorithms ensure pinpoint accuracy. Site selection plays a pivotal role, enforcing constraints on slope, hazards, and visibility.

Post-landing, the AM will ascend with lunar samples collected by the DM, docking with the TM for Earth return via the RM. This closed-loop retrieval demands flawless execution, where MM-4's benign terrain reduces variables. ISRO's simulations predict a high success margin, building on Pragyan rover data from Chandrayaan-3.

The OHRC's role cannot be overstated. Mounted on Chandrayaan-2's orbiter, it delivers sub-metre resolution imagery, vital for stereo mapping. For Mons Mouton, these datasets revealed subtle undulations invisible at coarser scales, allowing ISRO to discard riskier sites like MM-1 and MM-3.

Terrain hazards—craters, boulders, and steep scarps—pose existential threats to landers. MM-4's low hazard density translates to more viable parking spots for the 24x24-metre grids, facilitating safe touchdown and rover mobility. The five-degree slope further eases ascent preparations for the AM.

Strategically, landing at Mons Mouton advances ISRO's scientific goals. The site's proximity to Marius Hills-like domes hints at subsurface lava tubes, ideal for resource prospecting. Water ice traces, detected by Chandrayaan-1's Moon Mineralogy Mapper, could inform future habitats.

Chandrayaan-4 builds on India's sample return ambitions, echoing NASA's Artemis and China's Chang'e programs. Yet ISRO's indigenous tech stack—powered by LVM3 rocket—keeps costs lean, at around ₹3,500 crore. Launch is slated for 2027, pending final validations.

Site finalisation triggers next phases: lander prototyping at U R Rao Satellite Centre and ascent vehicle tests at Vikram Sarabhai Space Centre. Integration with the PM will occur in Bengaluru, leveraging HAL's clean rooms. Ground simulations using MM-4's digital twin will refine descent trajectories.

Global partners like JAXA may contribute rover tech, enhancing sample acquisition. The RM's heat shield, derived from Chandrayaan-3 upgrades, must withstand 11 km/s re-entry speeds. MM-4's elevation aids signal strength during critical phases.

This announcement reaffirms ISRO's site selection mastery, honed since Chandrayaan-1's 2008 impact probe. From polar ice hunts to equatorial volcanism, each mission refines the playbook. MM-4 positions Chandrayaan-4 for breakthroughs in lunar geology and in-situ resource utilisation.

As India eyes a sustained lunar presence, Mons Mouton's MM-4 becomes a cornerstone. Success here could pave the way for Bharatiya Antariksh Station by 2035, blending science with self-reliance.

Based On PTI Report