Moon landings after the space race

On ISRO's first moon mission, Chandrayaan-1, was a small piggyback lander. This lander, the Moon Impact Probe, was designed to impact the moon sometime after being released from the main vehicle. After separation from the main mission, the probe spun up for stability and fired its retro rocket motor. This caused the orbit of the lander to decrease and thus intersect the surface of the moon. After a 25-minute descent phase the probe "hard landed" with a velocity of 1.69 km/s.

Even though the mission was short it showed ISRO's capabilities of reaching the surface of the moon. Marking India to be the fourth nation to do so. Furthermore, the mission discovered the presence of water just before it hit the ground. This discovery was not made public until the Moon Mineralogy Mapper, a NASA experiment onboard Chandrayaan-1, confirmed this discovery. 

LCROSS employed an innovative impact strategy, utilising its Centaur upper stage and a Shepherding Spacecraft. On October 9, 2009, the Centaur rocket impacted the Cabeus crater near the Moon's south pole at a velocity of 9,000 km/h (5,600 mph), releasing the kinetic energy equivalent to 2 kilotons of TNT. This impact excavated over 350 metric tons of lunar material, creating a crater approximately 27 meters wide and 5 meters deep.

Four minutes later, the Shepherding Spacecraft flew through the debris plume, collecting crucial data before its own impact. The mission successfully confirmed the presence of water in the form of ice, detecting multiple lines of evidence for water within the ejecta. Spectral analysis revealed that water concentration in the excavated material was approximately 5.6% by mass. The discovery also included other volatile substances, such as methane, ammonia, and hydrogen, indicating that the lunar regolith in these shadowed regions harbours a mix of valuable resources.

OMOTENASHI is one of the CubeSats flying onboard the Artemis 1 mission to the moon. The objective of OMOTENASHI is to demonstrate low-cost landing techniques for the moon. After separation, the satellite will spin up and ignite a small solid rocket motor. The burn will last for about 15 to 20 seconds.  It will then separate the lander from the motor and inflate a 50cm airbag. This airbag ensures a safe landing. The final free-fall is about 100 meters and the final impact will be between 20 and 30 m/s.

After the successful launch in November 2022, the satellite was separated from the Orion spacecraft. Unfortunately, the team on the ground was not able to establish communications with the lander and were thus not able to start the landing sequence. The satellite remains in Lunar orbit. 

The Luna 25 mission was launched in August 2023 on top of a Soyuz-2.1b rocket. The mission is targeting a lunar landing at the end of August 2023. The mission is the first moon mission of Russia since Luna 24 and the first moon mission flown since the fall of the soviet union. The mission has been in development for quite some time, at least since 2010 when Phobos Grunt was launched. Originally the mission was to include the ESA Pilot-D and the Swiss  LINA-XSAN payload, but these were removed in the wake of the Russian invasion of Ukraine. 

Luna 25 crashed during its landing attempt. From the last updates, it seems that a malfunctioning thruster caused the spacecraft to hit the moon prematurely. The satellite was first placed in a 100km polar orbit and it was intended to be placed in an elliptical orbit with a periapsis of only 18km above the surface of the moon. When the thruster fired too long this orbit started to intersect the moon [187].

Currently, it is unclear how this mission failure impacts the planned Luna 26, 27, and 28 missions.

After the crash of Chandrayaan-2, ISRO officials announced a new moon lander. This lander was to learn from the mistakes of Chandrayaan-2. The main updates included a redesign of the landing engines and the landing software. The software now allowed for attitude corrections in all phases of flight and the control of the attitude was provided by four downwards-facing rockets. 

The lander landed successfully on November 23 2023, after which it deployed a moon rover. This landing makes India the fourth nation to soft land on the moon and the first lander on the lunar south pole. 

The laser altimeter is a device that emits laser pulses and measures the time it takes for them to bounce back from the ground. This allows SLIM to determine its altitude and velocity relative to the lunar surface.

The terrain camera is a device that captures images of the landing site and compares them with a pre-loaded map of the area. This allows SLIM to identify its position and orientation on the map, and to avoid any obstacles or hazards.

The navigation camera is a device that tracks landmarks on the lunar surface, such as craters or mountains, and uses them as reference points. This allows SLIM to estimate its location and trajectory, and to correct any errors or deviations.

The guidance, navigation and control system is a software that processes the data from the sensors and computes the optimal commands for the thrusters and attitude control system. This allows SLIM to autonomously adjust its attitude and velocity during the landing phase, and to achieve a soft and accurate landing.

SLIM's scientific objectives are to conduct investigation of the Moon's origins by landing near the Marius Hills Hole, a possible skylight of a subsurface lava tube that could provide clues about the Moon's volcanic history and potential habitability. SLIM will also test technology fundamental to exploration in low-gravity environments, such as wireless power transmission, optical communication, and miniaturized instruments.

The Hakuto-R lander has a long history starting in the days of the Google Lunar X Prize to kickstart the moon landers in 2007. Even though the Hakuto lander did not reach a flight-ready state during the competition it managed to fly in November 2022. This launcher included the Rashid rover, the first moon rover of the UAE.

After the launch in 2022, the lander reached the moon. On the 25th of April, the landing attempt was started but ended

with the lander not responding. Currently, the lander is considered lost.

The spacecraft, built by Astrobotic, was designed as a box-shaped lander supported by four legs, primarily constructed from aluminium iso grid shear panels and aluminium honeycomb mounting surfaces. It was equipped with five TALOS-150 667-N thrusters and four sets of three 45-N attitude control thrusters, using a hypergolic system composed of Mono-Methyl Hydrazine (MMH) and a 25% Mixed Oxides of Nitrogen (MON-25) oxidiser.

Peregrine was launched on a ULA Vulcan Centaur rocket and included an Earth orbit phase before cruising to the Moon, where it was supposed to enter a high, then medium, and finally a circular 100 km lunar orbit.

Shortly after launch, a propellant leak developed, preventing the lander from maintaining the necessary orientation for solar power acquisition. This critical issue led to the mission’s premature end, as the spacecraft could not continue its trajectory to the Moon. Instead, it was redirected to make a controlled reentry into Earth's atmosphere over the South Pacific Ocean on January 18, ending the mission.

The spacecraft is equipped with five 700 lbf main engines and twelve 25 lbf attitude control thrusters, using an upgraded hypergolic propulsion system with M20 fuel and MON3 oxidiser, providing precise thrust control essential for accurate lunar landings.

Griffin will be launched on a SpaceX Falcon Heavy rocket, with a similar phased approach to lunar orbit insertion as Peregrine. However, Griffin incorporates the Optical Precision Autonomous Landing (OPAL) Sensor, significantly enhancing landing accuracy to a 100 m x 100 m ellipse, a crucial upgrade for missions targeting scientifically valuable, but difficult-to-reach, lunar regions.

The main objective of LUPEX is to investigate the lunar polar region for the presence and potential usability of water, which could be a valuable resource for future human exploration and settlement of the Moon. The mission will also demonstrate new surface exploration technologies related to vehicular transport and lunar night survival, which are essential for sustainable exploration in the harsh environment of the polar regions.

The lander, developed by ISRO, will carry a payload capacity of 350 kg (770 lb) and will use a feature matching algorithm and navigational equipment derived from JAXA's Smart Lander for Investigating Moon (SLIM) mission for precision landing. The rover, developed by JAXA, will carry multiple instruments by both agencies, including a drill to collect sub-surface samples from 1.5 m (4 ft 11 in) depth.

LUPEX is poised to be a trailblazer in providing concrete answers to the scientific questions about the lunar water resources and their origin, distribution, and evolution. The mission will also pave the way for future collaboration between ISRO and JAXA in lunar exploration and beyond.

The Chandrayaan-4 mission, spearheaded by the Indian Space Research Organisation (ISRO), represents a significant milestone in India’s lunar exploration program. Scheduled for launch in 2027, this ambitious mission aims to return lunar samples to Earth, a feat achieved by only a few nations.

Chandrayaan-4’s mission architecture is both innovative and complex. It involves two separate launches using the LVM3 rockets. The mission comprises five modules: a lander, an ascender, a propulsion module, a transfer module, and a re-entry module. These modules will work in tandem to achieve the mission’s objectives. The lander will perform a soft landing on the lunar surface, where it will collect samples. The ascender will then transport these samples to the transfer module in lunar orbit. Finally, the re-entry module will bring the samples back to Earth for detailed analysis.

One of the key engineering challenges of Chandrayaan-4 is the demonstration of docking and undocking capabilities in lunar orbit, a critical technology for future crewed missions. Additionally, the mission will test precision landing techniques and the safe return of spacecraft through Earth’s atmosphere. These advancements are crucial for India’s long-term goal of sending astronauts to the Moon by 2040.

Chandrayaan-4 not only aims to enhance our understanding of the Moon but also to pave the way for future lunar missions. By mastering these complex technologies, ISRO is positioning India as a formidable player in global space exploration.