ISRO’s ambitious Chandrayaan 5 precision landing mission to Moon

The Indian Space Research Organisation (ISRO) and the Japan Aerospace Exploration Agency (JAXA) have embarked on a joint mission to the south pole of the moon, dubbed the Lunar Polar Exploration (LUPEX) mission. In ISRO’s Chandrayaan lunar exploration programme, the LUPEX mission is Chandrayaan 5. ISRO is providing the lander for the mission, while JAXA is providing a rover as well as the launch vehicle or the rocket to launch the mission. To be clear, the Chandrayaan 5/LUPEX mission will be launched from Tanegashima Space Center in Japan and not Sriharikota in India, on board a Japanese Hayabusa H3 rocket.

ISRO and JAXA conducted the feasibility study for the mission in 2017, with a joint review to clearly define the mission goals in 2018. Teams from JAXA and ISRO have been collaborating closely on the mission since then, which was initiated before the launch of the Chandrayaan 2 mission and the incredible success of the Chandrayaan 3 mission. The LUPEX mission is headed to the south pole of the Moon to better understand the distribution of water ice, and to determine the form that it is stored in. The LUPEX lander will not use a relay satellite, and will be able to communicate directly with ground stations.

ISRO and JAXA have been evaluating landing sites between Shackleton and the de Gerlache impact craters on the south pole of the Moon. The lander will be loaded with the technologies necessary for making a precision landing on the lunar surface, which means that the landing site will be less than 100 metres across. Conventionally, Moon Landers have landing zones that are square kilometres in size. Sunlight is an important consideration for selecting the landing zone, as it will be necessary to power the instruments on board the lander and the rover.

Illustration of the LUPEX rover prospecting for water. (Image Credit: JAXA). 

ISRO’s lander will have to be bigger than the Vikram lander used in the Chandrayaan 3 mission, as well as the lander for the Chandrayaan 4 mission. The lander will be equipped with ground penetrating radar and an infrared payload to peer into the surface of the Moon and determine how much water is present, in what form, and at what depth. The temperature probe from the Chandrayaan 3 mission indicated that the temperature drops off sharply with depth, increasing the chances of finding water ice at shallow depths on the Moon. The potential science results from the region is another important consideration when zeroing in on a landing site.

The Lander will be equipped with a flip out ramp that will lower the rover onto the surface. The Japanese rover will have payloads from USA, Europe, India and Japan, making Chandrayaan 5/LUPEX a truly international lunar mission. ISRO will be operating the lander on the lunar surface, while JAXA will be operating the lander. The rover will also be equipped with ground penetrating radar, and will attempt to discover subsurface water deposits during its trek, and mine it using a drill. ISRO and JAXA are looking to launch the Chandrayaan 5/LUPEX mission in the 2028-2029 timeframe.

Illustration of the rover rolling out of the lander. (Image Credit: JAXA). 

ISRO is developing the payloads for both the lander and the rover. One technically challenging operation that ISRO has to manage is lowering the 350 kg rover carefully onto the lunar surface. In the Chandrayaan 3 mission, the rover was housed in the belly of the Lander, but in the Chandrayaan 5/LUPEX mission, it will be on top. The Chandrayaan 5/LUPEX mission was originally slotted for launch in 2026 as the Chandrayaan 4/LUPEX mission, but the teams needed additional time to chart out the technically sophisticated and complex collaboration, and ISRO decided to accelerate its sample return mission.

The permanently shadowed craters in the highlands surrounding the south pole of the Moon are promising sites for finding water ice at or close to the surface. The heat from the Sun never reaches the bottoms of these craters. Water is an important resource in space travel, as it can be used to extract oxygen, which is an accelerant for rocket fuel. If humans can set up propellent plants on the Moon, and manufacturing facilities for rockets and spacecraft, then access to the rest of the Solar System promises to become dramatically cheaper. The Moon can be a staging ground and stepping stone for exploration of the Solar System. Understanding the distribution of water is crucial for India’s plans to establish a Moon Base by 2047.