Archontophoenix Alexandrae

Chandrayaan-4 (pronunciation^ⓘ; from Sanskrit: Chandra, "Moon" and yāna, "craft, vehicle") is a planned lunar sample return mission of the Indian Space Research Organisation (ISRO) and the fourth iteration in its Chandrayaan lunar exploration programme.^[1][2] The mission is currently under conceptualisation and expected to launch around 2028.^[3]

The plan for a lunar sample return mission was revealed by the director of Space Application Centre (SAC), Nilesh M Desai on 17 November, 2023 during the during the 62nd foundation ceremony of IITM in Pune.^[4] This was confirmed by S. Somanath, the chairman of ISRO during the National Space Science Symposium held in Goa on 26 February, 2024.^[5] He said that the mission is extremely challenging as it incorporates multiple launches, docking capability and robotic capability. He expressed the confidence buildup over the success of 'hop' operation of the lander and Earth return operation performed by the propulsion module of Chandrayaan-3.^[5][6] After the launch of INSAT-3DS, the chairman stated the insufficiency of the rocket capability leading to a 'novel design' for this mission and the secretary of the Department of Space (DoS) said that the mission incorporates 'high-end technology' and it is pending government approval for him to have a final word.^[1][7] Somanath stated that the mission demands docking capability both in Earth and lunar orbits and the agency is planning to demonstrate this capability through Space Docking Experiment (Spadex) which is slated for launch by year end.^[2][8]

The aim of the mission is to collect samples from the lunar surface and bring the samples safely to Earth for scientific studies. The objectives of this mission are:

1. To perform safe and soft landing on lunar surface.
2. To demonstrate lunar sample collection and containerization.
3. To demonstrate ascend from the Moon's surface.
4. To demonstrate docking and undocking in lunar orbit.
5. To demonstrate transfer of samples from one module to other.
6. To demonstrate return and re-entry to Earth for sample delivery.^[5]

The mission will be launched in two phases onboard two LVM3 rockets. The spacecraft will have five modules packed into two composites which are launched separately. The lander module with the ascender module attached on its top and supported by a propulsion module beneath it will be a single composite, while the transfer module along with the re-entry module will be another composite. The spacecraft will get assembled into an integrated module by docking in Earth orbit before proceeding to the Moon.^[5][2][9]

• Propulsion Module is similar to the propulsion module on Chandrayaan-3. It will ferry the combined modular spacecraft to the moon.^[10][11][3]
• Lander Module will land on the Moon with instrumentation. It supports the ascend stage along with the soil sampling instrumentation. It is designed to last 1 lunar day or 14 earth days on the moon.^[10][11][3]
• Ascender Module will eject from the lander and would launch from the Moon using the lander as a launch pad after the samples from the Moon are collected and stored. It will then enter low-lunar orbit.^[10][11][3]
• Transfer Module will collect the samples from the ascend stage, transfer them to the re-entry module, fire its engine to set both itself and the re-entry module towards Earth, release the payload and loop back around the Earth.^[10][11][3]
• Re-entry Module will hold the sample from lunar orbit. It is designed to survive atmospheric re-entry and land with the lunar regoliths.^[10][11][3]

Apart from the propulsion module, the transfer module is also equipped with an onboard Liquid Apogee Motor (LAM) for return operation maneuvers including the trans-Earth injection. As per earlier reports, the lander module will have six throattleable landing thrusters capable of producing 800 newtons of thrust each, while the ascender module will have two lift off thrusters capable of producing 800 newtons of fixed thrust each.^[12] The integrated assembly of all modules after docking in Earth orbit is expected to weigh atleast 6,727 kg (14,830 lb).^[12]

The landing site is planned near to Statio Shiv Shakti, the landing site of Chandrayaan-3 which is located between the Manzinus P and Boguslawsky M lunar craters near to the south pole region.^[13][14] ISRO had conducted comprehensive study of this landing site region regarding morphology, hydration and gravity anomalies using data obtained from payloads of Chandrayaan-2 orbiter, Lunar Reconnaissance Orbiter (LRO), Lunar Prospector and GRAIL.^[15][16]

• Chandrayaan Programme
• List of missions to the Moon
• Lunar Polar Exploration Mission