Chandrayaan - 3


Chandrayaan-3 is an upcoming mission that serves as a follow-on to Chandrayaan-2, with the primary objective of demonstrating safe landing and roving capabilities on the lunar surface. The mission consists of a Lander module (LM), a Propulsion module (PM), and a Rover. It will be launched into space by the LVM3 launch vehicle from the Satish Dhawan Space Centre (SDSC) SHAR in Sriharikota, India.

The Propulsion module will carry the Lander and Rover configuration to a lunar orbit of approximately 100 km. Notably, the propulsion module is equipped with the Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload, which aims to study Earth by collecting spectral and polarimetric measurements from the lunar orbit.

The Lander module carries several scientific payloads. One of them is Chandra’s Surface Thermophysical Experiment (ChaSTE), which is designed to measure thermal conductivity and temperature on the lunar surface. Another payload is the Instrument for Lunar Seismic Activity (ILSA), which aims to measure seismic activity around the landing site. Additionally, the Lander module incorporates the Langmuir Probe (LP), an instrument used to estimate plasma density and variations. To support lunar laser ranging studies, a passive Laser Retroreflector Array from NASA will also be accommodated.

The Rover module of Chandrayaan-3 is equipped with the Alpha Particle X-ray Spectrometer (APXS) and Laser-Induced Breakdown Spectroscope (LIBS). These payloads enable the Rover to derive the elemental composition in the vicinity of the landing site, providing valuable insights into the lunar surface.

The main function of the Propulsion module is to transport the Lander module from the launch vehicle injection until it reaches the final lunar orbit of 100 km. After separation, the Propulsion module will operate with its own scientific payload as an additional value. The Geosynchronous Satellite Launch Vehicle-Mk3 (GSLV-Mk3) has been identified as the launcher for Chandrayaan-3, placing the integrated module into an elliptic parking orbit of approximately 170 x 36,500 km in size.

The mission objectives of Chandrayaan-3 are threefold.

  1. It aims to demonstrate the capability of safe and soft landing on the lunar surface.
  2. It seeks to showcase the mobility of the Rover on the Moon.
  3. The mission aims to conduct in-situ scientific experiments, gathering valuable data and insights about the lunar surface.

To achieve these objectives, the Lander module incorporates advanced technologies and instruments. Laser and radio frequency-based altimeters are employed for altitude measurements, while laser Doppler velocimeters and a Lander Horizontal Velocity Camera are used for velocity measurements. The Lander module also utilizes laser gyro-based inertial referencing, an accelerometer package for inertial measurement, and a propulsion system consisting of throttleable liquid engines and attitude thrusters. Navigation, guidance, and control (NGC) elements are designed for the powered descent trajectory and associated software. Additionally, hazard detection and avoidance systems are integrated into the Lander module, including a Lander Hazard Detection & Avoidance Camera and associated processing algorithms. The landing leg mechanism ensures a stable touchdown on the lunar surface under different conditions.

To validate and demonstrate the functionality of these advanced technologies under Earth’s conditions, various special tests have been planned and successfully carried out. These tests include the Integrated Cold Test, which demonstrates the performance of integrated sensors and navigation using a helicopter as a test platform. The Integrated Hot Test involves closed-loop performance tests with sensors, actuators, and NGC, using a tower crane as the test platform. Additionally, the performance of the Lander leg mechanism has been tested on a lunar simulant test bed to simulate different touchdown conditions.

Overall, Chandrayaan-3 represents a significant advancement in India’s space exploration efforts, aiming to showcase the nation’s capability in safe landing and rover mobility on the lunar surface while conducting valuable scientific experiments to enhance our understanding of the Moon.

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