The Indian Space Research Organisation is set to launch Chandrayaan-3, India's third lunar mission, and a follow-on mission to Chandrayaan-2. The launch is scheduled for July 14, 2023, at 14:35 Hrs. IST from the Second Launch Pad, SDSC-SHAR, Sriharikota. 

Chandrayaan-3 will demonstrate end-to-end capability in safe landing and roving on the lunar surface. It consists of Lander and Rover configuration and will be launched by LVM3, a geosynchronous satellite launch vehicle. The propulsion module will carry the lander and rover configuration till the 100 km lunar orbit. The propulsion module has a Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload to study the spectral and Polari metric measurements of Earth from the lunar orbit.

On July 5, the encapsulated assembly containing Chandrayaan-3 was mated with the LVM3 launch vehicle at the Satish Dhawan Space Centre in Sriharikota and subsequently, the launch vehicle was moved to the launch pad where all the vehicle electrical tests were completed.

Chandrayaan-3 consists of an indigenous Lander module (LM), a Propulsion module (PM), and a Rover with the objective of developing and demonstrating new technologies required for Interplanetary missions. The Lander will have the capability to soft land at a specified lunar site and deploy the Rover which will carry out in-situ chemical analysis of the lunar surface during the course of its mobility. 

The Lander and the Rover have scientific payloads to carry out experiments on the lunar surface. The main function of the PM is to carry the LM from launch vehicle injection to the final lunar 100 km circular polar orbit and separate the LM from the PM. Apart from this, the Propulsion Module also has one scientific payload as a value addition which will be operated post-separation of the Lander Module. The launcher for Chandrayaan-3 is LVM3 which will place the integrated module in an Elliptic Parking Orbit (EPO) of size ~170 x 36500 km.

Chandrayaan-3 Payloads

Lander payloads: Chandra’s Surface Thermophysical Experiment (ChaSTE) to measure the thermal conductivity and temperature; Instrument for Lunar Seismic Activity (ILSA) for measuring the seismicity around the landing site; Langmuir Probe (LP) to estimate the plasma density and its variations. A passive Laser Retroreflector Array from NASA is accommodated for lunar laser ranging studies.

Rover payloads: Alpha Particle X-ray Spectrometer (APXS) and Laser Induced Breakdown Spectroscope (LIBS) for deriving the elemental composition in the vicinity of the landing site.

The mission objectives of Chandrayaan-3 are:

• To demonstrate Safe and Soft Landing on Lunar Surface
• To demonstrate Rover roving on the moon and
• To conduct in-situ scientific experiments.

To achieve the mission objectives, several advanced technologies are present in Lander such as,

• Altimeters: Laser & RF based Altimeters
• Velocimeters: Laser Doppler Velocimeter & Lander Horizontal Velocity Camera
• Inertial Measurement: Laser Gyro based Inertial referencing and Accelerometer package
• Propulsion System: 800N Throttleable Liquid Engines, 58N attitude thrusters & Throttleable Engine Control Electronics
• Navigation, Guidance & Control (NGC): Powered Descent Trajectory design and associate software elements
• Hazard Detection and Avoidance: Lander Hazard Detection & Avoidance Camera and Processing Algorithm
• Landing Leg Mechanism.

To demonstrate the above said advanced technologies in earth conditions, several Lander special tests have been planned and carried out successfully viz.

• Integrated Cold Test - For the demonstration of the Integrated Sensors & Navigation performance test using a helicopter as a test platform
• Integrated Hot test – For the demonstration of closed-loop performance test with sensors, actuators, and NGC using a Tower crane as a test platform
• Lander Leg mechanism performance test on a lunar simulant test bed simulating different touch-down conditions.

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