Chandrayaan-3 : Unstoppable Story

Chandrayaan-3, the successor to Chandrayaan-2, represents a significant leap in demonstrating comprehensive capabilities for safe lunar landing and surface exploration. The mission comprises a Lander module, a Rover module, and a Propulsion module. The launch will be facilitated by the LVM3 launch vehicle from the Satish Dhawan Space Centre (SDSC) in Sriharikota. The Propulsion module will carry the Lander and Rover configuration to a lunar orbit of 100 km. Notably, the Propulsion module incorporates the Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload, designed to investigate spectral and polarimetric measurements of Earth from the lunar orbit.

The Lander payloads on Chandrayaan-3 consist of various scientific instruments and experiments that aim to gather essential data on the lunar surface. These payloads include Chandra’s Surface Thermophysical Experiment (ChaSTE), which measures thermal conductivity and temperature, the Instrument for Lunar Seismic Activity (ILSA), which analyzes seismicity around the landing site, and the Langmuir Probe (LP), which estimates plasma density and its variations. Additionally, a passive Laser Retroreflector Array from NASA is also accommodated for lunar laser ranging studies.

On the other hand, the Rover payloads on Chandrayaan-3 include the Alpha Particle X-ray Spectrometer (APXS) and the Laser Induced Breakdown Spectroscope (LIBS). These sophisticated instruments enable the derivation of elemental composition in the vicinity of the landing site, providing crucial insights into the lunar surface.

Furthermore, Chandrayaan-3 represents a significant milestone in the Indian space exploration program, as it showcases indigenous technology and advancements required for interplanetary missions. The Lander module possesses the capability to execute a soft landing at a designated lunar site, and it will deploy the Rover module, which will conduct in-situ chemical analysis of the lunar surface during its mobility. The Lander and Rover modules are equipped with scientific payloads designed to perform experiments on the lunar surface.

The Propulsion module plays a crucial role in the Chandrayaan-3 mission by carrying the Lander module from the injection by the launch vehicle to the final circular polar orbit around 100 km above the lunar surface. Post separation of the Lander module, the Propulsion module also operates a scientific payload as an added value.

For the launch of Chandrayaan-3, the GSLV-Mk3 launcher has been identified. It will deliver the integrated module to an Elliptic Parking Orbit (EPO) with dimensions approximately 170 x 36,500 km.

The mission objectives of Chandrayaan-3 encompass demonstrating safe and soft landing on the lunar surface, showcasing the Rover's mobility on the moon, and conducting in-situ scientific experiments. These objectives drive the integration of advanced technologies within the Lander module.

Some of the advanced technologies incorporated in the Lander module include laser and RF-based altimeters for precise altitude measurements, laser Doppler velocimeters and a Lander Horizontal Velocity Camera for velocity determination, laser gyro-based inertial measurement for referencing and an accelerometer package for accurate measurement of acceleration. The propulsion system consists of throttleable liquid engines, attitude thrusters, and throttleable engine control electronics. Navigation, guidance, and control (NGC) systems enable the powered descent trajectory design and associated software elements. Hazard detection and avoidance are addressed by the Lander Hazard Detection & Avoidance Camera and processing algorithms. Additionally, the Lander module is equipped with a landing leg mechanism.

To ensure the successful deployment and operation of these advanced technologies, a series of specialized tests have been planned and executed for the Lander module. These tests include the Integrated Cold Test, which demonstrated the integrated sensors and navigation performance using a helicopter as a test platform, and the Integrated Hot Test, which involved closed-loop performance tests with sensors, actuators, and NGC using a tower crane as a test platform. Furthermore, Lander leg mechanism performance tests have been conducted on a lunar simulant test bed, simulating various touchdown conditions.

In terms of specifications, Chandrayaan-3 has a mission life of approximately one lunar day, equivalent to around 14 Earth days. The landing site, the primary target, spans an area of 4 km x 2.4 km at coordinates 69.367621 S and 32.348126 E. The Lander module includes payloads such as the Radio Anatomy of Moon-Bound Hypersensitive Ionosphere and Atmosphere (RAMBHA), Chandra’s Surface Thermo-physical Experiment (ChaSTE), Instrument for Lunar Seismic Activity (ILSA), and Laser Retroreflector Array (LRA). The Rover module is equipped with the Alpha Particle X-Ray Spectrometer (APXS) and the Laser Induced Breakdown Spectroscope (LIBS). The total mass of the integrated module, including the Propulsion module, Lander module, and Rover module, is approximately 3,900 kg. Power generation is provided by the Propulsion module at 758 W, the Lander module at 738 W with Bias, and the Rover module at 50 W. Communication is established between the Propulsion module and the Indian Deep Space Network (IDSN), the Lander module and the IDSN/Rover, and the Rover module with the Lander module. Furthermore, the Lander module encompasses various sensors, actuators, and mechanisms, including the Laser Inertial Referencing and Accelerometer Package (LIRAP), Ka-Band Altimeter (KaRA), Lander Position Detection Camera (LPDC), Lander Hazard Detection & Avoidance Camera (LHDAC), Laser Altimeter (LASA), Laser Doppler Velocimeter (LDV), Lander Horizontal Velocity Camera (LHVC), Micro Star sensor, Inclinometer & Touchdown sensors, and Reaction wheels.

In conclusion, Chandrayaan-3 represents a remarkable leap in India's space exploration efforts, demonstrating the nation's commitment to pushing boundaries and advancing scientific knowledge. The mission's objectives, advanced technologies, and comprehensive payload contribute to the ongoing exploration of the lunar surface, paving the way for future endeavors in lunar and interplanetary missions."