Space Odyssey of Chandrayaan-3

The historic launch of India’s third Moon mission, Chandrayaan-3 on-board LVM3-M4 rocket has given a major fillip to the country’s first human spaceflight programme as the same launch vehicle with ‘human rated’ capability, would be used for the ambitious Gaganyaan mission.  — Vinod Johri

The Bhartiya spacecraft Chandrayaan-3, atop an LVM3 rocket from Satish Dhawan Space Centre, blasted off from the Satish Dhawan Space Centre in Sriharikota, India, Friday, at 2.35 pm on July 14, 2023.Chandrayaan-3 is a follow-on mission to Chandrayaan-2 to demonstrate end-to-end capability in safe landing and roving on the lunar surface. ISRO has implemented several changes since the Chandrayaan-2 crash. ISRO divides Chandrayaan-3’s roughly 40-day journey to the moon into three distinct segments: the Earth-centric phase, the lunar transfer phase and the moon-centric phase. The mission will land on the moon on Aug. 23 or Aug. 24, if all goes according to plan.Chandrayaan-3 inched closer to lunar landing, with the significant Lunar Orbit Injection (LOI) undertaken on August 5 at approximately 7:00 pm.

According to the Indian Space Research Organisation (ISRO), the three main objectives of the roughly Rs. 615 crore equivalent to $75 million USD Chandrayaan–3 mission are to perform a safe soft landing near the lunar south pole, to deploy a rover and demonstrate its operation and to perform in-situ scientific experiments over the course of a single lunar day of operation (equivalent to about 14 Earth days).

Indian Space Research Organisation (ISRO) is the space agency of India. The organisation is involved in science, engineering and technology to harvest the benefits of outer space for India and the mankind. ISRO is a major constituent of the Department of Space (DOS), Government of India. The Department of Space executes the Indian Space Programme primarily through various Centres or units within ISRO.

The prime objective of ISRO and DOS is the development and application of space technology for various national needs. To fulfil this objective, ISRO has established major space systems for communication, television broadcasting and meteorological services; resources monitoring and management; space-based navigation services. ISRO has developed satellite launch vehicles, PSLV and GSLV, to place the satellites in the required orbits.

Its activities are spread across various centres and units. Launch Vehicles are built at Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram; Satellites are designed and developed at U R Rao Satellite Centre (URSC), Bengaluru; Integration and launching of satellites and launch vehicles are carried out from Satish Dhawan Space Centre (SDSC), Sri Harikota; Development of liquid stages including cryogenic stage is carried out at Liquid Propulsion Systems Centre (LPSC), Valiamala & Bengaluru; Sensors for Communication and Remote Sensing satellites and application aspects of the space technology are taken up at Space Applications Centre (SAC), Ahmedabad and Remote Sensing satellite data reception processing and dissemination is entrusted to National Remote Sensing Centre (NRSC), Hyderabad.

ISRO Chairman Shri Sreedhara Panicker Somanath explained why Chandrayaan-3’s solar-powered lander and rover are touching down in late August. It was stated that the landing would be on August 23 or 24, as ISRO  wants the landing to happen when the sun rises on the moon, so it gets 14 to 15 days to work. If landing cannot happen on these two dates, ISRO will wait for another month and land in September.

The spacecraft blazed its way to the far side of the moon in a follow-up mission to its failed effort nearly four years ago to land a rover softly on the lunar surface. A successful landing would make our country the fourth country, after the United States, the Soviet Union, and China, to achieve the feat.  

Scope of research 

The Chandrayaan-3 lander has its own thruster system, navigational and guidance controls, and hazard detection and avoidance systems. ISRO has implemented several changes since the Chandrayaan-2 crash. These improvements include the strengthening of the lander’s legs, increases to its landing-speed tolerance and the addition of new sensors to measure approach speed.  Once a safe landing has been achieved, it will be time for the Chandrayaan-3 rover to roll out. The rover is equipped with its own scientific payloads to investigate the moon, including the LASER Induced Breakdown Spectroscope (LIBS), which allows for the analysis of the chemical composition of the lunar surface; and the Alpha Particle X-ray Spectrometer (APXS), which will do the same for lunar rocks and soil around the Chandrayaan-3 landing site.  As the rover goes about its business, the lander that carried it down to the surface will do its own science work. The lander will use the Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere (RAMBHA) instrument to measure plasma — a gas of electrons and ions — at the lunar surface and how it changes over time. Meanwhile, the lander’s Chandra’s Surface Thermophysical Experiment (ChaSTE) will measure the thermal properties of the south polar region, and the Instrument for Lunar Seismic Activity (ILSA) will measure the moon’s seismicity to help flesh out the structure of the lunar crust and mantle. As this is all taking place, a passive experiment called the LASER Retro reflector Array (LRA), contributed by NASA, will be running in the background on the lander, collecting data that could help scientists better understand the dynamics of the moon system. 

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

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

The historic launch of India’s third Moon mission, Chandrayaan-3 on-board LVM3-M4 rocket has given a major fillip to the country’s first human spaceflight programme as the same launch vehicle with ‘human rated’ capability, would be used for the ambitious Gaganyaan mission. According to PTI sources, Indian Space Research Organisation is busy working on its flagship project, Gaganyaan, which envisages the demonstration of human spaceflight capability by launching a crew of three members to an orbit of 400kms for 3 days and bring them back safely to earth, by landing in sea waters.          

(Source : ISRO website, Times of India, Space research websites)

Vinod Johri: Retd. Additional commissioner of Income Tax, Delhi

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