CHANDRAYAAN-3

July 14, 2023

GS Paper III Science and Technology Space

Context:

ISRO is set to launch the Chandrayaan 3 spacecraft using the LVM3 rocket from Satish Dhawan Space Centre in Sriharikota, India.

About:

Chandrayaan-3 is India’s third lunar mission as well as second attempt to achieve a soft landing of a robotic lander on the moon’s surface. If the soft-landing succeeds, India will become the fourth country in the world to have achieved this.
It is a follow-up to the 2019 Chandrayaan-2 mission, which partially failed after its lander and rover couldn’t execute a soft-landing on the Moon.

Chandrayaan-3’s objectives:

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

How will Chandrayaan-3 get to the lunar surface?

Launch and Launch Vehicle: The mission starts with a launch aboard India’s LVM3 rocket (the country’s heavy lift vehicle capable of placing about 8 metric tons into low-Earth orbit).
Orbit Placement: The LVM3 will place the spacecraft and an attached propulsion module into an elongated Earth orbit with an apogee, or high point, of about 36,500 kilometers above the planet.
Propulsion module: This module will take the lander and the rover to the moon. Module itself does not land on the moon and instead settles on a parking orbit of 100 km x 100 km around the moon.
Landing site: The site has been moved slightly from the previous location on a plateau between two craters. The site, at around 70 degreeS near the Southern pole of the moon, was selected as there are several craters here that remain permanently in shade, and can be the store-house of water ice and precious minerals.
Lander and rover module: The lander and rover will separate from the propulsion module to land on the moon.
Preventing crash landing: The lander has engines that will slow down the fall, so that it descends gently onto the moon rather than crash-landing on it.
Touchdown of Lander and Rover: After the touchdown, the lander will remain stationary at the landing site, while the rover, which is a tiny, trolley kind of device with wheels will explore the moon.
Activity Duration:The lander and rover will be alive for 14 earth days, which corresponds to one moon day. Since the solar panels that provide electricity to the lander and rover need sunlight, they will be alive for one moon day, which is 14 earth days.

Advanced technology Equipments on lander to ensure proper soft landing:

Altimeters: To measure altitude
Velocimeters: To measure velocity, and cameras for hazard detection and avoidance.
Laser Doppler Velocity Meter: A new laser sensor has been added to better judge the lunar terrain before landing.

Rover Payloads:

Laser Induced Breakdown Spectroscope (LIBS): Determines the chemical and mineralogical composition of the surface.
Alpha Particle X-ray Spectrometer (APXS): Determines the elemental composition of the surface.

Lander payloads:

Radio Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere (RAMBHA): Measures how the local gas and plasma environment changes over time.
Chandra’s Surface Thermophysical Experiment (ChaSTE): Studies the surface’s thermal properties.
Instrument for Lunar Seismic Activity (ILSA): Measures seismic activity at the landing site in order to delineate the subsurface crust and mantle.
Laser Retroreflector Array (LRA): A NASA-provided retroreflector that allows for lunar ranging studies. Laser ranging is the process of zapping a reflector with a laser and measuring the time it takes for the signal to bounce back.
Gathering data:
- Lander and rover will study:
  - The surface and atmosphere of the Moon,
  - The low-height atmospheric characteristics and electrostatic characteristics of the Moon.
  - Constituents of the regolith (planetary surface)
  - Examine the ionised atmosphere’s behaviour in day and night
- Orbiter:
  - The orbiter will focus on Earth to look at signatures of life on the Pale Blue Dot so that it can aid in the search of exoplanets (planets beyond the solar system) that may support life.

Key differences between Chandrayaan-2 and Chandrayaan-3:

Expansion of landing area: Instead of trying to reach a specific 500mx500m patch for landing as targeted by Chandrayaan-2, the current mission has been given instructions to land safely anywhere in a 4kmx2.4km area.
Pictures from Chandrayaan-2: The lander will no longer depend only on the pictures it clicks during the descent to determine a landing site. High resolution images from the Chandrayaan-2 orbiter have been fed into the lander and it will click images just to confirm that it has reached the correct location.
Change in physical structure of lander: The central thruster on the lander has been removed, reducing the number from five to four. The legs have been made sturdier to ensure it can land even at a higher velocity.
Increased fuel and solar panels: More solar panels have been added to the body of the lander.
No orbiter: While Chandrayaan-2 comprised Vikram lander, Pragyan rover, and an orbiter, Chandrayaan-3 will reportedly use the Orbiter already hovering above the Moon launched withChandrayaan-2 for its communications and terrain mapping requirements.

Image Credits: Indian Express

Relevance of Chandrayaan-3 for India:

First soft landing near south pole: If everything goes well, the Chandrayaan-3 will become the world’s first mission to soft-land near the lunar south pole.
International collaborations: success of the mission would position India among the top four technologically-advanced space nations and pave the way for important international collaborations, similar to the recent Artemis Accord signing between ISRO and the American space agency NASA
Counterweight to China: The success of the ambitious lunar mission could also position India as a potential counterweight to China in the global space race.

Significance of the moon mission:

Moon is the closest cosmic body to earth, where space discovery can be attempted and documented.
It is described as a promising test bed to demonstrate technologies required for future deep-space missions.

Additional Information:

Why hasn’t any spacecraft ever landed near the lunar south pole?

Easy landing on Equatorial Region: All the previous spacecraft to have landed on the Moon have landed in the equatorial region, a few degrees latitude north or south of the lunar equator because the terrain and temperature are more hospitable and conducive for a long and sustained operation of instruments.
Abundant sunlight: Sunlight is present in abundance, at least on the side facing the earth, thus offering a regular supply of energy to solar-powered instruments.
Difficult polar terrain: The polar regions of the Moon, however, are very different, and difficult, terrain. Many parts lie in a completely dark region where sunlight never reaches, and temperatures can go below 230 degrees Celsius.
Presence of large craters: There are large craters all over the place, ranging from a few centimeters in size to those extending to several thousands of kilometers.

Why do scientists want to explore the lunar south pole?

Unexplored Region: Due to their rugged environment, the polar regions of the Moon have remained unexplored.
Water presence: There are indications of the presence of ice molecules in substantial amounts in the deep craters in this region — India’s 2008 Chandrayaan-1 mission indicated the presence of water on the lunar surface with the help of its two instruments onboard.
Study of the Solar System: The extremely cold temperatures here mean that anything trapped in the region would remain frozen in time, without undergoing much change. The rocks and soil in Moon’s north and south poles could therefore provide clues to the early Solar System.

News Source: The Hindu