Why in News?
Four years after the unsuccessful attempt of Chadrayaan-2, a successful soft landing will make India the fourth country, after the US, Russia, and China to achieve the feat.

Context:  
·         India's Chandrayaan-3 mission is set to launch on July 14th with the aim of completing a soft landing on the lunar surface. 
·         Built with a budget of $75 million, the mission will utilise the Fat boy LVM3-M4 rocket and will carry a range of scientific instruments to study the moon's surface.
 
All you need to Know about CHANDRAYAAN-3: 
Cost of Chandrayaan-3:
·         The Chandrayaan-3 is built on a budget of just under Rs 615 crore or $75 million.
 
Rocket launcher of Chandrayaan-3: 
·         The 43.5 metre tall rocket, 'Fat boy' LVM3-M4, is scheduled for the lift off.
·         The largest and heaviest LVM3 rocket (formerly GSLV MkIII), fondly called as 'fat boy' by ISRO scientists for its heavylift capability, has completed six consecutive successful missions.
·         The LVM3 rocket is a composite of three modules -- propulsion, lander and rover (which is housed inside the lander). 
·         While the first rocket's first stage is powered by solid fuel, the second stage is by liquid fuel and the third and final stage consists of a cryogenic engine powered by liquid hydrogen and liquid oxygen.
 
will happen after the launch vehicle's lift off? 
·         According to scientists, just over 16 minutes into its flight, the rocket will eject the Chandrayaan-3 spacecraft at an altitude of about 179 km. The spacecraft would orbit the earth for about 5-6 times in an elliptical cycle with 170 km closest and 36,500 km farthest from earth moving towards the lunar orbit.
·         The propulsion module along with the lander, after gaining speed would proceed for an over a month long journey towards reaching the orbit of the moon until it goes 100 km above the lunar surface.
 
When will Chandrayaan-3 reach moon? 
·         Chandrayaan-3 has a 3.84 lakh km distance to cover by its own. The lander carried by the spacecraft is expected to make a soft-landing on the moon on August 23 or 24 2023. After reaching the desired position, the lander module would begin its descent for a soft landing on the south pole region of the moon.
 
Why did they Choose July as the Month of Launch like Chandrayaan-2? 
·         The reason to fix the launch window during the month of July similar to Chandrayaan-2 mission (July 22, 2019) is because the earth and moon would be closer to each other during this part of the year.

What is special about Chandrayaan-3?  
The significance about Chandrayaan-3 mission is:
Unlike its unsuccessful predecessor, is that the Propulsion Module has a payload:
 SHAPE -- Spectro-polarimetric of HAbitable Planet Earth which is to study earth from lunar orbit.
ISRO said the SHAPE is an experimental payload to study the spectro-polarimetric signatures of the Earth in the near-infrared wavelength range.
Apart from the SHAPE payload, the Propulsion Module's main function is to carry the Lander Module from launch vehicle injection orbit to till lander separation.
RAMBHA-LP: The lander module after landing on the surface of the moon has payloads including RAMBHA-LP which is to measure the near surface plasma ions and electrons density and its changes.
ChaSTE Chandra's Surface Thermo Physical Experiment -- to carry out the measurements of thermal properties of lunar surface near polar region 
ILSA (Instrument for Lunar Seismic Activity) to measure seismicity around the landing site and delineating the structure of the lunar crust and mantle.
The Rover, after the soft-landing, would come out of the lander module and study the surface of the moon through its payloads APXS - Alpha Particle X-Ray Spectrometer - to derive the chemical composition and infer mineralogical composition to further enhance understanding of lunar surface.
LIBS: Rover, which has a mission life of 1 lunar day (14 Earth days), also has another payload Laser Induced Breakdown Spectroscope (LIBS) to determine the elemental composition of lunar soil and rocks around the lunar landing site.

What are the stages of Chandrayaan-3?  
The Indian space agency said, the moon mission is divided into three phases – 
·         The earth centric phase (Pre-Launch, Launch and Ascent and Earth-bound Manoeuvre)
·         The Lunar Transfer Phase (Transfer Trajectory) and
·         The Moon Centric Phase
Moon Centric Phase includes: Lunar Orbit Insertion Phase, Moon-bound Manoeuvre Phase, Propulsion Module and Lunar Module Separation, De-boost Phase, Pre-landing Phase, Landing Phase, Normal Phase for Lander and Rover, Moon Centric Normal Orbit Phase (100 km circular orbit) for Propulsion Module.
  
Why hasn’t any spacecraft ever landed near the lunar south pole?  
·         There is a very good reason why all the landings on the Moon so far have happened in the equatorial region.
·         Even China’s Chang’e 4, which became the first spacecraft to land on the far side of the moon — the side that does not face the earth — landed near the 45-degree latitude.
·         It is easier and safer to land near the equator. 
·         The terrain and temperature are more hospitable and conducive for a long and sustained operation of instruments.
·         The surface at equator is even and smooth, very steep slopes are almost absent, and there are fewer hills or craters. 
·         Sunlight is present in abundance, at least on the side facing the earth, thus offering a regular supply of energy to solar-powered instruments.
·         The polar regions of the Moon, however, are a 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. 
·         Lack of sunlight and extremely low temperatures create difficulty in the operation of instruments. 
 
Why don’t some parts of the lunar polar regions receive any sunlight? 
·         Unlike the Earth, whose spin axis is tilted with respect to the plane of the Earth’s solar orbit by 23.5 degrees, the Moon’s axis tilts only 1.5 degrees. 
·         Because of this unique geometry, sunlight never shines on the floors of a number of craters near the lunar north and south poles. 
·         These areas are known as Permanently Shadowed Regions, or PSRs.
·      In addition, there are large craters all over the place, ranging from a few centimetres in size to those extending to several thousands of kilometres.
 
Why ISRO wants to explore the Moon’s South Pole? 
·         Chandrayaan-3 will be the world’s first mission to soft-land near the lunar south pole. All the previous spacecraft have landed a few degrees latitude north or south of the lunar equator.
·         Due to their rugged environment, the polar regions of the Moon have remained unexplored. But several Orbiter missions have provided evidence that these regions could be very interesting to explore. 

Presence of Water:  
·         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.

Clues to History:  
·         In addition, the extremely cold temperatures here mean that anything trapped in the region would remain frozen in time, without undergoing much change. 
 
Scientific Discoveries: 
·         The rocks and soil in Moon’s north and south poles could therefore provide clues to the early Solar System.

Global Collaborations:  
·         ISRO-NASA successfully confirmed the presence of water from the data taken by Chandrayaan-1. Indo-Japan collaboration, LUPEX aims to send a lander and rover to the Moon’s south pole around 2024.
 
Technological Advancements: 
·         By undertaking missions to this region, ISRO can develop and demonstrate innovative technologies for soft landing, navigation, resource utilization, and long-duration operations that can be applied in future space missions.

Key differences between Chandrayaan-2 and Chandrayaan-3:  
Even as the mission architecture remains the same, there are certain differences between the two missions:
1.   The biggest difference between the two missions is in what's being taken onboard the GSLV-MkIII rocket. 
While Chandrayaan-2 comprised of Vikram lander, Pragyan rover, and an orbiter, Chandrayaan-3 will launch with just a lander and a rover.
Chandrayaan-3 will reportedly use the Orbiter already hovering above the Moon launched with Chandrayaan-2 for its communications and terrain mapping requirements.
2.    The Chandrayaan-3 lander mission is equipped with “lander hazard detection and avoidance cameras” for coordination with the orbiter and the mission control during the landing process on the surface of the Moon. 
While Chandrayaan-2 had just one such camera, Chandrayaan-3 has been fitted with two such cameras.
3.    Furthermore, the Vikram lander will have stronger legs than the previous version. The landing velocity has been increased from 3m/second to 2m/second. That means even at 3m/sec, the lander will not crash or break (its legs). 
4.   Another change is the addition of more fuel to Vikram so it has more capability to travel or handle dispersion. Furthermore, a new sensor has also been added. A new sensor called the laser doppler velocity metre, which will look at the lunar terrain was also added.
 5.   The ISRO chief had earlier shared details about what went wrong with the Vikram lander of Chandrayaan-2 as it went hurtling down towards the identified 500m x 500 m landing spot on the lunar surface with the engines designed to reduce its velocity developing higher thrust than expected. This time, ISRO stated that the area of landing has been expanded from 500m x 500m to four km by 2.5 km.
6.   ISRO said that Vikram lander now has additional solar panels on other surfaces to ensure that it generates power no matter how it lands.
 The spacecraft was also tested for the ability to withstand vibrations by flying it over different terrains using a helicopter, while cranes were used to test the landing processes.
7.    Chandrayaan-2 Orbiter was launched with an impressive list of nine in-situ instruments that are still operating in the Moon's orbit. 
In comparison, the propulsion module of the Chandrayaan-3 mission will have just a single instrument named Spectro-polarimetry of Habitable Planetary Earth (SHAPE), to study the spectral and polarimetric measurements of earth from the lunar orbit.
8.    Another addition to the Chandrayaan-3 mission is the Laser Retroreflector Array (LRA) being sent with the lander, which is a passive experiment to understand the dynamics of the Moon system.

Mains Question:  
Q: Briefly discuss the objectives and significance of ISRO’s Chandrayaan -3 Mission?