Chandrayaan 2 mission: India's Pride

How will Chandrayaan 2 Study the Moon?

Chandrayaan 2 mission

When Chandrayaan-1, India's first moon mission was launched on October 22, 2008 from Sriharikota using the polar satellite launch vehicle (PSLV), India became the fourth country to plant its flag on the lunar surface. On the moon, the mission conclusively detected traces of water along with magnesium, aluminium and silicon.

Now, close to decade later, India will launch its second lunar mission, Chandrayaan 2, on July 22, 2019 again from sriharikota using the Geosynchronous satellite launch vehicle (GSLV) Mark lll rocket.

The launch falls a day short of the 50th anniversary of the launch of the American mission Apollo 11 which took humans to the moon and back. The first moon landing occurred on July 20, 1969, on the Apollo 11 mission which was launched on July 16.


How will the Launch Work?

The GSLV Mark lll rocket will first launch the spacecraft into an Earth parking orbit (170 Km×40,400 Km).

Then the height of the orbit will be enhanced until the spacecraft can reach out the Lunar Transfer Trajectory. On entering the moon's sphere of influence, on-board thrusters will slow down the spacecraft, allowing it to captured by the moon.

Then it will be eased into a circular orbit (100 Km×100 Km). From this orbit, the lander and rover separate as a unit from the orbiter and through a series of braking mechanisms, the duo will "soft- land" on the moon on September 6, 2019.

What is Special about Chandrayaan 2 ?

Chandrayaan 2 vikram lander

Chandrayaan 2 will be the first mission to reach and study the South pole of the moon.

It is made up of an orbiter, a landar named 'Vikram', after Vikram A. Sarabhai, the founding father of space science research in India, and a rover named 'Pragyan', which means 'wisdom'. At about 3,877 kg, the spacecraft weighs nearly four times it's predecessor Chandrayaan 1. It will be launched by GSLV Mark lll, the Indian space research organisation's (ISRO'S) most powerful and massive launcher.

While Chandrayaan 1 sent its lander crashing into the moon, Chandrayaan 2 will use rocket technology to soft land 'Vikram', carrying its 'Pragyan' rover in a suitable high plain on the lunar surface between two craters, Manzinus- C and Simpelius N at a latitude of 70° South. The landing is scheduled for September 6 this year. The total cost of the project is about ₹978 crore. The lander-rover combo has an expected lifetime of 14 days, while the orbiter will continue for a year.

How does the 'Pragyan' Rover Operate and What Determines its Lifetime?

surface of moon

The time taken for the moon to complete one rotation on its axis is approximately equal to 29.5 earth days. This is also equal to the time it takes to complete one orbit around the earth.

That is why the same side always faces the earth. But because it takes 29.5 earth days to complete one rotation, every point on its surface experiences daylight for about half the time, or a little more than 14 days at a stretch. Moon days are nearly 14 earth days long.

Note that the landing is schedule for September 6, when we will see the first quarter of moon. This is a date when the lander will land at a point that is facing the earth and which has started receiving sunlight.
 
This point will receive light for nearly another fortnight which will match the expected lifetime of the lander-rover combo. Since the 'Vikram' lander and 'Pragyan' rover are powered by solar energy, they will be energized during this period by sunlight on the moon.

Once night falls, this energy will not be available as they are plunged into a dark and cold - 180° Celsius environment. If the lander-rover duo should kickstart after another half- rotation when day breaks once again, it will be a bonus for the ISRO.

The mission is not designed to survive this extreme cold, unlike some U.S and Chinese missions which survived on the "dark" side of the moon using special sources of warmth.


How will the Mission Study the Moon?

surface of moon

Using the Terrain Mapping Camera 2 which is on board the orbiter, the mission will produce images of the moon remotely from a 100 Km lunar polar orbit. While the moon rotates about its axis, along its east-west direction, say, the lunar polar orbit will be in the perpendicular direction, along the lunar north-south direction.

Thus, as the moon rotates, the orbiter gets a view of its entire surface from overhead. This data collected by the orbiter will be used to produce a 3D image of the moon's terrain. This is just one of the 8 instruments, or payloads, on board the orbiter.

The lander carries three such payloads of which will measure the electron density and temperature near the lunar surface; the vertical temperature gradient, and seismicity around the landing site.

The rover will carry two instruments or payloads which will collect and test samples from the moon's surface to identify what elements they contain. The rover moves on six wheels and once let down on the moon, can travel about 500 m from the lander.

What is the Success Rate of "Soft-Landing" on the Moon? 

There have been 38 attempts so far at "soft-landing" on the moon, with a success rate of 52% according to the ISRO website.

Why Should We have this Mission and Why Should We Study the Moon?

The moon offers pristine environment to study. It is also closer than other celestial bodies. Understanding how it formed and evolved can help us better understand the solar system and even earth itself.

With space travel taking shape and exoplanets being discovered everyday, learning more about earth's celestial neighbour can help in advance missions. Finally, it is a piece of larger puzzle as to how the solar system and its planets have evolved.

Payloads used in this Mission

LANDER PAYLOADS

  • RAMBHA has proven to be an effective diagnostic tool to gain information in highly dynamic plasma environments.
  • ILSA is a seismometer that can detect minute ground displacement, velocity, or acceleration caused by lunar quakes.
  • ChaSTE measures the vertical temperature gradient and thermal conductivity of the lunar surface.

ROVER PAYLOADS

  • APXS' primary objective is to determine the elemental composition of the moon's surface near the landing site.
  • LIBS' prime objective is to identify and determine the abundance of the elements near the landing site.

Important Terms

LIBS: 

Laser Induced Breakdown Spectroscopy

ILSA: 

Instrument for Lunar Seismic Activity

RAMBHA: 

Radion Anatomy of Moon Bound Hypersensitive ionosphere and Atmosphere

APXS: 

Alpha Particle X-ray Spectrometer

ChaSTE: 

Chandra's Surface Thermophysical Experiment

Thanks for reading!!

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