Chandrayaan-2

Chandrayaan-2

Darani Vasudevan

Chandrayaan- 2 (India’s Second Moon Mission)

V. Darani M.Sc., M.Phil., SET

From Earth to Moon’s South poleJourney An Overview

1 Chandrayaan-2

Mythology and Moon Moon is referred to as „Chandraâ€&#x; in Hindu mythology. He is regarded as the son of Sage Atri and his wife Anasuya. Chandra was born to them by the divine grace of Lord Brahma.

Chandra

married

27

daughters

(the

27

nakshatras of Hinduism) of Dhaksha. Dhaksha asked a favour from Chandra, that Chandra should treat all his 27 daughters equally. But Chandra was more attached to Rohini. The other daughters complained this to their father.

Dhaksha got angry and he cursed Chandra to lose his divine grace and lusture. Chandra was worried as his grace began to disappear. He did a severe penance to Lord Shiva.

Lord Shiva got pleased by his worship. So he blessed Chandra to regain his divine grace and

2 Chandrayaan-2

he also gave Chandra a position on his head.

Since then Chandra adorned Lord Shiva‟s head in his crescent form. This is considered as the mythology behind waxing and waning of moon.

During the churning of the ocean of milk, a demon disguised as deva to drink the divine juice that emerged out from the ocean of milk.

Chandra and Surya (the sun god) recognised the disguised demon and pointed him to Lord Vishnu. Lord Vishnu got angry and he cut of the demon‟s head with his chakra. As the demon drank the divine juice (amritha) he didn‟t die. Lord Brahma attached a snake‟s head to the headless body and attached the snake‟s body to the detached head of the demon. He named them Raghu and Kedhu and

3 Chandrayaan-2

also offered them a position among the navagraghas (9 planet gods of Hinduism).

Since then Raghu and Kedhu chases Surya and Chandra in astrology.

Due to his disastrous liaison with Guru Brahaspatiâ€&#x;s wife Tara, Mercury (budha) was born. Mercury disliked his father. In Indian astrology, mercury and moon are rival planets.

Chandra is one of the 9 planet gods of Hinduism.

Mythology

depicts

him

as

handsome, two armed deity, with a club in one hand and lotus in the other. His chariot is pulled by 10 white horses or an antelope.

He is also called as “Soma� as an indication that he presides over Monday (Somvar). He still holds an important position in Hindu mythology and worship.

4 Chandrayaan-2

Moon – The Natural Satellite Science has a different view on Moon which is entirely different from that of mythology.

According to science, moon is a natural satellite which shines bright at night with the light energy it absorbed from sun at day.

It is the earthâ€&#x;s only natural satellite and is an airless ball of rock. It is the fifth largest satellite in the solar system. Its average distance from earth is 384400 kilometres.

The moon rotates on its axis at the same time it revolves around the earth. To make one complete revolution, it takes 27 days and 8 hours. The diameter of the moon is 3474 kilometre. Its mean density is 3.34 grams per cubic centimetre. This shows that the moon is

5 Chandrayaan-2

composed of materials that are less dense when compared to the materials on earth.

Moon is thought to have an iron rich core. It has almost no coordinated magnetic field. It has no atmosphere. The sky from moon always appears dark. Its temperature ranges from 130ËšC to 110ËšC during day and around -153ËšC at night. Due to lack of air or atmosphere, no sound waves are transmitted on moon. Hence it always remains silent. It is the only celestial body on which humans have made manned landing.

The moon makes synchronous rotation (i.e.) it rotates about its axis in about the same time it takes to orbit around the earth. Because of this, the earth visualises the same face of the moon all the time. The side of the moon which faces

6 Chandrayaan-2

the earth is called the near side and the other side is called the far side (dark side).

Maria are found on the near side of the moon.

Maria are featureless dark plains on the surface of the moon which the astronomers believe to have contained water once upon a time. After analysis scientists have found that Maria are the solidified pools of basaltic lava. Maria can be clearly seen with naked eye.

The depressions on the surface of the moon are termed craters. These are formed due to the collision of comets, meteors and asteroids with the surface of the moon. One of the largest known craters in the solar system is the south pole Aitken basin located in the South pole of moon. It lies on the far side of the moon.

7 Chandrayaan-2

Terrae are the light coloured regions and are slightly elevated than Maria. Hence terrae can be compared with that of highlands and mountain ranges found on earth.

The unconsolidated solid material covering the moon is termed as regolith and is a layer of loose, heterogeneous superficial deposits. The regolith of older surfaces is generally thicker than for young surfaces. Astronauts found that the dust felt like snow and has the smell of gun powder as silicon dioxide makes up a vast composition of the dust. Hence it is believed that dust formation occurred during the collision of asteroids and meteors with the surface of the moon.

Chandrayaan-1 launched by Indian Space Research

Organization

(ISRO)

has

sent

8 Chandrayaan-2

evidence regarding the presence of large amount of water on the surface of the moon.

The scientist also reported that water is being formed at present.

Just like earth, the moon consists of crust, mantle and core. The acceleration due to gravity on the surface of the moon is about 1.625m/s2.

Mascons,

large

positive

gravitational

anomalies are the characteristics of the moon‟s gravitational field. Most of the tidal effects on the

earth

are

caused

by

the

moon‟s

gravitational pull. Tidal drag shows the earth‟s rotation by about 0.002 seconds per day. Due to conservation of angular momentum, the slowing of earth‟s rotation is accompanied by

9 Chandrayaan-2

an increase of the mean earth moon distance of about 3.8m per century or 3.8cm per year.

Eclipses occur only when the sun, earth and moon are all in a straight line. Solar eclipses occur near new moon when the moon is between the sun and the earth. On contrast, lunar eclipses occur near a full moon, when the earth is between the sun and the moon. As the moonâ€&#x;s orbit around the earth is inclined by about 5Ëš with respect to the orbit of the earth around the sun, eclipses do not occur at every full and new moon. For an eclipse to occur, the moon must be near the intersection of the two orbital planes.

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Indian Space Research Organization (ISRO) and Moon Indian Space Research Organization (ISRO) was formed under the Department of Atomic energy on August 15, 1969. Under the control of the Government of India, ISRO is the primary body for space research and one of the leading space research organizations in the world. It is headquartered at Bangalore.

Dr. Vikram Sarabhai is considered as the father of Indian Space programme. He played a major role in the formation of ISRO. Today India has the capability to build any type of satellite launch vehicle to place remote sensing, communication and meteorology satellites in different orbits.

11 Chandrayaan-2

It was a historic moment for India as the country launched its first unmanned mission Chandrayaan – 1 to the moon. Following the success of Chandrayaan -1, ISRO planned to launch the second version of Chandrayaan named “Chandrayaan-2.”

“The Indian Space Research Organization (ISRO) hopes to land a motorised rover on the moon in 2012, as a part of its second Chandrayaan mission. The rover will be designed to move on wheels on the lunar surface, pick up samples of soil or rocks, do on-site chemical analysis and send the data to the mother-spacecraft Chandrayaan-2, which will be orbiting above. Chandrayaan-2 will transmit the data to earth.”

- G. Madhavan Nair (Ex. Chairman, ISRO)

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Chandrayaan-2 Chandrayaan-2 is the second unmanned lunar exploration mission by ISRO at a projected cost of Rs. 976 crore. The mission includes a lunar orbiter as well as a Lander and rover.

ISRO planned to land a motorised rover on the moon as a part of Chandrayaan-2 mission. The wheeled rover was expected to move on the lunar surface, to pick up soil or rock samples for onsite chemical analysis and send data to earth through Chandrayaan -2 which will be in the lunar orbit.

On 12th November 2007, ISRO signed an agreement with Russian federal space agency

(ROSCOSMOS)

for

the

13 Chandrayaan-2

Chandrayaan-2

project.

As

per

the

agreement, ISRO would have the prime responsibility for the orbiter and the rover while ROSCOSMOS would provide the Lander. But the mission was postponed in January 2013 and rescheduled to 2016 because Russia was unable to develop the Lander on time.

ROSCOSMOS failed to provide the Lander even by 2015, hence India decided to develop the lunar mission independently.

Aim: The aim of the mission is to explore the unexplored south polar region of the moon.

To improve our understanding of the moon and the scientists believe that its discoveries would benefit India and also humanity as a

14 Chandrayaan-2

whole. To stimulate the advancement of technology, promote global alliances and inspire future generations of scientists and explorers.

Objectives: South pole is unimaginably cold, massively cratered and has areas that are either constantly bathed in sunlight or in darkness.

It remained an unexplored region in the history of space science. The South poleAitken basin in South Pole is known to have water ice hidden away on permanently shadowed crater walls and in regions just below the surface. The moon has been explored by the United States, Russia and China. These countries have successfully

15 Chandrayaan-2

carried out manned and unmanned missions on moon.

India became the first country to set out an unmanned mission to explore the South Pole region of the moon. Hence Chandrayaan-2 gained attention of scientists and people all over the world.

The prime objective of the mission is to gain a better understanding of the evolution of moon

through

detailed

topographical

studies, mineralogical analysis and a set of other experiments on the surface of the moon. Another objective is to demonstrate the ability to soft land on the lunar surface and operate a robotic rover on the surface.

Chandrayaan-1 discovered the evidence for water molecules on the surface of the moon.

16 Chandrayaan-2

Chandrayaan-2 mission focussed on the exploration of the South Pole of the moon as larger surface area of the South Pole remains in shade. Moreover, South Pole region has craters that are cold traps and are expected to contain a fossil record of the early solar system. The objective of the mission was to soft land the Lander and the rover in a high plain between two craters Manzinus C and Simpelius N, at latitude of about 70˚ South and to explore the region.

Team: The Scientists behind this great initiative were,  Kailasavadivoo Sivan – Chairman, ISRO  Ritu Karidhal- Mission Director

17 Chandrayaan-2

 Muthayya Vanitha- Project Director  K. Kalpana – Associate Project Director  G. Narayanan – Associate Project Director  G. Nagesh – Project Director (Former)  Chandrakanta

Kumar-

Deputy

Project

Director (Radio frequency systems)  Amitabh

Singh-

Deputy

Project

Director(Optical payload Data Processing, SAC) The effort and hard work of about 16500 Scientists of ISRO are responsible for the accomplishment of Chandrayaan-2 mission.

Launch Vehicle: The Geosynchronous satellite launch vehicle Mark III (GSLV MK III) was chosen to carry Chandrayaan-2 to its designated orbit. It is the

18 Chandrayaan-2

India‟s most powerful launcher till date. It is capable of launching 4 ton class of satellites to the Geosynchronous Transfer orbit (GTO). The components of GSLV MK III are S200 solid rocket boosters, L110 core liquid stage and L25 cryogenic upper stage. It is a three stage heavy lift launch vehicle developed by ISRO. Height

43.43 m

Vehicle diameter

4.0m

Payload firing

5.0m

diameter Stages

3

Lift off mass

640 tonnes

GSLV MK III will also be the launch vehicle for the future manned space mission. It got two nick names, „fat boy‟ and „Bahubali.‟

19 Chandrayaan-2

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GSLV MK III launches till date: Title

Date

LVM-3/CARE Mission

18th December 2014

GSLV MK III-

05th June 2017

D1/GSAT-19 mission GSLV MK III-

14th November 2018

D2/GSAT-29 Mission GSLV- MK III- M1/

22nd July 2019

Chandrayaan-2 mission

Three stages of GSLV MK III: First stage: It consists of two strap-on tanks fitted to the either side of the rocket. The tanks contain solid fuel that is burnt, providing the initial thrust to fly the rocket out of the Earthâ€&#x;s

21 Chandrayaan-2

atmosphere.

The

strap-on

tanks

remain

functional for 140 seconds after launch.

Second stage: It consists of the core booster that ignites 114 seconds after lift-off. The core booster burns liquid fuel and is the primary source of thrust after the strap-on tanks detach from the rocket fall back to the earth at around 140 seconds after launch.

Third Stage: It is a cryogenic engine installed in the top part of the GSLV MK III. The cryogenic upper stage provides the last mile thrust after the liquid core booster separate from the rocket.

Cryogenic engine (CE)-20 which develops a nominal thrust of 186.36 kN with a specific

22 Chandrayaan-2

impulse of 442 seconds in vacuum. The engine operates

on

gas

generator

cycle

using

LOX/LH2 propellants combination. The major subsystems of the engine are thrust chamber, gas generator, LOX and LH2 turbo pumps, igniters, thrusts and mixture ratio control systems, start up system, control components and pyro valves. The fifth hardware of CE-20 integrated

engine

earmarked

for

designated GSLV

MK

as

E6

III

is M1-

Chandrayaan-2 mission.

Specifications and Payloads of orbiter, Lander and rover: Orbiter: The orbiter is a box shaped craft with an orbital mass of 2379kg and solar arrays capable of generating 1000W power. The

23 Chandrayaan-2

orbiter can communicate with the Indian deep space network and the Lander. Hence it is set to observe the lunar surface and to relay communication between earth and vikram Lander. Its scientific payloads comprises of: Chandrayaan-2 Spectrometer presence

of

magnesium,

Large

Area

(CLASS)-

to

major

Soft

examine

elements

aluminium,

X-ray

silicon,

such

the as

calcium,

titanium, iron and sodium. The XRF technique will detect these elements by measuring the

24 Chandrayaan-2

characteristic X-rays they emit when excited by the sunâ€&#x;s rays.

Terrain mapping camera 2 (TMC-2)- Its objective is mapping the lunar surface in the panchromatic spectral band (0.5-0.8 microns) with a high spatial resolution of 5m and a swath of 20km from 100km lunar polar orbit.

The data collected by TMC2 will give us clues about the moonâ€&#x;s evolution and help us prepare 3D maps of the lunar surface.

Solar X-ray monitor (XSM)- This will observe the X-rays emitted by the sun and its corona and will measure the intensity of solar radiation in three rays and will support CLASS. The primary objective of this payload is to provide solar X-ray spectrum in the energy range of 1-15Kev. XSM will provide

25 Chandrayaan-2

high energy resolution and high cadence measurements (full spectrum every second) of solar X-ray spectra as input for analysis of data from CLASS. Orbiter High Resolution camera (OHRC)- It provides high resolution images of the landing site ensuring the Lander‟s safe touch down by detecting any craters or boulders prior to separation. The images it captures, taken from two different look angles, serve dual purposes.

Firstly, they are used to generate digital elevation models (DEMs) of the landing site.

Secondly, they are used for scientific research, post Lander separation. OHRC‟s images will be captured over the course of two orbits, covering an area of 12Km×3Km with a ground resolution of 0.32 M.

26 Chandrayaan-2

Imaging IR spectrometer (IIRS)- It has 2 primary objectives: (a) Global mineralogical and volatile mapping of the moon in the spectral range of approximately 0.8-5.0µm for the first time, at the high resolution of approximately 20nm. (b) Complete characterization of water or hydroxyl feature near 3.0µm for the first time at high spatial (approximately 80m) and spectral (approximately 20nm) resolutions.

IIRS will also measure the solar radiation reflected off the moon‟s surface in 256 contiguous spectral bands from 100 Km lunar orbit.

Dual frequency synthetic Aperture Radar (DFSAR)- the dual frequency (L and S) SAR

27 Chandrayaan-2

will provide enhanced capabilities compared to Chandrayaan-1‟s S –band miniSAR in areas such as L- band for greater depth of penetration (about 5m- twice that of S-band) and Circular & full polarimetry with a range of resolution options (2-75m) and incident angles (9˚-35˚) for understanding scattering properties of permanently shadowed regions. The main scientific objectives of this payload are high resolution lunar mapping in the Polar Regions, quantitative estimation of water-ice in the Polar Regions and estimation of regolith thickness and its distribution.

Chandrayaan-2

Atmospheric

compositional

Explorer 2 (CHACE 2)- This will continue the CHACE

experiment

carried

out

by

Chandrayaan-1. It is a Quadruple Mass

28 Chandrayaan-2

Spectrometer (QMA) capable of scanning the lunar neutral exosphere in the mass range 1 to 300 amu with the mass resolution of approximately 0.5amu. CHACE 2â€&#x;s primary objective is to carry out and in situ study of the composition and distribution of the lunar neutral exposure and its variability.

Dual

Frequency

experiment-

This

Radio

Science

studies

the

(DFRS) temporal

evolution density in the lunar ionosphere. Two coherent signals at X (8496 MHZ) and S (2240 MHZ) band are transmitted simultaneously from satellite and received at ground based deep station network receivers.

The payloads will collect scientific information on lunar topography, mineralogy, elemental

29 Chandrayaan-2

abundance, lunar exosphere and sign of hydroxyl and water ice.

Vikram Lander: The Lander is named „Vikramâ€&#x; to honour Dr. Vikram Sarabhai who is regarded as the fouder of Indian Space Programme. The Lander has a mass of 1471 kg (including the rover) and can generate 650W of solar power. The Lander can

30 Chandrayaan-2

communicate directly to the Indian deep space network, the orbiter and the rover. The Lander is designated to execute Indiaâ€&#x;s first soft landing on the lunar surface. Its payloads are: Radio

Anatomy

of

Moon

Bound

Hypersensitive ionosphere and Atmosphere (RAMBHA)- The lunar ionosphere is a highly dynamic

plasma

environment.

Langmuir

probes, such as RAMBHA, have proven to be an effective diagnostic tool to gain information in such conditions. Its primary objective is to measure factors such as, ambient electron density or temperature near the lunar surface and temporal evolution of lunar plasma density for the first time near the surface under varying solar conditions.

31 Chandrayaan-2

Chandraâ€&#x;s

surface

Thermo-

physical

experiment (ChasTE)- It measures the vertical temperature gradient and thermal conductivity of the lunar surface. It consists of a thermal probe (sensors and a heater) that is inserted into the lunar regolith down to a depth of approximately 10 cm. ChasTE operate in two modes, (a) passive mode operation in which continuous

in-situ

measurements

of

temperature at different depths are carried out (b)

Active

mode

operation

in

which

temperature variations in a set period of time, and the regolithâ€&#x;s thermal conductivity under contact, are estimated.

Instrument for Lunar Seismic Activity (ILSA)It is a triple axis, MEMS based seismometer that can detect minute ground displacement,

32 Chandrayaan-2

velocity or acceleration caused by lunar quakes. Its primary objective is to characterise the seismicity around the landing site. ILSA has been designed to identify acceleration as low as 100ng with a dynamic range of ±0.5g and a bandwidth of 40 Hz. The dynamic range is met by using two sensors- a coarse range sensor and a fine range sensor.

Pragyan- Rover: The Pragyan rover is a 6 wheeled vehicle with a mass of 27 Kg that runs on 50W of solar power and can travel upto 500M at a speed of 1cm per second. The rover can communicate directly with the lander. „Pragyan‟ is a Sanskrit word which means „wisdom.‟ Its payload includes:

33 Chandrayaan-2

Alpha particle X-ray spectrometer (APXS)- Its primary objective is to determine the elemental composition of the moonâ€&#x;s surface near the landing site. It achieves this through X-ray fluorescence spectroscopy technique, where Xray or alpha particles are used to excite the surface. APXS uses radioactive curium (244) metal that emits high energy, alpha particlesas well as X-rays enabling both X-ray emission spectroscopy

and

X-ray

spectroscopy.

Through

these

fluorescence techniques,

APXS can detect all major rock-forming elements

such

as

sodium,

magnesium,

aluminium, silica, calcium, titanium, iron and some trace elements such as strontium, yttrium and zinconium.

34 Chandrayaan-2

Laser

induced

breakdown

spectroscope

(LIBS)- Its prime objective is to identify and determine the abundance of elements neat the landing site. It does this by firing high powered laser pulses at various locations and analysing the radiation emitted by the decaying plasma.

Lander and rover are targeted for a location about 600Km from the South Pole. The lander was expected to last about one lunar day which is equal to 14 earth days.

There are 13 payloads in total, of which 8 are in orbiter, 3 in vikram and 2 in pragyan. Five payloads are made in India, three from Europe, two from US and one from Bulgaria.

Laser Retroreflector Array (LRA) is a payload from NASA- Its purpose is to understand the dynamics of earthâ€&#x;s moon system and also

35 Chandrayaan-2

derive clues on the lunar interior. It can carry out insitu elemental analysis and abundance in the vicinity of the landing site.

Space flight: ISRO announced the launch of Chandrayaan-2 on 15th July 2019 at 2:51 hrs (IST). When it was 56.24 minutes for the launch, leakage of Helium gas from the cryogenic machine was reported. Inorder to

heal this technical

problem, ISRO postponed the launch to 22nd July 2019 at 14:43hrs (IST).

The 20 hours countdown for launch began on 21st July 2019 at 18:43hrs (IST). ISRO announced that Chandrayaan-2 would circle the orbit of the moon after 48 days from launch.

36 Chandrayaan-2

GSLV MK III- M1 successfully injected Chandrayaan-2 into earth‟s orbit on 22nd July 2019 from the second launch pad at Satish Dhawan Space centre, Sriharikota. 16 minutes after the lift-off, the GSLV MK III injected Chandrayaan-2 into 170×40400km earth orbit.

37 Chandrayaan-2

For the first 17 days, the spacecraft was in earth bound phase before its orbit was finally raised to over 1.05lakh km. Following which a lunar

transfer

trajectory

that

took

Chandrayaan-2 to the proximity of moon.

After injecting the space craft a series of manoeuvres

were

carried

out

using

Chandrayaan-2â€&#x;s on board propulsion system to raise its orbit and place it in the Lunar Transfer trajectory. After entering the moonâ€&#x;s sphere of influence, on board thrusters slowed down the spacecraft for lunar capture.

Earth Bound Manoeuvre: First Earth bound Manoeuvre: First earth bound orbit raising manoeuvre for Chandrayaan-2

spacecraft

was

performed

38 Chandrayaan-2

successfully on 24th July 2019 at 14:52 hrs (IST) as planned using the on board propulsion system for a firing duration of 48 seconds. The new orbit was 230Ă—45163km.

Second earth bound manoeuvre: Second earth bound orbit raising manoeuvre for Chandrayaan-2 spacecraft was performed successfully on 26th July 2019 at 01:08 hrs (IST) as planned using the on board propulsion system for a firing duration of 883 seconds.

The orbit achieved was 251Ă—54829km.

Third earth bound manoeuvre: Third earth bound orbit raising manoeuvre for Chandrayaan-2

spacecraft

was

performed

successfully on 29th July 2019 at 15:12 hrs (IST) as planned using the on board propulsion

39 Chandrayaan-2

system for a firing duration of 989 seconds.

The orbit achieved was 276×71792km.

Fourth earth bound manoeuvre: Fourth earth bound orbit raising manoeuvre for Chandrayaan-2

spacecraft

was

performed

successfully on 2nd August 2019 at 15:27 hrs (IST) as planned using the on board propulsion system for a firing duration of 646 seconds.

The orbit achieved was 277×89472km.

Fifth earth bound manoeuvre: Fifth earth bound orbit raising manoeuvre for Chandrayaan-2

spacecraft

was

performed

successfully on 6th August 2019 at 15:04 hrs (IST) as planned using the on board propulsion system for a firing duration of 1041 seconds.

The orbit achieved was 276×142975km.

40 Chandrayaan-2

The spacecraft performed five orbit raising shifts to higher orbits bringing closer to the moon with each subsequent one. The five manoeuvres needed earth‟s burns of the spacecraft‟s onboard engines, with each thrust moving it close to moon‟s gravity. The spacecraft used earth‟s gravity to amp-up its own velocity using a technique popularly referred to as „gravity assists‟ to conserve fuel.

The final orbit raising took Chandrayaan 2 to a distance of 143585km from the earth. This is when the next critical manoeuvre of the mission was performed- “translunar injection,” where the spacecraft‟s trajectory was adjusted so it reaches the moon.

Spacecraft left earth‟s orbit and began its 384000km

journey

to

the

moon.

The

41 Chandrayaan-2

Chandrayaan-2 composite then had to slow itself down just enough by using its thrusters to fall into moon‟s gravity. The intersection of Chandrayaan-2 path with the moon‟s was predicted and planned well ahead of time.

When the moon approached the apogee of Chandrayaan-2, the on-board thrusters fired up precisely and slowed itself down for the lunar capture.

This controlled transfer required the liquid apogee motors to be fired in the opposite direction to the spacecraft‟s movement, hence slowing it down in a manoeuvre called retrofiring. The spacecraft‟s liquid apogee motor (thrusters engines) are retrofitted to make this lunar orbit insertion possible. This

42 Chandrayaan-2

allowed the spacecraft to come under the influence of the moon‟s orbit.

Lunar orbit insertion: Lunar orbit insertion (LOI) manoeuvre was completed successfully on 20th August 2019.

The duration of manoeuvre was 1738 seconds beginning from 09:02hrs (IST). With this Chandrayaan-2 was successfully inserted into a lunar

orbit.

The

orbit

achieved

was

114×18072km.

Following this, a series of orbit manoeuvres were performed on Chandrayaan2 spacecraft to enable it to enter its final orbit passing over the lunar poles at a distance of about 100km from the moon‟s surface.

43 Chandrayaan-2

Subsequently, the lander got separated from the orbiter and entered into a 100kmĂ—30km orbit around the moon.

Then it was expected to perform a series of complex, braking manoeuvres to soft land in the south polar region of the moon on 7th September 2019.

Second Lunar orbit manoeuvre: Second lunar bound orbit manoeuvre for Chandrayaan-2

spacecraft

was

performed

successfully on 21st August 2019 at 12:50hrs (IST), using the onboard propulsion system.

The duration of the manoeuvre was 1228 seconds.

The

118kmĂ—4412km.

orbit

achieved

was

44 Chandrayaan-2

Third lunar bound manoeuvre: Third lunar bound orbit manoeuvre for Chandrayaan-2

spacecraft

was

performed

successfully on 28th August 2019 at 09:04hrs (IST) using the onboard propulsion system.

The duration of the manoeuvre was 1190 seconds.

The

orbit

achieved

was

179kmĂ—1412km.

Fourth Lunar orbit manoeuvre: Fourth

Lunar

Chandrayaan-2

orbit spacecraft

manoeuvre was

for

performed

successfully on 30th August 2019 at 18:18 hrs (IST) as planned using the onboard propulsion system. The duration of the manoeuvre was 1155seconds.

124kmĂ—164km.

The

orbit

achieved

was

45 Chandrayaan-2

Fifth Lunar orbit manoeuvre: The

final and fifth lunar bound orbit

manoeuvre for Chandrayaan-2 spacecraft was performed successfully on 1st September 2019 at 18:21hrs (IST) as planned, using the onboard propulsion system. The duration of the manoeuvre was 52 seconds. The orbit achieved was 119kmĂ—127km.

The next operation was the separation of vikram lander from Chandrayaan-2 orbiter after which there would be two de orbit manoeuvre of vikram lander for its landing in South Polar region of the moon.

VIkram lander separated from orbiter: The vikram lander was separated successfully from Chandrayaan-2 orbiter on 2nd September

46 Chandrayaan-2

2019 at 13:15hrs (IST) and was located in an orbit of 119kmĂ—127km. The Chandrayaan-2 orbiter continued to orbit the moon in its existing orbit.

The health of the orbiter and lander was monitored

from

the

mission

operations

complex (MOX) at ISRO telemetry, tracking and

command

network

(ISTRAC)

in

Bengaluru with support from Indian Deep Space network (IDSN) antennas at Bylalu, near Bengaluru. The report was that all the systems of Chandrayaan-2 orbiter and lander were healthy.

First de orbiting Manoeuvre: The

first

de-orbiting

Chandrayaan-2

spacecraft

manoeuvre was

for

performed

successfully on 3rd September 2019 at 08:50hrs

47 Chandrayaan-2

(IST) as planned using the on board propulsion system. The duration of manoeuvre was 4 seconds. The orbit of vikram lander after this was 104km×128km.

Second de-orbiting manoeuvre: The second de orbiting manoeuvre for Chandrayaan-2

spacecraft

was

performed

successfully on 4th September 2019 at 03:42hrs (IST) as planned using the propulsion system.

The duration of the manoeuvre was 9 seconds.

The orbit of vikram lander was 35km×101km, while the orbiter continues to orbit the moon in an orbit of 96km×125km.

With this manoeuvre the required orbit for the vikram lander to commence it descent towards the surface of the moon was achieved.

48 Chandrayaan-2

The lander used its propulsion system to lower its orbit by deboosting. Deboosting was necessary to slow the velocity of the spacecraft enough to drop or deliver it into the moonâ€&#x;s gravitational field with which it achieved a nominal orbit around the moon. The lander continued moving in this new orbit for three days, during which it carried out checks on its systems and landing systems.

On 7th September 2019, Vikram began its descent from a height of 35km above the lunar surface with a velocity of around 6000kmph.

In just over 10 minutes, the lander dropped to a height of 7.4km above the surface of the moon and its speed got reduced to 526kmph. Over the next 38 seconds, the lander reduced its

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speed further to331.2kmph and reached a height of 5km above the lunar surface.

It was expected that, in next 1.5 minutes, the Lander would further reduce its altitude to 400metres and velocity to 100kmph. Once it was 400m above the lunar surface, it would suspend its descent briefly and hover for about 12 seconds to collect data on the lunar surface.

Over the next 66 seconds, the Lander was expected to reduce its altitude further to 100m above the lunar surface. At this altitude, the rover would again hover for about 25 seconds during which it would choose between the two predetermined landing sites. After choosing the site, it would first descend to a height of 60m and then a further drop to 10m in the next 25 seconds. From a height of 10m, the Lander

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would take 13 seconds to touch the surface of the moon at which point its velocity would be zero. At around 05:30hrs to 06:30hrs, Pragyan rover would be taken out of the lander which would move for 500m with a velocity of 1cm per minute and do researches on the lunar surface.

But unfortunately, Vikram lost communication with the ground station when it was 2.1km above the lunar surface, just ahead of soft landing.

On 8th September 2019, Chandrayaan-2 orbiter circling the moon spotted the Vikram Lander on the lunar surface and sent a thermal image of it to the ground station. This was an achievement because India became the first

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country to spot something which was lost in space.

The Scientists with all their efforts tried to reestablish communication with the Lander but their efforts were in vain. The Vikram remained unresponsive.

Though the mission was not fully completed it was almost a success because all payloads of orbiter are successfully powered and the orbiter continues to perform scheduled science experiments. The mission life of orbiter is one year during which it can take several pictures of the moon and send it to ISRO for research.

When Chandrayaan 2 was 2650km from the moonâ€&#x;s surface it took the first picture and sent it to ISRO. ISRO released it on 22nd August 2019. On 26th August 2019, ISRO released the

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second picture captured by Chandrayaan-2 when it was 4375km from the moon. The craters are clearly visible.

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54 Chandrayaan-2

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Indeed, India plans to develop a Chandrayaan3 moon mission in the coming years, and the nation also intends to send humans to moon. “We

have

not

established

any

communication with the lander yet. The project was developed in two parts- science and technology demonstration. We achieved total success in science objective while in technology

demonstration

the

success

percentage was almost full. That is why the project can be termed as 98 percent successful.�

- Kailasavadivoo Sivan (Chairman, ISRO)

References: https://www.isro.gov.in https://nssdc.gsfc.nasa.gov

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