In-Depth | Chandrayaan 2: India's second moon mission, carrying ‘a billion dreams’

India’s second Moon mission – Chandrayaan 2 – is set to soft land on the lunar surface in the wee hours of September 7.

Prime Minister Narendra Modi will be the Indian Space Research Organisation (ISRO)’s centre in Bengaluru, Karnataka to watch Chandrayaan 2’s soft landing on the Moon, along with 70 students from across the country.

At 2.43 pm local time on July 22, “taking a billion dreams to the Moon” Chandrayaan 2 lifted off on board ISRO’s Geosynchronous Satellite Launch Vehicle (GSLV) Mark III rocket from the Satish Dhawan Space Centre in Sriharikota, Andhra Pradesh.

Addressing the media shortly after the launch, ISRO Chairman K Sivan said his agency had "bounced back with flying colours" after the aborted first attempt.

On July 15, Chandrayaan 2’s launch was aborted due to a technical snag less than an hour before launch. Reports, unconfirmed by ISRO, later cited that a leak in the nipple joint of a helium gas bottle had been detected.

Sivan added that the launch was “the beginning of a historical journey of India towards the moon”.

People celebrate as they watch the live broadcast of Chandrayaan 2’s launch, inside an electronics showroom in Kolkata, India. (Image: Reuters)

Here’s all you need to know about the historic lunar mission that has captured the imagination of the country:

‘Taking billion dreams to Moon’

The programme was approved by then Prime Minister Manmohan Singh in September, 2008. For over 10 years, the mission was being meticulously planned by ISRO’s scientists.

Upon reaching Moon, Chandrayaan 2 will carry out scientific experiments on the lunar surface for 14 Earth days (1 lunar day). The orbital experiment will continue for about one year.

A general view of the control centre at ISRO Telemetry, Tracking and Command Network, Bengaluru, India. (Image: Twitter/@isro)

India has pumped in around Rs 978 crore (approximately $136 million) into the mission. The orbiter's structure was manufactured by the state-owned Hindustan Aeronautics Limited (HAL).

Objectives

The basic objectives of this mission are to demonstrate the ability to soft landing on the lunar surface and operate a robotic rover there.

On the scientific side, the aim is to study Moon’s topography, mineralogy, exosphere and hydroxyl signatures and water ice.

Remember, it was Chandrayaan 1 (2008) that had first discovered widespread presence of water molecules in the lunar soil.

The orbiter will create 3D maps of the lunar surface and study the water ice in the polar region.

ISRO scientists working on various modules of Chandrayaan 2 at the Satellite Integration and Test Establishment (ISITE) in Bengaluru, India. (Image: Reuters)

Buzz about the landing site

It has been extensively reported that Chandrayaan 2 attempt landing the southern polar region. Why was this region chosen?

The space agency has said that Moon’s South Pole is interesting because the surface area under shadow there is much larger than that at the North Pole. “There is a possibility of the presence of water in permanently shadowed areas around it. In addition, South Pole region has craters that are cold traps and contain a fossil record of the early Solar System,” the agency has said.

Also read | Chandrayaan 2's soft landing: Here's how you can watch the historic event

Components and phases

The mission involves four phases -- launch, orbiting, landing and roving.

Lander

The lander has been named 'Vikram' after Vikram Sarabhai -- widely regarded as the father of the Indian space programme.

On Vikram Sarabhai’s 100th birth anniversary on August 12, PM Modi said that it will be a tribute to Sarabhai from crore of Indians in true sense when ‘Vikram’ lander touches down on Moon.

The lander is programmed to slowly descend to a lower lunar orbit after being deployed from the orbiter. At that point, it will perform check of all on board systems before attempting a soft landing.

The landing process will be driven by Vikram’s propulsion system that of eight thrusters for attitude control and five liquid main engines. It will be able to land on surface with slope of up to 12 degrees.

Rover

Upon landing, Vikram will deploy a rover named 'Pragyan'. It will be operated on solar power. The artificial intelligence (AI)-powered rover has six wheels and can traversing 500 meters at the rate of one centimetre per second.

It has the capability of conducting on-site chemical analysis and sending the data back to the lander. The lander will in turn send it to ISRO. The rover carries two payloads to enhance the understanding of the lunar surface.

The rover will be controlled by an on-ground team. For assistance, the rover has been fitted with stereoscopic camera-based 3D vision.

Mission life of Chandrayaan 2’s various components (Image: Network18 Creative)

Long journey to the Moon

Chandrayaan 2 launched on board the tried-and-tested GSLV Mk III. It had a staggering lift-off mass of 3,877 kilograms.

Also read: All you need to know about GSLV-MkIII

The first phase was about placing Chandrayaan 2 in Earth’s parking orbit. It started sending images back to ISRO moments after it was parked in Earth’s orbit

This was followed by a series of manoeuvres which are called orbit-raising operations between July 23 and August 6.

These manoeuvres progressively increased Chandrayaan 2’s orbit five times.

Throughout this process, the spacecraft clicked pictures of the Earth using its LI4 camera and beamed them back to ISRO.

One of the first images of Earth captured by Chandrayaan 2 using its LI4 camera on August 3. (Image: Twitter/@isro)

After 23 days of circling Earth, Chandrayaan 2 was slung into a Trans Lunar Injection (TIL). This meant that it was headed towards the Moon. The final injection process was carried out using its own power by firing the liquid engine for about 1,203 seconds.

On August 20, Chandrayaan 2 entered the lunar orbit. A day later, the spacecraft sent its first image of the lunar surface back to ISRO. The picture was captured at an altitude of about 2,650 kilometres from the lunar surface.

Over the next two weeks, Chandrayaan 2 staged multiple de-orbiting manoeuvres. This helped it get closer to the Moon’s surface.

Another significant milestone was reached on September 2 when the lander separated from the orbiter along with the rover inside.

First image of the Moon captured by Chandrayaan 2 at a height of about 2,650 km from the Lunar surface on August 21. Mare Orientale basin and Apollo craters have been identified in the picture by ISRO. (Image: Twitter/@isro)

Throughout these processes, ISRO’s Mission Operations Complex (MOX) in Bengaluru was continuously monitored the spacecraft’s health with the support of Indian Deep Space Network (IDSN) antennas.

Ahead of the landing, the Orbiter High Resolution Camera (OHRC) will perform high-resolution observations of the landing site before the lander is deployed.

On September 7, the lander is expected to touch down at around 1.55 am. This is what ISRO Chairman K Sivan has described as "15 terrifying minutes".

Subsequently, the rover will roll out of the lander between 5.30 to 6.30 am.

India’s mark on the Moon

Historically, a total of 38 soft landing attempts have been made by various space agencies. This is ISRO’s first attempt. The success rate is 52 percent.

A successful mission will make India the fourth country after Russia, the US and China to pull off a soft landing on the Moon. Moreover, it would have carried “a billion dreams to the Moon”.

Key facts about soft landing (Image: Network18 Creative)