Chang’e-6 Breakthrough: China’s 2nd Successful Far Side Lunar Expedition

The Chang’e 6 robotic mission successfully landed inside Apollo Crater, which is part of the large South Pole-Aitken basin. According to Chinese space officials, the landing was achieved at 6.23 am (Beijing Time) on Sunday (June 2) equivalent to 3.53 am Indian Time. China’s space agency confirmed that the probe landed in the area they had chosen.

The China National Space Administration (CNSA) now has two successful landings on the far side of the Moon. The first was the Chang’e 4 mission, which placed a lander-rover combo on the lunar surface in January 2019. No other country has managed to accomplish even one far-side landing so far.

The goal of the Chang’e 6 mission is to collect samples from the Moon and bring them back to Earth. This will provide researchers with their first detailed look at material from this specific area of the Moon.

This is the sixth mission in China’s Chang’e Moon exploration programme, named after a Chinese Moon Goddess. The mission will use a mechanical arm and a drill to collect up to 2 kilograms (4.4 pounds) of material from the Moon’s surface and underground over a period of about two days (or 48 hours).

The samples will be placed in a metal vacuum container by an ascender on top of the lander. This ascender will then take the container to another module orbiting the Moon. From there, the metal vacuum container will be transported to a re-entry capsule, which is likely to be back on Earth around June 25, with a desert landing in China’s Inner Mongolia region.

These missions are more difficult to achieve because the far side of the Moon faces away from Earth, making communication tricky and requiring a relay satellite. The terrain is also more rugged, with deep craters, which means there are fewer flat areas for landing.

Chang’e 6 Moon Landing

The Chang’e-6 spacecraft lifted off on a Long March 5 rocket from the Wenchang Satellite Launch Centre on Hainan Island at 5.27 pm (Beijing time) on Friday (May 3), as announced shortly after by the CNSA.

Thirty-seven minutes after launch, the rocket’s second stage separated, placing Chang’e 6 into an Earth-Moon transfer orbit. Four days later, the 8.35-ton spacecraft, consisting of a lander, ascender, orbiter and return capsule, entered lunar orbit and began searching for an ideal landing spot.

On May 30, the lander and ascender separated from the orbiter and return capsule, according to South China Morning Post. At 6.09 am on June 2, the lander fired its 7.5K newton-thrust engine to cut down speed and started its descent from roughly 15 kilometres (9 miles) above the lunar surface.

During the descent, the lander’s cameras took pictures of the landing area and sent them to onboard computers to identify such hazards as large rocks, allowing the craft to navigate around them. Around 100 metres (328 feet) above the lunar surface, the lander hovered briefly to detect smaller obstacles and choose the final landing spot before descending slowly and steadily.

Just a few metres above the surface, the lander shut off its engine and gently touched down on the Moon, making China the only country to achieve a second soft landing on its far side.

Queqiao 2 Supports Moon Mission

The landing process was aided by Queqiao 2, a communications satellite orbiting the Moon that relays signals between the spacecraft and mission control. Queqiao 2 was launched in March this year and is now in lunar orbit.

After two-day surface operations by the lander are completed, the relay station will become crucial in helping the ascender launch from the lander’s top, dock with the orbiter and transport the cargo to the return capsule.

The Enigmatic Far Side of the Moon

The far side of the Moon, often referred to as the ‘dark side of the Moon’, is a bit misleading. While it seems dark from Earth, this side experiences both lunar day and night, getting plenty of sunlight. A lunar day lasts a little over 29 days and a lunar night lasts about two weeks.

This far side always faces away from Earth, making it largely unexplored. Its unique landscape and isolation from Earth’s electromagnetic field make it an excellent location for scientific studies in astronomy and geology. However, since it is invisible from Earth, communicating with this side of the Moon is challenging. To overcome this, missions use relay satellites to send data back to Earth.

Explaining ‘Dark Side of the Moon’

Only one side of the Moon is visible to Earth because of ‘tidal locking’. This happens because the gravitational forces between the Moon and Earth have synchronized the Moon’s rotation with its orbit around Earth. As a result, the same side of the Moon always faces us and the far side experiences day and night just like the near side.

Disclaimer: The views expressed in the article are solely those of the author.

(The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany)