From The Editors Science

China’s Lunar Probe Chang’e-4 Pulls Off Picture-Perfect Landing on Far Side of the Moon

In a never-before-attempted mission, China’s lunar lander, Chang’e-4, made a flawless touchdown on the far side of the Moon, state-run news channel China Central Television (CCTV) announced Thursday (Jan 3).

The China National Space Administration (CNSA) soft-landed the robotic probe in the targeted  Von Karman Crater – a huge southern hemisphere impact crater, measuring about 112 miles (180 kilometers) in diameter, located within an even bigger impact crater – the 1,600-mile (2,500-kilometer) South Pole-Aitken Basin.

Although Chang’e-4 had made it to the Moon’s orbit four days after launch, it began its final descent about three weeks later from an elliptical landing orbit almost 10 miles above the lunar surface.

When it was 100 meters above the landing site, the spacecraft briefly paused in its vertical approach, hovering over the landing zone to survey the topography below and selecting a relatively flat spot before resuming its descent.

The impeccable touchdown was appreciated by NASA Administrator Jim Bridenstine, who congratulated the mission team on “a successful landing on the far side of the Moon,” calling it “a first for humanity and an impressive accomplishment.”

The final approach phases were achieved autonomously by the spacecraft, as remote intervention from mission control in China was not possible during this stage of the mission.

“This is a great technological accomplishment as it was out of sight of Earth, so signals are relayed back by their orbiter, and most of the landing was actually done autonomously in difficult terrain,” Prof. Andrew Coates of UCL Mullard Space Science Laboratory (MSSL) in Surrey, England, was quoted by The Guardian as saying.

“The landing was almost vertical because of the surrounding hills,” Prof. Coates added.

Soon after landing, Chang’e-4 deployed its lunar rover named “Yutu-2” – Chinese for “Jade Rabbit-2” – which sent back the first ever close-up shot of the mysterious far side of our only known natural satellite.

The Chinese space agency also shared an image of Yutu-2’s deployment, along with pre- and post-landing images, all of which were relayed through the Queqiao (Magpie Bridge) satellite orbiting at the Earth-moon Lagrange point 2 beyond the far side.

Queqiao was, in fact, launched in May last year for the exact same purpose because direct communication with the far side of the Moon is impossible, what with the Moon’s entire mass blocking the exchange of direct signals to and from Earth.

The first image of the far side of the Moon (Image: China National Space Administration/Xinhua News Agency)
The first image of the far side of the Moon (Image: China National Space Administration/Xinhua News Agency)
Image of the far side surface taken during descent
Image of the far side surface taken during descent

While humans have glimpsed, and even mapped, the lunar far side in the past – thanks to NASA’s Apollo 8 mission half a century ago and the Soviet Luna 3 mission a decade prior to that – no spacecraft had ever touched down on the untrodden ground, until Chang’e-4 changed all of that.

In the past decade. or so, China has made rapid advances in space technology and is the only country in the world to have soft-landed a space vehicle on the Moon since the then Soviet Union’s 1976 Luna 24 mission to retrieve samples Moon soil.

China achieved the feat in December 2013, landing its Chang’e-3 rover on Mare Imbrium –  a vast lava plain within the Imbrium Basin on the near side of the Moon, becoming only the third country after Russia and the United States to achieve a lunar touchdown.

Encouraged by Chang’e-3’s success, China stepped up its lunar program for an even bigger mission, the first phase of which came to a successful conclusion with Chang’e-4’s Thursday landing on the targeted far side.

Comprising of a lander and a small rover, Chang’e-4 was, in fact, a backup spacecraft manufactured with the Chang’e-3.

It was only in 2015 that China announced its plans of using the spare space vehicle to launch something so complex that it had never been attempted before.

The nearly four-metric-ton Chang’e-4 has carried with it eight scientific instruments – four each on the lander and the rover.

The lander is equipped with the Landing Camera (LCAM), the Terrain Camera (TCAM), the Low-Frequency Spectrometer (LFS), and the Lunar Lander Neutrons and Dosimetry (LND).

And, the rover is carrying the Panoramic Camera (PCAM), the Lunar Penetrating Radar (LPR), the Visible and Near-Infrared Imaging Spectrometer (VNIS), and the Advanced Small Analyzer for Neutrals (ASAN).

Chang’e-4 has also carried a small experimental payload of silkworm eggs and seeds to check how they develop in the inhospitable lunar environment.

The huge amounts of science data and information these state-of-the-art space contraptions are capable of garnering will go a long way in helping researchers understand why the far side of our Moon is so vastly different from the side we’re familiar with.

For example, the lunar terrain on the tidally-locked near side is largely dark basaltic plains called the lunar maria, while the far side is mountainous and rugged and, hence, difficult to land anything on.

Since the Moon takes the same amount of time (28 days) to orbit our planet as it does to rotate once on its axis, we always get to see the same side of the natural satellite, with the opposite side forever hidden from view.

“Since the far side of the moon is shielded from electromagnetic interference from the Earth, it’s an ideal place to research the space environment and solar bursts, and the probe can ‘listen’ to the deeper reaches of the cosmos,” CNSA’s deputy director for the Lunar Exploration and Space Program Center, Tongjie Liu, was quoted by CNN as saying.

China’s next lunar run will be the Chang’e-5 sample-retrieval mission, which CNSA started preparing for in October 2014 when it launched the Chang’e-5T1 mission to run atmospheric re-entry tests on the -4Chang’e-5 capsule.

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