In a landmark moment for lunar exploration worldwide, Chinese space probe Chang’e-4 touched down on the far side of the moon, state media announced Thursday. Hailed as a massive technical feat, this is the first contact made with the perpetually dark half of the moon. The mission is believed to yield a better understanding of the moon, and help China in its ambitions to posit itself as a leading space power.
Journey to the moon
China’s National Space Administration landed the rover at 10:26 am (Beijing time) in the South Pole-Aitken Basin, the largest and oldest impact crater on the lunar crust. The robotic probe also sent back the first ever photograph of this previously unexplored side of the moon later in the day. The landing and the historic close-ups of the far side of the moon were broadcast on China Central Television (CCTV), following a highly secretive mission which even refused to divulge the timing of touch down in advance.
The Chang’e-4 rover is 1.5 metres (5 feet) long and about 1 metre (3.3 feet) wide and tall, with two foldable solar panels and six wheels.
The probe had first entered a lunar orbit on December 12, and reportedly moved into position for landing along a planned elliptical orbit late Sunday, according to the Xinhua news agency. China launched the probe early December, carried by a Long March-3B rocket, which had also launched the first Hongyun satellite as part of a mega-communications project spearheaded by China Aerospace Science and Industry Corp.
This project had launched the country’s first communication satellite for space-based broadband services last month.
The last leg
The Chang’e-4 probe started preparing for a soft landing last week, with the descent reportedly aided by a relay satellite called the Queqiao, or Magpie Bridge. The mission overcame a significant challenge in terms of direct communication with the spacecraft, which was cut off in the final phases of the approach.
Queqiao is situated in a “halo orbit” on the other side of the moon is free of radio frequencies, which is why signals to and from the rover stopped after Chang’e-4 was within 15km of the lunar surface. Since then, the craft was on its own and could not be operated remotely from ground control. It reportedly used a rocket booster to decelerate.
The probe briefly hovered about 100m from the surface to identify obstacles and gauge the gradient, with the help of a high-tech camera and laser tech. It managed to avoid boulders and ditches, finally selecting a relatively flat area in the Von Karman Crater and began a slow, vertical descent ending with a soft touchdown, according to a report by the Xinhua News Agency.
The crater was predicted to have a smooth volcanic floor and sits within the great Aitken basin.
According to general designer Sun Zezhou, the probe had pulled off a “smooth” and “precise” landing, calling it a “bull’s-eye.” Several hours after touchdown, the rover separated from the lander on the moon’s surface and began its mission. “China is on the road to become a strong space nation. And this marks one of the milestone events of building a strong space nation,” chief designer for the lunar mission, Wu Weiren, told CCTV.
What will the rover study?
The lander and the rover will explore the uncharted surface of the moon, reported the state-run media. Tidally locked to the earth, the moon rotates at the same rate as the blue planet while orbiting, which means that the “dark side of the moon” is never visible to earthly spectators.
The Chang’e-4 has been tasked with astronomical observation, surveillance of the moon’s topography, studying its mineral composition, and measuring the neutron radiation and neutral atoms. All this will contribute to a better understanding of the lunar environment, especially on the far side of the moon.
This half piques scientific curiosity especially because its geology is rougher, more cratered and replete with the earlier impacts than the nearside, where a succession of lava flows has altered the original composition.
Instruments aboard the Chang’e-4 lander and rover will also analyse the crust’s interaction with solar winds and how vegetative germination is possible in the weak lunar gravity.
In doing so, China aims to catch up with Russia and the US to become a major space power by 2030. The Asian nation already leads many western superpowers in economy and manufacturing sectors, and has been planning rapid expansion in science, technology and defence. Beijing is also planning to inaugurate its own manned space station by 2022 and conduct a maiden mission to Mars next year.
The latest historic feat has invited words of caution from rival US which has accused of threatening peace and security in the region with this landing and using it to inhibit space-based assets of neighbouring countries.
NASA administrator Jim Bridenstine called it an impressive announcement. Several space experts around the acknowledged the larger impact of this landing on the future of lunar expeditions and our understanding of earth’s only satellite, even though this is not the first attempt to shed light on its dark side. All previous expeditions have only seen it without ever landing on it, with the help of orbital images and satellites.
“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,” Professor Andrew Coates, a space scientist at UCL’s Mullard Space Science Laboratory, told the Guardian.
Prarthana Mitra is a staff writer at Qrius.