China preps for launch of historic lunar mission
If successful, Chang’e-4 will be a world’s first mission to the far side of the MoonEuropost
Early Saturday morning in China, a rocket will launch, carrying a lander and a rover bound for the Moon. This will mark the beginning of China’s ambitious lunar mission known as Chang’e-4, which will attempt to land spacecraft on the Moon’s far side - the region that always faces away from Earth - for the first time ever. Since no other nation has ever attempted such a feat, this means the mission, named after Chinese's goddess of the Moon, could catapult China into spaceflight history.
It’s considered a significant step because the lunar far side always faces away from Earth, so it's is free from interference from our planet's ionosphere, human-made radio frequencies and auroral radiation noise. Solar radio emission is also blocked during the lunar night.
"Hence, the lunar far side has been believed as the best place for the low-frequency radio astronomical observation," the researchers wrote in the recent paper.
Landing on the far side of the Moon is, however is definitely not an easy task. This near side of the Moon is the only region that we’ve landed on gently, because there’s a direct line of sight with Earth, enabling easier communication with ground control. To land on the far side of the Moon, however, one must have multiple spacecraft working in tandem. In addition to the lander itself, some kind of probe near the Moon that can relay communications from your lander to Earth is also required.
And that’s exactly what China has. In May, the China National Space Administration launched a satellite called Queqiao, specifically for the purpose of aiding with communications for the upcoming Chang’e-4 mission. After about a month in space, Queqiao settled into a spot facing the far side of the Moon, more than 37,000 miles away from the lunar surface. The satellite is now doing circles around a point in space known as the second Earth-Moon Lagrange point. It’s a place akin to a parking spot for spacecraft. At a Lagrange point, the gravitational forces of two bodies (stars, planets, etc) equal out in such a way that a spacecraft stays put in relation to the two entities. At this particular Lagrange point, Queqiao will stay facing the far side of the Moon, allowing communication between the spacecraft and Earth using a large curved antenna.
If it all works, China will be getting an up-close view of one of the most tantalizing areas of the lunar surface: the South Pole-Aitken basin. It’s believed that the Chang’e-4 lander and rover will touch down in the Von Karman crater inside this region after a 27-day flight, though the exact landing site hasn’t been confirmed. The South Pole-Aitken basin is a large impact crater on the far side of the Moon that’s roughly 1,550 miles in diameter and 7.5 miles deep. It’s thought to be one of the oldest impact sites on the lunar surface, but we don’t know exactly how old it is - and its true age could tell scientists a lot about the early Solar System.
Unfortunately, Chang’e-4 won’t be returning anything to Earth, so it probably won’t be able to tell us the exact age of the basin. But it should learn a few interesting tidbits. The Chang’e-4 rover will be carrying ground-penetrating radar to figure out what the structure of the Moon is like underneath the surface of the basin, which could tell us more about how this area formed. It will also have an instrument designed to figure out what the surface is made of in this region. And it’s carrying a Swedish instrument designed to figure out how particles streaming from the Sun interact with the lunar rocks. Meanwhile, the lander, which is tasked with carrying the rover to the Moon’s surface, will also be doing scientific research from its landing spot, taking advantage of its location on the Moon. Since these vehicles will be on the Moon’s far side, they’ll be shielded from much of the electromagnetic interference from Earth and don’t have to deal with our planet’s atmosphere. The lander will be studying the space environment and the Universe in low frequencies - something we can’t do from our planet. And of course, both the lander and the rover will carry cameras to take detailed images of the lunar surface, just as Chang’e-4’s predecessor, Chang’e-3, did.
And while it’s definitely unique, Chang’e-4 is just one step in the ladder of China’s decade-long mission plan. Following this probe, China plans to launch another robotic mission to the Moon next year called Chang’e-5, which is designed to return samples from the nearside of the Moon. If successful, it’ll be the first time lunar material has been brought back to Earth since 1976.