China's Chang'e-6 mission has achieved a remarkable milestone by collecting almost two kilograms of lunar samples from the far side of the moon. These samples will be showcased at the 15th China International Aviation and Aerospace Exhibition, also known as Airshow China, in November.
Why is the Far Side of the Moon So Mysterious?
The far side of the moon has always intrigued scientists due to its limited visibility from Earth. This is because the moon is tidally locked with our planet, meaning the same side always faces us. This phenomenon is the result of billions of years of magnetic interactions between the moon and Earth's oceans.
The first glimpse of the moon's far side came in 1959 when the Soviet Luna 3 spacecraft captured images revealing a landscape more cratered and sparsely populated with maria, the large, dark basaltic plains, compared to the near side.
In 2019, China's Chang'e-4 became the first spacecraft to land and conduct surveys on the moon's far side. Building on this achievement, Chang'e-6 successfully returned with 1,935.3 grams of samples in late June, marking a historic moment in lunar exploration.
Overcoming Communication Barriers
Exploring the far side of the moon presents unique challenges, primarily due to the difficulty in maintaining direct communication with spacecraft operating on the opposite side. The moon itself blocks direct signals, making real-time communication a significant hurdle.
China addressed this issue by developing advanced technologies, including the deployment of the Queqiao relay satellite. Positioned in a stable halo orbit around the Earth-Moon L2 Lagrangian point, Queqiao acts as a vital communication bridge, enabling continuous signal transmission between Earth and the far side of the moon.
Lagrangian points are strategic locations where the gravitational forces of two large bodies, like the Earth and the moon, balance the centripetal force felt by a smaller object, allowing the satellite to maintain a stable position relative to both bodies.
Despite the inherent instability of the L2 point, Queqiao's sophisticated maneuvering ensures it remains within the necessary vicinity, overcoming challenges such as solar pressure and other perturbative forces.
Innovative Re-entry Techniques
Another technological breakthrough enabling the success of the Chang'e-6 mission is the \"half-ballistic jump re-entry\" technique, also known as the \"stone skipping\" method. This technique ensures the safe return of spacecraft to Earth by utilizing Earth's atmospheric drag to decelerate the vehicle.
Upon initial contact with the atmosphere, the spacecraft slows down and briefly exits back into space before re-entering at a reduced speed and thermal load, allowing for a safe landing. This method was successfully employed by both Chang'e-5 and Chang'e-6 missions.
The advancements achieved through the Chang'e-6 mission not only enhance our understanding of the moon's far side but also pave the way for future deep-space exploration endeavors.
Reference(s):
Explainer: Why studying samples from the far side of the moon matters
cgtn.com
