这一“吻”，不简单！
The orbiter-returner of China's Chang'e-5 probe has separated from the ascender, waiting for the right time to return to Earth with lunar samples, according to the CNSA.
The separation took place on the moon orbit at 12:35 p.m BJT.
The Chang'e-5 probe's returner will fly back to Earth with about 2 kilograms of moon samples via the Earth-moon transfer orbit. After reenterring the atmosphere, it will land in Siziwang Banner of north China's Inner Mongolia Autonomous Region.
揭秘“嫦五”交会对接背后的故事
其中，轨返组合体以抱爪的方式与迎面而来的上升器实现“太空一吻”，让众多网友感叹不已。
嫦娥五号上升器携带月壤样品与轨返组合体可谓完成了一次“教科书式的对接”。这是我国航天器首次实现月球轨道交会对接。
然而，太空上这“浪漫”的一幕看似简单，但在几十万公里之外高速运行的飞行器上实现却并非易事，这其中离不开中国航天人的智慧和努力。
In one of the 11 steps to bring 2 kilograms of moon samples back to Earth, the ascender of China's Chang'e-5 lunar probe has docked with the orbiter module and is ready to return.
Docking in space is in no way similar to how it happens in Japanese animes, wherein robots often speed up and rush into the action, even producing loud, metal clunking sound. In reality, the docking process is very gentle, achieved at an acceleration of only a thousandth of a rocket.
If a loud clunking sound is produced, that may mean something has been broken. What's more, you can't really hear the sound because sound in general cannot travel in the vacuum of space.
All in all, it's a work of precision, instead of a collision.
How did the two parts "kiss" each other in space? Not long after the docking completed, the engineers at China Aerospace Science and Industry Corporation (COSIC) revealed the technologies they had developed for the Chang'e-5 mission.
“惯测小分队”
Acceleration measurement system
轨返组合体与上升器没有“擦肩而过”，多亏了“惯测小分队”。
这支“惯测小分队”由中国航天科工集团有限公司研制的高精度加速度计组合、石英挠性加速度计及I/F转换电路组成。在此次交会对接中，主要实施加速度测量的高精度加速度计组合是这支“惯测小分队”中的“队长”，这已经是它第三次陪伴“嫦娥”远赴月宫。
为了这一次“远行”，研制团队特地为组合产品增加了新部件——内部减振器。由于此次飞行对组合的抗冲击特性提出了更高的要求，增加内部减振器就像是给组合增加了一组吸振隔振的“坐垫”，有了这些“坐垫”的加持，即使外界环境存在较大的冲击和振动，加速度计组合仍能在相对稳定的环境下正常工作。
图源：中国航天科工集团
然而，减振器的设计和安装可不像加“坐垫”那样简单。航天科工三院33所设计师付继波介绍说：“减振器安装在组合的多个位置，就像是垫在了柜子的四角，受到冲击时各减振器的变形量存在微小差别，‘垫子’不等高了，加速度计组合就会发生转动，即使是非常微小的转动也会对测量精度带来很大的影响。”
为尽可能消除转动变形，团队用两个多月的时间进行了大量的冲击试验，最终将形变量控制在了角秒级，确保组合测量精度不受影响。
Acceleration describes the change in speed. When a rocket was ignited, its acceleration surge. But when the ascender travels at a static speed in space, the acceleration is zero.
The tool used to measure acceleration is called accelerometer, which also exists in our smartphones to detect motion and orientation – yeah, the "auto rotate" feature.
The accelerometer used on Chang'e-5 is mostly the same as in its predecessors, with one important difference: Many crash cushions were added to reduce the impact when the ascender performs big movements like lifting off from the moon.
"Those dampers were installed in many places. It's a bit like the corner cushion we stick on furniture," said Fu Jibo, an engineering designer working for COSIC. "The problem is, we have to put them in the correct location, so the accelerometer won't rotate after embracing impact."
It took him and his team more than two months to do experiments and find the best locations. The test result was great because they can limit the rotation under one arc second – less than 0.0003 degrees.
微波雷达
Microwave radars
嫦娥五号月球采样返回，是我国航天领域迄今为止最复杂、难度最高的任务。由中国航天科工集团二院25所研制的嫦娥五号交会对接微波雷达，作为中远距离测量的“助手”，成功引导完成了嫦娥五号的交会对接任务。该对接技术是嫦娥五号任务中“四大关键技术”之一。
微波雷达是一组成对产品，由雷达主机和应答机组成，分别安装在嫦娥五号探测器的轨道器和上升器上。当轨道器、上升器相距约100公里时，微波雷达开始工作，不断为导航控制分系统提供两航天器之间的相对运动参数，并进行双向空空通信，两航天器根据雷达提供信号调整飞行姿态，直至轨道器上的对接机构捕获、锁定上升器。随后，上升器中的月壤样品和容器转移至返回器中。
图源：中国航天科工集团
交会对接微波雷达总工程师孙武介绍，此前的载人航天工程任务中，我国航天器在近地轨道进行过多次交会对接，都应用了航天科工的微波雷达，优异的表现足以证明，我国已经成功掌握交会对接技术。但不同的是，这次是在距离38万公里之外的月球轨道，难度更大。
“与近地轨道相比，月轨环境更复杂，要克服月球引力影响，所以自动交会对接对微波雷达提出的要求极为苛刻。为此，微波雷达团队攻克了一系列关键技术。”孙武说。
此外，装有对接用应答机的上升器在落月时难免形成扬尘，这些肉眼不可见的干扰将会严重影响测角精度。
No, not the microwave oven we use at home. The radars used in the docking process happened to utilize the same kind of radiation as the home ovens do.
Radars are the eyes of the ascender-orbiter pair to "look" at each other. They are one of the four critical technologies used in the Chang'e-5 mission.
A set of radar consists of a microwave emitter and receiver. One is installed on the ascender and the other on the orbiter.
When the pair got close to each other, the radar was switched on to detect the distance between them.
"We have been used to do docking in the Earth orbit," said Sun Wu, chief engineer of the radar. "But the Chang'e mission is much harder because it happens much farther away from the Earth."
Satellite-based navigation like Beidou and GPS won't work at such distance, so the radars are the only thing to depend on.
In addition, the radars were also used as a data transmitting device like the WiFi we use at home.
To make sure the radars work as intended, the engineers at COSIC carried out 15 simulations and took the interference of moon dust into consideration.
"We want to bring no pity or defect into the space," said He Zhongqin, chief designer of the radar system.
如今，这份沉甸甸的“快递”已准备投递
给“嫦娥快递员”5星好评！
我们等你带着“土特产”平安回家~