Why is the picture so clear about this "world to earth call"?

On June 23, Nie Haisheng, Liu Boming and tanghongbo, the first astronauts of the Chinese space station era, welcomed a "high light moment" after they entered the Chinese space station. At 9.35 a.m., a world-to-earth call was staged in Beijing and 400 kilometers away from space.

Many viewers watching live broadcast were surprised to find that in this world call, not only the sound and the picture were not stuck, but also, compared with the past, the pictures and sounds transmitted by multiple machine stations on the Chinese space station in real time were clearer. On the screen of the command Hall of Beijing aerospace flight control center, the three relay satellites, namely, tianchain 2, 01, tianchain 1, 03 and 04, as well as the global monitoring and control stations and Yuanwang 6 survey vessels in Weinan, Xiamen and Namibia are quietly providing guarantee for this historic moment.

The first time a new generation of "sky chain" participates in manned space missions

"Thanks to the Samsung network of relay satellites, astronauts and the ground can make longer calls." Zhengyonghui, chief engineer of Beijing space information transmission center, told the global times that in 2003, when Yang Liwei, China's first astronaut, entered space, he had made several earth and earth calls, but every time it had a strict time window limit.

It is understood that in the early stage of China's manned space project, China mainly adopted the earth earth and sea-based communication link. Since China has no global monitoring and control stations and survey vessels, the spacecraft with a track height of 300-400 km is affected by the earth curvature and the visual field of sight, only when entering the field of view of China's measurement and control station (ship), Only by establishing short-term communication between the sky and earth in the flight arc, the status of spacecraft and astronauts is almost unknown to the ground personnel outside the field of view arc.

In order to change this situation, China's "tianchain 1" relay satellite system project was officially established. From 2008 to 2019, there have been two generations of five "sky chain" satellites successfully entering space. They constantly play the advantages of high orbit coverage and high-speed and large capacity data transmission, providing safe and reliable space-based measurement and control and data relay services for manned space missions, The number of astronauts who can talk to the ground increases greatly.

In 2013, the relay satellite system of Samsung network was realized, which guaranteed the communication between the ground and astronauts for the first time. Clear picture quality and smooth voice... Greetings and expectations from the ground were delivered to the sky at the first time.

"This time, the second generation relay satellite tianchain 2 01, which is independently developed in China, participated in manned space missions for the first time. With its existence, the transmission rate of audio and video between heaven and earth is higher, and the effect of the earth earth communication and the length of the available call have been improved," Zheng said.

The bandwidth rate of China space station is better than that of International Space Station

According to the Global Times reporter, tianchain-2-01, the first time involved in manned space missions, is the second generation relay satellite in China. It has the characteristics of wider coverage of panoramic beam, higher transmission speed and stronger multi-objective support capability. After the first generation relay network of the sky chain and the earth earth link were formed, the "sky chain" system has become the main measurement and control communication system for the autonomous and rapid rendezvous and docking between Shenzhou 12 manned spacecraft and the core cabin.

In this "earth earth call", the "space base station" composed of tianchain-1, 04 and tianchain 2-01 stars at the altitude of 40000 KM has established a network link between the core cabin of the Chinese space station and the ground station. The voice, video, email data and the downlink scientific experimental data between the space station and the ground can be transmitted at high speed through this link.

Yi Yusheng, director of the space station system measurement and communication subsystem of the Fifth Academy of space science and technology group, said in an interview with the media that more than 10 cable and wireless network cameras, as well as mobile devices such as mobile phones, pad and notebook computers, can be used as network terminals in the space station sky and core cabin. These terminals connect the acquired image and voice data to the Ethernet switch in the cabin through wired or wireless Wi Fi, and then transmit them to the ground through relay link through high-speed communication processor.

The downlink rate of this relay communication link is 1.2g, which is equivalent to 5g communication rate on the ground. The relay satellite ground station receives space data in real time, then transmits the data to Beijing flight control center, and then distributes it automatically according to different signs, with the delay of only seconds.

In addition, after the stable flight of the Chinese space station, the coverage of the earth and earth measurement and control can reach more than 90 percent through three relay satellites and relay antennas in the core cabin. After the three tanks form a combination, the coverage of the measurement and control can be close to 100% through the partial installation of the relay antenna in the other two experimental cabins. The interruption of the earth earth communication will not occur in the process of one and a half hour of the Chinese space station circling the earth. Yi Yusheng added.

Previously, Berlin Hou, deputy chief designer of China Space Station sky and core cabin, said in an interview with the global times. It is a unique advantage of the Chinese space station to apply the latest information technology to the Chinese space station compared with other on orbit space stations. Berlin said that the information technology currently used on the Chinese space station has a better bandwidth rate than the international space station. The concept of high-speed network of heaven and earth has been applied to the Chinese space station.