April 24, 2020 is a particularly memorable day. On this day 50 years ago, China's first artificial earth satellite Dongfanghong No. 1 was launched, and China became the fifth country in the world to develop and launch satellites on its own, and the prelude to the Chinese nation's exploration of space began.
The social benefits, economic benefits and national defense benefits of artificial earth satellites are very high. Over the past 50 years, China has vigorously developed the cause and industry of artificial earth satellites, Chinese and manufactured earth satellites, whether in terms of quantity and type, as well as in technology and application, have achieved rapid development, some have reached the world's advanced level, forming four series of communications and broadcasting, navigation and positioning, earth observation, space science and technology experiments, and some have become important space infrastructure in China.
From Dongfanghong No. 1 to Dongfanghong No. 5
Fifty years ago, a familiar song of "Dongfang Hong" resounded through space, and China became the fifth country in the world to launch a domestic satellite with a homemade rocket. Dongfanghong-1 thus became the beginning of the development of China's satellite industry.
At that time, the biggest challenge faced by researchers was to use the most rudimentary equipment to achieve China's first space mission. On April 24, 1970, Dongfanghong 1 was successfully launched as planned, ushering in a new era in China's aerospace. The music of "Dongfang Hong" uploaded from the satellite made the world hear the voice of the Chinese satellite. This melody, which remains in the memory of a generation, was simulated by researchers with electronic oscillations, and the music signal was transmitted to the ground receiving station through the short-wave transmission system of Dongfanghong No. 1, and then broadcast to the whole country.
Soon after the successful launch of Dongfanghong-1, the communications department urgently hoped that China's communication satellites would be launched as soon as possible to change the backward situation of China's communication technology. To this end, in June 1970, the China Academy of Launch Vehicle Technology and the China Academy of Space Technology respectively organized teams to carry out research on new technologies for launch vehicles and communication satellites.
After several years of program exploration and feasibility study, in 1975, the China Academy of Space Technology determined the choice of geostationary orbit test communication satellites. After solving a series of key technologies, on April 8, 1984, China successfully launched the first communication satellite Dongfanghong II carrying two C-band transponders, taking the first step in China's communication satellites. Since then, China has launched a number of communication satellites using the Dongfanghong-2 small-capacity spin stabilization platform, which has greatly changed the situation that it was difficult to watch and communicate in China's remote areas at that time.
The development of the medium-capacity communication satellite Dongfanghong-3 is the second step in the development of China's communication satellites. With the passage of time, the communication satellites using the Dongfanghong-2 platform can no longer meet the needs of the rapid development of China's satellite communications industry. In 1986, China officially launched the development of the second generation of communication satellites - Dongfanghong III. On May 12, 1997, Dongfanghong-3 was successfully launched, it loaded 24 C-band transponders, using many new technologies at that time, so that the level of China's communication satellites suddenly spanned 20 years.
In order to adapt to the trend of high reliability, long life and large capacity development of satellites in geostationary orbit, with the support of the state, the China Academy of Space Technology focused on the technical development of the Dongfanghong-4 large-capacity platform during the "Ninth Five-Year Plan" period. As China's third generation of geostationary orbit satellite platform, it has the characteristics of large output power, strong bearing capacity, long service life, etc., has launched a number of communication satellites using this large-capacity platform, and the maximum number of transponders for a satellite using the Dongfanghong-4 platform has reached 46.
Using the Dongfanghong No. 3 and No. 4 platforms, China has also developed and launched two generations of data relay satellites, the first mobile communication satellite, the first high-throughput satellite and the first live television satellite, as well as the "Beidou" navigation satellite and the Chang'e-1 and No. 2 lunar probes. At present, China is experimenting with the Dongfanghong No. 5 super capacity platform. The key performance indicators such as weight, power, and in-orbit life of the platform have been improved by leaps and bounds compared with before, which will fill the gap in the spectrum of Large Satellite Platforms in China and reach the international advanced level, which can meet the needs of large-capacity satellite applications in the next 20 years.
Left: Dongfanghong-1 satellite launch tower at the Jiuquan Satellite Launch Center (april 15, 2016). Xinhua News Agency
"Made in China" satellites shine in the sky
Application satellites directly serve the national economy and people's livelihood and national defense construction, and China has developed and launched more and more advanced application satellites. At present, China has developed three types of application satellites: communications, remote sensing and navigation.
The first category is communication satellites, mainly the Dongfanghong series of satellites. The second type is remote sensing satellites, which are known as "clairvoyance". They stand tall, see far, and are widely used, and are divided into three types: land satellite, meteorological satellite and marine satellite.
In terms of land satellites, retrievable remote sensing satellites are the earliest application satellites in China. The development of such satellites began in 1966. After overcoming the difficulties of satellite attitude control technology, satellite re-entry heat prevention technology and satellite recovery technology, China has successively 24 retrievable remote sensing satellites into orbit and 23 recovered.
The "Gaofen" series of satellites is an important part of China's "Gaofen" special project, aiming to build China's independent land, sea and air high-resolution Earth observation system, and greatly improve China's independent Ability to Obtain Earth observation information. The series of satellites covers a variety of types from panchromatic, multispectral to hyperspectral, from optical to radar, from sunsynchronous orbit to geosynchronous orbit, constituting a geoscience observation system with high spatial resolution, high temporal resolution and high spectral resolution capabilities. This year, they have played an important role in monitoring events such as the COVID-19 pandemic and the Xichang fire.
In addition, China has also developed and launched remote sensing satellites such as "Resources", "Environment", "Sky Painting" and "Remote Sensing", as well as many commercial remote sensing satellites such as Jilin No. 1 and Gaojing No. 1, with a maximum resolution of 0.5 meters.
In terms of meteorological satellites, China launched the first polar-orbiting meteorological satellite , Fengyun No. 1 A Satellite , in 1988 , and In 1997 , China's first geostationary orbit meteorological satellite , Fengyun No. 2 B Satellite , becoming the third country in the world to have both polar-orbiting meteorological satellites and geostationary meteorological satellites.
So far, China has successfully launched 17 "Fengyun" meteorological satellites, of which 7 are operating stably in orbit. The second-generation polar-orbiting meteorological satellite Fengyun-3 and the second-generation geostationary meteorological satellite Fengyun-4 have reached the world's advanced level, greatly improving the accuracy of meteorological forecasts. In addition, China has also launched the first global atmospheric carbon dioxide observation scientific experimental satellite.
In terms of marine satellites, since the launch of China's first marine satellite, the Ocean 1A water color satellite, in 2002, China has launched three Ocean 1 water color satellites, two Ocean 2 marine dynamic environment satellites and one "Sino-French ocean satellite". Water color satellites mainly serve the development and utilization of marine living resources, marine pollution monitoring and prevention, and coastal zone resources investigation and development. Marine dynamic environment satellites play an important role in marine disaster prevention and mitigation, marine environment forecasting, marine resources development, marine scientific research and international cooperation. For the first time, the Sino-French Ocean Satellite has achieved simultaneous observations of sea breezes and waves.
Experimental pioneers and scientific "rising stars" are on the rise
Satellite technology is very complex, often using many new concepts, new technologies, new materials, etc., so in practice, it is generally necessary to launch technical test satellites for relevant technical verification, and then launch service satellites after maturity to ensure the normal operation of satellite services.
China has launched a number of "practice" series of satellites, that is, technical test satellites. Early in the mission, they had the dual mission of space physical exploration and new technology experimentation, and later "practice" series focused mainly on new technology experimentation. For example, the Shijian 9 launched in 2012 is mainly used for satellite long-life, high reliability, high precision, high performance, domestic core components and satellite formations, and inter-satellite measurement and link tests. In 2016, the "pulsar test satellite" launched by China is the world's first satellite to try and verify the feasibility of the pulsar navigation technology system, and the tested technology can be used for the autonomous navigation of future spacecraft and lay the foundation for the navigation of deep space probes. In 2018, China launched the Zhangheng-1 electromagnetic monitoring test satellite for the study of the world problem of "earthquake forecasting".
With the rapid development of China's economy and science and technology, since the "Twelfth Five-Year Plan", China has begun to develop scientific satellites, implemented special projects for space science and strategic leading science and technology, and has launched a number of scientific satellites.
In 2015, China launched its first astronomical satellite, the "Wukong" dark matter particle detection satellite. It is currently the space detector with the widest range of observation energy bands and the best energy resolution, and the cost is low.
In April 2016, China launched the first microgravity science experiment satellite Practice 10. It is the satellite with the largest number of space experiment projects in China at a time, carrying out 19 experiments in six major fields, specifically for microgravity science and space life science space experiment research, some of which are the first in the world.
In August 2016, China launched the world's first quantum science experimental satellite "Mozi". It is the first time in the world that it has completed experiments of great scientific significance such as quantum entanglement distribution and quantum teleportation in the free space of the star and the earth under the large scale of space.
In 2017, China launched the first X-ray astronomical satellite "Wise Eye" hard X-ray modulation telescope. It was involved in monitoring gravitational waves from neutron star mergers in October 2017.
In August 2019, China's first space gravitational wave detection technology experimental satellite was successfully launched. The microgravity technology experimental satellite was later officially named Taiji I and successfully completed the first phase of the on-orbit test mission on September 20, 2019.
【Related links】Three stages of Chinese satellite technology development
Technical preparatory phase (1956–1970)
Carry out basic research on satellites and make technical, engineering and organizational preparations for the development of satellites. On April 24, 1970, the successful launch of China's first artificial earth satellite, Dongfanghong I, ushered in a new era of Chinese aerospace.
China's first ocean satellite, Ocean One
Technical test phase (1971-1984)
It mainly develops, launches and operates retrievable remote sensing satellites, experimental communication satellites and scientific exploration and technology test satellites. On November 26, 1975, the first retrievable remote sensing satellite was launched and recovered. On April 8, 1984, the first Dongfanghong-2 communication satellite was successfully launched and operated. During the test phase, China also developed and successfully launched 7 different types of space science and technology test satellites.
Gaofen-3 is the synthetic aperture radar satellite with the most imaging modes in the world
Engineering Application Phase (1985-present)
China's satellite engineering has moved from technical tests to engineering applications, and four series of satellites have been put into use. At the beginning, the initial operation stage of satellite services, which was mainly based on satellite service operation experiments, was when there were few types of satellites, short lifespans, and many failures. Since 2000, it has entered the stage of full operation of satellite services, and since then, not only the types and quantities of satellites have increased, but also the "gold content" has also been greatly improved. For example, remote sensing satellites have developed from recycling to transmission, and communication satellites have developed from spin stability and small capacity to three-axis stability and large capacity.
China's first astronomical satellite - "Wukong" dark matter particle detection satellite
Author: Pang Zhihao, Chief Science Communication Expert of National Space Exploration Technology
Editor: Zhang Peng
Photo: Unless noted, the pictures in this article are provided by the author