China's Fengyun meteorological satellite: From scratch to world-leading in 50 years

In January 1969, due to the invasion of strong cold air, severe ice disasters occurred in the Yangtze River and Yellow River basins, causing large-scale communication and transportation interruptions in my country. The US meteorological satellite monitored this disaster weather. On January 29, 1969, Premier Zhou Enlai met with representatives of the Central Meteorological Bureau (formerly the China Meteorological Administration) and other units and instructed that measures must be taken to change the backward appearance and develop our own meteorological satellite. From then on, the prelude to the development of China's meteorological satellite was opened.

Written by Dong Yaohai, Chen Wenqiang, Yang Jun

The development of Fengyun meteorological satellites is a microcosm of my country's reform and opening up and scientific and technological development. Through the unremitting efforts and independent innovation of aerospace and meteorological personnel over the past 50 years, meteorological satellites have become an indispensable scientific and technological support for modern meteorological services and national economic construction. The observation data of Fengyun meteorological satellites have provided a large number of public welfare, professional and decision-making services for the fields of meteorology, oceanography, agriculture, forestry, water conservancy, aviation, navigation and environmental protection, and have generated huge social and economic benefits. Today, Fengyun meteorological satellites have become one of the most effective and widely used civil remote sensing satellites in my country.

The development history of China's meteorological satellite

my country began developing meteorological satellites in the 1970s, and has now developed to the second generation. Among them, Fengyun-1 is China's first generation of polar orbiting meteorological satellites, Fengyun-2 is China's first generation of geostationary orbiting meteorological satellites, Fengyun-3 and Fengyun-4 are China's second generation of polar orbiting meteorological satellites and geostationary orbiting meteorological satellites respectively.

Since the launch of the first meteorological satellite, the Fengyun-1 polar orbit meteorological satellite, on September 7, 1988, my country has successfully launched a total of 19 "2-generation 4-type" polar orbit and geostationary orbit meteorological satellites after more than 30 years of development. As of October 2021, a total of 8 meteorological satellites are operating stably in orbit. Polar orbit meteorological satellites and geostationary orbit meteorological satellites constitute China's meteorological satellite monitoring system, realizing the operationalization of networked observation. China has become the country in the world after the United States and Europe to have two types of orbital meteorological satellites at the same time, and is an important pillar of the World Meteorological Organization's space-based integrated earth observation network.

At present, more than 2,700 domestic users and more than 120 countries and regions receive and use Fengyun meteorological satellite data. Fengyun meteorological satellites are listed in the international meteorological satellite sequence by the World Meteorological Organization and are the main satellites for global meteorological observation.

my country's meteorological satellites have developed from nothing to something, from weak to strong, and have made the leap from following foreign satellites to running side by side and then to partially leading the world. They now have global observation capabilities through high and low orbit networking, and their comprehensive performance has reached the world's advanced level.

The first polar-orbiting weather satellites

In 1970, my country decided to develop the first generation of polar orbit meteorological satellites, and the satellite development task was undertaken by the newly established Shanghai Aerospace Base. In 1977, the National Meteorological Satellite Program Demonstration Conference was held in Shanghai, and a new era of Chinese meteorological satellites began. The development of my country's first generation of meteorological satellites can be said to have started from scratch. After more than 10 years of research and development, Fengyun-1A was successfully launched in 1988.

Fengyun-1A is a cuboid with a height of 1.2m and a length and width of 1.4m. After the left and right solar panels are opened, the span is 8.6m. The satellite weighs 750kg and operates in a sun-synchronous orbit at an altitude of 901km. The satellite carries a multi-spectral visible light infrared scanning radiometer with 5 channels for obtaining visible light during the day and night, infrared cloud images, ice and snow cover, vegetation, ocean water color, sea surface temperature, etc. Its performance is comparable to that of the third-generation polar orbit meteorological satellite of the United States at that time. Soon after Fengyun-1A entered orbit, it was found that the water vapor emitted by the instrument polluted the infrared detector and the performance indicators declined. An accident occurred 39 days after the satellite was launched. The satellite encountered strong solar activity, and the onboard computer was hit by high-energy particles from the sun and flipped over. The images sent back were distorted, and the satellite attitude was severely deflected along the flight direction. The ground control center was unable to control the satellite attitude, and Fengyun-1A finally lost control completely and disappeared in the vast space.

Fengyun-1B was launched on September 3, 1990 using a Long March 4 rocket. It adopted pollution protection design and protection measures, and the satellite's image quality on orbit was good, exceeding expectations. The attitude control system was significantly improved compared to Fengyun-1A, but the system's reliability design was defective. After 165 days of normal operation on orbit, a sudden failure of the onboard computer caused the satellite's attitude to lose control. After 75 days of continuous rescue, it resumed normal operation. However, the onboard computer was affected by the space environment and its operation was unstable. The satellite worked intermittently until November 1991, with a total of 285 days of normal operation on orbit.

Fengyun-1A and Fengyun-1B made our space workers realize for the first time a series of unprecedented difficulties such as the contamination of optical remote sensing instruments, the impact of the on-orbit space environment and system reliability. Fengyun-1C learned from the experience and lessons and, after a series of improvements, the satellite's detection performance, adaptability to the space environment and system reliability have been greatly improved. Fengyun-1C was launched on May 10, 1999, with a design life of 2 years. It operated stably in orbit and served beyond its service life until June 2004, opening a new era of long-life, high-reliability, continuous and stable business operation of China's meteorological satellites. Fengyun-1D was launched in 2002 and has been operating stably in orbit for 10 years.

With its superior performance and stability, Fengyun-1C won the first prize of the National Science and Technology Progress Award in 2001. It was listed as one of the three major events in China at the end of the 20th century and engraved on the China Millennium Monument. In August 2000, the World Meteorological Organization included Fengyun-1C in the global application meteorological satellite sequence, making it an important member of the Global Earth Observation System (GEOSS). Fengyun-1C, together with meteorological satellites from European and American countries, has formed a satellite observation network for all-weather, three-dimensional and continuous observation of the earth's atmosphere, ocean and surface environment, greatly enhancing mankind's comprehensive observation capabilities of the earth system.

Compared with foreign countries, my country's meteorological satellite industry started late. In order to catch up with the advanced level of international meteorological satellite observation as soon as possible, my country's aerospace workers and meteorological workers worked together to propose the development concept of "small steps and fast progress" for meteorological satellite development. Specifically, it is to abandon the concept that the status of satellites of the same generation in foreign countries is completely consistent, so that each satellite of the same generation in my country has improved performance compared with the previous satellite, and use the development of a generation of 4 satellites to catch up with the development achievements of the 5th generation of polar orbit satellites in Europe and the United States. The performance indicators of Fengyun-1C and D satellites have been greatly improved compared with A and B satellites. The observation bands of remote sensing instruments have been increased from 5 bands to 10 bands, and the number of bands has doubled; the satellite life requirement has been increased from 1 year to 2 years, and the performance indicators have fully reached the international advanced level at that time.

Faced with the achievements, the eyes of my country's aerospace and meteorological personnel did not stop there. With the rapid development of my country's economy and society, the remote sensing instruments carried by the Fengyun-1 satellite could no longer meet the needs of meteorological modernization, so the proposal to develop my country's second-generation polar orbit meteorological satellite was put before everyone. "Equip one generation, develop one generation", while developing the Fengyun-1 satellite, the demonstration of the second-generation polar orbit meteorological satellite was launched.

The first generation of geostationary meteorological satellites

my country's first geostationary meteorological satellite, Fengyun-2A, was successfully launched on June 10, 1997. Since then, eight Fengyun-2 satellites have been successfully launched.

Fengyun-2 satellites have realized the "multi-satellite in orbit, coordinated operation, mutual backup, timely encryption" operation mode for the first time. The dual-satellite joint acquisition of an image of the entire Earth disk has been shortened from 30 minutes for a single satellite to 15 minutes, and observations of the Chinese region are carried out every 6 minutes, which has improved the efficiency of use and greatly enhanced the comprehensive meteorological monitoring capabilities of the entire territory of China, providing real-time dynamic data for climate monitoring and weather forecasting in my country and the world.

The main payload of Fengyun-2 satellite, the multi-channel scanning radiometer, is an optical remote sensing instrument. It uses the satellite's spin from west to east and the radiometer telescope's step from north to south to achieve two-dimensional observation of the earth. It has five bands, including visible light, infrared and water vapor, and can simultaneously conduct real-time and continuous observation and monitoring of the earth's atmospheric phenomena and rapid changes. It can obtain 28 20°×20° panoramic disk images of the earth every day; under (flood season) encrypted observation, cloud images can be obtained 48 times a day (28 panoramic disk images and 20 northern hemisphere images); cloud images of my country and surrounding areas can be scanned at a frequency of 5 to 6 minutes per image according to flexible and mobile business needs.

Fengyun-2 satellite occupies an important position in the global meteorological satellite observation network. In the past, satellite observation of the entire East Asia, especially the Indian Ocean and the Qinghai-Tibet Plateau, was very weak. Fengyun-2 satellite is located at 105°E. Its position determines that it is an indispensable part of the entire earth observation system. The observation data it obtains contributes to the international meteorological community and even the earth science community. In the space program of the World Meteorological Organization, Fengyun-2 satellite is listed as a backbone meteorological satellite, responsible for global weather and climate observation.

Launch history of Fengyun-2 satellite

The operational applications of Fengyun-2 satellite have provided a large number of public welfare and professional services in the fields of meteorology, ocean, agriculture, forestry, water conservancy, aviation, navigation, environmental protection, etc. It has been included in the international operational application meteorological satellite sequence by the World Meteorological Satellite Organization and has become an important part of the global space-based integrated observation system, providing services to users in all countries of the world.

After my country successfully launched its first geostationary meteorological satellite in June 1997, it successfully launched Fengyun-2C and Fengyun-2D on October 19, 2004 and December 8, 2006, respectively, realizing the "dual satellite operation and mutual backup" for the first time and the commercial operation of geostationary meteorological satellites. Among them, Fengyun-2C and its ground application system also won the first prize of the National Science and Technology Progress Award in 2007.

The successful launch of Fengyun-1 and Fengyun-2 ended my country's long-term reliance on foreign satellites for weather forecast satellite data. Since then, my country has become a country with both polar orbit and geostationary orbit meteorological satellites.

Second generation polar orbiting meteorological satellite

In September 2000, the state approved the Fengyun-3 satellite project. After eight years of research and development, China's first second-generation polar orbit meteorological satellite Fengyun-3A was successfully launched on May 27, 2008, and Fengyun-3B was successfully launched on November 5, 2010. The successful launch and operation of the two test satellites Fengyun-3A and B marked that China's second-generation meteorological satellites have fully entered the operational stage. Fengyun-3 completely replaced the Fengyun-1 satellite's earth meteorological observation mission. Since then, my country has launched Fengyun-3C, D, and E in September 2013, November 2017, and July 2021, respectively.

The mass of Fengyun-3A is 2298.5kg. It adopts a three-axis stable attitude control method and is equipped with 11 payloads, including a visible infrared scanning radiometer, an infrared spectrometer, a microwave thermometer, a microwave hygrometer, a medium-resolution spectroscopic imager, a microwave imager, a total ultraviolet ozone detector, a vertical ultraviolet ozone detector, an earth radiation detector, a solar radiation monitor and a space environment monitor. It has more than 90 detection channels and can detect any meteorological environment at any time of day or night. It can scan the world twice a day, with a scanning width of 2900km each time. The vertical detector carried on the satellite can conduct stereoscopic observation of the atmosphere within 30km above the surface, which greatly enhances the precision and accuracy of weather forecasts.

Many firsts created by Fengyun-3A

The world's first civilian dawn-dusk orbit meteorological satellite, Fengyun-3E (also known as Dawn), was launched on July 5, 2021. It operates in an 830km sun-synchronous dawn-dusk orbit, providing meteorological observation data to the world at dawn. Its launch fills the gap in my country's dawn-dusk orbit meteorological satellite technology, and realizes "morning orbit, afternoon orbit and dawn-dusk orbit" three-star network observation with Fengyun-3C and Fengyun-3D. The wind field measurement radar carried by Fengyun-3E realizes global sea surface wind field detection; the solar observation instrument carried realizes imaging observation of the source of space weather disturbances - the sun.

The technical indicators of the Fengyun-3 polar orbiting meteorological satellite have reached the level of the latest generation of meteorological satellites in Europe and the United States. It has achieved multiple leaps from two-dimensional remote sensing imaging to three-dimensional comprehensive atmospheric detection, from single optical detection to full-band wide spectrum detection, from kilometer-level observation to hundred-meter-level observation, and from domestic network reception to global network reception. The Fengyun-3 satellite has played an important role in monitoring large-scale natural disasters and ecological environment, studying global environmental changes, climate change laws, and disaster reduction and prevention; it can also provide global meteorological information for aviation, navigation and other departments. The World Meteorological Organization has included it in the new generation of the world polar orbiting meteorological satellite network.

Fengyun-3 is my country's second-generation polar-orbiting meteorological satellite, which can carry out all-weather, multi-spectral, three-dimensional and quantitative detection on a global scale. It mainly provides meteorological parameters for medium-term numerical weather forecasts and monitors large-scale natural disasters and the ecological environment. At the same time, it provides meteorological information for studying global environmental changes, exploring the laws of global climate change, and aviation and navigation.

Second-generation geostationary meteorological satellite

At 00:11 on December 11, 2016, the Long March 3B carrier rocket successfully launched the Fengyun-4A satellite at the Xichang Satellite Launch Center. Fengyun-4A is the first satellite of my country's geostationary orbit meteorological satellite from the first generation (Fengyun-2 satellite) to the second generation, and is also my country's first geostationary orbit three-axis stabilized quantitative remote sensing satellite.

Fengyun-4A uses the newly developed SAST5000 platform with a design life of 7 years. It has the real-time comprehensive observation capability of meteorological elements of "multi-spectral two-dimensional imaging + hyperspectral three-dimensional detection + ultra-narrow-band lightning detection" for the earth, and also has the ability to observe space weather such as space particles, radiation and magnetic fields. The multi-channel scanning imaging radiometer can obtain a 14-band earth disk image in 15 minutes, with a visible light spatial resolution of up to 500m and an infrared spatial resolution of 2 to 4km; the highest infrared sensitivity is 0.1K, and the calibration accuracy is better than 1K, reaching the advanced level of international payloads of the same type. The interferometric atmospheric vertical sounder uses a Michelson interferometer to achieve 1650 channels of infrared radiation detection. It is the first time in the world to obtain high-frequency atmospheric temperature and humidity vertical distribution information from the geostationary orbit. The on-orbit measured spectral resolution is 0.625cm-1, the radiation calibration accuracy is better than 1.5K, and the spectral calibration accuracy is better than 10×10-6. The lightning imager can obtain lightning detection data at a high frequency of 500 frames per second, conduct lightning event detection on the satellite in real time, and compare it with ground-based observation data to achieve real-time and continuous monitoring and tracking of thunderstorm systems. The radiometer, detector, and lightning instrument can jointly observe strong convective accumulation accompanied by obvious weather events on orbit. The fine structure and texture characteristics of strong convective clouds observed by the radiometer are combined with lightning events and clear sky area sensing data of the detector to provide early warning of regional disaster weather and improve the forecast accuracy of severe convective weather and disaster weather. It is of great value. The comprehensive detection capability of Fengyun-4A has reached the leading level of some international advanced satellites.

After the Fengyun-4A satellite was put into use, my country has carried out weather monitoring and forecasting, numerical forecasting, and climate monitoring more accurately. The lightning imager on the satellite can take 500 lightning pictures per second, detect the frequency and intensity of lightning in the area, and provide lightning warnings for the first time in China. The radiometer observes the typhoon area every 3 minutes, making up for the shortcoming of the low temporal resolution of the cloud images of the on-orbit satellite, and providing strong support for disaster and environmental monitoring, artificial weather modification, and space weather research.

On June 3, 2021, my country successfully launched Fengyun-4B. The two Fengyun-4A and B satellites realized more flexible dual-satellite network observation, bringing a leap in high-frequency weather observation capabilities. Fengyun-4B was the first in the world to achieve a spatial resolution of 250m in geostationary orbit and a frequency of 1min for small and medium scales (2000km×2000km), providing high-frequency and high-definition observation data for severe convective weather monitoring and meteorological support for major events. After seeing the nebula map of Fengyun-4B, people couldn't help but exclaim: "The earth has never been so clear."

Looking at the international situation, Fengyun-4 satellite has led China's high-orbit meteorological satellites to catch up with Europe and the United States and seize the international commanding heights. It has achieved the world's first vertical detection of the atmosphere in geostationary orbit, greatly improving the accuracy and refinement of weather forecasts. At the same time, its image positioning accuracy has reached the world's first-class level.

About the Author

Dong Yaohai

Member of the Science and Technology Committee of Shanghai Academy of Spaceflight Technology and chief model designer, he is mainly engaged in the research and development of meteorological satellites and the research of development strategies. He served as the chief designer of my country's Fengyun-3 and Fengyun-4 meteorological satellites, and presided over the development of the second-generation polar-orbiting meteorological satellites and geostationary orbit meteorological satellites. He is a national candidate of the "New Century Hundred Thousand Talents Project" and the first Shanghai Youth Science and Technology Talent. He has won 1 first prize and 1 second prize in the National Science and Technology Progress Award, and 7 provincial and ministerial awards and honors.

Chen Wenqiang

Chief Commander of the Science and Technology Committee of Shanghai Academy of Spaceflight Technology, mainly engaged in the development and project management of meteorological satellites. He served as deputy chief commander of my country's Fengyun-2 meteorological satellite and chief commander of Fengyun-4 meteorological satellite, and completed the development and launch missions of multiple Fengyun-2 meteorological satellites and Fengyun-4A and B meteorological satellites. He won 1 first prize of the National Science and Technology Progress Award and 1 provincial and ministerial award and honor.

Yang Jun

Director of the Engineering Office and Chief Engineer of the China Meteorological Administration, Executive Deputy Commander of the Fengyun Meteorological Satellite Project, and Chairman of the Satellite Meteorology Committee. He has been engaged in the research of Fengyun meteorological satellites and their application development for a long time. He is a candidate of the National "Million Talents Project". He has won 1 first prize and 1 second prize in the National Science and Technology Progress Award, and 8 provincial and ministerial awards and honors.

This article is authorized to be excerpted from Chapter 4 "The Past and Present of Meteorological Satellites" of "Starry China: Our Fengyun Meteorological Satellites" (Posts and Telecommunications Press, August 2022 edition).

Go to the "Fanpu" public account and click "Read original text" at the end of the article to purchase the book